IOL centration and placement

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.

i placed a video on google video that outlines some of these issues: http://video.google.com/videoplay?docid=4314566601407119722&q=oetting+iol+placement+video&total=1&start=0&num=10&so=0&type=search&plindex=0

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

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

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 or sterile inflamation and of endophthalmitis.

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

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

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 step toward 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 (see below), 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

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: