CHARACTERIZATIONS OF FLASH INTENSITY-SERIES ELECTRORETINOGRAPHY IN DOGS WITH DIABETIC CATARACT

Abstract

Diabetes mellitus is the common endocrine disease in humans and in dogs. Visual impairment in diabetic patients is caused by diabetic retinopathy. Dogs with diabetic mellitus rapidly develops bilateral cataract, leading to blindness. This study was to see the electroretinographic characteristics in response to the full-field intensity-series white flash electroretinography in diabetic dogs. Fifty dogs (46 diabetic eyes and 45 non-diabetic eyes) with late stage cataract were included in this study. Under general anesthesia, scotopic and photopic electroretinographic responses were recorded using JET lens as a corneal contact lens electrode and a needle as a reference electrode. In diabetic dogs, mean a- and b-wave responses were significantly reduced in amplitude (p<0.05) at all light stimuli. Negative ERG responses were found in some diabetic eyes. Mean oscillatory potential in diabetic dogs was significantly altered (p<0.05). Significant reduction of the mean flicker amplitude was also observed (p<0.05). In diabetic dogs, significant decrease of electroretinographic amplitudes not only is an indicative of reduction of neuronal signal, but also metabolic demand in ischemic retina. Negative ERG responses that were found in some canine diabetic eyes may possibly be related to severe inner retinal ischemia from central retinal occlusion. Changes of the oscillatory potential reflects early impairment of bipolar and ganglion cells. Flash electroretinography is an essential and sensitive diagnostic tool for early assessment of retinal function in diabetic dogs prior to cataract surgery consideration.