Wavefront aberrations in aging measured with Hartmann-Shack at 3- and 5-mm pupil sizes.

Abstract

Significance: Visual acuity (VA) depends on many factors. When the goal is to assess retinal health rather than performance, then using a 3-mm pupil reduces unwanted wavefront aberrations. The axis of astigmatism can still potentially change with age.

Purpose: When VA measurements are intended to quantify the status of the retina, extraneous optical aberrations can make the measured VA worse and introduce variability, particularly in aging eyes. Our study quantifies wavefront aberrations for a 3-mm pupil, which is similar to the theoretical optical size for best VA, versus a 5-mm pupil.

Methods: The wavefront aberrations of normally sighted adults (N = 39; age, 41.9 ± 16.3 years) were measured for a 3- and 5-mm pupil setting without pupil dilation, using a commercially available and semiautomatic instrument (Pentacam AXL WAV; Oculus Optikgeraete GmbH, Wetzlar, Germany). The mean wavefront errors from the average of three measurements with three samples each were computed for each Zernike term orders 1 to 6 and correlated with age. The difference of measurement 1 and measurement 2 provided the test-retest values.

Results: Each 3-mm pupil measurements had a reduced average aberration for all 26 aberrations Zernike values, and 21 of 26 were statistically significant (p<0.05). The variability of the Zernike values was less for the 3-mm pupil than for the 5-mm pupil for all 26 measured aberrations pooled (Zernike orders 1 to 6), which was statistically significant ( F = 54.625, p<0.001). Most mean aberrations did not vary significantly with age for a 3-mm pupil, except for vertical astigmatism, horizontal coma, spherical aberration, and vertical quadrafoil. Against-the-rule astigmatism was more common in subjects >60 than <40 years old (p=0.05).

Conclusions: The findings of this study indicate that measurements of VA to assess retinal health could be made less dependent on unrelated and unwanted anterior segment factors by using a 3-mm pupil, because the wavefront aberrations for a 3-mm pupil were less than those for a 5-mm pupil. The change with age in vertical astigmatism more than oblique is consistent with the expected increase in proportion of against-the-rule astigmatism.