Multifocal electroretinography (mfERG) in insulin dependent diabetics with and without clinically apparent retinopathy.

Purpose: To study the retinal function, using multifocal electroretinography (mfERG), in diabetic patients with mild and moderate retinopathy, and in diabetics without clinically apparent retinopathy.

Methods: Thirty-one patients with insulin dependent diabetes mellitus, eleven without any clinically apparent retinopathy, twelve with mild retinopathy and eight with moderate retinopathy, were studied. Ophthalmologic examination included testing of visual acuity, fundus inspection, fundus photography and mfERG. Sixteen subjects without eye disease and with normal visual acuity were used as controls for comparison of mfERG results.

Results: The patients had a mean diabetes duration of 23+/-9 years. All patients and controls had a visual acuity of 1.0. In the first order component of the mfERG there were significantly higher ring amplitudes in the diabetics compared to the controls (p=0.001). In the second-order component of the mfERG, there was a significantly prolonged implicit time in the diabetics who had retinopathy compared to those without any retinopathy (p=0.026). The third positive waveform in the ring amplitudes of the second-order component, were absent in 15/31 of patients with diabetes, but were easily distinguished in all the controls; p<0.001. This waveform was absent in 6/11 patients without retinopathy.

Conclusion: Patients with insulin dependent diabetes have specific abnormalities in both the first and the second-order component of the mfERG. These abnormalities reflect both vascular changes in the retina and, probably simultaneously, pathology in inner retinal function, also in the diabetics without clinically apparent retinopathy.