Effects of stimulus vergence on mean accommodation response, microfluctuations of accommodation and optical quality of the human eye.

This study was carried out on three observers by means of a highly sensitive infra-red optometer, the principle of which is recalled, associated with other measurement techniques. We found the accommodative "resting position" to coincide with minimum astigmatic ocular aberration, but not necessarily with maximum ocular optical quality, as suggested by Johnson. The amplitude of accommodation microfluctuations appears to vary in opposite directions with ocular optical quality; this result agrees with previous findings of Arnulf et al. The power spectrum of accommodation micrfluctuations we recorded ranged in frequency from 0 to 6 Hz. A relative activity maximum appears in the 1 to 6 Hz bandwidth for the "resting position" or the optimal quality position. We used Toates' s accommodation model as a frame of reference to interpret these results.