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N. Lopez–Gil, F. Lara, V. Fernandez–Sanchez; Effect Of Pupil Miosis And Spherical Aberration On The Accommodation Response . Invest. Ophthalmol. Vis. Sci. 2006;47(13):5844.
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Objective measurements of accommodation response usually do not take into account pupil miosis and changes in spherical aberration during accommodation. However both parameters could play an important role in the accommodation lag.
We used an Irx3 aberrometer (Imagine Eyes) to evaluate ocular aberrations in 15 young visually–normal adults (ages within 19 and 38) while their accommodation was stimulated with a target of vergence varying from 0 (far point) to 10 D in steps of 0.5 D. Precision of the measurements was first analyzed in one subject in which 20 measurements were obtained under the same conditions. Zernike coefficient up to eight–order were measured under two different conditions: for a pupil of 3 mm and for the natural pupil size. Accommodation was computed using different metrics which took into account the fourth– and sixth–order spherical aberration.
In average, SD of repeated measurement under natural pupil conditions was 0.4 D and 0.06 microns for accommodation and spherical aberration respectively. We found a decrease in spherical aberration with accommodation when the stimulus vergence increased from 0D to 5–8 D. This was followed by an increase in spherical aberration when the target vergence exceeded 8 D mainly due to the pupil miosis. Despite intersubject variability, accommodation lag was reduced by 0.5–1.0 D when the metric used to computed the accommodation state took into account the changes in spherical aberrations with pupil size. Such improved resulted in a systematic increase in the slope of the accommodative responses of all subjects, which became closer to the ideal response.
Lag of accommodation depends on the changes in spherical aberration during accommodation and both depend on the accommodative miosis. The results could be used to design IOL or contact lens that modify the spherical aberration of the eye in order to minimize the lag and to increase the accommodation amplitude.
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