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S.–H. Cheung, K.M. McHugh, G.E. Legge; Size and Location of the Physiological Blind Spot: Effects of Age and Target Size . Invest. Ophthalmol. Vis. Sci. 2005;46(13):4784.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Conventional perimetry typically assumes foveal fixation for referencing the visual field to retinal coordinates, but this is not practical for patients with central visual field loss. Referencing by the physiological blind spot (PBS) can be an alternative. Previous research has shown that the measured size and location of PBS changes with target size in conventional perimetry. Aging also affects sensitivity across the visual field. The current study measures the variability in the size and location of PBS with different target sizes in 2 age groups using a computer–based visual field test. Methods: Both eyes of 25 young (19 to 33 yr) and 10 older (50 to 65 yr) normally sighted participants were tested. Eight points along the border of PBS were located in the participant’s visual field by a bracketing method with a sequence of approximately 35 target detection trials. In each trial, the participant indicated whether or not s/he saw a black target briefly presented (250 ms) on a gray background at locations determined by the computer algorithm. The 8 border points were fitted with an upright ellipse to estimate the width and height of the PBS, and the horizontal (x) and vertical (y) coordinates of the PBS center. Three target sizes were used: 0.125°, 0.25° and 0.5° in diameter. Results: No significant age effect was found on the size and location of PBS. Average width and height of PBS decreased from 6.42° to 5.12° and from 9.29° to 6.26° respectively as target size increased from 0.125° to 0.5°. Target size had no significant effect on the location of the PBS center. Average x and y coordinates of the PBS center were 15.6° temporal and 1.5° below the horizontal meridian in the visual field. Standard deviation (across individuals) of the x and y coordinates in different conditions ranged from 0.63° to 1.02°. Conclusions: Target size affects only the size but not the location of PBS. Individual variation in the location of PBS within the population (approximately 1°) sets the precision of using PBS as a reference for field tests.
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