Infrared pupillometry in presbyopes fitted with soft contact lenses.

The influence of pupil size, lens centration, and translation on multifocal contact lens performance suggests that these parameters should be accounted for in the optical design of presbyopic contact lenses. The purpose of the present article is to complete the existing experimental data with clinical measurements of pupil diameter and lens position relative to the pupil in a group of presbyopes, with controlled target luminance, stimulus distance, gaze angle, and convergence. The experiments involve an infrared video-pupillometer and ring-marked contact lenses. Results on pupil aperture show that the effect of changing target distance is comparable in magnitude to that of varying luminance within the photopic range. The measured data on lens position confirm that soft contact lenses are generally decentered from the pupillary axis, usually in inferior temporal direction, and that their average translation between primary and downward gaze is very small. It is also found that the average relative position between lens and pupil centers is slightly modified by changes of luminance in far vision. All these results provide characteristic values which are helpful for the optical modelling of presbyopic contact lenses.