Are norms based on the original Teller Acuity Cards appropriate for use with the new Teller Acuity Cards II?

PURPOSE

We sought to compare visual acuity results obtained with the original Teller Acuity Cards (TAC), which are no longer commercially available, and the modified, laminated Teller Acuity Cards II (TAC II), which recently became commercially available.

METHODS

Sixty children were tested, 20 at each of 3 ages: 3.5 months, 11 months, and 30 months. Each subject's binocular grating acuity was measured once with the TAC and once with the TAC II, with the order of testing counterbalanced across subjects. Testers were aware that acuity cards were arranged in ascending order of spatial frequency, but they were masked to the absolute spatial frequencies of the gratings in the subset of cards used. Testers were also masked to acuity results until testing of the child was completed.

RESULTS

Repeated-measures analysis of variance with age as a between-subjects variable and card type as a within-subjects variable showed a significant effect of age (P < 0.001) and a significant effect of card type (P < 0.001), but no interaction between age and card type. Post hoc comparisons (with Bonferroni correction) showed that mean acuity score was significantly better with TAC than with TAC II at 3.5 months (0.2 octave, P < 0.05), 11 months (0.4 octave, P < 0.01), and 30 months (0.7 octave, P < 0.001).

CONCLUSIONS

These results suggest that normative grating acuity data obtained with the original Teller Acuity Cards need to be adjusted toward lower acuity values by approximately 0.5 octave to be appropriate for use with the new Teller Acuity Cards II.