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[Effects on eyestrain of outward stimuli for accommodation]
Tsuneto Iwasaki1, Akihiko Tawara, Nobuyuki Miyake
1Department of Ophthalmology, University of Occupational and Environmental Health, Japan. 1-1 Iseigaoka Yahatanishi-ku Kitakyushu 807-8555, Japan.
Purpose:
We investigated experimentally the effect on eyestrain of outward-shift stimuli for accommodation.
Methods:
Six female students fixed optical outward-shift stimuli for accommodation during 2 min immediately after 15 min of a sustained task on a 3-D display. Before and after the trial, their ocular functions were measured and their subjective symptoms were assessed. The outward-shift stimuli were applied by moving the targets of scenery images from far to near and near to far repetitively at around both eyes' far point position. As a control, stationary targets at the position of 0 D were used instead of moving targets. The same experiment was repeated twice for each subject.
Results:
In the first experiment, there were significant changes in the accommodative contraction time, the accommodation lag, and the myopic shift, and the subjective symptoms of "eyestrain" and "eye dryness" in the control group, but in the stimulus group there were only increases of the complaint of "eyestrain". In the second experiment, the changed items were the contraction time and the complaints of "eyestrain" and "eye dryness" in both groups. The outward-shift stimuli caused a tendency in the far point to shift outward in the first experiment, and there was a statistically significant inward shift in the second experiment.
Conclusion:
From these results, it is suggested that the outward-shift stimuli for accommodation are effective in relieving eyestrain following the deterioration of ocular functions except when the far point is shifted inward.