The test-retest variability of the charts was similar, with the 95% tolerance limit for change being ±0.14 logMAR for ETDRS, ±0.16 for reduced logMAR and ±0.18 for Snellen.

The aims of this study were to validate both printed crowded Kay picture (pCKP) and computerised CKP (cCKP) logMAR test acuity measurements against gold standard ETDRS letter chart scores.