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 (TAC).

METHODS

TAC was used to estimate grating acuity in 646 healthy infants and children born at due date +/- 2 weeks, all of whom underwent ophthalmologic and orthoptic evaluation. The sample consisted of 20 age groups from 0 to 36 months. Sixty-nine percent of the children attended day care centers in the city of São Paulo. The sample was composed of white (63.0%), mulatto (25.2%), African-Brazilian (11.0%), and Asian (0.8%) infants and children, most 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. The range of tolerance limits is approximately 2.5 octaves at most ages. There were no statistical differences among scores obtained by the different testers. There were no differences in VA due to race, sex, and first or second eye tested. The results on binocular (99.3%) and monocular (96.2%) testability and on mean test duration (13 minutes for one binocular and two monocular measurements) confirm the clinical applicability of TAC.

CONCLUSIONS

The binocular and monocular grating VA norms obtained in this large-sample study are different from the preliminary norms published with the TAC. Results from this and other studies (see Mayer et al, page 671, this issue) strongly point to a need for redefinition of the preliminary VA norms.