The Influence of Glasses on the Physiology and Ergonomics in Presbyopic People at Visual Display Workstations: Summary of Three Studies

Abstract

The present paper provides a summary of three studies concerning the influence of glasses on the physiology and ergonomics in presbyopic computer users. The first study was a survey of 175 VDU (visual display unit) workstation users wearing glasses, age 35 and older. In the second study 23 subjects of the survey study (first study) tested a progressive addition lens (PAL) for general purpose and a PAL for computer vision. Within the third study near- and far-point curves (range of clear focus) as a function of eye inclination of the 23 people of the lens-testing study (second study) were determined. People wearing glasses for far-vision (single vision lenses) reported higher scores of eye strain, musculoskeletal strain and head complaints with increase of the daily duration of computer work: the longer they worked at computer stations the higher the strain were scored. This effect did not appear with the other lens types. The subjects of the lens-testing study (second study) showed a head inclination 2.3° lower when wearing the PAL for computer vision. 44 % of the subjects decided in favor of the PAL for computer use. Focus range curves can show descriptively where clear vision is possible and where to best place the monitor (third study).