The international systems for classification of diabetic retinopathy and age-related macular degeneration, two major blinding diseases, were adapted from systems from two US clinical trials: the Early Treatment Diabetic Retinopathy Study and the Age-Related Eye Disease Study. These procedures evolved from exploratory efforts at the University of Wisconsin - Madison. This talk will examine the approaches used to develop such disease classifications, for the purpose of assessing how computerized image processing might be used to extend, and perhaps replace, manual evaluation of ocular images.