Weanling rats given a diet containing 300 mg/100 gm para-chlorophenylalanine develop characteristic anterior and posterior lens changes. Approximately 35% continue to complete cataract development and/or a peculiar retractile lens line. Including phenylalanine 1% or 5% to the same diet protects rats against mature cataracts. However, minor lens changes and the refractile line still appear. The absence of any ocular toxicity in monkeys treated with this agent at 300 mg/kg/ day for one year suggests a specific effect only in rats. Mature rats are more resistant to this cataractogenic effect. These lesions do not regress within one year after drug withdrawal.
Gralla EJ, Rubin L. Ocular Studies With Para-chlorophenylalanine in Rats and Monkeys. Arch Ophthalmol. 1970;83(6):734-740. doi:10.1001/archopht.1970.00990030734012