Longitudinal changes in objective accommodative response, pupil size and spherical aberration: A case study

Previous transverse and a handful of longitudinal studies have shown that the slope of the static accommodation response/stimulus curve declines as complete presbyopia is approached. Changes in pupillary miosis and ocular spherical aberration (SA) are also evident. This study further investigated longitudinal changes in the relationships between the monocular static accommodative response, pupil diameter and SA of a single adult.

A wavefront analysing system, the Complete Ophthalmic Analysis System, was used in conjunction with a Badal optometer to allow continuous recording of the aberration structure of the dominant eye in a low myope for a range of accommodative demands (-0.83 to 7.63 D) over a period of 17 years until the age of 50. Monocular accommodative response was calculated as the equivalent refraction minimising wavefront error. The associated longitudinal changes in pupil size and SA with accommodation were also recorded.

A decrease in accommodation response with age was found at almost all target vergences, with the changes being greatest for higher vergences. In addition, although absolute pupil diameter decreased with age, the rate of change in pupil diameter with accommodative stimulus remained approximately constant with age. Pupil constriction occurred for near stimuli even in full presbyopia. SA changed linearly with the accommodation response at all ages.

The objective amplitude of accommodation declined linearly with age as complete presbyopia was approached, while the slope of the response/stimulus curve also fell. It was hypothesised that the retinal image blur associated with the larger lags of accommodation at higher accommodative stimuli was reduced by pupil constriction and the resulting lower levels of SA.