Visual Ergonomics Research Articles

Invited Review Schematic eyes: history, description and applications

A schematic eye is a mathematical or physical model that represents the basic optical features of the real eye. By its nature, it is a simplified version and there is a range of schematic eyes that have been developed which offer different levels of simplicity or complexity, from the simplest reduced version that consists of a single refracting surface to the complex model with four aspheric surfaces and a gradient index lens.Schematic eyes have many applications, particular as teaching aids in optics, optometry, ophthalmology, psychology (vision and visual perception) and visual ergonomics. Besides showing the basic optical structure of the eye, the dimensions and other ocular parameters allow one to trace rays through the eye and determine the position, size and orientation of images and assess the aberrations and hence quality of the retinal image. However, there are many other applications which will be discussed in this article.This article will begin with the historical development of our knowledge of the structure and function of the eye from the first recorded writings of the ancient Greeks. It will then examine the range of schematic eyes currently available, describe their properties and applications and finish with a brief discussion of the probable direction of further developments. (Clin Exp Optom 1995; 78: 5: 176–189)

Instruments/techniques

We developed a system of coaxial video cameras that records monocular eye position and scene, and superimposes these images using a digital video mixer. We mounted miniature video cameras above and below a cube beam-splitting prism in the spectacle plane. An infrared emitting diode was imaged in the cornea to locate eye position. The technique was accurate to about 0.5 degrees within 15 degrees of primary gaze; however, we see its main advantages as being its low cost and simple design that, for some applications, does not require complex computer analysis and data manipulation. With improved camera optics, it has the potential for helmet mounting and use remote from a recording console. We used the instrument to monitor a reader's eye position when using low vision devices, and see applications of the technique in the field of visual ergonomics and sports vision.

Ocular surface area as an informative index of visual ergonomics.

A large ocular surface area (OSA) is thought to be one of the causes of eye irritation and eye fatigue. Because ocular surface is very sensitive to various irritants such as dust, heat, dryness, air flow, etc., a large OSA increases the possibility of eye surface exposure to such irritants. Thus, OSA is one of the most important indices of visual ergonomics. This paper aims at making OSA an exact and practical index by first describing an accurate method of measuring it, and then clarifying the relationship between OSA, the width of the palpebral fissure, and vertical gaze direction, all of which are thought to be strongly correlated with each other. We derived the following equations: 1) y = 0.039x1 + 3.36, r = 0.99, 2) y = 3.05x2 - 0.39, r = 0.97, 3) x1 = 72.7x2 - 91.4, r = 0.97, where x1 = vertical gaze direction (degrees), x2 = width or the palpebral fissure (cm), y = OSA (cm2). Finally, this paper also introduces the practical applications of OSA measurement, and notes the differences between OSA when VDT work (word processing using a keyboard and drawing a picture using a mouse) is performed and when traditional office work without a VDT (reading, drawing, and writing) is performed.

Visual ergonomics in the workplace: How to use a computer and save your eyesight

Visual ergonomics in the workplace: How to use a computer and save your eyesight

Visual comfort in VDT operation: physiological resting states of the eye.

To recommend a comfortable visual display terminal (VDT) workstation design in an aspect of visual ergonomics, physiological resting states of the eye in 3 visual systems, pupil, vergence, and accommodation, were objectively investigated in 3 experiments. Experiment 1 ascertained a positive display polarity (dark characters on a bright background) and an illumination level of 500 lx to be the most appropriate working conditions, by using pupil analysis and subjective visual comfort in 10 subjects. Dark vergence, in experiment 2, was evaluated to be at a distance of about 50 cm from the eye, as an average in 14 subjects. Dark vergence was found to shift farther with an upward gaze while a nearer shift occurred with a downward gaze. In experiment 3, the average dark focus for 11 subjects was found to be 1.4 diopters (D) or a distance of about 74 cm from the eye. The positive correlation between refractive status of the eye and dark focus was statistically significant (r = 0.602). The ergonomic recommendations for a VDT workstation obtained in this study are a positive display polarity with an appropriate lighting condition, a downward gaze, and a viewing distance between 50 and 70 cm. These recommendations are considered to reduce visual fatigue due to prolonged VDT work and to facilitate visual comfort at work.

特集・人間工学はなぜ役に立たないのか 情報機器（ＶＤＴ）と人間工学

特集・人間工学はなぜ役に立たないのか 情報機器（ＶＤＴ）と人間工学

Limits of visual perception in the technology of visual display terminals

Abstract Abstract. The limits of visual perception in present VDT technology for man-machine communication are considered. Essentially, these limits concern the reading of the displayed information and follow from the prevailing display conditions as to (i) luminous contrast, (ii) character shape, (iii) text layout and (iv) text colour. The effect of these conditions on legibility is quantitatively described from research results, and practical suggestions are given for improving display legibility, through changes in contrast polarity, character shape, layout and the way colour is used. Finally, a plea is made for including experts in visual ergonomics in the teams developing new display devices in the future.

Visual ergonomics in cartographic and lithographic work at the Topographic Service, Part 1: Optometric aspects and visual requirements : Royal Aircraft Establishment, Library Services Department, Farnborough, Translation No 1988, Dec 1978.

Visual ergonomics in cartographic and lithographic work at the Topographic Service, Part 1: Optometric aspects and visual requirements : Royal Aircraft Establishment, Library Services Department, Farnborough, Translation No 1988, Dec 1978.