The British journal of ophthalmology
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Patients taking hydroxychloroquine (HCQ) are at risk of developing classic bull's eye maculopathy. Currently, the standard Amsler grid (AG) is one of the most useful methods to identify such lesions. However, AG is a suprathreshold target and may not detect relative central scotomas. The aim of this study was to determine if the threshold Amsler grid (TAG) test, which varies light transmission through two cross polarising filters, allows increased detection of scotomas caused by HCQ toxicity. ⋯ By decreasing the perceived luminance of the suprathreshold AG, TAG testing provides a novel alternative to detect shallow scotomas and areas of depressed retinal activity secondary to HCQ toxicity.