Static aspects of eye and head movements during reading in a simulated computer-based environment with single-vision and progressive lenses.

Abstract

Reading with two different intermediate progressive lens designs was investigated regarding eye and head movement patterns and compared with movement patterns with a conventional single vision lens in a computer-based work environment. Two-dimensional eye (horizontal, vertical) and three-dimensional head (horizontal, vertical, and torsional) movements were recorded objectively and simultaneously at a rate of 60 Hz during reading of moderate contrast (40%) single- and double-page text formats at 60 cm with binocular viewing. In addition, global reading ability was rated subjectively for each lens. Subjects were 11 visually normal, presbyopic individuals aged 45 to 71 years selected by convenience sampling from a clinic population. Reading was performed with three types of spectacle lenses: a single-vision lens (SVL; 60 degrees horizontal [H] clear field-of-view [FOV]); a progressive addition lens (PAL) with a relatively wide intermediate zone (PAL-I; 7.85 mm, 18 degrees H clear FOV); and a PAL with a relatively narrow intermediate zone (PAL-II; 5.60 mm, 13 degrees H clear FOV). Many reading-related parameters, as well as eye- and head-movement parameters, were adversely affected by the PALs compared with the SVL. One reading-related parameter (i.e., number of regressions) differentiated between PALs. Subjective rating of global reading ability was highest with the SVL and lowest with the PAL-II. The optical design of a spectacle lens had significant impact on reading performance and on the combined eye-head movements initiated during reading. Both horizontal eye and head movements discriminated well between PALs and the SVL, but not between PALs, despite subjective preferences. This suggests that nonoculomotor factors contribute to patients' nonacceptance of PALs. Vertical eye and head movements and torsional head movements were not as discriminatory as were their horizontal counterparts.