Accommodative lag under habitual seeing conditions: comparison between adult myopes and emmetropes.

PURPOSE To clarify whether myopes show poor accommodative response and thus have a larger accommodative lag under natural seeing conditions. METHODS Forty-three adults without other ocular abnormalities were classified into the early-onset myopia (EOM, n=28) and the emmetropia (EMM, n=15) groups. The subjects wore glasses or contact lenses that they habitually used, and accommodative responses to four accommodative targets (16.0-50.5 cm from their eyes) were measured under a monocular or binocular condition using an open-field infrared autorefractometer. RESULTS Under a binocular condition, the accommodative lag for each target was significantly smaller in the EOM group (analysis of variance, P<.01), but the mean slope of the accommodative stimulus-response function did not significantly differ between the EOM and EMM groups (1.05+/-0.11 and 1.02+/-0.10 D/D, respectively). The mean slope under a binocular condition was significantly steeper than that under a monocular condition in both groups (paired t-test, P<.05). CONCLUSIONS In adults with EOM, the accommodative stimulus-response function was not impaired, and the habitual accommodative lag was rather small, probably due to the reduced accommodative demand by a vertex distance and/or the intentional undercorrection of spectacles.