cataract surgery for greenhorns

SLIK technique

2011-12-06T10:25:00.000-08:00

The sliding internal knot (SLIK) technique is a useful technique to secure a single piece acrylic (SPA) IOL.

Late in the bag dislocation seems to be an increasing problem especially among patients with pseudoexfoliation. In patients with a 3 piece IOL we have several options: we can remove the IOL from the bag and suture to the iris, we can remove the IOL from the bag and glue the haptics to the sclera, we can suture the haptics to the sclera, or we can exchange the IOL for an AC IOL. With a SPA IOL our options are more limited as we cannot suture this IOL to the iris or glue the thick haptics to the sclera.

In the video below we show a technique to suture the SPA IOL to the sclera using a sliding internal knot (ala Siepser). Janet Tsui, Alton Szeto and I described this in the JCRS (see prezi below). We simply pass one arm of a 9-O prolene suture below and the other above the haptic of the IOL after passing the needle through the sclera. Then a sliding internal knot is used to secure the haptic to the sclera. Duet forceps are used to cinch the knot down inside the eye. Two of these 9-0 prolene sutures are used (one for each haptic) to secure the IOL. The surgeon needs to make sure the suture is cut close to the knot so that the suture end does not iritiate the iris.

Here is a prezi showing the SLIK technique with the same beautiful drawings from Alton Szeto referencing our article in JCRS.

SLIK for late decentration on Prezi

tips for lefty learners of cataract surgery

2011-03-03T20:13:00.000-08:00

Introduction. Learning cataract surgery is hard enough when you are right handed like your mentor. However when you are left handed and your teacher is right handed it can be tough.    Everything seems backwards for both teacher and student. Here I will outline some tips on how to learn and teach cataract surgery when the lefty student meets the righty teacher.   I think there are 4 main issues:

Incision Location. Often surgeons will cheat a little bit superior or inferior of temporal toward their dominant hand.   However this can be a big issue when the dominant hands of teacher and student don't match. If the lefty student makes the incision at about 4 oclock for a left eye it may be convenient for the student but will be very hard for the right handed teacher if he/she needs to take over the case.   There are a couple of solutions to this issue. One is to make the incision exactly temporal at 3 (left eye) or 9 (right eye) oclock so that it is equal for student and teacher. Another solution is to make all of the incisions superior temporal. For the right eye the left handed learner operates superior  temporal convenient for his/her left hand. Then the teacher if he/she needs to take over can sit at the head (superior) and the incision will be convenient for the teachers right hand.  For the left eye the learner can sit at the head (superior) and make the incison superior temporal with his/her left hand.  The teacher on these left eyes can take over by sitting on the side (temporal) and the incision will be in a good location for their right dominant hand. So if the learner sits temporal on right eyes and superior for left eyes taking over the case by a righty will not be an issue.

Some instruments are handed.   Yes this is an issue!.   While scissors and clamps can be harder for lefties the big issue in ophthalmology is that some of the choppers are made for either right or left handed surgeons.     Very confusing as a right handed chopper is held in the righy's left hand. Getting a chopper for a left handed surgeon (to hold in his right hand) can be a problem as the student often has no control over the OR. Play the fairness card. lefty bigots! However dont wait too long as it will take time to get equipment orders approved and in the OR at most large institutions.   So i suggest that lefties plan ahead.    One of our residents developed some interesting strategies to use right handed choppers despite being a lefty for example see what we called the side saddle chop.

Mirror Image. Just like it is convenient for right handed surgeons to rotate the lens or tear the rhexis in a certain direction the same is true for lefties. But in the other direction.  This obvious point took me a while to figure out as a teacher. I like to take the rhexis around clockwise (i am a righty) and it did not occur to me until i had mentored several lefties that they may prefer the mirror of what i was doing and go in the other direction. The same is true for the direction of spinning the lens especially when chopping.

The IOL is made for the right hander.    The IOL haptic insertion into the optic is optimized for right handed surgeons. The IOL is designed so that it is very easy to insert when a right handed surgeon pushes the haptic/optic junction with a hook from the right side (with the right hand). As such lefties have to recognize this issue and simply use their non dominant hand right hand for this step. The good news is that while the IOL is optimized for right handed surgeon insertion; the IOL is easier for lefties to remove for the same reason (unfortunately this almost never comes up).

Summary.  Lefties should consider sittikng temporal on right eyes and sit superior on left eyes so the right handed attending can easily take over.  get a few left handed choppers.  Lefties should go clockwise for the rhexis and spin the lens counter clockwise while you chop.    Finally, lefties will have to use their right hand to hold the Kuglen or other hook to insert the IOL.

placing the capsular tension ring (CTR)

2010-10-03T19:41:00.000-07:00

The capsular tension ring (CTR) is very useful. Here I will discuss the use of the standard, unsutured CTR.

Indications The CTR is most commonly used when the zonules are weak in a limited area or together with a capsular tension segment (CTS) with more generalized zonular weakness. The CTR can also be used to help prevent capsular phimosis or to allow suturing of the ring and capsule later in patients with progressive or more generalized zonular weakness. Some surgeons have also suggested that the ring will help prevent posterior capsular opacification but I think that has not been proven.

CTR variations The CTR comes in many varieties that include standard rings in various sizes, CTR with one or two eyelets that allow one to suture them to the sclera (Cionni modification), and the Henderson CTR with waves that allow one to place the ring early and still remove cortical material (distributed by FCI in the US). A close cousin of the CTR is the Ahmed capsular tension segment (CTS) which has a partial ring and an eyelet that can be used temporarly to hold the capsule with a hook or sutured permanently to the sclera.    The standard CTR comes in a variety of diameters -- in general i would suggest using the larger ring (eg 13 mm in the AMO/Ophtec ring).

Injecting the CTR. Several techniques that have been described to place the CTR. The most simple and the technique that i use most often is to use an injector. The injector is simply a cylinder which has a spring loaded hook that pulls the ring into the cylinder with a plunger to push it back out.   Here is a video showing how to load the CTR into the injector and inserting the CTR into the capsular bag filled with OVD.

Here are is a video showing an example of a traumatic case using a CTR placed with an injector.

Here is a video showing the use of an injected CTR in a patient with RP to help prevent phimosis.

Injecting the CTR does place some tension on the existing zonules and sometimes too much stress. Here is a video showing a case where the placement of the CTR with the injector created too much stress on the zonules and actually made the situation worse.

Little fish tail placement of the CTR. Angunawela and Little described a nice CTR insertion technique to use when the zonules are very weak.  In this fish tail technique the center of the ring is pushed through the wound and the eyelets remain outside the ring which looked to Little like a fish tail. This insertion technique allows for much less tension on the zonules as the ring is inserted. The ring is bent a bit as it is placed through the 2.75mm wound, but it seems to snap back into position nicely.   Here is a video showing this technique.

Alternative fish tail #1. Getting the central portion of the ring into the eye with the Little Fishtail technique is the trickiest part. A variation of this technique is to use Duet micro forceps to place the central portion of the ring into the wound and the CTR into the capsular bag.  The remainder of the ring is then placed using forceps as described by Angunawela and Little. This seems like a very nice way to place a ring to minimize the stress on the zonules during placement but it does seem to stress the central portion of the ring a bit.   Here is a video showing this technique.

Alternative Fishtail #2. This fish tail modified technique uses a suture like a fish on a line to pull the injected eyelet back out of the eye to form the fish tail confguration. One of the issues with the little fish tail technique is getting the loop of the CTR into the eye without damaging the elasticity of the CTR.   In this modified technique you first insert the leading eyelet of the CTR into the anterior chamber with a suture through the eyelet and leave the trailing eyelet out of the eye.   You then use the suture and a hook to bring the leading eyelet back out of the eye keeping the loop in the anterior chamber which places the CTR into the familiar fish tail configuration. Then use forceps to place the CTR as described by little.   Here is a video showing this technique.

References:

1. Price FW Jr, Mackool RJ, Miller KM, Koch P, Oetting TA, Johnson AT. Interim results of the United States investigational device study of the Ophtec capsular tension ring. Ophthalmology. 2005 Mar;112(3):460-5.
2. Angunawela RI, Little B. Fish-tail technique for capsular tension ring insertion. J Cataract Refract Surg. 2007 May;33(5):767-9.

freeing and removing an IOL

2010-01-02T15:13:00.000-08:00

removing an IOL can be tricky. first you have to free the IOL from its capsular adhesions. then you have to get it out. here i will share a few tips on removing IOLs.

freeing the IOL from the capsule. The ease of IOL removal is mostly dependant on how long the IOL has been in the bag. IOLs which have been in the bag for a few weeks are very easy to free from the bag. IOLs that have been in the bag for years can be very hard to remove. Removing an IOL with an intact posterior capsule is far easier than when the patient has had a YAG capsulotomy.

the first step is to somehow get a visco dissection plane started between the IOL and the capsule.  I like to use dispersive OVD especially when the posterior capsule is not intact. with IOLs that have been in place for a while i like to use a 27 gauge needle attached to viscoat and use the sharp end to get under the capsule and then inject the viscoat. then i will sometimes use the Duet micro forceps (as shown in the video) to lift the capsule to get a canula under for more viscodissection. I also like to use a flat hydrodissction cannula for visco dissection as the flat surface makes it easier to get between the capsule and the IOL. most of your attention should be directed to freeing up the haptics with viscodissection. If the posterior capsule is intact the viscoat will often track around the optic and free it from it posterior attachments. after the capsular adhesions are freed try to spin the IOL clockwise to allow the haptics to spin free. sometimes the haptics are just too stuck and must be cut to free separately or are even left in the bag.

removing the IOL can be done through a small incision (refolding or cutting) or by extending the incision to the size of the optic.

The high index of refraction acrylic IOLs (eg. MA60, SA 60) can be refolded within the eye either using the folding forceps or the henderson technique.   The standard refolding technique uses a paracentesis across from the main wound (3.5 mm) to introduce a spatula to place under the optic while using an open IOL insertion forcep above the optic in the anterior chamber. while lifting with the spatula and coming down on top of the optic with the open insertion forceps the IOL can be folded inthe anterior capsule. once folded the optic is simply removed through a 3.5 mm or so wound   please use lots of OVD during this process. refolding the IOL only works well with thin acrylic IOLs likem the SNWF, SA60, MA60 and in my hands is virtually impossible with thick acrylic IOLs like the AR40 and the slippery IOLs like the silcon three piece IOLs.   see video of refolding.

