he author constructed an apparatus for measuring the visual acuity objectively by evoking optokinetic nystagmus. The stimulus for eliciting the nystagmus is vertically drawn lines on a white paper, which is driven horizontally by a motor. The width of lines ranged from 1.0mm to 15mm, the distance of each line being the same as the width of lines. The occurrence of nystagmus was verified by observing with corneal microscope and slit lamp.
At a distance of 5m, with few exceptions, the finest lines which elicited nystagmus was :determined. In the subjective determination of visual acuity, Landolt ring was used.
With this equipment and procedure, 156 persons, 312 eyes were examined. A comparison has been made between the gap width of the Landolt ringg and the width of line. The results are compiled into table. A statistical treatment shows a highly significant correlation (coefficient, 0.96) for the relation between the gap width of the ring and line width which elicited nystagmus. The mutual relationship of these two values is expressed as regression equation.
From this results, it is concluded that this procedure is suitable for the objective determination of visual acuity.
The author also tried to establish whether the arresting of optokinetic nystagmus is suitable for the objective visual acuity measurement. This method, however, failed to show any reliability.
The various methods previously used for the objective measurement of visual acuity are reviewed.
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