UoC "European-wide" charts

The visual acuity charts developed for the Early Treatment Diabetic Retinopathy Study (ETDRS) offered a rigorous chart design and test protocol, that has been widely adopted in basic and clinical vision research. Today, the ETDRS format forms the gold standard for measuring visual acuity

A limitation of the original ETDRS charts is that they do not allow for European-wide implementation, since they contain letters from the Latin (Roman) alphabet, which are not readable by all European citizens.

To facilitate reliable visual acuity screening for clinical trials and exchange of patient data between doctors, clinics and researchers throughout Europe and beyond, researchers at the University of Crete (Dr. Sotiris Plainis, Prof. Miltiadis Tsilimbaris and Prof. Ioannis Pallikaris), have developed modified ETDRS charts that contain only capital letters that are common to all three European alphabets (Latin, Greek, Cyrillic), and are thus recognizable for a much wider population, as indicated in the map below.

Extended Geographical area in which the Modified ETDRS charts may be used

The new charts have been validated against the original ETDRS charts in Greece, Bulgaria and Belgium (see relevant article). They were found to produce comparable visual acuity scores with a test-retest repeatability of about 0.10 logMAR (see ARVO poster).

For the new charts, only the Sloan letters C, O and H were maintained; the letters C, D, N, R, S, V, and Z were replaced with E, P, X, B, T, M, and A.  All letters were constructed on Snellen’s 5x5 grid and are compatible with the specifications of the Sloan letters.

Charts for measuring both distance and near/intermediate visual acuity are available.

Innovative aspects

The UoC charts

•             remain faithful to the ETDRS format thus ensuring adherence to the gold standards of visual acuity measurement

•            are legible by all EU citizens (including pending member Bulgaria)

•            are legible by all European nationalities (except Armenian)

•            have been validated against the original ETDRS charts and were found to produce comparable visual acuity scores

•            form an ideal alternative to the ETDRS charts for European-wide clinical trials.