City Research Online

Abstract

Computers have become ubiquitous in the modern world and most people spend several hours each day viewing computer displays. With the advent of LCD flat panel displays and the increase in graphical processing power, computer displays have rapidly evolved from barely legible text displays to the modern graphical user interface. Despite the improvement in the design and legibility of computer displays, complaints of visual discomfort are still surprisingly common amongst computer users. In many cases, the problems stem from poor workstation design, inappropriate working practices or uncorrected refractive errors or binocular vision anomalies. However, the fact that symptoms often persist when these factors have been addressed suggests that the design of computer displays may be suboptimal in a number of respects.

There is a vast literature relating to the ergonomics of displays and yet there is still a lack of good quality data on the effects of key parameters on user efficiency and reading speed. In particular, there is very little information about the potential benefits of changing screen colours.

The first part of this thesis describes a series of experiments designed to systematically examine the effects of contrast, font size, font style, letter spacing, contrast polarity, antialiasing and screen colour on the comfort and visual efficiency of users with normal vision. A series of tests were devised to assess user efficiency including search tasks and modified versions of the MNRead and Wilkins Rate of Reading tests. In general, user efficiency judged by performance in these tasks proved to be remarkably immune to changes in screen parameters and it is concluded that the default settings used on most displays is close to optimal. Many subjects subjectively preferred a background colour other than white although this preference was seldom rewarded by a measurable improvement in efficiency. However, changing the background colour did seem to reduce the prevalence of asthenopic symptoms.

The second part of the thesis describes a series of investigations designed to examine the potential benefits of changing selected display parameters for individuals with Age Related Maculopathy, Primary Open Angle Glaucoma and Retinitis Pigmentosa. Of particular interest was the effect of changing screen colours given the anecdotal evidence that some patients with these conditions gain some benefit from coloured lenses. The relatively small number of subjects and the heterogeneous nature of the groups limited the scope of the conclusions that could be drawn from this study. However, it is clear that the visual performance of many visually-impaired individuals can be greatly enhanced by the correct selection of screen parameters, particularly font size, contrast and in some case, colour. A computer programme to assist in the optimisation of these parameters was developed as the final part of this work.

Publication Type:	Thesis (Doctoral)
Subjects:	R Medicine > RE Ophthalmology T Technology
Departments:	Doctoral Theses School of Health & Psychological Sciences > Optometry & Visual Sciences School of Health & Psychological Sciences > School of Health & Psychological Sciences Doctoral Theses

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