Fifteen young adults were included in the first part of the study, consisting of repeated reading of a standard A4 reading task and a 90° reading task (10 men and 5 women, mean age, 28.9 ± 7.4 years [SD]). In the second part of the study, comparing saccadic and reading head movement propensities, a further 30 subjects were recruited, bringing the study group to 45 subjects. The group comprised 24 men and 21 women (mean age, 48.8 ± 21.2 years), including 13 subjects aged between 18 and 30 years, 8 subjects between 30 and 45 years, 11 subjects between 45 and 65 years, and 13 subjects between 65 and 85 years. The older subjects were included in the study because of the larger saccadic head movement propensities in the elderly. In prior observations, we have found a significant increase in saccadic head gain with age of 0.068/decade (P < 0.0001; Proudlock FA, Shekhar H, Gottlob I, unpublished observations, 2003).
All subjects had full corrected visual acuity and normal stereoscopic vision and were free from any otologic or neurologic deficits other than presbyopia. Presbyopic subjects wore single near-vision lenses with a visual field in excess of 70° horizontal and 55° vertical. The study received local ethics committee approval and was performed with the subjects’ consent after explanation of the nature and possible consequences of the study. The study was performed in accordance with tenets of the Declaration of Helsinki.