The henderson (bonnie henderson boston ma) technique for folding soft IOLs such as the IQ single piece acrylic is very slick.   dr henderson's technique is to simply pull on an externalized haptic (with 0.12 or similar toothed forcep) while pushing on the optic 180 degrees across from the wound (inside the eye) with a hook (eg. Kuglen) amazingly the IOL folds itself and pops out of the eye.   see video.

There a few ways to cut an IOL to get the optic small enough to remove through a small incision.   One classic technique is to only cut about 2/3 through the IOL and make what looks like a Pac Man and rotate the IOL out through the wound as shown in the video.

You can also cut the IOL completely in half or into thirds and bring out the pieces.  i like to use the Osher mildly serrated cutter from Duckworth and Kent as shown in this video. you can usually keep the IOL from flopping around too much by holding the externalized haptic with this cutter.    if you are in a bind you can even use Vanna scissors to cut the IOL.

i also think the Duet forceps and IOL cutters can be handy to cut IOLs and haptics. you can use the Duet forceps through a paracedntesis to stop the IOL from flopping about and hitting the cornea. both the cutter and the forceps can pass through a paracentesis. here the Duet system forcep is used to hold an IOL while cutting in the video.

phaco for soft lenses

2009-12-21T21:08:00.000-08:00

Alot is written about phaco on hard lenses; but, in many ways the soft lenses are the most dangerous. Soft lenses tend to jump to the phaco needle which can lead to capsule rupture. soft lenses are hard to crack which can make the divide and conquer very difficult.  Here i discuss 2 strategies for soft lenses to increase safety for these tricky lenses.

Prolapse. The simplest strategy for very soft lenses is to simply prolapse the soft lens into the anterior chamber. even better is to prolapse just the nucleus. First i like to hydrodissect, careful to keep the cannula over the lens, to avoid prolapse. then spin the lens. Then perform hydrodelineation and allow the nucleus to prolapse into the anterior chamber. in a perfect world you can just prolapse the nucleus (sometimes soft lenses have a denser central core) and leave the epinuclear material in the bag.  Then remove the nucleus with the phaco needle with epinuclear settings (linear control of vacuum 0-350, asp at like 30-35 fixed, little power or ozil).   remove the epinuclear material with the phaco needle and a shizzle manuever or with the I/A tip.

Soft Chop. The technique I like best for the soft lens is to use a soft chop with no vacuum. avoiding vacuum is very important as the phaco needle can rapidly move through the soft lens material into the capsule. The idea is to use the phaco needle to hold and support the soft lens while slicing through the lens with the chopper.  as you can see in the video below, you will not be able to use the usual chop where you embed and hold the nucleus and cannot use a vertical chop.   instead the phaco needle simply supports the lens and the chopper goes deep (I like the Siebel chopper) and moves in a horizontal fashion just to the left of the phaco needle moving to the left when reaching the needle to split the lens. the lens does not always dramatically break into pieces. however after you slice the lens into pieces (i usually use 6) you will find that the lens will come into the anterior chamber with epinuclear setting (similar to those above). often the nucleus comes first leaving the epinuclear material which comes in a separate step using a shizzle or the I/A tip.

phaco chop with ozil

2009-12-15T16:52:00.000-08:00

I really like to use the Alcon Infinity Ozil system for phaco chop. i think there are 3 distinct phases to phaco chop with the ozil and they are outlined below:

Chop Phase. In this phase we are chopping the nucleus into 6 pieces. I like to start using longitudinal ultrasound (no Ozil) as i think the side to side motion of the Ozil does not allow one to occlude as tightly as when you use longitudinal ultrasound. I recommend a high fixed aspiration flow rate (AFR) and high fixed vacuum cut off.   By fixed i mean that no matter where i am in position 2 or 3 of the foot pedal the vacuum and AFR are the same.   I usually have the AFR at about 30-35 and the vacuum cut off at about 300-350. This will require a fairly high bottle height 90-110 to keep surge to minimum depending on how much fluid you are losing around the wound.  You will need to adjust the longitudinal ultrasound power depending on the density of the nucleus (40-80%).   I like to use either a burst setting or a 4 Hz frequency pulse (Dr Howard Fine coined the term choo choo chop as it sounds like a train).   I like to use a horizontal chop for the intial crack and then a sort of hybrid horizontal and vertical to break the halves in 6 pieces.   I like the Siebel Chopper as shown in the video below

When doing the initial phaco chop (assuming you are right handed) you want the left side of the completely embeded phaco needle to be in the center of the lens.    Then imagine a line drawn from the left side of the phaco needle out to the periphery of the lens under the cpasule. this is the line of the chopper as it slices through the lens.   As you chop toward the needle (horizontal chop) and get just to the left side of the phaco needle lift up a bit on the needle and push down a bit on the chopper (vertical chop) as you simultaneously also push the instruments away from each other. (best learned from video below). After the nucleus is divided in half with the initial chop rotate the lens clockwise about 60 degrees to begin to break each half into thirds. The chopping is similar for the halves except i usually dont go out so peripheral and accentuate the vertical part of the motion over the horizonal. I usually try to break each half into thirds or 6 pieces total.

Segment removal phase. After the lens is chopped into 6 pieces I switch to the Ozil mode.   Similar to the chopping settings, I like a high fixed AFR and fixed vacuum for this mode.   I usually have the AFR at about 30-35 and the vacuum cut off at about 300-350 with a continuous Ozil at 70-100%. The side to side motion of the Ozil creates less repulsive force than the longitudinal ultrasound and the material really flows into the tip and out of the eye.   If you encounter a very hard nucleus you may need to add in some longitudinal phaco power to keep the tip from occluding as it sometimes does with only Ozil.

Shizzel phase.   After the nucleus is removed you often have some epinuclear material left over. I like to switch to a low setting of Ozil (<40%) with linear control of the AFR (max at 30-35) and vacuum (max at 300-350).   By linear I mean that the harder I push the pedal into position 2 the more AFR and higher vacuum cut off I get.   This mode gives you very fine control (venturi like) when grabbing the delicate epinuclear material helping to prevent you from swiss cheesing through it to the bag. Shizzle is a term coined by Drs Graff and Friedrichs of Iowa that refers to holding the epinuclear material high with the phaco while sweeping under to push out the subincisional material (the Shizzel is best appreciated on video).

Here is the video of Ozil phaco chop.

Learning phaco chop is best done in steps or stages.   Start by simply getting used to having the chopper in the eye while doing divide and conquer. Then transition to chopping parts of the lens like a quarter or a half as in stop in chop. The white cataracts are great for your first chop cases as they are brittle and easily chop and as the delicate capsule is easy to see with the Trypan stain.

Here is a video outling some of the steps to learning phaco chop

iris prolapse

2009-09-13T11:35:00.000-07:00

Iris prolapse can create problems during surgery and can lead to iris damage which can be dysfunctional.

Iris prolapse typically comes from a wound which is too short or from an iris which is floppy and/or poorly dilated. The actual prolapse of the iris usually occurs during hydrodissection and can create transillumination defects, loss of iris tissue, iridodialysis, and hyphema. It is important for eye surgeons to know how to preserve the iris when prolapse occurs and i suppose, more importantly, to prevent it from occuring in the first place.

Wound too short. When the wound is too short one of the best options to prevent iris prolapse is to simply close the short wound and move to another site. Often however moving to another site is difficult as the brow, a bleb, or the surgeons handedness get in the way of this solution. A nice simple solution is to place a single iris hook under the incision to pull the iris under the incision preventing prolapse. If the pupil is also small it can be useful to place 4 hooks in a diamond configuration with one hook under the wound to both prevent iris prolapse and to open the small pupil. Iris rings such as the Malyugin ring can be used also but if the wound is very short the iris can still prolapse with the ring.

Floppy iris. When the patient is at risk for a floppy iris (intraoperative floppy iris syndrome) from an alpha blocker (especially Flomax or tamsulosin) or some other cause (eg ischemia ) it may be best to prevent iris prolapse with iris hooks or a Malyugin ring especially if the pupil is small. The most common time for iris prolapse is during hydrodissection when the fluid wave passes around the lens and out the eye taking the iris out too. Excessive and especially dispersive viscoelastic can make hydrodissection more risky for iris prolapse. I like to remove viscoelastic above the lens prior to hydrodissection to help prevent this complication. Gentle rocking of the lens will help to release trapped fluid behind the lens which will lower the pressure and deepen the anterior chamber.

Repositing the iris. When iris prolapse occurs the emphasis should be on preserving the iris and preventing further prolapse. The first step following prolapse is to use the paracentesis to remove fluid pressure from within in the eye which is pushing the iris out. Then using a viscoelastic cannula gently reposit the iris. After the iris is back into position consider placing an iris hook under the wound to keep the iris from further prolapse. below you will find a video showing these techniques Rarely, iris prolapse willl occur when you face posterior pressure from a choroidal hemorrhage, choroidal effusion, or misdirection of aqueous.

References:

Chang DF, Braga-Mele R, Mamalis N, Masket S, Miller KM, Nichamin LD, Packard
RB, Packer M; ASCRS Cataract Clinical Committee. ASCRS White Paper: clinical
review of intraoperative floppy-iris syndrome. J Cataract Refract Surg. 2008
Dec;34(12):2153-62. 

Chang DF. Use of Malyugin pupil expansion device for intraoperative
floppy-iris syndrome: results in 30 consecutive cases. J Cataract Refract Surg.
2008 May;34(5):835-41.

Chang DF, Campbell JR. Intraoperative floppy iris syndrome associated with
tamsulosin. J Cataract Refract Surg. 2005 Apr;31(4):664-73.

wound too long

2009-09-12T18:13:00.000-07:00

Making the wound too long can lead to several problems.

As is so often true in eye surgery, early problems can compound and lead to even bigger problems. A long wound can make it difficult to properly center the capsulorhexis as it can be hard to control the tear in the subincisional area. A decentered rhexis can lead to trouble with cortex removal and IOL placement. A long wound can make movement of instruments in the eye very difficult as they can distort the cornea clouding the view. The phacoemulsification needle in the long wound will meet more resistance and can get hotter which can lead to wound burn. One of the most common and difficult problems with the long wound is corneal edema that comes from irrigating into the corneal stroma rather than the anterior chamber with a long wound. All of these issues decentered rhexis, corneal disotortion, and corneal clouding can make subincisional cortex removal nearly impossible.

