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

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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 ≥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.

Section snippets

Subjects

Subjects were 482 children who were enrolled in kindergarten or first grade in a school on the Tohono O'odham Reservation in southern Arizona during the 2005/2006, 2006/2007, or 2007/2008 academic years. All were participants in a longitudinal study of the development and treatment of astigmatism-related amblyopia, in children age 6 months through first grade. All study participants who are at least 3 years of age undergo an eye examination with cycloplegic refraction, followed by assessment of

Study Sample

A total of 482 kindergarten and first-grade children were enrolled in the study and completed the eye examination between September 2005 and August 2008. Data were excluded from 3 children who refused cycloplegic drops at the eye examination, 16 children who were older than 8 years of age at the vision testing session, and 25 children who did not complete the vision testing session. The mean age of the final sample of 438 children was 6.2 years (SD 0.6; range, 5.2-7.8 years) at the exam, and

Acknowledgments

The authors thank the Tohono O'odham Nation, the Indian Oasis/Baboquivari School District, the Bureau of Indian Affairs Office of Indian Education Programs (BIA OIEP, Papago/Pima Agency), the San Xavier Mission School, and our NIH/NEI Data Monitoring and Oversight Committee (Maureen Maguire, PhD [former chair], Robert Hardy, PhD [current chair], Morgan Ashley, Donald Everett, MA, Jonathan Holmes, MD, Cynthia Norris, and Karla Zadnik, OD, PhD).

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Supported by grant U10 EY13153 (EMH) from the National Eye Institute of the National Institutes of Health, Department of Health and Human Services; by unrestricted funds to the Department of Ophthalmology and Vision Science from Research to Prevent Blindness (JMM); and by a Career Development Award from Research to Prevent Blindness (EMH).

Presented in part at the 2007 Annual Meeting of the Association for Research in Vision and Ophthalmology, Fort Lauderdale, Florida, May 6-10.

Study conducted at the University of Arizona.

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