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T. Sugawara, S. Mizunoya, S. Yamamoto, J. Uehara; Separation of Photopic Negative Responses and I-Wave by White-on-White Stimuli. Invest. Ophthalmol. Vis. Sci. 2008;49(13):3802.
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To record the photopic negative response (PhNR) and separate the PhNR from the i-wave (off-component) with a long-duration white stimuli presented on a white background (W/W) in normal subjects and patients with unilateral optic atrophy.
PhNRs were elicited by W/W stimuli using a contact lens electrode with built-in LEDs. Ten normal volunteers and 10 patients with unilateral optic disc atrophy due to glaucoma and traumatic and ischemic optic disc neuropathy were studied. To separate the i-wave from the PhNR, the stimulus durations of 3, 5, 10, and 16.4 msec were used. The ratios of the amplitudes of the affected eye/fellow eye ratios (AF/FE) of the PhNRs elicited by 3 msec and by 10 msec stimuli were calculated in cases of unilateral optic atrophy. The mean deviations (MDs) were determined with a Humphrey field analyzer, and the MDs were >10 dB between the AE and FE in these cases.
In normal subjects, the peak latency of the i-wave increased and the PhNR was more clearly separated from the i-wave as the stimulus duration increased. The photopic ERG waveform appeared deformed by 16.4 msec stimuli, and thus 10 msec stimuli were selected to record the PhNRs. The AF/FE ratios of the PhNR amplitude were 0.72 to 3 msec stimuli, and 0.58 to 10 msec, and this difference was not significant. However, the PhNR was more evident to the 10 msec stimuli even in cases of unilateral optic atrophy.
The PhNR can be elicited by 10 msec W/W stimuli with a good separation of the i-wave under routine clinical recording conditions.
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