Eccentric rhexis. the long wound can make it difficult to maintain the proper diameter in the subincisional area which leads to a decentered rhexis. You can help prevent this by using a paracentesis with a smaller instrument like a needle or Duet micro-forceps to create the rhexis under the wound. The ecentric rhexis can lead to several problems as the case proceeds. the subincisional cortical material can be very difficult to remove. occasionally a decentered rhexis can lead to IOL decentration as the more peripheral capsule can catch the edge of the optic and with contraction decenter the IOL. also the eccentric rhexis can lead to poor placement of the IOL with one haptic in the bag and one in the bag which is the most common cause of IOL decentration.

Corneal distortion. The long wound can make lateral movement of instruments very difficult as the cornea gets striae and loses clarity. One solution is to use smaller instruments such as the needle for the rhexis or smaller diameter forceps (such as the MST Duet forceps). another simple solution is to funnel the inside portion of the corneal wound which allows for lateral movement with less striae. sometimes placing ocucoat or cornea coat on the surface will lessen the striae and corneal distortion but not always. be careful of phaco burn from the longer wound.

Corneal edema. the long wound can force the irrigation port to hydrate the wound. Keep the phaco needle as central as possible to avoid irrigating into the wound. Move the irrigation sleave toward the needle tip during coaxial phaco to place the irrigation port closer to the needle tip and farther from the corneal wound. if the corneal is beginning to cloud in the subincisonal area then remove the subinicional cortex first in case you lose your view. consider using a bimanual system to better keep the irrigation out of the wound. rarely you may have to finish the case later.

Difficulty with subincisional cortex. the long wound alone can make removal of the subincisional cortex tricky. however the long wound with subsequent eccentric rhexis and corneal edema can be really tricky. Use 90 degree tip to the remove sub-incisional cortex first. consider a bimaual approach if available. consider repeat hydrodissection of the subincisional cortex through a paracentesis. often you can simply push the material toward the periphery of the bag with a Drysdale or viscoelastic, place the IOL, then remove the cortex with the safety of the IOL to hold the posterior capsule away. poor visibility of during sub incisional cortical removal is a time of risk for capsular tear.

Consider moving to another site. Some times the best approach is to simply abandon the original incision and move to another site with a proper incision. Often this is difficult as the brow or handedness get in the way of this solution. make sure the alternative incision is not long too!

Here is a video highlighting some of these points.

anterior vitrectomy

2009-07-19T18:45:00.000-07:00

Vitreous can be very difficult for the anterior segment surgeon. when it presents we can be tempted to take short cuts which can lessen the safety of our surgery. being prepared is your best defense and here i will present a few tips based on my experience with the vitreous.

The cause of vitreous prolapse in your case is important as it may guide your surgical reatment and IOL location. A capsular tear can cause vitreous prolapse with an anterior tear extending posteriorly probably being most common. Primary posterior tears from the phaco needle being too deep or from a strike from the I/A device or another instrument are also common. It is best to find a cause which does not involve the surgeon such as a tear extending from a preexisting weakness from a posterior polar cataract, iatrogenic (different surgeon) from pars plana vitrectomy, or from penetrating lens trauma. Besides tears zonular dialysis can lead to vitreous prolapse and can come from your surgery with forceful rotation or pulling on the capsule with the I/A or from pre-existing conditions such as trauma, PXF, or Marfan’s.

For me the first sign of vitreous prolapse is denial. I begin to think that something is not right but and find lots of reasons why everything is really OK. denial is a powerful force for me. More objective signs of vitreous loss are the chamber suddenly deepens, the pupil widens, the residaul lens lens material is no longer centered or doesnt spin, lens particles no longer come to the phaco needle, and a big sign would be lens particles sink to the back of the eye.

3 basic principles of vitrectomy are to 1) go bimanual with separate irrigation and cutting devices, 2) close the chamber, and 3) cut low and irrigate high. if you follow these 3 principles you can keep most of the vitreous out of the front of the eye and away from the wound, iris, cornea where it can cause so much trouble. most importantly you can help to limit the amout of vitreous expression and its risk of retinal detachment.

go bimanual with separate device for irrigation and cutting is fairly easy now as most machines will allow this or assume this from the start. some machines such as the alcon 10,000 had a coaxial device and you had to remove a sleeve to make it bimanaul. i like to use a 23 gauge cortex extractor cannula to irrigate with the cutter usually in my dominant hand.

close the chamber so that no fluid can get out with the vitrectomy instruments in the eye. this will require you typically to close your main incision and add a paracentesis if you are doing traditional coaxial phaco. through one paracentesis you will place your irrigation cannula and through another larger paracentesis you will place your vitreous cutter/aspirator. if you use a 3.0 mm or similar phaco wound for the vitreous cutter apsirator the chamber will not be controlled and fluid and vitreous will stream through this wound around the cutter. you need to make the area of least resistance for any fluid or vitreous to leave the eye be the aspiration/cutter device. see the video showing the importance of closing the chamber to control the flow of vtreous.

With control of the chamber and bimanual instruments you can cut low and irrigate high. You will want to have the cutter/aspirator low to get at the root of the vitreous while irrigating high in the closed chamber to create a fluid pressure differential to push the vitreous toward the cutter. if you irrigate in the area of the cutter/aspirator you may push the vitreous away from the cutter and even worse more anterior toward the wound. in this video you can see the use of the 3 principles to remove the vitreous and some residual cortical material.

there are 3 basic phases in the case when vitreous presents: early in the case with most of the crystalline lens in the eye, with only some cortical material left (most common), and while placing the IOL.

When vitreous presents early during nucleus removal clean up is the most difficult. the vitreous is often entwined in the nuclear pieces. it can be very difficult to get posterior enough with the cutter to cut off the vitreous at its source with all of the nuclear pieces in the way. and most importatnly it is hard to not bump the pieces through the capsular tear to fall south into the back of the eye. you have a big decision to make right up front: convert to ECCE or not. if the nucleus is hard and mostly in one piece i would strongly consider converting the a large incision ECCE. the video below outlines the issue with conversion to ECCE and ther steps are listed below:

If topical do subtenons injection
Close temporal incision and create standard ECCE superiorly (or extend existing wound)
Have Wescott scissors ready when looping out lens to cut vitreous
Close with 2 vicryl safety sutures
Anterior vitrectomy, Weck cell vitrectomy
Dry removal of residual cortical material with syringe on 27 gauge cannula
Use J-cannula if needed for subincisional material
Consider staining with preservative free dilute kenalog
Place IOL if possible in sulcus or AC (if AC, don’t forget peripheral iridotomy)
Miochol to bring pupil down—seats sulcus IOL, peaked pupil helps to detect vitreous

Sometimes even with early loss of vitreous with nuclear material left you can carefully proceed with phacoemulsification. the key is to provide some separation between the space with vitreous and the area of phacoemulsification. the pace is slowed down with a low bottle height and low vacuum (Osher slow motion phaco). here are the steps.

Seal off capsular hole with liberal use of viscoat (cohesive OVD will not work)
Keep phaco occluded in the lens as much as possible to avoid pulling on the vitreous
Lower the vacuum and bottle height
Consider using a sheets glide to seal off hole -- trap nucleus in AC
Work with one or two large pieces (rather than chopping into many small bits that can more easily fall south

The most common time for vitreous is while removing the last bit of nuclear material or during cortical removal. The main emphasis during this phase is to remove any residual cortical material following vitrectomy. loss of small amounts of cortical material to the back of the eye or leaving small amounts in the anterior segment will often present no difficulty. Preserving capsule for lens placement in the sulcus is important also. the steps when vitreous comes in this phase are:

Place viscoat in area of tear or dialysis before removing instruments
as always split into irrigating cannula (eg. 23g. cortex extractor) and the vit cutter (w/o sleeve)
Suture wound and use two paracenteses one for the cutter and one for irrigating cannula
Irrigate high and cut/suck low – creates a pressure gradient to push the V back
Settings low vacuum 100 range, low bottle height 50 range, max cut rate
Dry removal of residual cortical material with syringe on 27 gauge cannula
Use J-cannula if needed for subincisional material
Consider staining with kenalog (see below)
Place IOL if possible in sulcus (see video below) or AC (if AC don’t forget peripheral iridotomy)
Miochol to bring pupil down

The least common time for vitreous is while placing or just after placing the IOL. Usually in this phase very little vitreous comes forward. the main issues surround the IOL. will it be stable in the bag or should the IOL (or often an appropriate IOL) be placed in the sulcus. here are the steps for dealing with vitreous in this phase and a video showing this situation.

Stabilize the IOL by placing one haptic out of the wound or in the AC
Anterior vitrectomy as described above – attempt to get the cutter below the IOL
Place both haptics in the sulcus if possible (cannot use SA60 in sulcus consider alt fixation)
Use weck cell sponge to ensure wound is clear
Consider stain
Miochol to check pupil

Most patients who have an anterior vitrectomy do very well. it is important to be honest with the patient about what happened. i usually tell them:

"the thin membrane that surrounds the cataract tore during surgery. I had to take some extra time to remove the gel from the back of the eye. I was able to remove all of the cataract and place the artifical lens. i think everything is going to be great but i will have to watch you a little more closely for a while"

In summary the most important thing to remember with anterior vitrectomy is to control the chamber and use bimanual instrumentation.

IOL placement with a posterior capsular tear

2009-07-09T08:25:00.000-07:00

Loss of the posterior capsule and its potential support for the IOL is one of the most difficult challenges we face as cataract surgeons. Efficient management of this complication is important for the long term health of the operative eye. Here I will present a few suggestions on IOL placement in this situation and a few videos that may be helpful for the beginning surgeon.

The initial challenge is to adequately remove the residual lens material and vitreous while leaving as much capsule as possible to assist in supporting the IOL. It is very important that the vitreous has been completely removed from that the anterior segment as outlined in other sections of this blog. Then you must face the often tough decision of whether to place the IOL in the bag, sulcus, a combination of the bag and sulcus, or in the anterior chamber. You should also be ready to place sutures to secure the IOL to the iris if the sulcus placement is not stable.

Bag placement. Sometimes even with a posterior capsular tear an IOL can be gently placed in the bag most commonly when the tear is round or converted to a round tear. It is very important that the posterior capsular tear is stable as the force of placing the IOL can extend the tear further, releasing more vitreous, and could lead to placement of the IOL onto the retina. Here is a video of a planned posterior capsular rhexis and the gentle placement of a single piece acrylic into the bag.

