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S.R. Chamot, P.W. Ferrez, I. Questel, G.N. Lambrou, C.E. Riva; Time-Course and Spatial Distribution of the ONH Blood Flow Response to Diffuse Luminance Flicker in Monkeys . Invest. Ophthalmol. Vis. Sci. 2003;44(13):360.
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Purpose: To investigate the time-course, magnitude and spatial distribution at the optic disc rim of blood flow changes induced by diffuse flicker stimulation. Methods: In one eye (OD) of each of 12 anesthetized cynomolgus monkeys, the blood velocity (Vel), volume (Vol) and flow (F) at the rim of the optic disc were measured by laser Doppler flowmetry in response to 15Hz diffuse luminance flicker (30° field centered at the disc, 2100 Lux, 100% modulation). The time course of Vel, Vol and F for a 30-s stimuli was recorded at various sites (8 - 15 around the clock) of the rim. The magnitude (RVel, RVol and RF) and time constant of the responses were determined. In 4 animals, the coefficients of variation were determined based on 10 successive recordings. Results: In all animals, Vel, Vol and F increased significantly during flicker (ANOVA, p < 0.001). Most of the increase occurred within 10s after flicker onset. The group average RVel, RVol and RF (N = 12) amounted to 24 ± 8 (mean ± standard deviation), 10 ± 12 and 37 ± 14%, respectively. The reproducibility coefficient range of RVel, RVol and RF was 17 - 58%, 44 - 94% and 18 - 34%, respectively. RF was maximum (28 ± 13%) at 10 o'clock (temporal side) and minimum (9 ± 6%) at 1 o'clock (nasal side). Globally, the response was higher temporally than nasally (ANOVA, p < 0.001) but no superior versus inferior difference was observed (ANOVA, p = 0.2). Conclusions: Reproducible flicker-induced blood flow responses can be obtained in anesthetized normal monkeys. These responses have a time-course and magnitude that are comparable to those recorded in humans. The larger RF measured at the temporal rim could be due to a number of factors such as axons' distribution and diameter.
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