Comparison of the Snellen and Spectrum LogMAR visual acuity charts in schoolgoing children

Background: This article is part of a doctoral study conducted by Dr T.I. Metsing under the supervision of Dr W. Jacobs and Dr R. Hansraj. Aim: To investigate the equivalence of a standard Snellen chart to that of the Spectrum LogMAR chart amongst children of school-going age. Setting: The study was conducted through the University of Johannesburg, with data collected from the district of Ekurhuleni in the province of Gauteng, in South Africa. Methods: Visual acuity (VA) data on uncompensated distance was collected from three randomly selected schools in Cauteng from 206 children aged between 6 and 17 years (mean age and standard deviation of 10.13 +/- 2.45 years). Unaided monocular and binocular VAs were measured using the Snellen chart (SC) at 6 m and the Spectrum LogMAR chart (SLC) at 3 m. Data was analysed using the Statistical Package for Social Sciences software. Results: The mean VAs of both eyes (BE), right eye (RE) and left eyes (LEs) obtained using the SLC of 0.84 minutes (6/5), 0.91 (6/55) and 0.96 (6/5.8), respectively, fell within the normal ranges of 6/6 or better. The mean VA scores of BE, RE and LEs obtained using the SC were 1.07 min (6/6.4), 1.11 min (6/6.7) and 1.18 (6/7.1), respectively, and fell below 6/6. The difference in the mean VAs scores for the SC and SLC of BE, RE and LE were found to be statistically significant (p = 0.00). Conclusion: Monocular and binocular mean VAs for the SLC were found to be one line better than that for the SC. The slightly better performance of the SLC could be attributed to potential theoretical advantages of the LogMAR chart.