[Reduction of asthenopia-related to accommodative relaxation]

We investigated experimentally the effect of accommodative relaxation by outward shift stimuli for accommodation on asthenopia.

Twenty female students fixed on optical outward-shift stimuli at accommodation for 2 min immediately after 15 min of a sustained task on a 3-D display. Before and after the trial task and the outward shift stimuli, their accommodative step response was measured and their subjective symptoms were assessed. The outward shift stimuli in the optical system, which was set on a refractometer, were presented by moving the target scenery images from far to near and near to far repetitively a round both eyes' far point position. At the same time as the accommodation measurements, the changes of refraction were recorded from the same eye.

While looking at the outward shift stimuli, the refraction of 9 out of 20 subjects showed an outward shift and that of the other 11 subjects shifted inward. The post-trial value of contraction (from far to near) time of accommodative step response in the inward-shift group was markedly prolonged, from 0.86 s to 0.97 s (p = 0.043), and the post-trial accommodative power at the far target was shifted outward; from +1.21 D to +1.13 D(p = 0.048). The subjective symptoms of "ocular fatigue", "eye heaviness" and "eye dryness" also increased after the is(p = 0.0035, p = 0.0038, p = 0.0162, respectively). In the outward-shift group, however, no statistical changes were found.

From these results, we suggested that accommodative relaxation produced by outward shift stimuli at accommodation is effective in reducing of asthenopia following the deterioration of accommodative functions.