Visual Evoked Potential: A Tool for Detection of Preretinopathy and Prognostication in Diabetes OC10-OC12
Dr. Anjamparuthikal Aboobekar Haris,
Flat 8B, Clearway Colossal Vennala, Ernakulam, Kottayam-682028, Kerala, India.
Introduction: Diabetic Retinopathy (DR) is a common complication of Diabetes Mellitus (DM) that affects retinal blood vessels. It is the leading cause of blindness in the age group of 20 to 74 years despite the fact that visual loss due to DM may be preventable by glycaemic control. Unfortunately, in many cases, the patient is asymptomatic until it is too late for effective treatment. Diagnosis of retinal changes and determination of prognosis can be done by studying the pattern Visual Evoked Potential (VEP).
Aim: To investigate the ability of VEP in detecting preclinical neuro-degenerative changes in patients with diabetic preretinopathy by studying changes in VEP, in terms of P100 wave latency in diabetic patients without retinopathy.
Materials and Methods: This study included 35 diabetic patients without retinopathy and 35 non-diabetic controls. They were selected from patients attending the outpatient Department of Ophthalmology for the screening of DR. Controls were selected from the bystanders of the patients who came to the Ophthalmology outpatient department. VEP study was done in subjects and controls and the latency of P100 wave was analysed. P100 wave of VEP was chosen as it was the most reliable with less inter-subject variability. Mean P100 wave latency of both groups were compared and analysis was done checking for any variation in P100 wave latency with respect to the duration of diabetes and the control of diabetes. Data was analysed using SPSS-16. Studentâ€™s t-test was applied when two groups were compared while ANOVA (Analysis of Variance) test was applied for multiple group comparisons. The p-value <0.001 is considered significant in this study.
Results: There was a significant prolongation of P100 wave latency in diabetics without retinopathy. It was also found that there was positive correlation between prolongation of P100 wave latency and the duration of diabetes. In patients with good diabetic control the prolongation was less, as compared to those with poor diabetic control.
Conclusion: Analysis of P100 wave of VEP is helpful in the detection of diabetic preretinopathy changes. This could be a better tool for the detection of very early retinal changes before any clinical evidence of retinopathy has set in. Better glycaemic control by means of exercise, diet or change or increase in dose of medicines could prevent the early development of retinopathy if done at this stage.