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Alberto Colotto, Benedetto Falsini, Tommaso Salgarello, Giancarlo Iarossi, Maria Elena Galan, Luigi Scullica; Photopic Negative Response of the Human ERG: Losses Associated with Glaucomatous Damage. Invest. Ophthalmol. Vis. Sci. 2000;41(8):2205-2211.
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purpose. To evaluate in glaucomatous eyes the photopic electroretinogram (ERG)
negative response (PhNR), a component that follows the b-wave peak and
is thought to be correlated with inner retinal activity.
methods. Eleven patients with open-angle glaucoma (OAG) and moderate field loss
(Humphrey 30-2 [Humphrey Instruments, San Leandro, CA] mean deviation≤
−6 dB), eight with ocular hypertension (OHT), and eight age-matched
normal subjects were tested. Optic discs of patients and control
subjects were evaluated by confocal scanning laser ophthalmoscopy. ERGs
were recorded to long-duration stimuli (250 msec) of photopic luminance
(78 candelas [cd] /m2), presented in the macular region
(12° × 12° field size) on a steady, adapting background.
Amplitudes of the a-wave and b-wave and the PhNR were measured. Pattern
reversal ERGs to 30-minute checkerboards were also recorded from
patients and control subjects.
results. Compared with control subjects, patients with OAG showed reduced PhNR
(average reduction: 62%, P < 0.01), but normal a-
and b-wave amplitudes. In patients with OHT, PhNR and a- and b-wave
amplitudes did not differ from control values. In individual patients
with OAG, PhNR amplitudes were correlated positively with pattern ERG
amplitudes (r = 0.80; P < 0.01) and
central (12°) perimetric mean deviations (r = 0.68; P < 0.05) and negatively with cup-to-disc area
ratios (r = −0.79; P < 0.01) and
cup shape measures (r = −0.78; P <
conclusions. Similar to that found in monkeys with experimentally induced glaucoma,
the PhNR is selectively altered in human glaucoma. The correlation
between PhNR losses and clinical parameter abnormalities suggests that
this component depends on inner retina integrity and may be of clinical
value for detecting glaucomatous damage.
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