LARGE-SAMPLE POPULATION AGE NORMS FOR VISUAL ACUITIES OBTAINED WITH VISTECH-TELLER ACUITY CARDS

Purpose. To determine population age norms in the first three years of life for binocular and monocular grating visual acuity (VA) obtained with Vistech-Teller Acuity Cards (TAG). Methods. TAC was used to estim ate grating acuity in 646 healthy infants and children born at due dat e +/- 2 weeks, all of whom underwent ophthalmologic and orthoptic eval uation. The sample consisted of 20 age groups from 0 to 36 months. Six ty-nine percent of the children attended day care centers in the city of Sao Paulo. The sample was composed of white (63.0%), mulatto (25.2% ), African-Brazilian (11.0%), and Asian (0.8%) infants and children, m ost of whom (97%) were from low-income families. Tests were conducted by eight highly trained testers, six of whom were orthoptists. Results . Binocular and monocular norms for grating VA are presented in terms of tolerance limits for 90% of the population with 95% probability. Th e range of tolerance limits is approximately 2.5 octaves at most ages. There were no statistical differences among scores obtained by the di fferent testers. There were no differences in VA due to race, sex, and first or second eye tested. The results on binocular (99.3%) and mono cular (96.2%) testability and on mean test duration (13 minutes for on e binocular and two monocular measurements) confirm the clinical appli cability of TAC. Conclusions. The binocular and monocular grating VA n orms obtained in this large-sample study are different from the prelim inary norms published with the TAC. Results from this and other studie s (see Mayer et al, page 671, this issue) strongly point to a need for redefinition of the preliminary VA norms.