Microfluctuations of Wavefront Aberrations of the Eye

Abstract

Purpose: To investigate fluctuations in the wavefront aberrations of the eye and their relation to pulse and respiration frequencies.

Methods: Using a wavefront sensor, we measured the dynamics of wavefront aberrations of the eye to 4th radial order Zernike aberrations of the left eye of 10 young subjects. Simultaneously, the subjects’ pulse signals were collected by a PowerLab system. The instantaneous heart rates (respiration frequency) were derived from the pulse signals. We used an auto–regressive process–based power spectrum analysis for the Zernike aberration signals, as well as pulse and instantaneous heart rate signals. Linear regression analysis was performed between the frequency components of Zernike aberrations and the pulse and instantaneous heart rate frequencies. Cross spectrum density estimation and coherence analysis were applied to investigate the correlation between fluctuations of wavefront aberrations and pulse and instantaneous heart rate. The correlations between individual Zernike aberrations were determined.

Results: A frequency component of all considered Zernike aberrations was found to be significantly correlated with the pulse frequency (all R2>0.51, p<0.02), and a frequency component of 9 out of 12 Zernike aberrations was also significantly correlated with the respiration frequency (all R2>0.46, p<0.05). The highest correlations among Zernike aberrations occurred between astigmatism at 45 degrees and secondary astigmatism at 45 degrees, between defocus and spherical aberration, and between astigmatism at 0 degree and secondary astigmatism at 0 degree.

Conclusions: Higher order aberrations are related to the cardiopulmonary system in a similar way to that reported for the accommodation signal and pupil fluctuations. The correlations among the Zernike aberration terms are highest between the second order and fourth order terms with same the angular frequencies.