Localizing functional damage in the neural retina of adolescents and young adults with type 1 diabetes.

Purpose: It is unknown which regions of the retina are most susceptible to damage by diabetes mellitus. We hypothesized that the standard and slow-flash (sf-) multifocal electroretinogram (mfERG) will localize retinal regions of greatest vulnerability.

Methods: A total of 55 adolescents and young adults with type 1 diabetes and without diabetic retinopathy (DR) or with mild nonproliferative DR and 54 typically-developing, age-similar control participants underwent mfERG and sf-mfERG testing. The amplitude and implicit time of the first order response of the standard mfERG and of three multifocal oscillatory potentials (mfOPs) of the sf-mfERG were compared between groups at the level of hexagons, quadrants, and rings using separate mixed model ANOVAs. Spatial mapping of the P values from post hoc pairwise comparisons illustrated patterns of retinal dysfunction.

Results: Delays in mfERG implicit times were evident across the tested retinal areas in the diabetes group. Delays in sf-mfERG implicit times were found at different eccentricities for each mfOP in the diabetes group. The greatest delays were noted in the periphery for mfOP1, in the midperiphery for mfOP2, and in the macular region for mfOP3. There were no significant group differences in amplitude for the mfERG and sf-mfERG protocols.

Conclusions: Delays in mfERG and sf-mfERG responses suggest that the inner retina is particularly vulnerable to diabetes. Localizing regions of early dysfunction will help guide future studies to examine early structural damage associated with DR.