Important Factors In Lighting Advice

B. J.M. Melis-Dankers¹ , A. de Booij², F. W. Cornelissen³, and A. C. Kooijman³

1 Visio R.I.N., P.O.Box 144, NL-9750 AC, Haren,
² Sonneheerdt, Ermelo,
³ Laboratory of Experimental Ophthalmology, University of Groningen,
The Netherlands.

We have investigated the impact of visual acuity, contrast sensitivity, object detection, object recognition and subjective appreciation of the illumination level in determining the lighting requirements of visually impaired people.

We selected 13 adult clients of our rehabilitation centre for the visually impaired, who experienced problems under normal lighting conditions. We measured their ability to detect and recognise carefully selected objects in a calibrated realistic visual environment at seven illumination levels: 5, 15, 50, 100, 250, 500, 1000 and 2000 lux. In addition we measured contrast sensitivity and visual acuity at the same illumination levels using the GECKO (Groningen Edge Contrast Chart) and the Lighthouse ETDRS 2000 letter chart, respectively. The subjective appreciation of the lighting was obtained by extended observation and interview and scored on a scale of 0 to 10.

Surprisingly, neither contrast sensitivity nor visual acuity were sufficient to predict the illumination level which was experienced as optimal by the subject. Most subjects tended to prefer higher illumination levels than predicted on the basis of their visual performance parameters. However, contrast sensitivity and visual acuity appeared to provide a good indication of the lower and upper limits of the illumination level.