Reliability of three different visual acuity testing procedures in school children.

AIM

To evaluate the usability and reliability of three different visual acuity (VA) testing procedures using Landolt C's in 8 positions with a semi-automated computer program in school children.

METHODS

100 school children (median 7 years, 59 boys and 41 girls) were included; only the better eye was tested. We used the semi-automated computer program CORVIS.VT in a forced choice method. Three different test strategies were employed, each two times: A) DIN, B) Standard-Staircase and C) Best-PEST procedure with sequences A, B, C or A, C, B.

RESULTS

Average testing time was 100 s +/- 45 (DIN), 59 s +/- 36 (Staircase) and 77 s +/- 25 (Best-PEST). The mean VA estimated with DIN was equivalent to that with the Best-PEST procedure. However, the mean VA with Standard-Staircase was one line less. In DIN, 76% of the retest scores were within 0.1 logMAR unit of the initial test score (Staircase: 72%, Best-PEST 73%). The 95% confidence interval of test-retest reliability was calculated to be -0.05 +/- 0.24 logMAR in DIN, +0.02 +/- 0.32 logMAR in Staircase, and 0.00 +/- 0.29 logMAR in Best-PEST.

CONCLUSION

A high percentage of children aged 6 to 9 years (98%) can be tested with Landolt C's (8 positions). We found a decreasing test-retest reliability starting from DIN via Best-PEST to Staircase in this configuration.