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S. Machida, Y. Toba, A. Ohtaki, Y. Gotoh, M. Kaneko, D. Kurosaka; Photopic Negative Response of Focal Electoretinogram in Glaucoma. Invest. Ophthalmol. Vis. Sci. 2008;49(13):6105. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
To determine whether a significant correlation exists between the photopic negative response (PhNR) of the focal electoretinogram (fERG) and the morphology of retinal neurons or the retinal function in glaucomatous eyes.
Seventy-three eyes of 38 patients with open angle glaucoma and 31 normal eyes were studied. The fERGs were elicited by stimuli of 165 cd/m2 on a background of 6.9 cd/m2. The stimulus duration was 10 ms and the spot size was 15 degrees. The recordings were made at the macula region and the supero-temporal and infero-temporal regions of the macula. The structure of the optic nerve head and retinal nerve fiber layer thickness (RNFLT) corresponding to each retinal area were evaluated by scanning laser ophthalmocopy and laser scanning polarimetry, respectively. The mean of the total deviation was obtained by static visual field testing using the 10-2 and 24-2 programs. The optimal cut-off amplitudes of the PhNR that discriminated glaucomatous eyes were obtained from the ROC curves.
The amplitudes of the b-waves and oscillatory potentials were not significant different between normal and glaucomatous eyes in all retinal areas. In contrast, the amplitudes of the a-wave (P<0.05) and PhNR (P<0.0001) were significantly reduced in glaucomatous eyes. The PhNR amplitudes were linearly correlated with the corresponding RNFLT and with the areas of the rim and cup in both retinal regions (r=0.43 to 0.56, P<0.0001). The PhNR amplitudes were significantly correlated with the decrease of the mean total deviation obtained from the corresponding visual field (polynominal fit, r=0.57 to 0.63, P<0.0001). When the optimal cut-off values were used, the sensitivity and specificity of the PhNR amplitude were 94.9 and 87.1%, respectively.
The reduction of the PhNR represents a local decrease in the retinal sensitivity of the neurons in glaucomatous eyes. The high sensitivity and specificity suggest that the focal ERGs can be used as a functional measure to detect functional loss in glaucomatous eyes.
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