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Age-related changes in visual tracking.

BACKGROUND
To reassess conflicting findings in earlier studies on the effect of aging on smooth pursuit and saccadic eye movements, we compared visual tracking in a large number of elderly normal subjects aged 75 to 93 years and a group of young adults aged 18 to 43 years.


METHODS
Saccades and smooth pursuit were induced by a laser target projected onto a screen. Eye movements were recorded with electrooculography and analyzed with a digital computer.


RESULTS
Smooth pursuit gain was significantly decreased at all target velocities in the older subjects, and the difference between young and old increased with increasing target velocity and acceleration. Peak saccade velocity was significantly slower for amplitudes exceeding 20 degrees, and saccadic reaction times were prolonged in older subjects compared with younger subjects. Mean saccade accuracy was not significantly different between age groups. Within tests, variability increased with aging for smooth pursuit, saccadic reaction time, and saccadic accuracy measurements.


CONCLUSION
The increased intratest variability in older subjects probably resulted from nonspecific changes in alertness and attention commonly occurring with aging, whereas the decreased gain of smooth pursuit and saccades with increasing stimulus magnitude most likely resulted from age-related neural degeneration in specific visuomotor pathways.