Chaos in ocular aberration dynamics of the human eye

Abstract

Since the characterization of the eye’s monochromatic aberration fluctuations in 2001, the power spectrum has remained the most widely used method for analyzing their dynamics. However, the power spectrum does not capture the complexities of the fluctuations. We measured the monochromatic aberration dynamics of six subjects using a Shack-Hartmann sensor sampling at 21 Hz. We characterized the dynamics using techniques from chaos theory. We found that the attractor embedding dimension for all aberrations, for all subjects, was equal to three. The embedding lag averaged across aberrations and subjects was 0.31 ± 0.07 s. The Lyapunov exponent of the rms wavefront error was positive for each subject, with an average value of 0.44 ± 0.15 µm/s. This indicates that the aberration dynamics are chaotic. Implications for future modeling are discussed.

Are the fluctuations in dynamic anterior surface aberrations of the human eye chaotic?

“…Chaos theory studies the behavior of dynamic systems, in which simple deterministic equations can predict apparent random events [11]. Hampson and Mallen [9] suggested that the fluctuations in the aberrations of the whole eye are chaotic in nature, and therefore the underlying equations can determine the behavior of aberrations. In a separate study [10], no correlations between the two eyes of an individual in the chaos of ocular aberrations for the whole eye were found.…”

“…Hampson and Mallen [9] suggested that the fluctuations in the aberrations of the whole eye are chaotic in nature, and therefore the underlying equations can determine the behavior of aberrations. In a separate study [10], no correlations between the two eyes of an individual in the chaos of ocular aberrations for the whole eye were found.The effect of the tear film fluctuations on the wholeeye aberrations has also been examined by fitting a scleral contact lens to preserve the tear film between the eye and the lens for a single participant [9]. The authors concluded that fluctuations in the tear film may be a source of noise that "dilutes" the chaos in the aberrations of the whole eye [9].…”

“…The effect of the tear film fluctuations on the wholeeye aberrations has also been examined by fitting a scleral contact lens to preserve the tear film between the eye and the lens for a single participant [9]. The authors concluded that fluctuations in the tear film may be a source of noise that "dilutes" the chaos in the aberrations of the whole eye [9].…”

“…The authors concluded that fluctuations in the tear film may be a source of noise that "dilutes" the chaos in the aberrations of the whole eye [9]. To examine this, we investigated chaos in the fluctuations of anterior surface aberrations only and considered the correlation of this chaos, if any, between the two eyes of an individual.…”

“…Power spectrum analysis has been used to study the dynamic behavior of wavefront aberrations in many studies [8]; however, recent studies by Hampson and Mallen [9,10] utilized chaos theory to describe fluctuations in the dynamic wavefront aberrations of the whole eye. Chaos theory studies the behavior of dynamic systems, in which simple deterministic equations can predict apparent random events [11].…”