Abstract
Purpose:
Retinal image quality in the peripheral visual field is thought to contribute to visual control of eye growth and myopia progression. The contribution of spherical aberration is of particular interest because accommodation typically causes a sign reversal that can have a large impact on accommodative lag and image quality. Thus we aimed to measure spherical aberration in central and peripheral visual field as a function of accommodative demand.
Methods:
A scanning Shack-Hartmann wavefront aberrometer (Wei & Thibos, 2010 Opt Express 18: 1134) was employed to measure ocular aberrations along 37 different lines-of-sight over the central 26 degree visual field in 30 seconds. Aberrations were measured sequentially using light reflected from a small spot produced on the fundus by an incident probe beam that pivoted around the center of the eye’s entrance pupil. Scanning mirrors that steered the incident probe beam also de-scanned the reflected light into a fixed wavefront sensor. Accommodation was stimulated over the range 0-6D by an acuity target in a Badal configuration. Target and room illumination was reduced to promote pupil dilation. Spherical aberration coefficients C40 (primary) and C60 (secondary) for elliptically foreshortened pupils (Wei & Thibos, 2010, Optom Vis Sci 87, E767-777) describe ocular wavefront error over a fixed, 6mm circle concentric with the eye’s pupil.
Results:
Primary spherical aberration varied significantly in sign and magnitude over the visual field but always changed in the negative direction during accommodation. For 6D of accommodation, changes in C40 ranged from 0.1 to 0.4 microns RMS, with larger values occurring for larger eccentricities. These changes are much larger than the population mean values reported previously (Mathur, Atchison, & Charman, 2009. J Vis 9, 20 21-11). This discrepancy may be due to several factors, including individual variation, duration of measurement sequences, and the problematic interpretation of aberration coefficients obtained over elliptical pupils. Unlike C40, secondary spherical aberration C60 was typically positive and did not vary significantly with accommodation
Conclusions:
Spherical aberration in peripheral vision changes significantly during accommodation, which may provide a potential clue for visual control of eye growth.
Keywords: 626 aberrations •
404 accommodation