Abstract
PURPOSE: To determine the range of eye movement in normal human subjects and to investigate the effect of age and gaze direction on eye movement. PATIENTS AND METHODS: A prospective observational study. We enrolled 261 healthy subjects, 5-91 years of age. Photographs were obtained in the cardinal gaze positions and processed using Photoshop. The processed images were analyzed using the Image J program to measure the angle of eye movement. The angle of eye movement was quantified using a modified limbus test. We measured the angle of eye movement in adduction, abduction, elevation, and depression. RESULTS: The ranges of eye movement were 44.9 ± 7.2° in adduction, 44.2 ± 6.8° in adduction, 27.9 ± 7.6° in elevation, and 47.1 ± 8.0° in depression. The ranges of eye movement in the younger group were higher than that in the older group in adduction, abduction, and elevation (P < 0.001, P = 0.013, and P < 0.001, respectively), except in depression (P = 0.790). There were significant negative correlations between the angles of horizontal and upward gazes and age (R = -0.294 in adduction, R = -0.355 in abduction, and R = -0.506 in elevation, all P < 0.001). However, the angle of downward gaze was not significantly correlated with age (R = 0.017, P = 0.722). CONCLUSIONS: The angle of upward gaze most rapidly decreased with age than the angle of other gaze. Unlike the age-related decline of range in horizontal and upward gazes, only downward gaze was not impaired by increasing age. Differences in eye movement range based on gaze direction and their associated aging mechanisms should be considered when assessing eye movements.