Visual Evoked Potential in Patients of Type 2 Diabetes Mellitus with and without Diabetic Retinopathy

Diabetes mellitus is a leading public health care problem, with increasing incidence and its long term complications. Diabetic retinopathy is a common complication of DM that affects retinal blood vessels. Unfortunately, in many cases the patient is asymptomatic until it is too late for effective treatment. VEPs are produced by electrical activity of the visual cortex in response to light or pattern stimulation of the eye. It can detect functional loss in the visual pathway from retina to the visual cortex.

The aim of the study is to compare latencies and amplitudes of P100 waveform of VEP in diabetic and control subjects and to determine whether changes in VEP response occur before clinically evident diabetic retinopathy on fundus examination.

PRVEP was recorded in 60 diabetic patients including 30 patients without any retinopathy and 30 others with non-proliferative diabetic retinopathy(NPDR), and compared to 60 age and sex matched normal non diabetic healthy controls. VEP was recorded using pattern reversal stimulation with RMS EMG MARK II machine. P100 wave latencies and amplitudes were obtained in all the subjects.

Our results show significantly prolonged P100 latencies of VEP’ s in Type 2 DM patients and DR patients when compared to controls. The difference between diabetics with retinopathy and controls were significant in terms of P100 amplitude. However, there was no significant difference observed in the P100 amplitudes of VEP’ s in Type 2 DM patients without retinopathy when compared to controls.

The present study clearly shows that changes in VEP may be detected in diabetics before the onset of retinopathy. Thus, a routine VEP assessment should be recommended to all the diabetic patients, for the early identification of visual defects and for early and proper management of the disease.