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E Logean, B Falsini, CE Riva; Optic Nerve Head Blood Flow Responses Elicited Using Pattern Contrast Reversal Checkerboard Stimuli . Invest. Ophthalmol. Vis. Sci. 2002;43(13):3314.
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Purpose: To determine the blood flow (F) change at the neuro-retinal rim of the optic disk in response to pattern contrast reversal checkerboard stimulation of different contrasts and temporal frequencies. Methods: In 2 normal volunteers F was continuously measured using a near infrared laser Doppler flowmeter mounted on a fundus camera. Stimuli at a spatial frequency of 0.4 cycles/deg were displayed on a video monitor (field of 20 deg) and viewed by reflection at a dichroic mirror located between the subject eye and the camera objective lens. Stimuli were applied for approximately 50 sec. The stimulus-induced change in F (RF) was expressed as the % change in the mean value of F during the last 20 sec of stimulation relative to the mean over 20 sec of pre-stimulus F. The effect of contrast (6 to 94 % in 7 steps) was investigated at a temporal frequency of 8 Hz and that of temporal frequency (2 to 32 Hz in 5 steps) at a contrast of 94 %. Results: In both subjects, RF was significantly linearly correlated with the stimulus contrast (correlation coefficient r = 0.66 and 0.68, p<0.001). Expressed as a function of temporal frequency, RF displayed a band-pass behavior with a maximum at 8 Hz, similar to pattern ERG amplitude. Conclusion: This study demonstrates that the change in blood flow at the neuro-retinal rim in response to pattern contrast reversal checkerboard stimulation depends upon the contrast and frequency of the stimulus. Pattern stimuli being specific to activate retinal ganglion cells, they offer new opportunities in the study of visually evoked optic nerve vasoactivity in physiological and disease conditions, such as glaucoma.
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