A Simple Haploscopic Method for Quantitating Color Brightness Comparison

Neuro-ophthalmic disorders may cause a subjective difference in the brightness perceived by each eye. We developed a unique clinical device to measure this difference. The device consists of a disk equipped with graded neutral-density filters that fits into a View-Master stereo viewer (View-Master International Group, Inc., Portland, Oregon). This device provides simultaneous viewing of a stimulus target for each eye, and is administered in a random, forced-choice format that allows assessment of patient reliability. We administered this test to 37 control subjects and 84 patients with a variety of disorders. Thirty-six of the 37 control subjects (97%) and 51 of the 84 patients (61%) had no measured relative brightness deficit and no errors. Of the 34 subjects who had abnormal results, 21 (62%) isolated a relative brightness deficit within 0.2-log unit steps without error, and 28 (82%) did so within 0.4-log unit steps. This device proved to be a simple, reliable instrument for measuring relative brightness perception.

The Amsler grid is a suprathreshold target and thus may fail to detect relative scotomas. If the grid is viewed through two cross-polarizing filters creating low luminance conditions (threshold Amsler grid testing) the test is far more sensitive. Ten patients with disorders of the macula with normal standard white Amsler grid testing were studied with three other Amsler grid tests. Of the 15 involved eyes, 12 had visual field defects present with threshold Amsler grid testing. Tangent screen examination showed defects in 10 of these 12 eyes. The two red grids used were not as sensitive as the threshold grid. Three eyes had metamorphopsia with the white grid which became the site of a visual field defect with threshold testing. Threshold Amsler grid testing is a rapid and sensitive technique for the evaluation of the central 10° of visual field in patients with maculopathies.