Sulcus Placement. Usually when you have a posterior capsular tear the IOL is placed in the sulcus. The most important thing is to have a proper IOL for the sulcus ready to go in your OR at all times. The best IOL for the sulcus has a large optic that allows for mild decentration and a better view of the retina. The best IOL for the sulcus has long haptics that will center the IOL even in large eyes. The best IOL for the sulcus has smooth thin haptics to reduce chaffing of the posterior leaf of the iris^{3, 4}. I prefer acrylic over silicon IOLs for sulcus implantation as patients with capsule trauma are at increased risk for retinal detachment and the possible use of silicon oil. I like the Alcon MA50 3 piece IOL as it has wide haptics, a large yet injectable 6.5 mm optic and it is acrylic. Others advocate for the large Starr silicon IOL (AQ2010V) as they feel that the larger haptics and rounded optic edge out weigh the advantage of the acrylic material. Please remember to always use a large 3 piece IOL for this job and not a single piece acrylic (SPA). SPA IOLs are not designed for the sulcus and the large square edge haptic can cause uveitis, hyphema, vitreous hemorrhage, and glaucoma.

The second most important thing is to place the IOL with both haptics in the sulcus. If you place one haptic in the sulcus and the other in the bag the IOL will be unstable and often decentered. One reason that it is hard to get both haptics in the sulcus is that the most common area of damage to the capsule is directly across from the wound. This area is vulnerable to radial tears as OVD is often running low as the capsulorhexis passes this point and this area is vulnerable as the phaco tip and chopper are active in this region. Unfortunately this is the same area where the leading haptic naturally flows during IOL insertion. If the capsule is damaged in this area then the sulcus is poorly defined and the leading haptic can end up posterior to the anterior capsule rather than in the sulcus as intended. Defining the sulcus with a viscous dispersive viscoelastic (e.g. Viscoat) will greatly ease placement of the haptics.

Combination of Sulcus and Bag. . When you have a posterior capsular tear with a nicely centered and intact anterior capsulotomy you have more options. One of the nicest options is to first place the IOL in the sulcus and then prolapse the optic posteriorly capturing it by the anterior capsule while leaving the haptics securely in the sulcus [1]. This technique allows coverage of most of the IOL edge with capsule, allows the centered anterior capsulotomy to keep the IOL centered, and still allows suture fixation of the sulcus based haptics to the iris if needed. Here is a nice video showing this technique:

Rarely, you will encounter the situation with a late tear of the posterior capsule when a SPA IOL is already placed in the bag. In this situation you should strongly consider simply exchanging the SPA IOL for a 3 piece IOL designed for the sulcus. However another option with a perfectly centered intact anterior capsulotomy is to anteriorly displace the optic from the bag such that the optic is captured by the anterior capsulotomy and the haptics remain in the bag which protects the iris from the square edge. Here is a video showing this technique which will rarely present.

AC IOL. When the IOL cannot be adequately supported by the sulcus, surgeons have several options: place an AC IOL, suture the IOL to the iris, or suture the IOL to the sclera. Another option which is often not available in an emergent setting is to use an iris clip IOL such as the Artisan but this IOL has not been approved for this indication by the US FDA [2]. None of these approaches is clearly superior. Wagoner as part of an American Academy of Ophthalmology study reported that there is no significant difference in results when comparing AC IOLs, iris sutured IOLs, or scleral sutured IOLs when capsular support is insufficient [3]. As such practical concerns such as availability of devices, ease of the procedure, and surgeon preference drive this decision. I have outlined the placement of AC IOL in this blog.

Iris sutured IOLs offer some practical advantages over scleral sutured IOLs in the emergent situation of a posterior capsular tear (I almost never place scleral sutured IOLs in this situation). One advantage is that you can place a 3 piece IOL in the sulcus and then asses if the residual capsule alone will support the IOL. If the 3 piece IOL does not center or seems unstable, the IOL can be readily sutured to the iris without changing the IOL or explanting haptics to tie scleral based suture. The IOL optic is moved anteriorly and captured by the pupil with the addition of acetylcholine (Miochol-E Novartis). The haptics are sutured to the peripheral iris using modifications of McCannel’s technique [4] with either an external knot [5,6] or with a sliding internal knot as described by Chang [7]. Typically 10-O prolene suture is used with a long curved needle such as a CTC-6 needle (Ethicon # 9090G-SD) to secure the haptics to the iris. Here is a video where the zonlues were severly damaged and after placing the IOL in the sulcus the IOL was sutured to the iris.

Suturing IOLs to the sclera especially in an emergent setting is probably the most difficult option. Techniques to suture IOLs to the sclera often employ special IOLs with haptic eyelets [8], require more robust suture material such as 9-O prolene, and may require a scleral flap or tutoplast to cover the external suture material [9]. The routine use of 10-O prolene suture material has been reconsidered as many of these sutures eroded and broke over time. Additionally, suturing an IOL to the sclera after placing the IOL is difficult as the haptics would have to be externalized to set the suture which is more complicated than the iris suture technique.

In summary if the sulcus seems sufficient to support the IOL then the surgeon should place a large 3 piece IOL in the cililary sulcus. If after placement in the sulcus, the IOL does not seem stable, then the surgeon can supplement the capsule support with iris fixation sutures and the long term results seem excellent [10]. If it is clear that the sulcus will not support an IOL, then i tend to place an AC IOL as it is a simpler procedure and offers at least similar results to scleral or iris sutured IOLs [3].

References

Gimbel HV, Sun R, Ferensowicz M, Anderson Penno E, Kama, Intraoperative management of posterior capsule tears in phacoemulsification and intraocular lens implantation, Ophthalmology, 2001 Dec;108(12):2186-9; discussion 2190-2.
Oetting TA, Newsom T, Bilateral Artisan lens for aphakia and megalocornea: Long-term follow-up, J Cataract Refract Surg. 2006 Mar;32(3):526-8.
Wagoner MD, Cox TA, Ariyasu RG, Jacobs DS, Karp CL; Intraocular lens implantation in the absence of capsular support: a report by the American Academy of Ophthalmology, Ophthalmology. 2003 Apr;110(4):840-59.
McCannel MA. A retrievable suture idea for anterior uveal problems. Ophthalmic Surg 1976; 7(2):98–103.
Stutzman RD, Stark WJ, Surgical technique for suture fixation of an acrylic intraocular lens in the absence of capsule support J Cataract Refract Surg. 2003 Sep;29(9):1658-62.
Condon GP., Simplified small-incision peripheral iris fixation of an AcrySof intraocular lens in the absence of capsule support, J Cataract Refract Surg. 2003 Sep;29(9):1663
Chang DF, Siepser slipknot for McCannel iris-suture fixation of subluxated intraocular lenses, J Cataract Refract Surg. 2004 Jun;30(6):1170-6.
Buckley EG, Safety of transscleral-sutured intraocular lenses in children, J AAPOS. 2008 Oct;12(5):431-9. Epub 2008 Aug 15
Oetting TA, Johnson AT, Tisseel and Tutoplast cover, J Cataract Refract Surg. 2007 Dec;33(12):2153, Comment: J Cataract Refract Surg. 2008 Jun;34(6):881-2; author reply 882.
Condon GP, Masket S, Kranemann C, Crandall AS, Ahmed II, Small-incision iris fixation of foldable intraocular lenses in the absence of capsule support, Ophthalmology, 2007 Jul;114(7):1311-8.

phaco machine basics

2009-07-04T14:04:00.000-07:00

Phacoemusification machines can be overwhelming at first. Here i will try to simplify them as best i can to help those that are just getting started using them. I think it is important to have a good understanding of how they operate and not simply rely on past settings, equipment representatives, and/or the circulating nurses to run these devices critical to your success as a cataract surgeon.

These machines have four main components and software that ties the components together. First a system of irrigation which is typically just a bottle that is hung at variable heights above the surgical eye. Second the foot pedal which allows the surgeon to control the machine. Third an ultrasound hand piece which typically has crystals which vibrate the phaco needle with various power waveforms controlled by the phaco machine. And finally and most importantly, the pump, which is classically either a flow based or vacuum based device.

The irrigation system on phaco machines is typically is just an adjustable bottle held higher than eye to allow infusion of fluid. The machine can adjust the bottle height for various phases of the surgery. For example when the vacuum goes up during segment removal the bottle height typically will need to be higher to maintain the anterior chamber. similarly when you are doing anterior vitrectomy the bottle height should go way down. The machine can also turn the fluid on and off. When the foot pedal goes from position 0 to 1 the fluid is typically turned on by the phaco machine. Some phaco machines can detect when the irrigating fluid bottle is getting near empty but most cannot.

The foot pedal is typically controlled with the dominant foot (w/o shoes w/socks). although some such as the famous surgeon Jim Davidson (marshaltown iowa) suggests that the phaco foot pedal is simpler than the microscope pedal and uses his non-dominant foot for the phaco machine saving the dominant foot for the microscope. The most basic function of the accelerator like portion of the foot pedal is common across all brands with 4 positions: Position 0 – everything is off; Position 1 – irrigation is on, no pump, no U/S; Position 2 – irrigation is on, pump is on, no U/S; Position 3 – irrigation is on, pump is on, U/S is on. some of the foot pedals are wireless now such (eg. Stellaris) but most have a cable that connects to the phaco machine

The ultrasound (U/S) hand piece vibrates the phaco needle at a set rate in the 20,000 to 40,000 HZ range. The vibration is typically delivered by electrically stimulating crystals with a resonate frequency and the crystals are connected to the phaconeedle. many of the modern hand pieces have as many a 4 crystals to allow the needle to handle more load from a hard cataract. Increasing the U/S power typically increases the excursion of the needle but not the frequency which usually remains stable. With increasing load, such as a very hard cataract, the frequency and excursion may not keep up. when setting up the pahco machine for the case one must "tune" the handpiece. the machine sends pulse to the handpiece and sees how much power must be delivered to move the needle. this "tuning" helps to adjust for subtle variations from different needles and handpieces.

