BACKGROUND: The Amsler chart, a printed grid with a central fixation mark, is widely used to test for central/paracentral scotomata and metamorphopsias. Abnormal results are easily recognised but are not directly accessible to quantitative analysis. Negative results may be misleading, because it is never known how good an observer the subject is. METHODS: A new version was created in computer graphics. The grid was made to sweep the tested area in an optic flow manner. The sweeps provided seamless coverage, counteracted the Troxler fade-from-view effect, and encouraged stable fixation. Simulations of scotomata and metamorphopsias allowed quantitative evaluations of subject performance. RESULTS: Normal observers consistently detected absolute paracentral scotomata subtending > or =2 degrees . Grid deformation was consistently detected at 4' near fixation, whereas up to 20' was needed at the grid border. A patient with real metamorphopsia reproducibly nulled the apparent deformation of the grid in a manner closely matching his own renditions. CONCLUSIONS: The classical Amsler grid can be made to meet modern demands of quality control and quantitative measurements. The new "MacuFlow" test is freely accessible on the internet. Test results can easily be transmitted electronically for evaluation at distance.
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