BACKGROUND True diabetic cataracts are rare and have been infrequently reported in the literature. They often have a rapid onset, appear as white punctate or stellate opacities, and can resolve without treatment. The following case report describes reversible cataracts as a complication of diabetes mellitus with photodocumentation. METHODS A fifty-two-year-old white male was examined 5 days following the initiation of insulin therapy for severe hyperglycemia. The patient complained of sudden onset visual disability and extreme glare. He was given a complete ophthalmic examination and was monitored for 3 months. RESULTS The patient was diagnosed with acute posterior subcapsular cataracts secondary to diabetes mellitus. Within the following 7 weeks the lens opacities resolved without intervention. During this time period, the patient also exhibited a transient hyperopic refractive change. CONCLUSIONS The transient nature of the diabetic cataract is related to changes in lens hydration. Biochemical changes that occur as a result of rapid changes in blood sugar cause the lens fibers to swell, forming a cataract. The same mechanism is responsible for the hyperopic refractive change. Patients presenting with this condition have been shown to stabilize within 3 months.