RESUMO
BACKGROUND: Hemianopia commonly complicates stroke and, less frequently, head injury and brain tumours. Patients' activities of daily living are often affected although these can be ameliorated by appropriate behavioural therapy. Identifying a field defect is the first step in the rehabilitation process. An online visual field test (an 'app') was developed as part of a free to use web based therapy site for patients with hemianopic alexia, called Read-Right (http://www.readright.ucl.ac.uk). This study is an attempt to validate this test by comparing with a clinical 'gold standard'-the Humphrey automated visual field analyser. METHODS: 22 patients had their visual fields assessed with both techniques on the same day. The criterion validity of the Read-Right was examined by comparing it with Humphrey 10-2 and 24-2 perimetry using the following measures: (1) sensitivity and specificity; (2) κ statistics; and (3) intraclass correlation. RESULTS: Read-Right demonstrated high sensitivity and specificity, particularly for the undamaged field. In the damaged field, κ values were highly significant, especially for points along the horizontal meridian. The intraclass correlation score for the damaged field indicated excellent correlation between the two tests. Read-Right perimetry performed well on all measures. It had a tendency to under call damaged points offset from the horizontal meridian, and this and other aspects of the test will be revamped. CONCLUSION: Read-Right is not designed to replace standardised visual perimetry; it does, however, offer a quick and easy assessment that can be used to screen patients. The test is available as part of two free to use web based therapy applications.