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L. S. Gray, L. Macfadden, D. Seidel, M. Collins; The Effect of Accommodation Upon Monochromatic Higher Order Aberrations in Myopia and Hyperopia. Invest. Ophthalmol. Vis. Sci. 2010;51(13):4298.
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© ARVO (1962-2015); The Authors (2016-present)
To investigate the effect of accommodation upon monochromatic higher order aberrations (MHOA) in myopic and hyperopic subjects.
Eleven myopic subjects (Average MSE -3.22±2.21D; mean axial length 25.02±0.87mm; mean age 20.7±1.1 years) and eleven hyperopic subjects (Average MSE 4.20±2.20; mean axial length 21.77±0.82; mean age 20.1±1.5) participated in the experiment. All subjects were visually normal, with VA ≤0.0 logMAR, and cylindrical error of ≤1.25DC. Subjects were fully corrected with daily disposable contact lenses and pupil dilation was induced with 2 drops of 2.5% phenylephrine hydrochloride instilled 50 minutes prior to measurement. Five measurements of MHOA were obtained using the Zywave Aberrometer for all viewing conditions. Subjects viewed a high contrast letter target array in a +5D Badal system, aligned perpendicularly to the measurement axis of the instrument via a semi-silvered mirror. Baseline measurements were obtained with the internal fixation target, and subjects were then asked to fixate on the letter within the Badal system, which corresponded to the position of the centre of the internal fixation target. Measurements of MHOA were then obtained at accommodation stimulus levels of 0D and 4D. The presentation of accommodation levels was randomized across subjects.
For the 0D accommodation stimulus, the hyperopic group showed significantly greater magnitude of both total 3rd order (p<0.01) and positive spherical aberration (SA, p<0.01). The magnitude of both total 3rd order and SA decreased significantly with accommodation in both myopic (p<0.01) and hyperopic (p<0.01) groups. The decrease in SA with accommodation was significantly greater in the hyperopic group (p<0.01). The change in SA with accommodation was significantly correlated with the magnitude of SA at the 0D accommodation stimulus level in both the myopic (r=0.84, p<0.01) and hyperopic (r=0.88, p<0.01) groups. At the 4D accommodation stimulus level, all myopic subjects exhibited negative SA, whereas all hyperopic subjects maintained positive SA despite larger reductions in SA with accommodation.
Shorter, hyperopic eyes have larger amounts of MHOA, in particular, greater amounts of positive SA. Negative aberrations produced by the crystalline lens during accommodation are also greater in these shorter, hyperopic eyes. These results may have implications for our understanding of the influence of aberrations in the development of ametropia.
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