The phaco machine can set up a variety of ultrasound modes. In continuous mode the ultrasound energy is on on when the pedal is in position 3 and increases in excursion or power the deeper the surgeon is into position 3 up to a set maximum. In pulse mode the ultrasound contains pulses of ultrasound where it is on (set %) and then off (set %) for a set frequency. the deeper the pedal is into position 3 the more power each pulse will have up to a set maximum. The typical pulse will have a 50% duty cycle with an on time equal to the off time. the classic pulse setting is the howard fine "choo choo chop" setting with a low frequency of about 4 Hz and 50% duty cycle that is useful to acquire a piece for chopping and kind of sounds like a choo choo train. another common setting is to increase the frquency to about 100 Hz and have an on time which is less than off time creating hyperpulses which seem to run more cool to protect against wound burn. finally most machines feature a burst mode where stepping further into position 3 decreases the time between bursts of phaco such that when the pedal is fully engaged the power is continuous.

Recently some machine handpieces have featured an oscillatory component in addition to the classic longitudinal ultrasound. AMO features a figure 8 motion of the phaco needle in it latest phaco machine. Alcon in the infinity Ozil machine has a rotational feature in addition to the longitudinal ultrasound. as this rotational energy does not directly push away the nucleus pieces like the longitudinal ultrasound does the nuclear bits seem to come more readily to the tip in these modes.

The phaco pump is the most important and complex part of the phaco machine. The pump comes in two basic varieties: vacuum based (eg venturi) and flow based (eg peristaltic). A vacuum based pump creates more vacuum (mmHg) when the pump works harder. A flow based pump creates more flow (cc of fluid/min) when the pump works harder. In a real world it is hard to separate flow from vacuum as the resisitance in the tubing keeps the two related. the parameters of the pump will depend on the phase of the surgery. you will want very little fluid flow during sculpting and you will want alot of vacuum when removing the segments or when holding onto the nucleus during chopping. You might want to look over the classic definitive text in this area by Barry S. Seibel, Phacodynamics.

In pumps the vacuum, flow rate and resistance to flow in the tubing are related. I find it useful (maybe because i used to be an electrical engineer) to compare the fluid relationship to Ohm's law (E=IR) where the relationship between current I (analgous to flow rate) , voltage E(analogous to vacuum) and resistance R (analogous to resistance to flow in tubing) are related. just like it is impossible to have a pure current source or voltage source it impossible to create a pure vacuum or flow based pump. but these pumps do behave differently in practice and so it is important to understand how to operate them to your specifications.

Vacuum Pumps. The most common of these are Venturi pumps (Stellaris, Millennium, Accurus) where compressed air passes over a column of air creating a vacuum proportional to the flow of air over the column (this is similar to the way a wing creates lift). Increasing pump power increases vacuum directly; flow rate indirectly based on the amount of resistance to flow. Typically a Venturi pump requires an external source of compressed air (Millennium) or an internal compressor (Accuris or Stelaris) which has limited acceptance of this pump. The compressed gas flows over the open top of a rigid column or cassette attached to tubing creating vacuum. Flow rate for a particular amount of vacuum is then dependant on the resistance of flow to the fluid. This is roughly analogous to electric current voltage relationship (Ohm’s. This law) i=e/r where e = voltage (analogous to vacuum); i = current (analogous to flow rate); r = resistance (analogous to tubing and occlusion). As such with a given vacuum setting of the pump when you have less resistance in the tubing the flow rate will increase and conversely when you have more resistance you will get less flow through the tubing.

Controlling the vacuum based pump is very simple as you only have to set the vacuum and have no setting for flow rate. Typically you would use a fixed vacuum (ie. no matter how deep you are into position 2 or 3 the vacuum stays the same) for sculpting and to hold while chopping. You would typically use a variable vacuum (ie. the deeper into position 2 the more vacuum and faster the pump) to remove epinuclear material and for I/A of the cortex.

Flow based pumps. The most common flow based pump is the peristaltic pump (Infinity, Sovereign, and Legacy). With peristaltic pumps the faster the pump goes the more cc/min of fluid passes through the tubing or the more flow. This is often refered to as the aspiratiion flow rate (AFR). Increasing the power of the pump increases the flow rate directly and vacuum indirectly through the resistance of the tubing. So the vacuum is just dependant on the amount of fluid flow and this relationship is roughly analogous to electric current voltage relationship (Ohm’s law): e=ir where e = voltage (analogous to vacuum); i = current (analogous to flow rate); r = resistance (analogous to tubing resistance). As such you will only get some vacuum if there is some resistance to flow (or some occlusion).

These flow based machines typically have a setting for the flow rate but also have a vacuum cut off. the vacuum cut off is the point at which the pump will stop if a certain vacuum is reached. so you set the flow rate and pump humms along until the vacuum rises (due to increased resistance) to the vacuum cut off point and then the pump simply stops. so even though with peristaltic machines you have a vacuum and a flow rate setting you can only make the pump work harder by increasing the flow rate. setting the vacuum higher only sets the point higher at which the pump stops when this vacuum is reached.

With modern peristaltic pumps (eg. Infiniti) for each foot position 2 you can have fixed or variable flow; fixed or variable vacuum cut off. if you want the pump to be responsive to pressing harder on the pedal (eg for I/A) you would use a variable setting such that the aspiration flow rate or at least the vacuum cut off increases as you step down into position 2. when you set both the flow rate and the vacuum cut off to be variable so that it increases as you step into position 2 the peristaltic pump begines to feel more like a venturi pump. you typically would set the pump low and fixed for sculpting (80 mmHg vacuum cut off: 20 cc/min flow rate); higher but still fixed for chopping and segment removal (300 mm Hg and 30 cc/min); and high and vairable for I/A where you need more control (500 mmHg and 50 cc/min flow rate). i usually use roughly a 10:1 ratio of vacuum cut off:flow rate with the infinity and legacy for segment removal, chopping and I/A.

Which pump is better?. There is no clear favorite for every situation. For certain parts of the procedure the flow based pumps seem better like sculpting the groove as you can set the vacuum low with a reasonble flow rate. For other parts of the procedure like I/A and anterior vitrectomy vacuum based pumps are better as the vacuum is not related as much to occlusion (resistance to flow). for years the flow based pumps were most popular in part at least because the early vacuum based pumps required an external compressed gas line and as the peristalitic were cleverly marketed as "safer" for divide and conquer. recently, as the phaco procedure has moved more toward higher vacuum for chopping and away from scupting the vacuum based pumps are getting more popular.

Vacuum based pumps seem to have less post occlusion surge during segment removal and material seems to come to the tip better for irrigation aspiration. vacuum based pumps are clearly better for vitrectomy as the vitreous comes to the tip even without occlusion from the guillotine which can be frustrating with flow based pumps. The disadvantage of the venturi pump which is the most common vacuum based pump is the need for compressed gas and the need for a rigid cassette.

Flow based pumps seem to be better for low vacuum jobs like sculpting. With modifications such as setting the vacuum and the flow to increase with increasing position 2 on the foot pedal the flow based pumps can be more responsive for I/A like the vacum based pumps. The flow based pumps do not require compressed gas.

Pearls for Small Pupils

2009-04-04T07:55:00.000-07:00

I use three techniques to manage small pupils: stretching, iris hooks, and the Malyugin ring.

Pupil stretching used to be one of the main ways that I would force mydriasis. This is really a good technique if you have posterior synechiae or if the patient has been on Pilocarpine chronically. However, more and more I am avoiding using pupil stretching techniques because it is contraindicated in patients that are on Flomax (or other alpha blockers) as it can lead to even more problems with iris prolapse. Compounding this problem is the reality that so often patients cannot remember having been on Flomax (or their other medications). Because my practice is concentrated at our VA Hospital here in Iowa City, I have a lot of patients who have been on either Flomax or junior varsity versions of this alpha blocker in the past (Hytrin, Cardura, saw palmetto…) and so if they have a small pupil I just assume that have had Flomax. I also think pupil stretching should be avoided in patients with shallow chambers, as there is a tendency for iris prolapse in those patients as well.

The technique that I use for pupil stretching is to use two Kuglen hooks -- one through the paracentesis and the other through the main wound. The hook through the paracentesis grabs the pupil and pulls it towards the paracentesis and then the other hook pushes 180 degrees across from the paracentesis to stretch the pupil. The stretch is held for a few seconds and it is not uncommon that you will notice some hemorrhage along the pupil. This is a good thing as it shows that there has been some change in the pupillary sphincter. Following stretching of the pupil, you need to use a dispersive viscoelastic which is highly viscous to help push the pupil open. There is really only one highly cohesive dispersing viscoelastic for me -- Viscoat; although others, such as Healon D and Vitrax, may be available in your area. I like to place the Viscoat in a circular pattern, around and around, to gently push the pupil out. You often find that at first you didn’t think there was much effect from the pupil stretch, and then after adding the Viscoat in this fashion, you gain enough mydriasis to safely proceed with surgery.

I will also caution you that during hydrodissection, the fluid wave can catch the dispersive viscoelastic, pulling the iris with it out of the eye, producing prolapse of the iris. As such, I recommend that you remove the viscoelastic over the lens, before hydrodissection, either using the automated irrigation/aspiration unit or use a syringe with BSS to wash out some Viscoat. This will reduce the likelihood of iris prolapse during hydrodissection. However, you just need to be careful during hydrodissection to avoid iris prolapse.

Iris hooks are a great technique for the small pupil and I use them often, although I don’t use them as often as I used to as I am transitioning some to the Malyugin ring, which I will discuss below. Iris hooks are great for shallow chambers, they are great for complex cases where you might have to convert to a large incision extracapsular procedure or if you have to use complicated suturing of IOLs or Cionni rings during the case which would make an internal device such as a Malyugin ring more difficult. I usually avoid iris hooks if there is a bleb present, because it is sometimes hard to work around the bleb and you have to be very careful not to damage the bleb. They are also harder when there are narrow lid fissures because the hooks get in the way of the lids, and so I tend to avoid them in that situation.

The way I like to use iris hooks, I described in a paper with Louis Omphroy.¹ In this technique, we use a diamond configuration of the hooks such that there is one hook under the main incision, one across, and then one hook 90 degrees to either side of the wound. This creates, relative to the incision, a diamond configuration of the iris. I like to use a 27 gauge needle, a Grieshaber knife, or a 75 blade to make the four paracenteses for the iris hooks. You want to make these as posterior as possible and you want to make them short and angled slightly down, such that the hook, when it is placed in the eye, is aimed towards the iris. I like to place the hooks before I add viscoelastic so that the chamber is not so deep that it makes it very difficult to grab a hold of the iris. After placing the hooks, then I add viscoelastic and make the incision just anterior to one of the hooks. I tend to use a Kelman McPherson and a straight tie to place the hooks as shown in the video below.

