Abstract
Abstract: :
Purpose: To examine testability of and agreement between 2 tests for screening visual acuity in young children. Methods: Subjects were 1257 3- to 5-year-old children enrolled in Head Start at a Vision in Preschoolers Study clinical center. Approximately 2/3 of the children had failed a routine Head Start vision screening. Acuity was tested at 10/100, 10/32, 10/25 and 10/20 for 3-year-olds and at 10/100, 10/25, 10/20 and 10/16 for 4- and 5-year-olds. Optotypes were the letters H, O, T, and V for the HOTV and circle, square, house and apple for the Lea symbols. Single lines of optotypes with a crowding bar surround were used. Examiners were optometrists and ophthalmologists. Order of administration was balanced between the two tests and the examiner for the second test was masked to the results of the first test. Children who could correctly identify the four optotypes binocularly at 3 ft. using a lap card were considered testable. Acuity was scored as the smallest line on which the child was able to correctly name or match 3 out of 3 or 3 out of 4 optotypes. Agreement between tests was assessed using the Kappa statistic (K). Results: Overall, the testability was high for both the HOTV (98.64%) and the Lea symbols (98.65%) tests. Testability increased with year of age for the HOTV test (95.95% of 3-, 99.55% of 4-, and 98.55% of 5-year olds; p=0.01) and the Lea symbols test (97.17% of 3-, 98.81% of 4-, and 99.41% of 5-year olds; p=0.02). The distribution of acuity scores was similar for each test. Although the right eye was always tested first, there was no difference in scores between eyes (p=.99). Identical scores were obtained in 67% of all eyes and scores differed by no more than 1 category in 86% of eyes. Agreement between test scores was lower for 3-year olds (K=.33) than for 4-year olds (K=.55) and 5-year olds (K=.42) (P<.001). Conclusions: Testability was nearly 99% for each visual acuity test. Between-test agreement was moderate overall. Both testability and agreement were lowest for the youngest children. These results open the possibility that the two tests, when used in an identical screening format, may be used interchangeably for screening of 3- to 5-year-old children.
Keywords: screening for ambylopia and strabismus • visual acuity