Visual acuity as measured with Landolt C chart and Early Treatment of Diabetic Retinopathy Study (ETDRS) chart

Background We compared the Landolt C chart checked under normal clinical conditions and the Early Treatment of Diabetic Retinopathy Study (ETDRS) chart, using standard clinical research protocols for subjects with normal vision, cataract and maculopathy. Methods This prospective, comparative study was approved by the hospital Institutional Review Board. Patients with cataract and maculopathy were included, with the normal fellow eyes analyzed as normal vision group. Differences between the two charts were analyzed using Student's t-test. Results Normal and cataract eyes showed no statistically significant differences between methods. In the maculopathy group, ETDRS acuity (0.714 +/- 0.393) was better than Landolt C acuity (0.845 +/- 0.579), but the differences were not statistically significant (p=0.152). Furthermore, if after dividing visual acuity into subgroups, > 20/200 and <= 20/200 by Landolt C acuity, the latter subgroup had significant differences between the two tests (p < 0.001). ETDRS acuity (1.014 +/- 0.319) was better than Landolt C acuity (1.419 +/- 0.385). The average acuity difference was 4 lines. Conclusions For maculopathy patients with VA <= 20/200, the ETDRS chart had a better score than the Landolt C chart.