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J Vernon Odom, Hoover Chan, Radouil Tzekov; Effect of Diopsys NOVA LCD Display Luminance Changes on the Steady-State Pattern Electroretinogram (PERG). Invest. Ophthalmol. Vis. Sci. 2019;60(9):2491.
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Stimuli for pattern electroretinograms (PERGs) are frequently presented on LCD monitors that have a luminance change at pattern reversal (luminance artifact). We determined the contribution of the luminance artifact to steady-state PERG.
11 subjects were tested; 6 male and 5 female; ages 23 to 50 years. All subjects had visual acuity correctable to 20/30 or better.The Diopsys NOVA system provided stimulation and recording. The stimulus consisted of a square field subtending 24 x 24 deg. at 24 inches. The standard stimulus consisted of a 64 square-wave horizontal bars (i.e. 32 cycles; 1.3 cpd) reversing at 15 rps. Mean luminance was 112.3 cd.m-2. Contrast was 85%. A luminance reduction of 0.92 cd.s.m-2 and 7.8 ms duration generated an observable flicker at each reversal. Two control stimuli were also tested. A no-pattern-visible stimulus (referred to as no-pattern) consisting of 1024 horizontal bars each 1 pixel high (i.e. 22 cpd) with the same mean luminance, nominal contrast and flash strength and a no stimulus condition (monitor turned off) were also presented. Testing occurred on two occasions at least one week apart for each subject. Averaging 100 artifact-free time periods of 200 milliseconds in duration obtained the PERG waveform . Testing time lasted approximately 25 seconds per average during which the subject was allowed to blink freely. High and low pass filters were 0.5 and 30 Hz respectively. The averaged PERG results were Fourier analyzed and magnitude analyzed
The results showed a clearly recordable PERG with a mean magnitude of 1.51 µV that was significantly greater than the no-pattern control condition (p<0.001) while the no-pattern control condition did not differ from monitor off condition (p>0.5).
Under the stimulus and recording conditions presented, the flicker associated with each reversal had no measurable effect on the recorded PERG. We did not examine the reason 15 Hz flicker was not recordable, but several possibilities exist. The higher luminance of the background may adapt the response to the negative flicker, or different retinal pathways with slightly different timing may cancel out in the first harmonic of luminance flicker (cf. Odom et al. Optometry and Physiological Optics, 1992).
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
Magnitude under 85% contrast, diffused, and no stimulus conditions, repeated twice one week apart.
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