A comparison of Lea Symbol vs ETDRS letter distance visual acuity in a population of young children with a high prevalence of astigmatism

J AAPOS. 2009 Jun;13(3):253-7. doi: 10.1016/j.jaapos.2009.01.007. Epub 2009 Apr 5.


Purpose: To compare visual acuity results obtained by use of the Lea Symbols chart with results obtained with Early Treatment Diabetic Retinopathy Study (ETDRS) charts in young children who are members of a population with a high prevalence of astigmatism.

Methods: Subjects were 438 children ages 5 through 7 years who were enrolled in kindergarten or first grade on the Tohono O'odham Reservation: 241 (55%) had astigmatism >or=1.00 D in one or both eyes (range, 0.00-6.75 D). While wearing best correction, each child had right eye visual acuity tested with the 62 cm by 65 cm Lea Symbols chart at 3 m and with the 62 cm by 65 cm ETDRS chart at 4 m. Visual acuity was scored as the smallest optotype size at which the child correctly identified 3 of a maximum of 5 optotypes. ETDRS visual acuity also was scored based on the total number of letters that the child correctly identified.

Results: Correlation between Lea Symbols visual acuity and ETDRS visual acuity was 0.78 (p < 0.001). Mean Lea Symbols visual acuity was one-half line (0.04-0.06 logMAR) better than mean ETDRS visual acuity (p < 0.001). The difference between Lea Symbols and ETDRS visual acuity was not correlated with the mean of the Lea Symbols and ETDRS visual acuity scores, which ranged from -0.3 logMAR (20/10) to 0.74 logMAR (20/110).

Conclusions: In this population of young children, in whom the primary source of reduced visual acuity is astigmatism-related amblyopia, the Lea Symbols chart produced visual acuity scores that were about 0.5 line better than visual acuity scores obtained with ETDRS charts.

Publication types

  • Comparative Study
  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Astigmatism / diagnosis*
  • Astigmatism / epidemiology*
  • Astigmatism / therapy
  • Child
  • Child, Preschool
  • Eyeglasses
  • Humans
  • Indians, North American / statistics & numerical data
  • Prevalence
  • Reproducibility of Results
  • Vision Tests / instrumentation*
  • Vision Tests / methods
  • Vision Tests / standards
  • Visual Acuity*