Abstract
Abstract: :
Purpose: To describe an animal model as a predictor of the risk of calcification of various intraocular lens materials in the human eye Methods: Various hydrogel intraocular lens materials were implanted intramuscularly in rabbits up to 90 days. The materials included Material "A": a hydrogel copolymer made of 2-hydroxy ethyl methacrylate (2-HEMA) and methyl methacrylate (MMA), Material "B": highly purified hydrogel copolymer and Material "C": heparin surface modified highly purified hydrogel copolymer. Scanning electron microscopy (SEM) energy dispersive x-ray spectroscopy (EDS) as well a various chemical analyses were performed to identify the chemical nature of surface and matrix deposits on the intraocular lens materials. These results were then correlated to human clinical observations with lenses composed of the same materials. Results: Calcification was observed and identified on the Material "A" lenses and to a much lesser degree this was also seen with Material "B" lenses at 30 and 90 days after rabbit muscle implantation. Very little or no calcification could be identified on the Material "C" lenses at 30 and 90 days. The clinical observations confirm that gradual (3-6 months post-op) lens opacification, in a small percentage of patients, which were identified as calcium deposits on explanted lenses, was reported with Material "A" lenses. This resulted in the discontinuation of the sale of these lenses. The clinical observation with the Material "B" lenses with more than 12 months of clinical follow up, show no similar cases of opacification of the lens surface. To date only limited clinical experience exists with the heparin surface modified highly purified hydrogel intraocular lenses. Conclusion: Significant calcification on Material "A" implanted in rabbit muscle for up to 90 days correlates with the clinical observation of intraocular lens opacification. The lower level of calcification of the Material "B" lenses also correlates with the absence of opacification of the intraocular lens material clinically. Based on the muscle implant results, it is anticipated that the heparin surface modification of highly purified hydrogel intraocular lens materials will reduce the risk of both short term and long term calcification of the lens surface. Use of this animal model may prove helpful in predicting the risk of calcification of hydrogel and other intraocular lens materials prior to clinical implantation.
Keywords: 316 animal model • 338 cataract • 334 calcium