Posterior capsular opacity remains major unmet need in cataract surgery

Issue: July 25, 2011

ByRichard L. Lindstrom, MD

Richard L. Lindstrom

I would like to share a few personal thoughts on posterior capsular opacity.

I performed my first phacoemulsification combined with posterior chamber lens implantation while a Heed Fellow in Dallas with William S. Harris, MD, in 1977. At that time, there were two significant unmet needs in regards to capsular management. The first was the lack of a safe, effective and minimally invasive technique to treat capsular opacity once it developed. The second was the absence of a way to reduce or prevent its occurrence.

When I first joined Dr. Harris, we performed posterior capsulotomy via a limbal entry with a discission knife at the slit lamp. This was a procedure requiring significant skill, as it was easy to subluxate the IOL, shallow the anterior chamber or drag a vitreous strand back to the wound. This procedure was not for the faint of heart. During my fellowship, we developed a pars plana approach, and I helped design reusable and disposable knives for pars plana posterior capsulotomy. This approach reduced the chance of lens subluxation, anterior chamber shallowing and vitreous strands to the wound. In addition, passing the blade through the prepped conjunctiva as we do today for injection of intravitreal medications reduced the risk of endophthalmitis.

I was pretty happy with this approach until I visited Daniele Aron Rosa, MD, in Paris and was allowed to treat patients under her guidance with the YAG laser. This was definitely a disruptive technology advance, and I returned home to purchase one of the first YAG lasers in America. We studied our outcomes with the YAG laser and discovered several interesting findings. The most common risks of YAG laser capsulotomy were a mark on the posterior surface of the IOL and an IOP spike. We learned we could almost eliminate the pressure spike by applying a topical antihypertensive. We studied the impact of the IOL marks on visual performance and found that even 50 direct hits with 5 millijoules in the central 4 mm of the optic’s posterior surface did not reduce performance as tested with an Air Force resolution target when the IOL optic was under water. We also learned, using tissue culture with corneal endothelial cells, that there was not enough IOL material monomer released to cause meaningful cytotoxicity or inflammation.

These were reassuring findings, as it was impossible to open most capsules without some marking. The most severe complication we encountered was retinal detachment. The highest-risk patients were young male axial myopes, and these patients remain at high risk today and deserve to be so informed. Our data suggested that if YAG laser capsulotomy were delayed for 1 year, the incidence of retinal detachment was reduced. While this is a soft finding, I continue to try to delay YAG laser capsulotomy in high-risk patients for 1 year when possible.

In the early years of phacoemulsification with posterior chamber lens implantation, we opened many posterior capsules at the time of surgery. The procedure was completed, the wound closed and the anterior chamber deepened. Using a 25- to 30-gauge needle on a 3 cc syringe containing balanced salt solution bent toward the bevel, the needle was passed under the IOL, the syringe aspirated to pull the capsule away from the vitreous face and engage it on the needle, and a central tear created inside the optic edges. A gentle push on the plunger released the capsule, and in many cases an intact hyaloid face could be maintained. Still, when studying the outcomes of these patients as compared to those with an intact capsule, we found a higher incidence of cystoid macular edema (CME) and retinal detachment. With the development of the YAG laser, this led us to leave most capsules intact at the end of surgery. Nonetheless, in many third-world settings a primary capsulotomy may well be preferable, because access to postoperative YAG laser capsulotomy is usually lacking.

I continue to use this technique in these settings. I find very interesting the recent work by Oliver Findl, MD, and others that suggests with modern surgical technique, viscoelastic, posterior capsulorrhexis and posterior optic capture, a primary posterior capsulotomy can be done without increasing the risk of CME or retinal detachment. Despite the ease with which a YAG laser capsulotomy is performed, the avoidance of late postoperative capsular opacity is the ultimate goal. If these findings are confirmed by others, I could see myself adopting this approach.

This leads me to the next great unmet need, which persists several hundred years after Jacques Daviel pioneered extracapsular cataract extraction: the prevention of visually significant posterior capsular opacity. We have learned much about reducing the rate of capsular opacity, but total prevention remains an elusive goal. The single monolayer of clear cells that migrates across the capsule and undergoes fibrous metaplasia resulting in capsular contraction is a desirable healing response, resulting in good fixation and sequestration of the IOL. However, even this normal healing response can result in mild loss of contrast sensitivity, capsular striae with unwanted visual dysphotopsias and, in some cases, IOL distortion, tilt, decentration or extreme capsular phimosis. In other cases, early capsular fibrosis can also impair vision. This fibrotic response is nearly routine in children, encouraging many to do primary capsulotomy and even anterior vitrectomy at the time of surgery in very young children.

I find significant inflammation increases the incidence of visually significant early capsular fibrosis, so treatment in the early postoperative period with a topical steroid and NSAID seems logical to me to reduce this unwanted occurrence, along with the other potential benefits including reduced postoperative CME. I teach to preload the eye before surgery with both topical steroid and NSAID application, and evidence is accumulating that this approach generates many benefits, including a larger pupil during surgery, a clearer, thinner cornea with better first day postoperative visual acuity, and reduced inflammation leading to a lower incidence of CME and capsular fibrosis. This is an easy, no-cost way to enhance outcomes in cataract surgery. Just give the postoperative topical steroid preoperatively as well with the antibiotic and NSAID, if used.

Late capsular opacity from lens epithelial cell (LEC) proliferation and migration remains the primary enigma to resolve. We can reduce the incidence of this annoying development with good cortical cleanup and an IOL with a continuous sharp posterior edge. Some myths that seem to be inconsistent with good clinical trials include the finding that posterior capsular polishing or peripheral anterior capsular vacuuming of LECs appears to offer no benefit in reducing LEC migration and late posterior capsular opacification. In addition, it does not appear that hydrophobic acrylic material offers any benefit over silicone in reducing LEC migration. Where hydrophilic acrylic fits in the hierarchy is still somewhat indeterminate, awaiting quality long-term clinical trials, but my impression is that the incidence of capsular opacity from LEC migration may be somewhat higher with this material. On the positive side, hydrophilic acrylic is the easiest IOL material to perform a YAG laser capsulectomy behind, and some of my favorite microincision IOLs are made of hydrophilic acrylic material.

Many agents can kill LECs, including radiation, cryotherapy, hypotonic agents such as distilled water, and medications such as antimetabolites. In addition, creative approaches using monoclonal antibodies to LECs have been investigated. Sadly, to date, no approach has offered proven clinical utility. We desperately need a way to prevent posterior capsular opacity. Such a treatment is likely also to retain long-term capsular elasticity, allowing the many accommodating IOLs in development to perform better.

I believe much more research and development dollars need to be targeted to this unmet need. With 18 million cataract operations being performed annually and growing, the individual, laboratory or company that solves this vexing problem will, without any doubt, be richly rewarded. Perhaps a major foundation or individual can be found to offer a prize for the solution, although no shortage of riches awaits those who resolve this enigma. We must reignite the quest for a solution to our current No. 1 unmet need in cataract surgery: posterior capsular opacity.