EyeWorld Asia-Pacific June 2011 Issue

27 EW CATARACT/IOL June 2011 Dealing with lens epithelial cells There are also pharmacological methods of dealing with PCO, although fundamental problems have been associated with many of them. One of the concepts involves locking up the lens epithelial cells in the equatorial capsule. The surgeon performs a posterior capsulorhexis and prolapses the optic through that or uses what’s called the bag-in-the-lens, a Belgian-designed lens. The rhexis has to be 5 mm in diameter, it has to be central, and there must be a concentric posterior capsulorhexis. The lens is placed so that both anterior and posterior rhexes lie in this groove in the lens, and these eyes maintain an entirely clear posterior capsule because there is no posterior capsule. However, a recent report by Liliana Werner, MD, PhD, research associate professor, ophthalmology and visual sciences department, John A. Moran Eye Center, University of Utah, Salt Lake City, Utah, USA, showed that these go on to develop massive Soemmering’s rings. While the posterior capsule is clear, there’s a downside, so this is not the answer to PCO prevention. Another concept concerns the killing of all the epithelial cells in the capsular bag using a device called the Perfect Capsule (Milvella, North Sydney, Australia), which is held over the capsulorhexis by a suction ring in the eye at the time of surgery. The inside of the capsular bag is isolated and then irrigated with a solution to kill the lens epithelial cells. Once again, although it sounds like a good concept, clinical studies have been rather disappointing. The lens epithelial cells are probably protected by remnants of overlying hydrophilic cortical material so things like aqueous solutions can’t penetrate. Two years after surgery, these eyes have the same amount of PCO as the control eyes. The idea of removing all of the cells from the bag has also been explored using a variety of instruments and techniques. The problem here is that we have to remove the equatorial cells. If we just remove the anterior capsule cells, the eyes get more PCO. The reason for this is we reduce the fibrosis in the anterior capsule so we restrict the fibrosing force within the capsular bag. This means we don’t push the lens implant against the posterior capsule as tightly as we would with a fibrosed posterior capsule, so cells can get in and cause PCO. The ARC Laser (Nuremburg, Germany) is a new device developed for cell removal. It uses laser shockwaves, and we can blast all the cells off the capsule, so we end up with a capsule that is acellular as long as we can go around for 360 degrees and treat it all. It also seems to remove adhesion molecules. The technology sounds quite promising and clinical trials are ongoing in Germany at the moment. In theory, though, the problem with this focal laser treatment is if we miss a few cells, PCO could develop. Another problem is we don’t know if there’s any danger that the laser shockwaves could damage the iris or the ciliary body. In Britain, my colleagues and I recently tested this cell removal idea by taking human postmortem capsular bags and growing them in a new laboratory cultured model. It’s the best model that has been described so far and involves performing surgery on a human postmortem lens and growing it in an incubator for weeks following the operation. What we showed was if we take a pair of eyes from the same patient, do the surgery, put an IOL in each eye, and kill all the lens epithelial cells in the fellow eye, 3 or 4 weeks post-op, we would see that in the control eye, the IOL is fibrosing into the bag, just as in a human eye. In the treated eye, however, the lens wobbled. This indicated that with the current lens design, we need lens epithelial cells there to fix and stabilize the IOL. If we are going to kill all the cells in the bag, we have to radically change the design of the lens implant. There are some fundamental questions there, and no one knows what the long-term consequences of killing all the cells in the human eye are. Do we need the cell bed to maintain the collagen and the elasticity of the bag? Does removing these cells ultimately cause degeneration of the capsular bag? New ideas Open-bag devices are a novel idea. Studies on the Synchrony lens (Abbott Medical Optics, Santa Ana, Calif., USA) have reported very low rates of PCO. It seems there’s a possibility that by keeping the capsular bag open after surgery and allowing circulation of aqueous into the capsular bag, we may be removing cytokines and growth factors and therefore we don’t stimulate the lens epithelial cells to proliferate in the same way. There are a number of companies that are involved in making such devices, although it’s entirely experimental at this point. We will also have to see whether the Synchrony lens, when it comes into standard clinical practice, continues to have low PCO rates when it’s being used by a lot of surgeons. With the other three approaches to dealing with lens epithelial cells all having fundamental problems, the idea of opening the capsular bag is different and worth exploring. EW Editors’ note: Dr. Spalton has no financial interests related to his comments. Contact information Spalton: +44 020 7935 6174, practice_manager2@davidspalton.com Getting informed consent Despite the fact that this is an extremely rare complication, Dr. Bass urges practitioners to take heed with regard to consent forms. “I have looked at a number of consent forms from a number of practices and they don’t mention that if the patient has a history of macular problems, there could be a risk of this developing,” Dr. Bass said. “In any patient, doctors should mention this when they’re listing all of the possible things that could happen. Although it’s extremely rare, there is a possibility that there could be the development of a posterior segment abnormality in the form of choroidal neovascularization.” In this particular case, Dr. Bass considers herself lucky that all eventually turned out well. “The next day this young lady’s brother came in and said, ‘It wasn’t on the consent form that this could happen,’” Dr. Bass said. “Thankfully, when her vision returned to normal, he no longer had any reason to be upset because there were no long-lasting effects.” Dr. Bass thinks it is important for patients to understand that this complication is a possibility, however small, so that they can determine if they are willing to take the risk. “There are some patients who say, ‘Even if it’s rare, it’s still there and I don’t want to have the LASIK,’” she said. Overall, Dr. Bass stressed that LASIK has proven to be an extremely safe procedure. “I know there are individual reports of people having some issues, but there are millions of these procedures being done and a very small number of patients have problems,” she said. “But it’s important to still be aware of the occasional patient who can have problems to avoid getting into trouble legally.” EW Editors’ note: Dr. Bass has no financial interests related to her comments. Contact information Bass: 212-938-5865, sbass@sunnyopt.edu On the lookout continued from page 24