New methodology to measure the dynamics of ocular wave front aberrations during small amplitude changes of accommodation

Abstract

This is the unspecified version of the paper.This version of the publication may differ from the final published version. Abstract: We present a methodology to measure the systematic changes of aberrations induced by small changes in amplitude of accommodation. We use a method similar the one used in electrophysiology, where a periodic stimulus is presented to the eye and many periods (epochs) of the stimulus are averaged. Using this technique we have measured changes in higher order aberrations from 0.006µm to 0.02µm and correlated them with amplitude changes of accommodation as small as 0.14D. These small changes would have been undetectable without epoch averaging. The correlation coefficients of Zernike terms with defocus were calculated, demonstrating higher values of correlation for epoch averaging. The accurate monitoring of defocus at the start of the accommodation response has shown some interesting trends that may be related with the mechanisms behind accommodation. Permanent repository link

Wavefront curvature sensing for the human eye

“…As the astigmatism prescription of Subject 2 is much larger, the variability in angle will be much smaller as it will be strongly dependant on the variability of the ratio between C 5 and C 6 in Fig. 6(d) [23]. The behaviour of the higher order aberrations appears to be in line with previous reports of large populations [24][25][26], although the sample is too small to draw any conclusions in this respect.…”

“…In addition to this, the larger error in defocus observed in the phase plate and calibration plots discussed before may have had an effect in the measurements. The large standard deviations for the angle in Subjects 1 and 3 are consistent with the very small amount of astigmatism present in those eyes and the larger changes expected in this angle as the two Zernike components change relative to each other in phase with fluctuations of accommodation [23]. As the astigmatism prescription of Subject 2 is much larger, the variability in angle will be much smaller as it will be strongly dependant on the variability of the ratio between C 5 and C 6 in Fig.…”

Chaos in ocular aberration dynamics of the human eye

“…The mean limit of predictability across subjects was 1.16 ± 0.35 s, and the mean Lyapunov exponent was 0.36 ± 0.26 D/s. As the other aberrations in the eye show some correlation with accommodation microfluctuations, this may partly explain the chaos observed in their fluctuations [44,45]. From Fig.…”

Multifractal nature of ocular aberration dynamics of the human eye

“…Hence there are aspects of its dynamics that are unlikely to be due to the effect of other physiological systems on the eye. As other aberrations show a correlation with accommodation [34,35], it is likely that regulation of the accommodation loop will impact upon fluctuations in these other aberrations also.…”