I like the Malyugin ring and use it most of the time now for small pupils. The Malyugin ring comes in two sizes; one with an internal diameter of 6.2 mm and the other with an internal diameter of about 7 mm. The Malyugin ring is great in patients that are on alpha blockers such as Flomax². It is great in patients that have narrow lid fissures because it does not involve any external manipulation to the eye and so you don’t have to have proptosis or great exposure. I would recommend avoiding the Malyugin ring if you think you are going to convert to an extracap as this is very difficult with the ring as opposed to being relatively easy when using iris hooks. I would avoid the Malyugin ring when using other intraocular hardware such as Cionni rings or suturing inside the eye, as the Malyugin ring can get in the way (relative to iris hooks) when doing these complex procedures.

The Malyugin ring is placed with a special inserter into the eye and the leading eyelet is engaged onto the iris and then one toes down a bit as the ring is pushed further in, trying to engage the lateral eyelets as well. Very often, only one of the two lateral eyelets is also engaged in the initial insertion process. The trailing eyelet often is very difficult to disengage from the inserter without introducing a hook through the paracentesis to push the ring slightly to the side to allow the inserter to exit the eye. I tend to use a Kuglen hook to subsequently place the eyelets that were not initially engaged with the inserter; a Lester hook can also be used or Sinskey hook.

Retraction of the Malyugin ring is probably the trickiest thing. You want to first disengage the leading eyelet which is across from the wound and then you want to disengage the leading eyelet and T it up slightly to the side and anterior. Use plenty of viscoelastic so that you don’t engage the IOL during this process and that so that the cornea is safe. The inserter is then placed in the eye slightly to the side of the eyelet, but over the ring, and then is turned such that the hook is over the entire eyelet and then pulled back and engaged onto the eyelet and pulled back into the inserter. It is most important that you not completely retract the ring into the inserter, as funny things happen when you do this. As shown in the video below, odd things will happen if you try to totally retract the ring, so just pull it back so that it is just thin enough to come back through the wound and pull it out of the eye.

There are two choices for the Malyugin ring; one which is 6.2 mm in internal diameter which is useful for most cases, but if the pupil starts off big or if you are going to use a particularly large IOL, then I would recommend using the 7.0 mm Malyugin ring. We tend to stock both in the operating room here, and use the smallest ring that you can to get the job done. The advantage of the smaller ring is that it is easier to insert and easier to retract, and the advantage of the larger ring is that you can use it when the pupil starts off bigger.

References:

1. Oetting TA, Omphroy LC. Modified technique using flexible iris retractors in clear corneal cataract surgery, Cataract Refract Surg 2002;28(4):596-8.

2. Chang DF. Use of Malyugin pupil expansion device for intraoperative floppy-iris syndrome: results in 30 consecutive cases, Cataract Refract Surg 2008;34(5)835-41.

operating microscope basics

2009-01-08T19:32:00.000-08:00

It is very important to learn how to operate the microscope before your first day in the OR.

Basics of the Microscope pedal. While there are some subtle variations among models and manufacturers the basics of the microscope footpedal and operation of the micropscope are similar. The microscope has a starting XY position which is centered at the start of the case and then small variations in this initial position are made using the foot pedal which makes small XY adjustments of the microscope. The scope also has a starting focal point (i suppose this is the Z position) which is set up at the start of the cases and small variations from this are made during the case using the foot pedal which moves the focal point of the scope up and down. Often the intensity of the light can be also be controlled with the foot pedal.

All of your extremities will be busy: one foot for the microscope pedal, one foot for phaco pedal, one hand for the phaco handpiece, and the other hand for the chopper. Most surgeons use non dominant foot to control the microscope pedal. unless you are a soccer player your left foot is probably not that coordinated. as such you should practice using the pedal way before your first case. most people take off their shoes so that they can feel the microscope pedal better.

Foot pedal switches. The typical positions of the microscopes foot switch controls are shown below. The foot pedal is designed so that the foot can sit on a rasied foot rest. A rocker swith in front of the foot rest is most important and moves the scope up and down to make small changes in focus. a rocker switch behind the foot rest controls the zoom or magnification. the magnification is typically low during wound construction and is increased during steps such as capsulorhexis which require more magnification. Several inches in front of the foot rest is the joy stick which controls the XY position of the scope. both the XY position and the focus shuold be centered prior to the case (usually a switch on the scope) and manually put into optimal initial position to allow maximal excursion of these functions during the case.

When you arrive in the OR ask yourself: “where will I be sitting? Are you operating from a superior approach -- Superior approach is preferred when you may have a large incision with lots of sutures (eg. ICCE, ECCE, tough phaco when you may convert) and/or when you may have iris trauma (tolerated better under the lid) and when you are doing a trabeculectomy and want the bleb under the lid. Typical phaco is from a temporal approach to avoid the brow. i usually do rights eyes a bit inferior and temporal (eg 8 oclock) and left eyes superior andtemporal (eg 2 oclock); however. some surgeons like Dr Tim Johnson are always true temporal whether operating on the right or left eye.

Proper Sequence to adjust Equipment to your body

1. Place retrobulbar block first (give it time to work while setting up scope)

2. Put assistant’s eyepiece and camera on proper side of microscope

3. Push center focus and center XY position buttons on microscope (may be same button)

4. Adjust ocular inter-pupillary distance and zero both objectives

5. Lower surgeons chair

6. Raise bed height to just allow both feet under bed onto both pedals

a. Dominant foot – phaco pedal

b. Non dominant foot microscope footswitch

c. Take off shoes (wear white Nike crew length socks)

7. Manually move entire microscope (not footswitch) so that you are in focus

8. Raise surgeon chair height enough to allow surgeon to see comfortably into oculars

9. Prep and Drape

consent for cataract surgery

2009-01-08T18:41:00.000-08:00

The consent is of course the most important part of the pre-operative visit -- especially if things go wrong later. consents can be tricky as different patients want different levels of detail. the consent for cataract surgery has also gotten a bit trickier as toric and presbyopic IOLs have entered our practice. here i'm going to briefly focus on the essentials for consenting patients for cataract surgery.

5 essential parts of a consent

identify yourself and your role in the surgery
describe the two options – cataract surgery or hold off on cataract surgery
describe the procedure briefly
describe potential risks – 1/100 chance vision will be worse after surgery
describe potential benefit – 9/10 chance vision will be normal with glasses following surgery

Talk your patient through the procedure briefly

we replace your cloudy natural lens with a clear artificial lens
use the words: injection(w/RB), cut, and possible stitches in your discussion
no we don’t use the laser (much confusion about Yag for secondary cataract)
we may patch your eye overnight following the surgery
we will prescribe new glasses when the eye is stable – 2-4 weeks post op

Benefits:

95 % better than 20/40
96 % better vision than pre-op
I lower these percents with increasing retinal or optic nerve disease

Risks:

1% vision worse than pre-op
death (<1:100,000)>
loss of eye (<1:10,000)>
irregular pupil (1:100)
after cataract (1:20 requiring laser in 2 years with sa60/ma60)

Document

Functional visual disability, give examples
Complete consent form legibly
In pts chart write something like:

“I discussed the risks and benefits of cataract surgery with Mr. Jones and his son in terms they seemed to understand. Mr. Jones expressed to me that he understood the small but real risk of surgery, including loss of vision as outlined in the consent form, and he decided to have surgery”

learning phaco chop

2009-01-08T18:22:00.000-08:00

i think the best way to learn phaco chop is transition in stages

1) divide and conquer
2) divide and conquer using the chopper to get used to this instrument in the eye
3) chop one of the quarters during divide and conquer
4) stop n chop
5) stop sooner n chop
5) phaco chop with medium densitiy or white cataract which easily chop

stop n chop

as you transition from divide and conquer to phaco chop use stop n chop. stop n chop is the technique where you STOP doing divide and conquer and start CHOPping after you have split the nucleus in 2. it is a play on words from paul koch who invented it and named it after a grocery stores chain STOP N SHOP that is common on the US east coast. this technique is a great way to transition from divide and conquer to phaco chop.

good old fashioned divide and conquer is a great technique as it is relatively easy and can even be done with a one handed technique; but, it uses a fair amount of phaco energy. phaco chop is great as it uses little phaco energy; but, it takes more coordination with both hands, can result in damage to the anterior capsule from the chopper, and the nuclear pieces can get stuck together or the "jig saw Puzzle problem" which can be frustrating. stop n chop bridges the gap between these two as it uses less energy than divide and conquer, allows the half pieces to be moved about which makes a chopper strike on the capsule and the jig saw problem less likely.

In the next case (below) dr shriver (one of our great past residents) does a great job performing phaco chop on this mature white lens. white lenses are usually a perfect consistency for chopping as they are sort of chalky so it splits or chops easily and not too hard, too leathery, or too elastic. on the other hand divide and conquer with these lenses is tricky as there is no epinucleus as a protective shell and they often spin so easily that making the groove with divide and conquer can be difficult.

In the case below we show another nice example of chopping technique for nucleofractis done by by dr jordan graff and me (drops on cornea) when he was a resident at iowa a couple of years ago. he uses a mainly a horizontal with just a touch of vertical technique. at this point in his training he had done about 60 cases.

(for more cataract videos check ouot my facebook cataract surgery page: http://www.facebook.com/video/video.php?v=5741526614)

Another even smaller step to transition to phaco chop we call "stop sooner and chop" in this technique you make 1/2 a groove and then rotate the lens. instead of continuing with the other half of the groove as you do with stop and chop you embed the phaco tip into the ungrooved part and then chop the lens in half. having 1/2 a groove already present makes it easy to set your depth. having 1/2 a groove already makes it easier to chop the nucleus completely in half. here is a video showing that technique:

Finally here is a video of my technique for phaco chop using the Ozil system from Alcon.

secondary anterior chamber AC IOL

2009-01-07T20:35:00.000-08:00

Anterior Chamber (AC) IOL are a great option for the rehabilitation of aphakia in patients intolerant of their contact lenses. You need to be ready to do place an AC IOL in case your case gets complicated and you loose capsular support to place the IOL behind the iris. Your OR should always have stocked AC IOLs ready to go incase they are needed when things go south.

this is the best article comparing IOL selection with loss of capsular support:

Wagoner MD, Cox TA, Ariyasu RG, Jacobs DS, Karp CL, Intraocular lens implantation in the absence of capsular support: a report by the American Academy of Ophthalmology. Ophthalmology. 2003 Apr;110(4):840-59

In the following video i show a recent case where i placed an AC IOL in a patient with a history of congenital cataract who is aphakic and intolerant to her contact lenses. we considered her options and decided to place an AC IOL as she had no history of glaucoma, had a normal angle, and was so young. we placed miochol to bring down the pupil, used Viscoat in case some of the OVD was retained in the vitreous, placed a peripheral iridotomy with the anterior vitrectomy handpiece, and closed the 6 mm scleral tunnel with 2 10-O nylon sutures.

