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P. Tsoka, S. Plainis, T. Giannakopoulou, V. Tsapaki, P. Nikolitsa, J. Moschandrea, M. K. Tsilimbaris; Validation of a Modified ETDRS Chart for European-Wide Use in a Population Using the Cyrillic alphabet. Invest. Ophthalmol. Vis. Sci. 2008;49(13):3143.
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To validate the UoC visual acuity chart, a modified ETDRS chart developed for European-wide use (Plainis et al., 2007), in a population using the Cyrillic alphabet.
The UoC chart contains a set of letters recognisable by European citizens using the Latin, the Greek and the Cyrillic alphabets: the Roman letters C, D, R, V, S and Z (contained in the standard ETRS chart) are substituted with E, P, B, M, A and T, respectively. The charts were validated in a cohort of 310 school children (620 eyes), with a mean age of 12.5 (SD 1.4) yrs, in a Bulgarian city (Stara Zagora). Visual acuity was assessed with the habitual refractive correction, once using the standard ETDRS charts and twice using the UoC charts. The intra-class correlation coefficient (ICC) was used to assess the test-retest reliability of the UOC chart. Limits of agreement were calculated for differences in visual acuity scores (test-retest variability) between measurement occasions for the UoC chart. Standard method comparison measures (Bland-Altman analysis) were used to assess agreement between the two charts.
The ICC was estimated to be 0.968 (95% CI from 0.958 to 0.975) for the RE and 0.961 (95% CI from 0.950 to 0.970) for the LE. The test-retest variability (TRV) of the UoC charts were found to be ±0.10 for both RE and LE. The UoC charts produced on average slightly higher logMAR scores (0.015 for RE, 0.019 for LE) compared to the standard ETDRS charts. However, Bland-Altman scatter plots revealed that 97.1% of the values for the RE and 97.4% for the LE lie between the limits of agreement.
The UoC chart was found to have excellent test-retest reliability and offers an acceptable level of test-retest variability when compared to the published estimates of the gold standard ETDRS chart (±0.07 to ±0.11). Moreover, it produced significant agreement in VA scores with the standard ETDRS chart, replicating measurements on a Greek population. The UoC forms a valid alternative to the ETDRS chart, offering the advantage of containing letters recognisable by all European citizens.
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