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Len Zheleznyak, Atanu Ghosh, Antoine Barbot, Geunyoung Yoon; Impact of refractive error on the meridional effect in peripheral vision. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):1727.
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© ARVO (1962-2015); The Authors (2016-present)
Optical blur in the peripheral retina is known to be highly anisotropic due to astigmatic wavefront aberrations and may play a role in emmetropization. In addition, peripheral vision is characterized by the meridional effect, a neural mechanism favoring radially-aligned gratings. The goal of this study was to investigate the impact of refractive error and anisotropic peripheral blur on the meridional effect for neural contrast sensitivity (CS) using an adaptive optics (AO) vision simulator.
An AO vision simulator was used to correct subjects’ wavefront aberrations at 0, 10 and 20 degree temporal retinal eccentricities. CS at 2 cpd was measured with horizontal and vertical grating orientations at each eccentricity in monochromatic light (630 nm). All vision testing was performed with a 5.8 mm artificial pupil using the right eye of 10 cyclopleged subjects (refractive error: -5.5 to +2.0 D). Subjects’ native aberrations were recorded at each eccentricity with a Shack-Hartmann wavefront sensor to quantify the modulation transfer function (MTF). Neural CS was defined as the ratio of the CS divided by the diffraction-limited MTF.
With increasing eccentricity, subjects’ native wavefront aberrations led to significantly higher contrast of horizontal gratings as compared to vertical gratings. The average ratio of horizontal to vertical MTF values at 2 cpd at 0, 10 and 20 degrees for emmetropes was 0.99+0.01, 1.22+0.19 and 1.50+0.32 and for myopes was 0.98+0.07, 1.20+0.29 and 1.55+0.39, respectively. The average ratio of horizontal to vertical area under the MTF up to 10 cpd at 0, 10 and 20 degrees for emmetropes was 0.95+0.05, 1.15+0.13 and 1.34+0.27 and for myopes was 0.94+0.18, 1.20+0.36 and 1.64+0.57, respectively. The meridional effect was observed for all subjects, with a greater magnitude at 20 degree eccentricity in the myopic group. The average ratio of horizontal to vertical neural CS at 0, 10 and 20 degrees for emmetropes was 1.04+0.09, 1.39+0.27 and 1.40+0.19 and for myopes was 1.00+0.25, 1.31+0.29 and 1.89+0.89, respectively.
The meridional effect was observed in all subjects in the absence of anisotropic blur, however, this effect was greater in myopic subjects. In addition, the change in meridional effect across the retina with respect to native aberrations was significantly correlated with refractive error.
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