Bilateral monocular diplopia secondary to occult diabetes mellitus

A 68-year-old man presented with transient, bilateral, vertical, monocular diplopia as an initial manifestation of diabetes mellitus. The diplopia was determined to be of lenticular origin, but was not found to be secondary to the usual refractive changes. Rather, it is presumed to be due to prismatic alterations caused by index of refraction differences within the crystalline lenses. It is not known what other factors relate to the development of this type of diplopia in the diabetic patient.