Smooth Pursuit in Elderly Adults Studied With Apparent Motion.

The variability of smooth pursuit eye movements was studied in a group of healthy subjects for horizontal apparent motion by a method that does not require direct measurements of eye movements. It was found that the individual smooth pursuit efficiencies for binocular perception in group of healthy elderly subjects (mean age 61 years) as well as in the group of healthy young adults were distinctly differentiated. Furthermore, we have not detected any age-related decrease in the fraction of subjects showing high smooth pursuit efficiencies. This fact demonstrates that the human oculomotor system is relatively resistant to the effects of aging. At the same time, an appreciable increase of percentage of persons with directional asymmetry of smooth pursuit has been found among elderly adults. A higher smooth pursuit efficiency was noticed reliably more often in the direction from left to right rather than in the opposite direction. Subject eye movements were recorded with i-View XTM Hi-Speed 1250 eye tracking system (SMI Inc.). These records confirmed that the smooth pursuit accuracy of older adults is less than that of young persons, at least in some directions of tracking.

The Influence of Monocular Spatial Cues on Vergence Eye Movements in Monocular and Binocular Viewing of 3-D and 2-D Stimuli.

The influence of monocular spatial cues on the vergence eye movements was studied in two series of experiments: (I) the subjects were viewing a 3-D video and also its 2-D version-binocularly and monocularly; and (II) in binocular and monocular viewing conditions, the subjects were presented with stationary 2-D stimuli containing or not containing some monocular indications of spatial arrangement. The results of the series (I) showed that, in binocular viewing conditions, the vergence eye movements were only present in the case of 3-D but not 2-D video, while in the course of monocular viewing of 2-D video, some regular vergence eye movements could be revealed, suggesting that the occluded eye position could be influenced by the spatial organization of the scene reconstructed on the basis of the monocular depth information provided by the viewing eye. The data obtained in series (II), in general, seem to support this hypothesis.