Events leading to the onset of various ocular complications are being investigated. Specifically, the role of the enzymes aldose reductase and aldehyde reductase in the onset and progression of retinopathy, cataract, keratopathy, pupil function changes, and iris and ciliary process structure changes associated with diabetes and galactosemia are being studied. In addition, methods for either delaying or preventing the onset and progression of these complications through the pharmacological control of these enzymes are being developed. Events leading to the formation of several types of cataracts are also being investigated as are methods for controlling the onset of these cataracts through pharmacological intervention.