Improved biocompatibility of intraocular lenses by heparin surface modification: a 12-month implantation study in monkeys.

To evaluate the long-term biocompatibility and potential side effects of heparin surface modification of a poly(methyl methacrylate) intraocular lens (IOL), a heparin surface modified IOL was implanted in the left posterior chamber of 24 cynomolgus monkeys and a reference IOL (without surface modification) was implanted in the right eye in 12 of these animals. Twelve eyes were not operated on. Eleven eyes in seven monkeys were lens extracted as a control of the surgical method. Slitlamp examinations and intraocular pressure recordings were made one day, one and two weeks, and 1, 2, 2 1/2, 3 1/2, 6, 8, 10, and 12 months after the operation. Eleven monkeys were sacrificed after 3 1/2 months and the remaining animals after 12 months for morphological examination of the eyes. Slitlamp and morphological examinations showed that cell deposits, pigmentation, and posterior synechias were significantly less in eyes with heparin surface modified IOLs than in eyes with reference IOLs throughout the 12-month observation period. The intraocular pressure was equally reduced in eyes with heparin surface modified IOLs and reference IOLs for about one month, after which it returned to normal. No side effects following the implantation of heparin surface modified IOLs were observed. We concluded that heparin surface modification of IOLs is efficient for long-term reduction of cell deposits and posterior synechias after implantation in monkey eyes and may also be effective in lowering the degree of side effects to IOL implantation in humans.