Eyestrain in VDU Users: Viewing Distance and the Resting Position of Ocular Muscles

Abstract

Without fixation stimuli--for instance, in darkness--accommodation and convergence of the eyes reach an intermediate state that is relatively stable within a subject but which ranges from about 30 cm to infinity across subjects. This study investigated whether these oculomotor positions in darkness are related to visual strain. During work at a visual display unit (VDU), visual strain at a viewing distance of 50 cm was stronger than at 100 cm (with characters twice as large). The more distant the individual's dark convergence, the greater was the visual strain at the 50-cm viewing distance. When subjects were free to adjust the viewing distance to their comfort level, they chose distances between 51 and 99 cm (mean 74 cm) with characters 5 mm tall.

Visual Fatigue and Performances for the 40-min Mixed Visual Work with a Projected Screen

“…This finding was consistent with Shieh and Lin's study [10], which suggested that maintaining a brighter ambient illumination level (about 450 lux), rather than reducing it to a lower level (200 lux). Based on our experimental settings, the luminance contrast ratio (L background /L text ) of the projected text was controlled at 3:1.…”

“…The issue of visual fatigue at a computer workstation has been noted in the previous studies [8][9][10][11]. Some VDT tasks can cause symptoms of fatigue and some can result in temporary reduction of visual ability.…”

Eye discomfort and work with visual display terminals.

“…Another important factor for eye discomfort was short distances between the eyes and the VDT, consistent with the findings of some studies (33,34) that suggeste d an increase in fatigue with short distances, especially in individuals with a disparity betwee n the (shorter) viewing distance and the individual's (longer) dark convergence. For dryness, there was an apparent interaction in our study between large variations in the distance to the eye task objects and the use of monofocal glasses during VDT work.…”

Mammography workstation design: effect on mammographer behaviour and the risk of musculoskeletal disorders

“…Therefore, this should be possible without adopting extreme postures. However, it is preferable that mammographers use the digital magnification tool, as using external magnification will not change the finite pixel size of the VDU screen, and moving the head close to the VDU screen has been associated with eye strain 15,16 . Therefore, magnification tools should be simple and intuitive to operate, and as similar to the known activity of using a magnifying glass as possible.…”