Corneal dystrophy and the intraocular lens

corneal dystrophy and the intraocular lens G. Maxwell Stubbs, M.D. Melborne, Australia Harold Ridley's brilliant notion to create a pseudophakos in the nineteen forties has opened up a new era for victims of cataract, but its protagonists have remained few indeed. It is true that implantation can be extremely difficult, but the average competent surgeon is well able to cope with the manipulations involved. Why then do only a relative handful of us implant lenses in any number at all? Certainly, my early dreams of routine implantation for every case have not been fulfilled. There is no doubt, of course, that a successful result is a very successful one, delighting the patient and gratifying the surgeon in a way that few other procedures can equal. Reluctant though I am to dwell on the depressing side of our work, however, I would like today to present a philosophical paper dealing with my own clinical impressions formed over thirteen years of implant surgery, an approach which I feel has its place beside the double blind trial. There are many situations where consideration of an implant must arise, the ubiquitous contact lens not always performing as it should, and I have learned to dismiss, because of their comparative insignificance, all complications other than that of corneal dystrophy. It has occurred in about 10% of my cases, a figure approximating to that of 11 % given by C.D. Binkhorst in reference to his intracapsular cases a few years ago. I am hoping, of course, that implementation of the extracapsular technique he now recommends will reduce this figure to 1% or less, an incidence I can happily ask my patients to risk. I am still wondering, however, whether the long term results will confirm the complete efficacy of this remedy. There is much evidence to support the idea that actual contact between the lens and the endothelium is responsible for endothelial, stromal, and eventually epithelial oedema, an early modification to the iris clip lens involving reduction in the length of the anterior loops, in an effort to avoid contact. Pearce reported changes over the feet of Choyce anterior chamber implants, consistent with my own observation that narrowing of the upper part of the anterior chamber involved in wound healing frequently results in contact with the anterior loop of an iris clip lens when it is disposed vertically. I have implanted these lenses with their loops horizintally in latter years, eliminating this particular problem.

The quickest way to produce corneal dystrophy is to traumatize the endothelium during operation. I reported various complications in 1967, my figures comparing then with those of Barraquer, and although there is no doubt that some of my poor results were due to fumbling, I doubt very much whether this factor can be taken into account where he is concerned. It is, course, all too easy to dismiss reports of this complication by ascribing it to clumsy surgery, but I am sure that we have all experienced this tragedy where the extraction has been uneventful, and the implantation as easy as posting a letter. Unhappy results have still followed, often years later. C.D. Binkhorst has postulated that a compounding of many factors, minute traumata occurring during surgery, and afterwards by repeated mechanical contact with the endothelium, ultimately producing significant changes. However, in my own series, even where the implant has been disposed horizontally, dystrophic changes have almost invariably occurred in the upper part of the cornea, often remaining confined to this area, contiguous with the position of the incision. This has caused me to wonder whether trophic chan~es similar to those seen after denervation of other organs could be occurring. Perhaps some individuals are genetically susceptible in this way. There is no doubt that pre-existing changes should be taken into account, Manschot describing degeneration in endothelial tissues post mortem, where no clinical dystrophy had been present. In early years, I habitually introduced material such as acetylcholine directly into the anterior chamber, and I have ceased this practice, endeavouring always to use precisely the technique I apply to routine cataract extractions without implants, so as to eliminate all factors other than the implant. Identical preoperative and postoperative medication is used, followed by a simple intra capsular extraction using keratome and scissors and the cryoprobe, with no alpha chymotrypsin, and careful approximation of the wound with virgin silk. The operation is performed with a 6x head worn microscope, which allows one unlimited mobility for intraocular manipulations through both cornea and wound. This simple technique, involving great care in avoiding contact with corneal endothelium, excessive buckling of the cornea, and prolonged exposure, is usually followed by a rapid recovery, the anterior chamber and cornea clearing within a few days. However, tragedy has sometimes resulted, frequently after a few years. One of the most disappointing being a patient recently presenting with gross bullous keratopathy whose implant I removed, after eight years of apparently perfect tolerance. I would dearly love to gain some idea of the results of corneal grafting without disturbance of the implant. 39

This unfortunate patient, and others like him, where implantation has been without incident, the implant securely fixed in an apparently rigid iris diaphragm behind a deep anterior chamber, where it would seem impossible for any part of the implant to touch the cornea, has caused me to doubt that simple mechanical factors are the only problems we have.

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