We performed two tissue culture experiments designed to compare the effects of various posterior chamber optics on lens epithelium. In the first experiment, we recorded, by phase contrast microphotography, the migration of rabbit lens epithelium exoplants placed adjacent to the optic of various posterior chamber lenses. In the second experiment, we used phase contrast microphotographs to document the effects of various posterior chamber optics when gently placed on a confluent layer of rabbit lens epithelium. From our in vitro studies, we conclude the following: There is inhibition of lens epithelial migration and even cytotoxic effects from direct contact with polymethylmethacrylate optics; glass optics have appreciably less effect on lens epithelium; polymethylmethacrylate optics with ridges (complete annulus or incomplete) do not inhibit lens epithelial migration as well as planoconvex lenses, and they do not have a cytotoxic effect except at the points of contact between the ridge and the supporting surface.

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It has been a clinical impression that posterior chamber lens implants in some way inhibit opacification of the posterior lens capsule after extracapsular cataract extraction. The mechanism of this inhibition is unclear; it may be related to mechanical contact or blockage of migration of lens epithelial cells, or possibly to the leeching of toxic factors from the lens itself. A better understanding of the exact mechanism of opacification inhibition may have important clinical implications for intraocular lens design. For example, some lens designs that facilitate Nd:YAG capsulotomy by physically separating the posterior chamber lens and the posterior capsule may result in less inhibition and in fact more opacification of posterior capsules. We performed in vitro tissue culture studies of the effect of the polymethylmethacrylate (PMMA) optic of a planoconvex intraocular lens on cultured rabbit lens epithelium. These studies demonstrated both inhibition of lens epithelial migration beneath the PMMA optic (plano side down) as well as metaplasia and necrosis of lens cells growing directly beneath the optic. The clinical implications of these studies for intraocular lens design are discussed.

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