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Suresh Viswanathan, Laura J. Frishman, John G. Robson, James W. Walters; The Photopic Negative Response of the Flash Electroretinogram in Primary Open Angle Glaucoma. Invest. Ophthalmol. Vis. Sci. 2001;42(2):514-522.
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purpose. To determine whether the photopic negative response (PhNR) of the
electroretinogram (ERG) is reduced in patients with primary open angle
methods. ERGs were recorded with DTL electrodes from 62 normal subjects (16 to
82 years), 18 POAG patients (47 to 83 years) and 7 POAG suspects (46 to
73 years) to brief flashes (<6 ms), and also in a few subjects to long
(200 ms) red, full-field ganzfeld flashes delivered on a rod-saturating
blue background. At the time of ERG measurements, the intraocular
pressures of most of the patients were controlled medically. Visual
field sensitivities were measured with the Humphrey C24-2 threshold
test and optic nerve head cup-to-disc ratio (C/D) was determined by
binocular indirect ophthalmoscopy.
results. ERGs of normal subjects contained a slow negative potential following
the a- and b-waves, the PhNR, that increased slightly in latency with
age. The a- and b-wave amplitudes and implicit times of POAG patients
were similar to age-matched controls. In contrast, their PhNRs were
small or virtually absent. PhNR amplitudes were reduced even when
visual sensitivity losses were small, and were correlated significantly
(P < 0.05) with mean deviation (MD), corrected pattern SD
(CPSD), and C/D across the population of POAG patients whose MD losses
ranged from 1 to 13 dB, CPSDs from 0 to 11 dB and C/Ds from 0.6 to 0.9.
PhNRs of most POAG suspects also were small.
conclusions. PhNR amplitudes in POAG patients are smaller than those of normal
subjects. PhNR amplitudes are reduced when visual field sensitivity
losses are mild and become even smaller as sensitivity losses increase.
There is a potential role for the PhNR in early detection and possibly
in monitoring the progression of glaucomatous
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