Maximum angle of ocular duction during visual fixation as a function of age

Purpose: To measure and compare the maximum angle of ocular auction in healthy individuals as a function of age. Methods: A calibrated arc perimeter was modified to display one of six randomly presented targets (high contrast Snellen equivalent letters), in both vertical (supra/infraduction) and horizontal (ab/adduction) gaze to the dominant eye of 204 healthy volunteers with best-corrected visual acuity. A bite-bar and headrest were employed to prevent head movement. Using a modified method of limits for discrimination threshold, a maximum mean angle of ocular duction was determined by stepping a target out in 5° steps until an error was reported and thereafter bracketing around the limits of the target identification in 1° steps. A mean threshold value was determined as the angle at which a subject obtained a correct response 75% of the time in two and as many as three trials in each of four randomly presented directions of gaze (abduction, adduction, supraduction and infraduction). Results: A decrease in mean maximum duction angle was found over all age groups in all four directions (p < 0.001), with a steep decline beginning in the sixth decade and almost doubling in the oldest age group tested (80-95 year-olds). The percent of change in mean maximum angle of duction due to age from the 14-19 to the 80-95 year-olds was: abduction 21%, adduction 24%, supraduction 35%, infraduction 26%. Conclusion: Baseline data are useful to differentiate normal changes occurring with age from early signs of disease. Additionally, disease progression and effects of treatment can be monitored