It is well accepted that the accommodation system is characterized by steady-state errors in focus. The purpose of this study was to correlate these errors with changes in ocular wavefront aberration and corresponding image quality when accommodating. A wavefront analyzing system, the Complete Ophthalmic Analysis System (COAS), was used in conjunction with a Badal optometer to allow continuous recording of the aberration structure of the eye for a range of accommodative demands (up to 8 D). Fifty consecutive recordings from seven subjects were taken. Monocular accommodative response was calculated as (i) the equivalent refraction minimizing wavefront error and (ii) the defocus needed to optimize the modulation transfer function at high spatial frequencies. Previously reported changes in ocular aberrations with accommodation (e.g., the shift of spherical aberration to negative values) were confirmed. Increased accommodation errors for near targets (lags) were evident for all subjects, although their magnitude showed a significant intersubject variability. It is concluded that the one-to-one stimulus/response slope in accommodation function should not always be considered as ideal, because higher order aberrations, especially changes of spherical aberration, may influence the actual accommodative demand. Fluctuations may serve to preserve image quality when errors of accommodation are moderate, by temporarily searching for the best focus.

The present study provides quantitative data on the ocular rigidity coefficient based on measurements in a large series of living human eyes. A positive correlation between the ocular rigidity coefficient and the patient's age was documented.

The present results suggest a nonlinear pressure-volume relation in the living human eye characterized by an increase in rigidity at higher IOP levels. The increased OPA and decreased pulse volume relate to the decreased POBF and the increased mechanical resistance of the ocular wall at high IOP levels.

Preliminary clinical results suggest that epi-LASIK is a safe and efficient method for the correction of low myopia. Further studies will establish this method as an alternative surface ablation procedure.

Based on manometric data, increasing AL is associated with decreased OR, OPA, and POBF. These results suggest decreased pulsatility in high myopia and may have implications on ocular pulse studies and the pathophysiology of myopia.