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H. Radhakrishnan, W. N. Charman; Effect of Age on Changes in Ocular Aberrations With Accommodation. Invest. Ophthalmol. Vis. Sci. 2007;48(13):967.
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To investigate the changes in aberrations with monocular accommodation as a function of age.
Second- and higher-order wavefront aberrations and pupil size were measured as a function of accommodation demand over the range 0-4 D, in the right eyes of 48 normal subjects with ages between 17 and 56 years. Higher-order ocular Zernike aberrations were analysed for the natural pupil size in terms of their equivalent defocus, and were also determined for fixed pupil diameters of 4.5 mm in the unaccommodated eyes and 2.5mm in the accommodating eyes.
With relaxed accommodation (0D accommodation stimulus), most higher-order Zernike coefficients averaged to approximately zero, with the exception of C40 which averaged to a low positive value (0.035 microns). The major change with age was in the value of C40, which increased in positive value over the age range studied, although the total higher-order RMS wavefront aberration did not increase. When the data were analysed for natural pupils, spherical aberration and horizontal coma were found to change systematically in the positive direction with age, whereas vertical coma changed in the negative direction. The equivalent defocus of RMS error for natural pupils showed no significant correlation with age (p>0.05). With active accommodation, spherical aberration was found to reduce and become negative as the accommodative response increased in the younger subjects (<40 yrs). Near-zero aberration spherical aberration was found at accommodation levels of about 0.5 D in the youngest subjects (<20 years) and at around 2-3 D in subjects between 20 and 39 years. In the older subjects (>40 yrs), the spherical aberration showed only small changes, some of which were positive, within the limited amplitude of accommodation available. Other higher-order aberrations and the RMS of higher order aberrations did not appear to change systematically with accommodation, except in the oldest subjects.
As the pre-presbyopic eye ages, the changes in aberration that occur over the range of accommodation response alter. In younger eyes, spherical aberration tends to change with accommodation from a positive to a negative value: in older eyes (around 40 years and above) spherical aberration remains positive and may even increase over the small amplitude of available accommodation. These changes may relate to the changes with age in the form and extent of the gradients of refractive index within the lens.
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