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.
Get full access to this article
View all access options for this article.
References
1.
BMDP. (1988). Biomedical computer programs.Berkeley: University of California Press.
2.
Brown, C. R., and Schaum, D. L. (1980). User-adjusted VDU parameters. In E. Grandjean and E. Vigliani (Eds.), Ergonomic aspects of visual display terminals (pp. 195–200). London: Taylor & Francis.
3.
Deutsche Industrie Norm (DIN) 66234. (1984). Bildschirmarbeitsplätze. Teil 6: Gestaltung des Arbeitsplatzes [VDU workplaces. Part 6: Design of the workplace]. Berlin: Beuth.
4.
Dixon, W. J., and Massey, F. J. (1969). Introduction to statistical analysis.New York: McGraw-Hill.
5.
Finney, D. J. (1971). Probit analysis.Cambridge, England: Cambridge University Press.
6.
Francis, E. L., and Owens, D. A. (1983). The accuracy of binocular vergence for peripheral stimuli. Vision Research, 23, 13–19.
7.
Glasser, G. J., and Winter, R. F. (1961). Critical values of the coefficient of rank correlation for testing the hypothesis of independence. Biometrica, 48, 444–448.
8.
Gould, J. D., and Grischkowsky, N. (1984). Doing the same work with hard-copy and with cathode ray tube (CRT) computer terminals. Human Factors, 26, 323–337.
9.
Grandjean, E. (1987). Design of VDT workstations. In G. Salvendy (Ed.), Handbook of human factors (pp. 1359–1397). New York: Wiley.
10.
Grandjean, E., Hunting, W., and Pidermann, M. (1983). VDT workstation design: Preferred settings and their effects. Human Factors, 25, 161–175.
11.
Grandjean, E., Nishiyama, K., Hünting, W., and Pidermann, M. (1982). A laboratory study on preferred and imposed settings of a VDT workstation. Behaviour and Information Technology, 1, 289–304.
12.
Helander, M. G., and Rupp, B. A. (1984). An overview of standards and guidelines for visual display terminals. Applied Ergonomics, 15, 185–195.
13.
Heuer, H., Hollendiek, G., Kröger, H., and Römer, T. (1989). Die Ruhelage der Augen und ihr Einfluβ auf Beobachtungsabstand und visuelle Ermüdung bei Bildschirmarbeit [The resting position of the eyes and the effect on viewing distance and visual fatigue at VDU work]. Zeitschrift für Experimentelle und Angewandte Psychologie, 36, 538–566.
14.
Hung, G. K., Ciuffreda, K. J., and Semmlow, J. L. (1986). Static vergence and accommodation: Population norms and orthopics effects. Documenta Ophthalmologica, 62, 165–179.
15.
Human Factors Society. (1988). American national standard for human factors engineering of visual display terminal workstations (ANSI/HFS 100-88). Santa Monica, CA: Author.
16.
Jaschinski-Kruza, W. (1988a). A hand optometer for measuring dark focus. Vision Research, 28, 1271–1275.
17.
Jaschinski-Kruza, W. (1988b) Visual strain during VDU work: The effect of viewing distance and dark focus. Ergonomics, 31, 1449–1465.
18.
Jaschinski-Kruza, W. (1990a). Effects of stimulus distance on measurements of dark convergence. Ophthalmic and Physiological Optics, 10, 243–251.
19.
Jaschinski-Kruza, W. (1990b). On the preferred viewing distances of screen and document at VOU work, Ergonomics, 33, 1055–1063.
20.
Lieberman, H. R., and Pentland, A. P. (1982). Microcomputer-based estimation of psychophysical thresholds. The Best PEST. Behavior Research Methods and Instrumentation, 14, 21–25.
21.
Millodot, M. (1986). Dictionary of optometry.London: Butterworth.
22.
Moses, R. A. (1971). Vernier optometer. Journal of the Optical Society of America, 61, 1539.
23.
Murch, G. (1982). How visible is your display?Electro-Optical System Design, 14, 43–49.
24.
O'Shea, W., Ciuffreda, J., Fisher, S. K., Tannen, B., and Super, P. (1988). Relation between distance heterophoria and tonic vergence. American Journal of Optometry and Physiological Optics, 65, 787–793.
25.
Owens, O. A. (1984). The resting state of the eyes. American Scientist, 72, 378–387.
26.
Owens, O. A., and Leibowitz, H. W. (1980). Accommodation, convergence, and distance perception in low illumination. American Journal of Optometry and Physiological Optics, 57, 540–550.
27.
Owens, O. A., and Wolf-Kelly, K. (1987). Near work, visual fatigue, and variations of oculomotor tonus. Investigative Ophthalmology and Visual Science, 28, 743–749.
28.
Pickwell, O. (1989). Binocular vision anomalies: investigation and treatment.London: Butterworth.
29.
Sheedy, J. E., and Saladin, J. J. (1983). Validity of diagnostic criteria and case analysis in binocular vision disorders. In C. M. Schor and K. J. Ciuffreda (Eds.), Vergence eye movements: Basic and clinical aspects (pp. 517–540). Boston: Butterworth.
30.
Simonelli, N. M. (1980). Polarized vernier optometer. Behavior Research Methods and Instrumentation, 12, 293–296.
31.
Tyrrell, R. A., and Leibowitz, H. W. (1990). The relation of vergence effort to reports of visual fatigue following prolonged near work. Human Factors, 32, 341–357.
32.
Weston, H. C. (1949). Sight, light and efficiency.London: Lewis.
33.
Wilkins, A. (1986). Intermittent illumination from visual display units and flourescent lighting affects movements of the eyes across text. Human Factors, 28, 75–81.
34.
Wilkinson, R. T., and Robinshaw, H. M. (1987). Proofreading: VDU and paper text compared for speed, accuracy and fatigue. Behaviour and Information Technology, 6, 125–133.
35.
Wolf, K. S., Ciuffreda, K. J., and Jacobs, S. E. (1987). Time course and decay of effects of near work on tonic accommodation and tonic vergence. Ophthalmic and Physiological Optics, 7, 131–135.
36.
Yekta, A. A., Jenkins, T., and Pickwell, D. (1987). The clinical assessment of binocular vision before and after a working day. Ophthalmic and Physiological Optics, 7, 349–352.
