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V. Fernandez-Sanchez, R. Montés-Micó, A. Cerviño, N. López-Gil; Changes on the Estimation of the Objective Amplitude of Accommodation for Different Pupil Sizes. Invest. Ophthalmol. Vis. Sci. 2008;49(13):4559. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Objective measurement of the amplitude of accommodation (AA) can be calculated monoculary using certain metrics from aberrometric outcomes obtained during accommodation stimulation. However, those metrics depend in general on pupil diameter, which not only varies during accommodation but also with light room conditions. In this study we analyze whether the objective measurements of AA undergo a modification when the pupil size of the unaccommodated eye varies.
We measured ocular aberrations in 20 normal eyes (12 subjects) with ages ranging from 20 to 42 years using an aberrometer while their accommodation was stimulated with a target. Target’s vergence varied in a range larger than subject’s range of vision (steps of 0.5 D). AA was calculated as the mean of three repeated AA measurements obtained from wavefront outcomes on each subject under two starting points (unaccommodative state) conditions: (1) dim room light (about 2 cd/m2) and (2) photopic room light (about 50 cd/m2).
Mean pupil diameter were 6.1 mm and 4.6 mm for condition (1) and (2), respectively. Although it was found intrasubject AA variations up to more than 1 D between pupil conditions, the mean intersubject changes for conditions (2) and (1) was 0.13±0.87D. This represents about 5% of reduction (not statistically significant p=0.6) in the AA of accommodation for condition (2) in relation to (1). A high correlation (R= 0.93) was found between the AA obtained at both conditions. The changes in AA found between both conditions were smaller than the mean standard deviation obtained whiting the 3 AA (0.54 D).
The size of the pupil of the unaccommodated eye (which depends on the room illumination) does not seem to play a relevant role in the measurement of the AA. These results agree with the fact that the most important change during accommodation for the AA is not the change of pupil size but optical aberrations, especially defocus and spherical aberration.
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