The simultaneous interocular brightness sense test. A test of optic nerve function
E. S. MacMillan, D. Cummins, G. Heron and G. N. Dutton
Department of Vision Sciences, Glasgow Caledonian University, Scotland.
OBJECTIVE: To describe and establish control data from controls for a
simultaneous interocular brightness sense test in which the apparent
brightness of two independently viewed light patches was compared. DESIGN:
Dichoptic viewing was achieved by dissociation of right and left eyes using
a septum and cross-polarization. Brightness matches were obtained by using
adjustments to the illumination of the left retina while the illumination
of the right retina was kept constant. OBSERVERS: Ninety-one control
observers (age range, 20 to 91 years) participated in the study to provide
normal brightness-matching data. RESULTS: Effects from ocular dominance,
age, and long- and short-term adaptation were negligible, but the test was
sensitive to anisocoria. Just noticeable differences in dichoptic
brightness matching were proportional to retinal illuminance; this finding
was consistent with the Weber-Fechner law. CONCLUSION: The test is quick
and simple to complete and appears to offer considerable scope for the
assessment of visual function when differences in the functional integrity
of the optic nerves of the right and left eyes are suspected.
