Eyeworld

EW CATARACT/IOL 47 Center, University of Utah, Salt Lake City, showed these go on to develop massive Soemmering's ring. 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 suc- tion 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 ep- ithelial cells. Once again, although it sounds like a good concept, clinical studies have been rather disappoint- ing. The lens epithelial cells are probably protected by remnants of overlying hydrophilic cortical mate- rial so things like aqueous solutions can't penetrate. Two years after sur- gery, 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 ex- plored using a variety of instruments and techniques. The problem here is that we have to remove the equato- rial cells. If we just remove the ante- rior capsule cells, the eyes get more PCO. The reason for this is we re- duce the fibrosis in the anterior cap- sule 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 A.R.C. Laser (Nuremburg, Germany) is a new device developed for cell removal. It uses laser shock- waves, 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 treat- ment 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 post-mortem cap- sular bags and growing them in a new laboratory cultured model. It's the best model that has been de- scribed so far and involves perform- ing surgery on a human post- mortem 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 ep- ithelial 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 stabi- lize the IOL. If we are going to kill all the cells in the bag, we have to radically change the design of the lens im- plant. 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 elas- ticity of the bag? Does removing these cells ultimately cause degener- ation of the capsular bag? New ideas Open-bag devices are a novel idea. Studies on the Synchrony lens (Ab- bott Medical Optics, Santa Ana, Calif.) have reported very low rates of PCO. It seems there's a possibility that by keeping the capsular bag open after surgery and allowing cir- culation of aqueous into the capsu- lar 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 compa- nies that are involved in making such devices, although it's entirely experimental at this point. We will also have to see whether the Syn- chrony 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 finan- cial interests related to his comments. Contact information Spalton: +44 020 7935 6174, practice_manager2@davidspalton.com February 2011

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