Diabetic Retinopathy & Medical Retina - aioseducation

70th AIOC Proceedings, Cochin 2012
Evaluation of Pattern Erg, Ph Nr, Osc. Potential
and 30Hz Flicker in Diabetic Retinopathy
Dr. J.L.Goyal, Dr. Babita Karothia, Dr. Ritu Arora, Dr. Basudeb Ghosh
It has been reported that after 20 years of diabetes, more than 90% of patients
with type I and about 60% with type II diabetes will have some form of
retinopathy1. In DR, the primary pathogenesis is generally believed to involve
the retinal vessels. However, it has become increasingly clear that diabetic
retinopathy affects not only retinal vasculature, but also neural elements
of the retina. 2,3,4 Retinal ganglion cells (RGC) are particularly susceptible to
glutamate excito-toxicity, which plays an important role in ischemic diseases
like diabetic retinopathy. 5
Several studies, over the years, have confirmed that Electrophysiology is
capable of detecting early biochemical and functional abnormalities of the
retina before changes are evident with either fluorescein angiography or
by direct ophthalmoscopy. 6,7 Thus, it can occupy a key position in assessing
treatment directed to preventing or slowing down these subclinical processes.
Design: Prospective, Cross-sectional study.
MATERIALS AND METHODS
In this study 60 eyes were selected. These included 20 eyes of diabetics without
NPDR, 20 eyes of diabetics with NPDR and 20 eyes in the control group. Patients
with history of diabetes of at least 2 years’ duration with best corrected visual
acuity of at least 6/60 were included. Controls consisted of age- matched non
diabetic individuals without any anterior or posterior segment abnormalities.
Electrophysiological tests were performed using Medelec Synergy System
with Ganzfeld Stimulator, in accordance with the latest ISCEV guidelines.
Amplitude and latency of different waves were compared amongst the 3
groups.
Placement of Electrodes:
ERG waves were recorded using the following 3 electrodes:
Ground electrode – surface Ag /Agcl disc electrode over the forehead
Reference electrode – surface Ag /Agcl disc electrode over lateral canthus
Active Electrode
1) Contact lens jet electrode over the cornea for PhNR, Ops and 30 Hz
Flicker.
2) Gold foil electrode placed over the inferior limbus for Pattern ERG.
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