Abstract
Abstract: :
Purpose: The role of head movements in the elderly during visual tasks is uncertain. We have investigated head movements during simple horizontal saccadic and anti-saccadic tasks, smooth pursuit and reading. Methods: A high resolution infrared pupil and head tracker was used to simultaneously record eye and head movements at 250 Hz in 45 normal subjects ranging from 20 to 83 years. Subjects were instructed to follow a target moving randomly from 10° to 60° in 10° steps (saccadic test). The test was repeated with the subject attempting to look in the mirrored position of the target with respect to a central point (anti-saccadic test). The subjects also performed smooth pursuit tasks (20°/s and 40°/s) and a reading task of two different sizes of text width. Head movement propensity was estimated from the mean head movement amplitude in relation to the mean gaze shift amplitude. Results: Head movement propensity significantly increased with age during saccades (P<0.000), antisaccades (P<0.000), smooth pursuit at 20°/s (P<0.05) and 40°/s (P<0.05), and reading of a wide text width (P<0.01). Head gains during a standard reading task were much smaller compared to the other tasks and were not significantly different. Conclusions: Aging results in increased head movement propensity during simple visual tasks. In contrast, reading head movement propensities during a standard reading task are small even in the elderly, possibly because of the importance of minimising head movements to provide stable fixation.
Keywords: eye movements: saccades and pursuits • aging • reading