Abstract
Purpose: :
Evaluate full-field electroretinogram findings in patients with isquemic diabetic retinopathy and correlate with visual prognosis
Methods: :
A group of 30 patients with pre-proliferative and proliferative diabetic retinopathy without previous photocoagulation had retinal function evaluated by full-field electroretinography according to the International Society for Clinical Electrophysiology of Vision standard protocol. The responses analyzed were: scotopic rod response, scotopic maximal response, scotopic response for oscillatory potentials, photopic single-flash response and photopic 30Hz flicker for cone response.
Results: :
30 eyes of diabetic retinopathy group and 20 eyes of subjects without diabetes were randomly selected. Mean age of diabetic retinopathy group (± 1 SD) was 53.56 ± 9.91 years. The mean time of the diagnosis of diabetes was 13.96 years. Mean values amplitude for rod response was 184.23 ± 62.29 µV, 322.47 ± 93.76 µV for maximal response; 59.02 ± 38.04 µV for oscillatory potentials; 84.15 ± 38.19 µV for single-flash cone response and 59.43 ± 23.55 µV for light adapted 30 Hz flicker response. Mean values b-wave implicit time was 97.48 ± 11.02 ms for rod response; 35.81 ± 6.02 ms for single-flash cone response and 36.18 ± 6.39 ms for 30 Hz flicker response. No statistically difference was found between the groups for rod response, maximal response, cone response and amplitude of light adapted 30 Hz flicker response by gender. Statistically significant difference (p-value < 0,001) was found between the diabetic retinopathy group and the normal group in oscillatory potentials and also b-waves implicit times for rod response, cone response and flicker response. Diabetic patients with more severe condition, as vitreous hemorrhage and tractional retinal detachment (5 patients) had lower responses for oscillatory potentials (4 patients), maximal response (4 patients) and cone response (5 patients) when comparing to normal group.
Conclusions: :
The oscillatory potentials derive from the inner plexiform layers involving bipolar cells, amacrine cells and ganglion cells which are also involved in the physiopathology of the diabetic retinopathy. These findings suggest that changes in the oscillatory potentials and b-waves implicit times in the diabetic retinopathy may be the first sign of injury of the retina in this disease. Furthermore, an increased degree of loss in amplitude of oscillatory potentials may be a distinctive feature of diabetic retinopathy with poor visual prognosis.
Keywords: electroretinography: clinical • diabetic retinopathy