[Visual acuity measured via the Freiburg visual acuity test (FVT), Bailey Lovie chart and Landolt Ring chart].

INTRODUCTION

If different ways for correcting refractive errors of the human eye have to be compared, accurate and reproducible measurement procedures are necessary.

METHODS

Binocular visual acuity of 130 students without pathologies was measured with the Freiburg Visual Acuity Test, the Bailey-Lovie chart and a Landolt ring chart (4 orientations). The reproducibility of the FVT was determined by repeated measurements.

RESULTS

The average visual acuity was 1.93 +/- 0.03 (= 20/10.4) with the FVT, 1.82 +/- 0.03 (= 20/11) with the Landolt ring chart, and 1.48 +/- 0.02 (= 20/13.5) with the Bailey-Lovie chart. 50 % of all repeated measurements with the FVT were within an interval of +/- 0.035 logMAR from the mean value. 95 % were within +/- 0.1 logMAR. Results of earlier studies are discussed.

CONCLUSION

On average, visual acuity values found with the Freiburg Visual Acuity Test were slightly larger as compared to the Landolt ring chart (difference = 0.025 logMAR). Taking the maximal difference of 0.05 logMAR tolerated by the international standard DIN EN ISO 8597 into account, both tests are equivalent. The results found with the Bailey-Lovie chart were substantially lower as compared to the Landolt ring chart (difference = 0.09 logMAR). The Freiburg Visual Acuity Test has a high reproducibility and measures visual acuity on a continuous scale that is not limited to the traditional visual acuity steps. Thus, it can be recommended as a reference procedure for comparative visual acuity studies.