SCREENING FOR AMBLYOPIA - A COMPARISON OF PEDIATRIC LETTER TESTS

Aims/background-The measurement of visual acuity is the most widely ac cepted indicator of amblyopia and is thought by some to be the only ef fective screening test. The aim of this study was to investigate the e ffectiveness of the traditional single optotype Sheridan-Gardiner test (SGT) in the measurement of visual acuity and the detection of amblyo pia, compared with the log based linear format Glasgow acuity cards (G AG). Methods-In the present study visual acuity was measured monocular ly in 702 primary 1 schoolchildren using both acuity tests. Results-A significant difference was found in the mean (SD) visual acuity measur ed with GAC (0.9 (0.08) modified logMAR) and SGT (1.13 (0.09) modified logMAR), df = 632, t = -59.08, p = 0.0001. The majority of children ( 89.3%) achieved visual acuities better than 6/6 in either eye when usi ng the single optotype test. If the 95% confidence limits for a signif icant interocular difference in acuity are used as criteria for the de tection of unilateral amblyopia, GAC were found to be the most sensiti ve, correctly identifying 100%, while SGT identified 55% of the childr en with unilateral amblyopia. Conclusion-The results of this study hig hlight several problems with both the test format and testing procedur e in the present school screening system.