Effects of glare on binocular vision and reading behaviour performing computer work

Abstract: We spend more and more time working with computers. When we do so our central visual field lacks three-dimensional (3D) features and this leads to reduced binocular control and may result in eye-related symptoms. When other factors such as direct and indirect glare are added to a computer work situation further stress is placed on the visual system and binocular control may be even further reduced and our reading behaviour may also be influenced. These factors are likely to contribute to the vision- and eye symptoms referred to collectively as computer vision syndrome (CVS). Three areas of clinical study are included in the context of using a computer screen for demanding near visual tasks. This research aimed to explore the theoretical relationship between: (1) the importance of centrally placed 3D features in respect to accommodation and vergence mechanisms; (2) the influence of degraded stimuli and/or degraded retinal image on the quality of binocular vision as an indicator of visual fatigue; (3) the influence of degraded stimuli and/or degraded retinal image on eye movements when reading. Paper I clarified the importance of implementing centrally placed 3D fixation stimuli to contribute to increase vergence accuracy and fixation stability. Paper II evaluated the influence of disability glare on binocular coordination. The results indicated that binocular coordination increased in instability with the severity of glare and there was a more pronounced effect when lighting condition created direct glare. Paper III described the influence of disability glare on eye movements when reading. It is clear that these eye movements were negatively affected in the direct- and indirect glare lighting conditions. Paper IV evaluated the threshold luminance of direct glare using a subjective response regarding eye symptoms in addition to an evaluation of the effect on binocular coordination as a benchmark. Direct glare of 2000 cd/m2 was found to decrease the instability of binocular coordination with an increased level of eye pain. In conclusion, these findings argue for a more pronounced relationship between reduced cues of centrally placed 3D features when working with computers with elevated exposure to disability glare. Direct glare appears to degrade the visibility of the retinal image to such a high degree that it can be identified as the most pronounced inappropriate lighting condition. Evaluation of the luminance threshold of direct glare suggests that it reasonable to recommend that stray light toward the eyes should be significantly lower than 2000 cd/m2. This research has taken a step in the direction of justifying the importance of following lighting design recommendations in computer work environments.