The Sonksen logMAR test of visual acuity: II. Age norms from 2 years 9 months to 8 years.

PURPOSE: To establish age norms and interocular differences in visual acuity between 2 years 9 months and 8 years for the Sonksen logMAR Test. METHODS: Cross-sectional population-based study. Binocular measures of linear visual acuity were achieved in 2,940 children and monocular measures were achieved in 2,820 right eyes and 2,821 left eyes, respectively. Measures for both right and left eyes were achieved by 2,807. Asymmetric logistic models were used to construct smoothly changing age-related centile curves showing how visual acuity changes with age in a normative population sample. RESULTS: All curves demonstrated an increase in visual acuity with age that was steepest between 2 years 9 months and 5 years 3 months. Equivalent centiles for linear visual acuity were better when viewed binocularly than monocularly; the difference was least between the 95th centiles (best levels) and greatest between the 5th centiles (worst levels). There were no clinically significant differences between group measures of visual acuity from right and left eyes-average within child difference 0.0095 logMAR units, 95% CI, 0.0059-0.013. Interocular differences did not vary significantly with age (p = 0.73). The 90th and 95th centiles for interocular difference were 0.125 and 0.175 log units, respectively. CONCLUSIONS: This study demonstrates how visual acuity varied with age for the Sonksen logMAR Test and presents the findings in the clinically useful format of centile charts.

The Sonksen logMAR Test of Visual Acuity: I. Testability and reliability.

PURPOSE: To develop a standardized logMAR test of visual acuity for young children and establish testability and reliability. METHODS: Two thousand nine hundred ninety-one children, aged 2 to 8 years 6 months, from a population sample of 4671 were recruited from schools and preschool facilities and tested. Ability to name or match letters, accept occlusion, and achieve binocular single and binocular and monocular measures of linear visual acuity were recorded. Inter- and intratester reliability was assessed for a random selection of 215 children. RESULTS: Two thousand nine hundred seventy-four (99.4%) matched or named letters, 2966 (99%) achieved binocular single, 2940 (98%) achieved binocular linear, and 2807 (94%) achieved monocular linear (for both eyes) measures. Binocular linear measures were achieved in 50% aged less than 3 years, 80% aged 3 to 3(1/2), 92% aged 3(1/2) to 4, and 99% aged 4 years and over. Binocular linear measures were achieved in 86% of 2- to 3-year-olds and 96% of 3- to 3(1/2)-year-olds who matched or named letters; monocular linear measures were achieved in 86 and 95%, respectively, of these age groups who then accepted occlusion. The median time for completion of the test (binocular and monocular) was 3 minutes 55 seconds. The 95% limits of agreement for the same observer and for different observers were +/-0.13 and -0.19, +0.15 for binocular linear and -0.16, +0.15, and -0.17, +0.13 for monocular linear measures, respectively. CONCLUSIONS: The Sonksen logMAR Test provides reliable binocular and monocular measures of linear visual acuity in a high proportion of children from the age of 2.5 years.