A compact rarebit test for macular diseases.

Abstract

Rarebit testing implies probing for gaps in the neuro-retinal receptive field matrix, using bright microdots on a dark background. Previous reports have found rarebit testing useful for the detection of macular lesions. In its original implementation, the test requires darkroom facilities and a long test distance (2 m). A self-contained rarebit test device was realised using a modified miniature data projector driven by a laptop computer. Its performance was assessed in normal subjects and in patients with advanced age-related macular degeneration. Normal subjects (N=49) produced test results very similar to those reported for the original rarebit fovea test. The patient group (N=12) performed significantly worse. The reproducibility was good, and the mean test time was 142 s. The new test allows portable rarebit testing for neuro-macular damage, without the need for a darkroom. It may prove useful for screening for early age-related macular degeneration.