Please always remember to place a peripheral iridotomy. i think this is best done with the anterior vitrector as shown in the video. I would like to show you pictures from a patient who came to me for a second opinion following complex cataract surgery about a year ago. during her surgery the functional support of the capsule was lost and the surgeon placed an AC IOL. the patient was bothered by a chronic head and brow ache and had elevated intraocular pressure. here is what she looked like that day:

You can see she has iris bombe and no patent peripheral iridotomy is visible. i took her to the laser and performed a Yag peripheral iridotomy. I chose a spot near the haptic at about 10 oclock as this region of the iris was posterior and safely away from the cornea. immediately following her Yag PI the iris bombe resolved and she was more comfortable. here is a picture from just a few days later showing the IOL and iris in good position.

IOL centration and placement

2008-03-29T20:11:00.002-07:00

A perfectly placed IOL is centered and right side up in the capsular bag. Perfect placement of the IOL relies on controlling the preceding steps of the cataract surgery. The first step of IOL placement immediately follows the removal of all the lens material. The capsular bag is reformed with an ophthalmic viscoelastic device (OVD) or viscoelastic. I typically use a cohesive OVD to fill the capsular bag. I am careful to inject a wave of OVD ahead of the cannula to protect the posterior capsule from the relatively sharp cannula. I try to fill the capsular bag without releasing OVD anterior to the anterior capsule into the sulcus, as this can compresses the bag and makes IOL placement more difficult.

Sometimes the wound must be extended to allow IOL placement. With typical coaxial phacoemulsification the needle requires an incision from 2.5-3.0 mm. Depending on the type of IOL and the insertion technique you may need to extend the wound to as much as 4.0 mm for a foldable IOL and 6.0 mm for a PMMA IOL. Extension of the wound is typically done with the keratome or a crescent blade. It is better to make a well formed and controlled extension of the wound than stretch the wound during lens placement. Stretched wounds often leak and require sutures or increase the risk of infection. Many of the newer IOL insertion systems do not require enlargement of the wound beynd that required of the phacoemulsification needle.

Placing a PMMA IOL is simple, as no folding is required, but does require a larger wound that can extend rehabilitation time and induce astigmatism. The wound is extended to 6.0 mm for a typical PMMA IOL with an optic size of 6.0 mm. Kelman-McPherson (or similar) forceps are used to grasp the trailing haptic and adjacent ½ of the optic. Hold the forceps on their side to keep the IOL flat while placing the leading haptic through the wound and down into the capsular bag. The forceps are released and repositioned onto the trailing haptic which is then placed into the capsular bag. A Kuglen hook (or similar instrument) may be used to place the trailing haptic.

Foldable IOLs may be placed with forceps rather than with an injector especially when using a three piece IOL design. Forceps placement requires a larger incision than is needed when using an IOL injector but is a very controlled process. As IOLs get thicker with increasing dioptric power, the incision may need to be slightly larger with high power IOLs (4.0 vs. 3.5 mm). There are 2 basic folding strategies using forceps. The first strategy involves folding the IOL axially along the axis of the haptics and the second strategy shifts the fold 90 degrees so that the haptics fold onto each other which looks something like a “moustache” (see video). An IOL with an axial fold is easier to insert, allowing for a smaller incision, but requires a 2 step procedure to place both haptics in the bag. An IOL with a moustache fold is harder to insert, requires a larger incision, but as the IOL unfolds both haptics slip into the bag in one step.

The most common technique to insert a foldable IOL is through an injector. These systems use a plunger to squeeze an IOL through a cartridge into the eye. The single piece acrylic and silicone plate haptic IOLs are the simplest to use with injectors. These designs have haptics that are sturdy and resistant to damage from the plunger as it forcefully pushes the IOL through the cartridge. The three piece IOLs are more difficult to inject as the haptics are more fragile and susceptible to plunger damage. The cartridge tip of the injector system can damage Descemet’s membrane. Surgeons should ensure that the tip is under Descement’s by placing the “toe down” as the cartridge passes through the posterior cornea.

When placing the IOL surgeons need to be sure that the IOL is right side up. All common IOLs (except plate haptic) are made with the haptics in the same configuration. IOLs are designed to rotate in only one direction safely – clockwise. The haptics are designed so that a right handed surgeon can most easily rotate the IOL into position using a hook at the junction of the optic and haptic. If the IOL is upside down the haptics will create an “S”, reminding you to Stop and flip the IOL. When a 3 piece IOL is left upside down it can cause a significant myopic shift. This is because the haptics in 3 piece IOLs are often angulated to push the optic posteriorly and support the vitreous face. When the IOL is upside down, the haptics push the optic into a more anterior position which creates a myopic shift.

IOL designed for rotation by right handed surgeon

When upside down the IOL looks like an “S” so Stop

While placing the IOL surgeons should confirm that both haptics are in the capsular bag. When one haptic is in the bag and one in the sulcus the IOL will not center. As the diameter of the capsular bag is more constrained than the sulcus, the optic of the misplaced IOL will decenter toward the sulcus placed haptic. This can be remedied by adding OVD and rotating the IOL clockwise while pushing posteriorly with a hook at the junction of the optic and IOL.

If the IOL still does not center despite having both haptics in the bag there are 2 most likely possibilities: haptic damage requiring IOL removal and zonular dialysis. IOL decentration from small amounts of zonular dialysis can often be overcome by rotating the IOL. Rotation of the IOL is especially effective with three-piece IOLs. Aligning the the three-piece haptics to the axis of weakness supports the zonules and often centers the IOL. If rotation does not work adding a capsular tension ring may center the IOL.

When the capsular bag is not perfect IOL placement is more difficult. A single anterior capsular tear that has not gone radial is a common problem that usually causes no long term problems. Some surgeons will make a controlled radial incision 180 degrees away and place an IOL in the bag. Another option is to place a single piece acrylic in the bag as this IOL places little tension on the bag which makes extension of the radial tear less likely (figure 7). The final option for an anterior capsular tear is to place a three-piece IOL in the sulcus. The foldable single piece IOLs (both the acrylic and plate haptic) are not a good choice for the sulcus as their haptics can cause pigment disruption of the iris and inflammation and their smaller size allows lens dislocation.

If the posterior capsule is not intact the IOL is usually placed in the sulcus. The wound can be extended to allow placement of a large PMMA IOL into the sulcus but more commonly a foldable IOL is placed into the sulcus using either forceps or an injector. If the posterior capsular tear is round or has been rounded by creating a continuous posterior capsulotomy, the IOL can be gently placed into the bag.

If the capsule is not adequate for IOL support the surgeon has several options, none of which is clearly superior. An anterior chamber IOL can be placed if the angle is healthy, although this requires extension of the wound to 6 mm. The IOL can be sutured to the iris with 10-O Prolene suture using a foldable IOL. Another option is to suture the IOL to the sclera using either a foldable IOL, or extending the wound to for a large PMMA IOL with eyelets on the haptics designed for suturing to the sclera.

References:

Thomas A. Oetting, MD, Cataract Surgery for Greenhorns, MedRounds Publishing, 2005, (available at http://www.medrounds.org/cataract-surgery-greenhorns)

Oetting, TA, Beaver HA, Johnson AT, Intraocular Lens Design Material and Delivery, in Essentials of Cataract Surgery, Henderson, Slack, Thorofare NJ, chapter 17, pages 133-146.

Chang, DF, TA Oetting, T Kim, Curbside Consultation in Cataract Surgery, Slack, Thorofare NJ, 2007.

staining the vitreous with kenalog

2008-01-27T17:04:00.002-08:00

One of the trickiest parts of an anterior vitrectomy is seeing the vitreous.

You can often see the nearly invisible vitreous strands pushing another structure aside or detect that the vitreous has occluded an I/A aspiration port. However directly seeing the vitreous is difficult. Scott Burk at Cincinatti Eye helped to solve this problem with his description of using Kenalog (off label) to stain vitreous that had prolapsed into the anterior chamber (ref below). As Kenalog is not approved by the FDA for this indication and as some retinal surgeons have had sterile and even infectious endophthalmitis from using Kenalog its use is controversial. However it is a very useful adjunct to anterior vitrectomy. For more detail on vitrectomy pls see: http://www.medrounds.org/cataract-surgery-greenhorns/2005/10/chapter-5-managing-surgical.html or the section in this blog.

Dr Burk described a process to wash the preservative off of the Kenalog to use in the anterior chamber. His process dilutes the 40mg/ml Kenalog 10:1 and washes off the preservative with a filter. I have summarizied the steps of his technique below and show the technique in the video. Please keep in mind that this is not approved by the FDA for this technique and does carry some risk of TASS (sterile anterior chamber inflamation) and of endophthalmitis. you can also use the preservative free kenalog which is now available and dilute it 10:1 which although more expensive is easier and is approved for intraocular use.

Preparing the Kenalog Stain

TB syringe to withdrawn 0.2 ml of well shaken Kenalog (40mg/ml)
Remove the needle and replace with a 5 (or 22) micron syringe filter (Sherwood Medical)
Force the suspension through the filter and discard the preservative filled vehicle
The Kenalog will be trapped on the syringe side of the filter
Transfer the filter to a 5 ml syringe filled with balanced salt solution (BSS)
Gently force the BSS through the filter to further rinse out preservative
Repeat rinsing a few times
Place a 22 gauge needle on the distal end of the filter
Draw 2 ml of BSS into the syringe through the filter to resuspend the Kenalog
The Kenalog (now without preservative and dilute 10:1) will stain vitreous strands white

one of the nice things about the kenalog stain is that you can better understand the fluid dynamics of vitreous removal. you can see the vitreous streaming around the cutter with a leaking wound. you can see the vitreous heading better toward the cutter if you hold the cutter low and the irrigation cannula high. here is a video showing these principles.

