In Reply.
—We thank Engerman for reading and responding to our recent publications in the Archives involving studies conducted in dogs fed galactose long-term and are happy to respond. As a pioneer in using the dog as an animal model for retinal changes associated with diabetes, Engerman has established the validity of both the diabetic and galactose-fed dog as appropriate models of human diabetic retinopathy. Clearly, the major biochemical link between the initial lesions observed in the diabetic dog and the galactose-fed nondiabetic dog is the aldose reductase-catalyzed conversion of excess intracellular glucose or galactose to their respective sugar alcohols. Based on Engerman's initial observations, we initiated a series of long-term studies in dogs.Our studies were designed to clarify the initiating lesions and progression of diabetic retinopathy through a combination of histologic and clinical techniques. These have documented the progression of retinal lesions from background retinopathy through advanced retinopathy