Monkey Model of Neonatal Monocular Pseudophakia

Abstract

The safety and efficacy of correcting monocular aphakia during infancy with an intraocular lens was evaluated using a monkey model. The study was conducted at the Yerkes Regional Primate Research Center. A translucent contact lens was placed on the right eye of a group of newborn Rhesus monkeys to simulate a congenital cataract. When the monkeys were 2-weeks-old, a lensectomy was performed on the right eye coupled with the implantation of an intraocular lens (IOL) into the posterior chamber. The fellow eyes were then randomized to part-time occlusion therapy or no treatment. The monkeys were then examined at regular intervals for complications. Visual acuity and contrast sensitivity was evaluated using forced-choice preferential looking and operant testing. The pseudo-phakic eyes were studied histopathologically at the end of the study. A variety of complications occurred postoperatively including fibrin encapsulation of the intraocular lens, glaucoma, haptic breakage, and lens reproliferation into the pupillary space. Grating acuities were excellent for the pseudophakic eyes of the monkeys that received part-time occlusion therapy, but severely reduced in the pseudophakic eyes of the monkeys that received no treatment of the fellow eyes. An unexpected finding was that the pseudophakic eyes were consistently shorter than their fellow phakic eyes. The implantation of an intraocular lens into an infantile monkey eye can be associated with a variety of serious complications. Intraocular lenses custom-designed for infantile eyes may reduce the incidence of these complications. In eyes not developing these complications, excellent visual acuities can be obtained if the fellow eyes are occluded part-time.