Abstract
Purpose: :
Convex mirrors are universally used to see a rear or side area in factories and automobiles. However, the ocular accommodative responses to images observed through a convex mirror have not yet been fully examined. This study investigated the effects of the convex mirror on human ocular accommodative systems.
Methods: :
Seven young adults with normal visual function were recruited. Each subject was ordered to binocularly watch a target located 2.00 m (0.50 D) from their right eyes through a convex mirror. The steady-state accommodative responses of their right eyes were measured with an infrared optometer for 50 seconds. The measurements were performed twice for each subject. The accommodative responses through a plane mirror were also measured as controls.
Results: :
The average ocular accommodation of all subjects while viewing through the convex mirror were significantly nearer than through the plane mirror (1.54 D in the convex mirror and 0.39 D in the plane mirror, p<0.0001, t-test ) although all subjects perceived that the position of the target through the convex mirror was farther away than through the plane mirror. The fluctuations of ocular accommodation were significantly larger while viewing through the convex mirror than through the plane mirror for each subject (p<0.001, F-test respectively). Moreover, all of them felt blurred vision and discomfort while viewing through the convex mirrors.
Conclusions: :
The convex mirror was thought to cause the ‘false recognition of distance’, which would induce the large accommodative fluctuations and the blurred vision. Caution is necessary when using convex mirrors.