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A modified ETDRS visual acuity chart for European-wide use
Sotiris Plainis1, Paraskevi Tzatzala, Yiannis Orphanos
1Institute of Vision and Optics, University of Crete, Greece. plainis@med.uoc.gr
Summary
A modified visual acuity chart (UoC) uses letters readable by European citizens, proving as valid as the standard ETDRS chart for multinational trials. This enhances accessibility in vision testing.
Area of Science:
- Ophthalmology
- Optometry
- Clinical Research
Background:
- The standard Early Treatment Diabetic Retinopathy Study (ETDRS) visual acuity (VA) chart uses Sloan letters not recognized in many European alphabets.
- This limits the applicability of the ETDRS chart in multinational clinical trials involving diverse linguistic populations.
Purpose of the Study:
- To evaluate a modified ETDRS chart, the University of Crete (UoC) chart, designed with letters readable by all European citizens.
- To assess the validity and comparability of the UoC chart against the standard ETDRS chart for visual acuity measurements.
Main Methods:
- Modified UoC charts replaced specific Sloan letters (C, D, R, N, V, S, Z) with universally recognizable European letters (E, P, B, X, Y, A, T).
- Visual acuity of 227 students was tested using both standard and UoC charts.
- Letter identification difficulty was assessed using psychometric functions for five subjects.
Main Results:
- Bland-Altman analysis showed no statistically significant differences in visual acuity values between the standard and UoC charts.
- Despite interletter variability in identification thresholds, the modified set of Sloan letters demonstrated equal identifiability compared to the original set.
Conclusions:
- The modified log MAR UoC charts are a valid alternative to the ETDRS chart for assessing visual acuity in multinational clinical trials.
- The UoC chart offers improved accessibility by including letters recognizable by a broader population, including European citizens and users of the Cyrillic alphabet.
