Child Visual Acuity Standards

Visual acuity in children is essential in the detection and monitoring of visual problems. A standardized system for acuity testing is also needed for preschool and young aged children to enhance testability and reliability of visual screening. A chart specifically designed for VA assessment for the pediatric population has been included in the Optonet Vision Unit. The chart consists of single lines of 5 symmetrical letters with uniform contour interaction, according to international guidelines.

Linear visual acuity with symmetrical letters (instead of symbols) has been shown to constitute a reliable and testable method of VA measurement in children from the age of around 2.5 years to 7 years.1,2,3,4 The task of identifying those letters (with a matching card) is similar to that used for adult standard VA testing, therefore, the use of VA charts with symmetrical letters for children will ease their transition to adult testing, and also facilitates comparison with adult values. The letters O, X, H, T, U and V5,1,3 are easy to match, and have been incorporated to children’s VA charts in the vision unit.

Similarly, a stereoscopic test using the same symmetric letters, for the evaluation of binocular vision quality in children, has been included in the vision unit and is also being used to collect normative data in that population.

VA and stereoacuity data are being collected through the Optonet Project from different practices, in order to generate normative curves that may be useful to assess normal visual development of infants and young children of different ethnicities around the world.

This study is expected to provide Child Growth Standards (CVAS) to establish the normative model for normal physiological VA and Stereoacuity development from 2.5 years to 7 years of age.

References

1. McGraw, P. V. & Winn, B. Glasgow Acuity Cards: a new test for the measurement of letter acuity in children. Ophthalmic Physiol. Opt. J. Br. Coll. Ophthalmic Opt. Optom. 13, 400–404 (1993).
2. McGraw, P. V., Winn, B., Gray, L. S. & Elliott, D. B. Improving the reliability of visual acuity measures in young children. Ophthalmic Physiol. Opt. J. Br. Coll. Ophthalmic Opt. Optom. 20, 173–84 (2000).
3. Salt, A. T., Wade, A. M., Proffitt, R., Heavens, S. & Sonksen, P. M. The Sonksen logMAR Test of Visual Acuity: I. Testability and reliability. J. AAPOS Off. Publ. Am. Assoc. Pediatr. Ophthalmol. Strabismus Am. Assoc. Pediatr. Ophthalmol. Strabismus 11, 589–96 (2007).
4. Sonksen, P. M., Wade, A. M., Proffitt, R., Heavens, S. & Salt, A. T. The Sonksen logMAR test of visual acuity: II. Age norms from 2 years 9 months to 8 years. J. AAPOS Off. Publ. Am. Assoc. Pediatr. Ophthalmol. Strabismus Am. Assoc. Pediatr. Ophthalmol. Strabismus 12, 18–22 (2008).
5. Sheridan, M. D. What is normal distance vision at five to seven years? Dev. Med. Child Neurol. 16, 189–195 (1974).

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