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Gili Ferman-Attar, Ygal Rotenstreich; The Diagnostic Significance of the ERG a/b Ratio in Retinal Disorders. Invest. Ophthalmol. Vis. Sci. 2011;52(14):6073.
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© ARVO (1962-2015); The Authors (2016-present)
To investigate the electroretinogram (ERG) a-wave to b-wave (a/b) ratio in retinal disorders including retinitis pigmentosa (RP), cone-rod dystrophy (CRD) and congenital stationary night blindness (CSNB) in comparison to ocularly healthy individuals.
In a retrospective study the ERG records of both eyes of 128 subjects, including 53 RP patients, 12 CRD patients, 9 CSNB patients and 50 normal subjects were examined. All ERG testing were performed according to ISCEV standards protocol. ERG a-wave to b-wave ratio was calculated for scotopic condition in three incremental light intensities stimuli (2.44cd-s/m2, 23.5cd-s/m2, and 252cd-s/m2) and for photopic condition in two incremental light intensities (2.44cd-s/m2 and 7.8cd-s/m2). The averages of the a/b ratios were compared between each group of subjects under each illumination.
The average ERG a/b ratios for RP, CSNB and CRD patients and normal subjects are presented in the table. The average photopic and scotopic ERG a/b ratios in the RP and CSNB groups were significantly higher than that of normal subjects for all light intensities stimuli (P<0.001). The scotopic a/b ratios of the CSNB group was higher than the RP group for the dimmer light intensities (P<0.01). The scotopic and photopic a/b ratios of the CRD group were statistically higher from normal subjects in response to the brighter light intensities (P<0.05). The scotopic a/b ratio in RP patients was significantly higher than in CRD patients under the dimmer light intensity (P<0.05).
There is significantly higher a/b ratios in RP, CRD and CSNB as compared to normals for stimuli of different light intensities. In CSNB the inner compared to outer retina was found to be more affected than the RP and CRD patients in the scotopic condition. In the RP patients the inner retina was found to be more affected than the outer retina compared to CRD patients in the scotopic condition. These measures can help to elucidate the amount of pathology in the inner versus the outer retina in different types of retinal dystrophies.
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