Accommodation of an endocapsular silicone lens (Phaco-Ersatz) in the aging rhesus monkey.

Background: After accommodative changes of endocapsular silicone lenses in presenile nonhuman primates had been confirmed by several authors, this pilot study was designed to evaluate the ability of an artificial lens to restore accommodation in the senile eye of a rhesus monkey that had previously lost most of its accommodative capability.

Methods: An injectable silicone lens was implanted in one eye of six rhesus monkeys who were older than 17 years. Accommodation was documented as the amount of decrease of anterior chamber depth after pilocarpine stimulation.

Results: Four months after surgery, the decrease of anterior chamber depth was higher in the operated eye with the silicone intraocular lens in the two monkeys who had marked presbyopic changes in the natural lens. One monkey was kept for more than 4 years, retaining a decrease of at least 0.5 mm with the silicone lens, whereas the natural lens failed to show any accommodative change.

Conclusions: These findings support recent reports that presbyopia is primarily a consequence of lenticular aging rather than ciliary muscle factors. A pliable injected lens may therefore have the potential to restore accommodation in the senile primate eye.