Electroretinogram and Visual Evoked Potentials in Patients with Type ll Diabetes Mellitus

Background: Retinopathy is a severe and common complication of diabetes. The pathology seems to be characterized not only by the involvement of retinal micro vessels but also by a real neuropathy. Before the onset of micro vascular lesions, the retina of the eye undergoes subtle functional changes that are not detectable by fundus photography. Electrophysiological investigations allow a more detailed study of the visual function. These techniques are safe, repeatable, quick, and objective. Objective: To study pattern electroretinogram (PERG) and pattern reversal visual evoked potentials (PRVEP) in type 2 diabetic patients without diabetic retinopathy (DR) or with mild non-proliferative DR (mNPDR) to detect changes by comparing with those of healthy control. And to assess the correlation of the parameters with diabetes duration and the level of Glycosylated Haemoglobin A1c (HbA1c). Materials and Methods: It was a cross-sectional study, included two groups (diabetic patients and the healthy). Age range was preset at 40-65 years. For all the participants, a detailed clinical history was collected, a comprehensive ophthalmic examination and thorough blood investigations were performed, then {PRVEP (60', 15'), PERG} were recorded and (waveform, peak time, amplitude) of tests components were analyzed. Results: Mean (P100, N135) peak times of PRVEP were statistically significantly delayed in (50) eyes of type 2 diabetics without DR when compared to (36) eyes of control (p-value<0.01), abnormalities in waveforms like (double peaks, broad peak) were also observed in diabetics. There were alterations in other parameters (amplitudes of PRVEP, peak times and amplitudes of PERG) but the changes were not statistically significant. No statistically significant changes were found in (6) eyes of diabetic patients with mNPDR. No statistically significant correlation was obtained between diabetes duration or the level of HbA1c and delay of peak times or reduce amplitudes in patients. Conclusions: Electrophysiological tests are sensitive and useful investigations for the early identification of visual dysfunctions before the development of overt retinopathy in type 2 diabetics. PRVEP is more sensitive than PERG to monitor alterations and it may be sufficient to screen the patients in this stage.