Background: Rarebit testing implies probing for gaps in the neuro-retinal receptive field matrix, using bright micro dots 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).
Methods: A self-contained rarebit test device was realized using a modified miniature data projector driven by a laptop computer. Its performance was assessed in normal subjects and in patients with age-related macular degeneration.
Results: Normal subjects (N = 49) produced test results closely similar to those reported for the original rarebit fovea test. The patient group (N = 12) performed significantly worse. Reproducibility was good. Mean test time was 142 s.
Conclusion: 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.