Induction of subcapsular cataracts in cynomolgus monkeys by echothiophate

Sixteen eyes of 13 cynomolgus monkeys were treated topically twice daily with echothiophate iodide. The dosages were increased gradually over several weeks to plateau levels ranging from 125 to 500 mug daily. The opposite eyes of the ten unilaterally treated monkeys received a control solution (DILUENT) identical save for the absence of echothiophate. All 16 echothiophate-treated eyes developed posterior subcapsular cataracts and 15 developed anterior subcapsular cataracts. The lenses in all ten DILUENT-treated eyes remained clear. The cataracts in the echothiophate-treated eyes strongly resembled those attributed to cholinesterase inhibitors in humans. They were first noted from 2 1/2 to 14 weeks after beginning echothiophate treatment. Prior total iridectomy caused a more rapid progression and/or greater severity of lens changes. Higher echothiophate dosages caused the cataracts to appear more rapidly.