Drivers Beware:
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Head Posture and Vision

by Dennis Zacharkow, PT
© 2015

As early as 1865, Dr. Fahrner of Zurich, Switzerland stressed an important postural principle that is just as critical today: The first slight reaching forward of the head is the start of the postural collapse when sitting.1

This slight forward bend of the head, a major cause of neck pain, back pain, and headaches, is due to reading and writing at horizontal desks and gazing at computer screens, tablets, and smart phones that are positioned too low. Why does a horizontal desk for reading and writing or a low computer screen height result in the head being brought forward from its balanced, upright posture? Simply because the line of sight must be perpendicular to the book, paper, or screen in order to see it clearly (Figure 1).

(With computer work, there may be a slight trade-off regarding the line of sight being perpendicular to the screen. It may be necessary to tilt the screen downwards to avoid glare.)

Reading Posture

The correct position for reading while maintaining an upright head posture is with the book perpendicular to the line of sight, approximately 60 degrees from the horizontal, 14-20 inches from the eyes (depending on the print, light, and the eyes of the reader), and approximately at the height of the chin.2

Proper reading posture can be accomplished with an adjustable reading stand.

Writing Posture

Writing at a desk with a high inclination may cause books, papers, and pens to slide off the desk, and it may also lead to an increase in arm fatigue. Therefore, the best compromise for a writing surface is an inclination of 10 to 15 degrees from the horizontal, keeping the upper arm vertical, and the forearm inclined from the horizontal to coincide with the plane of the desk top inclination3 (Figure 2).

This inclination for writing can be accomplished on many desks by slightly elevating the two desk legs located furthest from the chair. The slightly inclined writing surface can then be enhanced with an adjustable reading stand for proper reading posture.

Computer Posture

Regarding computer work, the further one can sit from the screen, the better, as it is more relaxing for the eyes and reduces fatigue.4 This is why a large computer screen with greater height to the characters is recommended.4

The recommended viewing distance for current computer screens is approximately 25 to 40 inches from the eyes to the screen.5,6

To maintain an upright head posture with the eyes naturally directed slightly downward, the center of the computer screen should be positioned approximately 10 to 15 degrees below eye level (Figure 3).

References

  1. Fahrner: Das Kind und der Schultisch. Zurich, Schulthess, 1865. Translated in Cohn, H.: The Hygiene of the Eye in Schools. London, Simpkin, Marshall and Co., 1886, pp. 94-98.
  2. Bennett, H.E.: School Posture and Seating. Boston, Ginn and Company, 1928.
  3. Freudenthal, A., van Riel, M.P.J.M., Molenbroek, J.F.M., and Snijders, C.J.: The effect on sitting posture of a desk with a ten-degree inclination using an adjustable chair and table. Applied Ergonomics, 22:329-336, 1991.
  4. Jaschinski-Kruza, W.: Visual strain during VDU work: the effect of viewing distance and dark focus. Ergonomics, 31:1449-1465, 1988.
  5. Grandjean, E.: Postures and the design of VDT workstations. Behaviour and Information Technology, 3:301-311, 1984.
  6. Jaschinski-Kruza, W.: Eyestrain in VDU users: viewing distance and the resting position of ocular muscles. Human Factors, 33:69-83, 1991.

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