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Abhiram S. Vilupuru, Austin Roorda, Adrian Glasser; Changes in ocular aberrations during accommodation in rhesus monkeys. Journal of Vision 2002;2(10):123. doi: 10.1167/2.10.123.
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Purpose: The availability of information on changes in aberrations during accommodation across the entire lens diameter is limited because the iris obscures the lens periphery. We investigated the changes in ocular aberrations during accommodation over the entire diameter of the crystalline lens to compare optical changes between the center and periphery and understand the nature of lenticular accommodative changes.
Methods: Accommodation was stimulated in anesthetized 10 year old rhesus monkey via an electrode implanted in the Edinger-Westphal nucleus of the brain. Prior bilateral complete iridectomies allowed the entire lens diameter to be studied. Aberrations were measured five times each at 10 amplitudes of accommodation ranging from zero to about 10D in both eyes with a Shack-Hartmann wavefront sensor. In addition, wavefront sensor images recorded at maximum accommodation were analyzed over entrance pupil diameters ranging from 3 to 8mm.
Results: With a fixed entrance pupil diameter of 8mm, RMS error (defocus removed) increased systematically with increasing accommodation from about 1 micron to 3.5 microns. There was a systematic progression toward negative spherical aberration and an increase in vertical coma with increasing accommodation. Magnitudes of all Zernike terms except defocus decreased systematically with decreasing entrance pupil diameter. In the accommodated eye, decreasing entrance pupil diameter from 8 to 3 mm resulted in about a 3D increase in power of the eye.
Conclusions: The greater increase in optical power in the paraxial region of the lens as compared to its periphery (hence the increasing negative spherical aberration) combined with accommodative miosis serves to maximize amplitude while maintaining acceptable image quality. This increase in negative spherical aberration during accommodation may arise from spatially varying forces imparted by the capsule, which has local variations in thickness and elasticity over its surface.
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