References

Burk SE, Da Mata AP, Snyder ME, Schneider S, Osher RH, Cionni RJ. Visualizing vitreous using Kenalog suspension J Cataract Refract Surg. 2003 Apr;29(4):645-51

Burk, SE, Question 32: When and How Do I Stain the Vitreous With Intracameral Kenalog? from Chang DF, Oetting TA, Kim T, Curbside Consultations in Anterior Segment Surgery, Slack Inc, Thorofare NJ, 2007.

converting to ECCE

2008-01-27T17:04:00.001-08:00

Conversion to ECCE often comes at a difficult time. The lens is about to fall south, the vitreous has prolapsed and the surgeon is stressed.

Understanding the steps and process of conversion to ECCE is essential and study before the crisis will help soothe the stress when this inevitable process occurs. We will cover several areas: identifying patients at risk for the need for conversion to ECCE, indications for conversion, conversion from topical to sub-tenon’s, wound preparation, expressing the lens material, closure of the wound, placement of the IOL, post operative issues and a brief section on anterior vitrectomy. For more detailed instructions please refer to: http://webeye.ophth.uiowa.edu/eyeforum/tutorials/Cataract-ECCE/Cataract-Surgery-Complex-Conversion-Extracaps-ECCE.htm

One of the most important parts of the pre-operative process for cataract patients is to assess the difficulty factors that may lead to conversion to ECCE or otherwise complicate the procedure. You may want to add operative time to your schedule or ask for additional equipment. You may want to change to a superior limbal wound which facilitates conversion to an ECCE rather than a temporal clear corneal incision. You may want to do a retrobulbar block rather than topical anesthesia as the case may last longer or is more likely to become complicated. Or you may want someone more experienced to do the case. for more detail on dkifficulty factors please see: http://www.medrounds.org/cataract-surgery-greenhorns/2005/09/chapter-1-assessment-difficulty.html

Conversion to ECCE is indicated when phacoemulsification is failing. Sometimes this is due to a very hard lens which does not submit to ultrasound or a lens that is hard enough that the surgeon is concerned that the required ultrasound energy will harm a tentative cornea, e.g. Fuchs’ endothelial dystrophy or posterior polymorphous dystrophy (PPMD). Sometimes one will convert to ECCE when an errant capsulorhexis goes radial especially with a hard crystalline lens when the surgeon is concerned that the risk of dropping the lens is too great with continued phacoemulsification. Rarely now with Trypan Blue dye, a surgeon will choose to convert to ECCE when the anterior capsule is hard to see and capsulorhexis must be completed with the can opener technique. More often the conversion is indicated when the crystalline lens is loose from weak zonules or a posterior capsule tear which make phacoemulsification less safe than extending the wound and removing the residual lens material. Indications for conversion to ECCE include: Hard crystalline lens or unstable endothelium, Radial tear in anterior capsule with hard lens, Poor visualization despite Trypan dye,
Posterior capsular tear, and Zonular dialysis.

Converting to subtenon’s anesthesia. Often we convert cases from topical clear corneal to ECCE. While the ECCE can be done under topical it is usually more comfortable and safer to give additional anesthetic which is typically a sub tenon’s injection of bupivicaine and lidocaine. This will provide some akinesia and additional anesthesia. There is usually subconjunctival hemorrhage and if the injection is made too anterior it can cause chemoisis and ballooning of the conjunctiva. The steps of the sub tenon’s injection are shown in the video below(1):

A major decision step when converting to ECCE is to either extend the existing wound or close and make another. The ECCE will require a large incision of from 9-12 mm which is closed with suture. The decision to extend the existing wound or make a new wound hinges on several factors: location of the original wound, size of the brow, past surgical history, and possible need for future surgery.

Making a new incision during conversion is identical to that for a planned ECCE. The original incision is closed with a 10-O nylon suture. The surgeon and microscope are rotated as the surgeon should sit superior. The steps to make a new superior incision are:

Conjunctival peritomy of about 170 degrees
Use 64 or crescent blade to make limbal groove with a chord length of 11mm
Bipolar cautery for hemostasis
Use keratome to make initial incision starting in groove into AC
Extend initial incision to full length of groove (with scissors or knife)
Safety sutures are preplaced usually 7-O vicryl

Extending an existing incision can be tricky and the technique is different for scleral tunnels compared to clear corneal incisions. However in both cases the original extension is brought to the limbus. In the case of an original scleral incision the incision is brought anterior to join the limbus on either end before extending along the limbus for a chordlength of about 11mm. In the case of an existing corneal incision the corneal incision is brought posterior toward the limbus before extending the wound along the limbus for a chord length of about 11mm. When iris hooks are being used in a diamond configuration the wound can be extended to preserve the sub-incisional hook and the large pupil(2). The steps include:

Conjunctival peritomy of about 170 degrees,
Use 64 or crescent blade on either side of the existing wound to make a limbal groove with a chord length of 11mm
Bipolar cautery for hemostasis
Use Crescent to bring existing scleral wound anterior or existing corneal wound posterior to join limbus
Extend initial incision to full length of groove (with scissors or knife)
Safety sutures are preplaced usually 7-O vicryl.

One has to be far more careful when removing the nucleus during the typical conversion to ECCE which comes along with vitreous loss. First the anterior capsule must be large enough to allow the nucleus to express which may require relaxing incisions in some cases. When the zonules are weak or the posterior capsule is torn the lens cannot be expressed with fluid or external pressure as is often done with a planned ECCE with intact capsule/zonlules. After any vitreous is removed, the lens must be carefully looped out of the anterior chamber with minimal pressure on the globe. If the posterior capsule and zonlues are in tact than the lens can be expressed as described with a planned ECCE.

Placement of the IOL IOL selection with ECCE conversion depends on the residual capsular complex(3,4). The key to IOL centration is to get both of the haptics in the same place: either both in the bag or both in the sulcus.

When the posterior capsule is intact following a conversion to ECCE the anterior capsular opening is usually poorly defined which can make bag placement difficult. If the anterior capsule and thus the bag is well defined, then place a single piece acrylic IOL without folding it directly and gently into the bag using kelman forceps.

When the posterior capsule is intact and the anterior capsule is poorly defined then place a 3 piece IOL in the sulcus such as a large silicone IOL or the MA50 acrylic by placing these directly and unfolded into the sulcus with kelman forceps. Make sure that both haptics are in the sulcus.

When the posterior capsule is damaged, if enough anterior capsule and posterior capsule is left to support the IOL, define the sulcus with viscoat and place the IOL directly in the sulcus. Make sure both haptics are in the sulcus. If the IOL does not seem stable then place McCannel sutures to secure the IOL to the iris or remove and replace with an AC IOL (don’t forget to place a PI with vitrector).

When the capsule is severly damaged and cannot support an IOL then place the IOL in the anterior chamber. Use kelman forceps to place the IOL, then secure the chamber, and use a sinsky hook to place the AC IOL into its final position. (don’t forget to place a PI with vitrector).

Postoperative care for patients following conversion from phaco to ECCE is a bit more complicated and focuses on preventing cyctoid macular edema and limiting induced astigmatism. Often the care is very similar to that of a planned ECCE with about 3 post operative visits one the same day or next, one a week later, and one about 5-6 weeks later. Depending on the amount of astigmatism the patient may require several visits to sequentially remove sutures to eliminate induced astigmatism.

References

1. Oetting, TA, Cataract Surgery for Greenhorns, Available at http://medrounds.org/cataract-surgery-greenhorns.%20accessed%20September%209, 2007
2. Dupps WJ Oetting TA, Diamond iris retractor configuration for small-pupil extracapsular or intracapsular cataract surgery. J Cataract Refract Surg Vol 30(12):2473-2475
3. Chang DF, Oetting TA, Kim T, Curbside Consultations in Anterior Segment Surgery, Slack Inc, Thorofare NJ, 2007
4. Henderson BA, Essentials of Cataract Surgery, Slack Inc, Thorofare NJ, 2007

using the eyesi simulator

2008-01-27T17:04:00.000-08:00

Cataract surgery is difficult to learn, often both for the surgeon and patient. The holy grail for educators in this area has been a simulator that would allow practice without placing patients or attending coronary arteries at risk. The first versions of simulators are rolling off the lines now and we were fortunate that the VAMC in Iowa City purchased one of the EyeSi devices from VR Magic for our residents. Here we will describe how this fits into our curriculum and show a few videos that demonstrate its capabilities.

The first step for, I suppose any educational project is to establish stages of development and objectives for each stage. Much like the boy scouts have cub scouts, boy scouts, eagle...; we developed stages for our program using Dreyfus stages of novice, beginner, advanced beginner, proficient, and expert. We assumed that almost no resident will make expert in only 3 short years and that almost all will make the proficient stage. The objectives for each stage are measurable and we established resources to allow stage progression http://webeye.ophth.uiowa.edu/eyeforum/pdf/580oett.pdf .

Our objectives for the beginner (typically a first year at iowa) include the use of the wet lab and the simulator with a focus on developing a facilty with instruments within the eye. Our residents begin to do the easier parts of cases which we call "backing in" where residents do the last steps of a perfect case started by a senior resident. The might just fold the lens the first week, then fold and inset the lens, then fold and insert and also remove the OVD.. The simulator in this phase requires a set of tasks simulating the use of instruments within the eye, the capsulorhexis, and some basic steps of phacoemulsification.

Our objectives for the advanced beginner (typically a second year at iowa) is to use the simulator for more advanced practice and to begin to do whole cases. Our goal during this year is for the resident to be able to do whole cases in less than 45 minutes but do not expect them to be able to use both hands and the attending will typically control the paracentesis instrument.

The objectives for the proficient stage (third year at iowa) are more difficult and involve increasingly efficient and complex surgical tasks. The simulator has been less imortant so far for us in this regard however it does at times prompt discussion. The video below shows a simulator case where the lens fell due to zonular stress which prompts a discussion on what to do next and what are the risk factors for droppin the nucleus.

While we are thinking about it what are the risks for dropping the nucleus? Zonular issues such as pseudoexfoliation, RP, h/o uveitis, h/o trauma, and marfans are certainly important. Other risky situations where you must be very careful with hydrodissection include radial tear, posterior polar cataract, penetrating lens trauma, and early cataract after vitrectomy. This reminds me of the following video: