The fast oscillation of the EOG in diabetes with and without mild retinopathy

There is ample evidence that the retinal pigment epithelium (RPE) is affected in diabetes, and that epitheliopathy may be among the early changes. The fast oscillation (FO) of the electro-oculogram (EOG) reflects the activity of the RPE, most notably the mechanisms responsible for pumping fluid and ions in the retina-to-choroid direction. The FO was measured in three groups of subjects: normal controls, eyes of diabetic individuals with no evidence of retinopathy, and eyes of diabetics with mild background retinopathy. FO amplitude, light trough voltage and dark peak voltage in both diabetic groups were all significantly reduced, independent of retinopathy status. The peak to trough ratio was unaffected. These changes, reduced voltages and smaller light-evoked voltage changes, are consistent with a decrease in the resistance of the RPE and may relate to accumulation of fluid in the sub-retinal space.