Abstract
Background: Adjustment of the ocular accommodative system is an important phenomenon
allowing for optimal vision at different distances.
Aim: The study compared the refractive behaviour of the human eye under different ambient
lighting conditions for different target brightness.
Setting: Auto-refraction measurements were taken of the participants in the Department of
Optometry at the University of Johannesburg.
Methods: Five African participants from a single ethnic group aged between 20 years and
25 years, had 40 successive auto-refractor (Nidek AR 610) measurements taken on the right
eye of each participant in a bright and dark room using the illuminated and dark targets
(LL and DL); dark target in the illuminated and dark room (LD and DD).
Results: A change in the refractive state of all participants was observed on LL and LD, except
for one, who experienced myopic shifts. The largest significant difference in the variancecovariances
and the means was approximately 2.40 dioptre (D). The other participants’ shifts
in means were approximately the same and varied between 1.00 D and 1.50 D stigmatic shift.
For the DL to DD conditions all participants, except for one, underwent a hyperopic shift of
about 0.50 D.
Conclusion: The refractive behaviour of the human eye appears to be dependent on ambient
light conditions as well as target illumination or luminance.
Contribution: The study is scientific and clinical, and focuses on changes in refractive
behaviour under different lighting conditions, falling within the scope of the journal. Key
insights are that there is a change in the refractive behaviour of the eye under different ambient
conditions.