Abstract
The characteristics of the on- and off-responses in the human diabetic retina by a “long-duration” multifocal electroretinogram (mfERG) paradigm were investigated. Changes in the retinal antagonistic interaction were also evaluated in the early stage of diabetes mellitus (DM). Twenty type II diabetic patients with no or mild non-proliferative diabetic retinopathy (NPDR) and twenty-one age-matched healthy controls were recruited for “long-duration” mfERG measurements. A 61-hexagon mfERG stimulus was displayed under two chromatic conditions (white/black and blue/black) at matched luminance. The amplitudes and implicit times of the on-response components (N1, P1 and N2) and off-response (P2) components were analysed. The blue stimulation generally triggered greater mfERG amplitudes in P1, N2 and P2 (p<0.05) than those from white stimulation in both control and diabetic groups. The diabetic group showed significantly greater N2 amplitude than the controls under white stimulation in mid-retinal regions (Rings 2 and 4) (p<0.05). When the stimulus was changed from white to blue, the diabetic group showed a smaller percentage change in N2 amplitude than the controls in peripheral retinal region (Ring 5) (p<0.02). When a stimulus is changed from white (broad-band spectral stimulation) to blue (narrow-band spectral stimulation), a decrease in the involvement of lateral antagonism would be expected. The larger amplitude of the on-response component (N2) in the diabetic patients suggested an imbalance of lateral antagonism, and the lesser percentage change of N2 amplitude in the diabetic group may indicate an impairment of the cross-talk at the middle retinal level in early stages of DM.
Highlights
Diabetic retinopathy (DR) is an ocular vascular complication associated with diabetes mellitus (DM) which has a rapid increase of incidence in Asia [1]
Among the diabetic subjects, whose fundus photos were graded by the masked retinal specialist, 6 out of 20 were classified as “mild non-proliferative diabetic retinopathy (NPDR)”, 2 as “no DR”, and 12 as between “mild NPDR” and “no DR” because only trace defects was found on the fundus photos and could not be defined as tiny microaneurysms
As 14 out of 20 diabetic subjects had the conditions below mild NPDR, it was hard to further subdivide into smaller local groups to compare the multifocal electroretinogram (mfERG) results with the local fundus vascular changes
Summary
Diabetic retinopathy (DR) is an ocular vascular complication associated with diabetes mellitus (DM) which has a rapid increase of incidence in Asia [1]. DR is one of the leading causes of blindness among the working population [2]. It is proposed that damage of the vascular endothelium and pericytes, as well as the acceleration of cellular apoptosis, contribute to vascular leakage in the retina and the clinically visible signs of DR [3]. Functional and structural deficits in the eye have been found in diabetic patients. Colour discrimination ability was shown to deteriorate with or without DR [4,5,6].
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