Flash-Electroretinographic Investigation of Retina Dysfunction in Subjects With Multiple Sclerosis

Abstract

It is interesting question which factors play role on processing of visual dysfunction by effecting retinal layers in MS. Although the main pathological changes occurring in the visual system of multiple sclerosis patients can be found in the optic nerve, but retinal abnormalities have also been reported. The ERG ensures possibility of cantitative and sensitive assessment in evaluating of retinal dysfunction. In our study we investigated retinal function in MS patients with history of visual impairment. The aim of our study is to investigation whether of correlation exists between functional optic nerve and retinal impairment in MS patients. Fifteen patients -thirty eyes- with a diagnosis of definite MS -8 men and 7 women- and 12 age matched control subjects -twenty two eyes- were included in the study. Skin neddle electrodes and corneal lens electrodes were used for all the recordings. F-ERG was recorded by a of white flash stimuli of light with 1 joule at 2 Hz flicker to both eyes in a dark room. A wave with positive component, b wave with negative component and a-b peak-to-peak amplitude were calculated. There was no difference in "a "wave amplitude and latency between eyes of patients and normal subjects. Neverthleses the mean value of second wave latencies in group with MS were significantly prolonged (p<0.05). The F-ERG in 20% of the patients with satisfactory recordings was significantly abnormal in the affected subjects according to normal values. On the other hand the VEPs results were abnormal in 87.5% of patients with MS. There was positive correlation ERG with duration of illness (p=0.02), VEP amplitudes (p=0.001) and very strong correlation with VEP latencies (p=0.001). These results provide neurophysiological evidence that retinal damage is not due loss of myelin but is an early feature of demyelinating optic neuritis. The damage prefentially affects the retinal elements associated with the generation of the "b" wave of the ERG , probably the glial cells of Müller.