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  • Title: Aging effects on the visually driven part of vergence movements.
    Author: Yang Q, Le TT, Kapoula Z.
    Journal: Invest Ophthalmol Vis Sci; 2009 Mar; 50(3):1145-51. PubMed ID: 18952920.
    Abstract:
    PURPOSE: To examine gain, speed, and temporal characteristics of initial and closed-loop components of vergence eye movements in young and elderly subjects. METHODS: Vergence eye movements in 13 elderly and 10 young adults were examined. A table with light-emitting diodes was used to elicit vergence starting from near (convergence, 40-20 cm; divergence, 20-40 cm) or from far (convergence, 150-40 cm; divergence, 40-150 cm). Vergence eye movements were recorded with a video eye tracker or an infrared eye movement device. RESULTS: There were no aging effects on the gain or peak velocity of vergence. Vergence duration was longer in elderly than in young adults, but only for the second, closed-loop components, driven by visual feedback. Elderly and young adults showed higher peak velocity and gain for convergence than for divergence. CONCLUSIONS: This observation is discussed in the context of physiological evidence of a robust convergence, rather than a divergence, generator at the brain stem level. Such a specific effect of aging on the duration of the closed-loop component is attributed to the reduced capacity of cortical processing of visual binocular disparity; slowing of vergence would allow good final accuracy.
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