Development and validation of the Greek version of the MNREAD acuity chart

Background: The aim of this study was to develop MNREAD acuity charts in the Greek language (MNREAD-GR) and establish their repeatability in a normal-sighted population.

Methods: One hundred and eighty Greek sentences were constructed based on the design principles of the Minnesota Low Vision Reading Test. The software used to validate them for width was adjusted to the parameters of the non-Latin characters used in the Greek language (MNTest-GR) and width-validated sentences were then checked for literacy by two language teachers. Pilot testing followed in 20 adults and two groups of 20 children. Subsequently, three versions of the MNREAD-GR chart were printed and validated for repeatability: 20 adults read MNREAD-GR charts 1, 2 and 3 in random order over two sessions. A linear mixed-model analysis was performed for near visual acuity (VA), maximum reading speed and critical print size to identify the contribution of each source (individual subject, session, chart and residual error) to the total variance. Subject variance determined the intraclass correlation coefficient.

Results: One hundred of the initial 180 sentences were validated with MNTest-GR and approved for literacy correctness. Of those, 57 sentences were selected after pilot testing, and used in the final printed chart in random distribution among three versions. The intraclass correlation coefficients were 0.72 for VA, 0.87 for maximum reading speed and 0.46 for critical print size. The between-charts within-session within-subject component accounted for a maximum five per cent of the variance. The between-sessions within-subject component had a maximum of one per cent. The coefficient of repeatability was 0.08 logMAR for VA, 46.96 words per minute for maximum reading speed and 0.10 logMAR for critical print size.

Conclusion: The created MNREAD-GR acuity chart is a standardised clinical test that can be used reliably to measure near acuity, reading speed and critical print size in Greek-speaking literate patients of all ages.