Is conversion of decimal visual acuity measurements to logMAR values reliable?
- 21 Downloads
To assess if conversion of decimal visual acuity (VA) to logMAR is reliable for clinical and research purposes.
Right eye VA of 74 consecutive patients was measured with 5 min interval, using (a) the ETDRS chart (VAlog), (b) a decimal chart at 6 m (VA6m), and (c) a decimal chart at 4 m (VA4m). VA was the smallest line whereby four of five optotypes were correctly identified. Decimal scores were converted to logMAR using the formula logMAR = −log(decimal acuity). The agreement between VAlog, VA4m, and VA6m was assessed by the Bland-Altman method.
Linear regression analysis of the difference between VAlog and VA6m or VA4m showed a significant slope (p = 0.001), with greater disagreement at higher VA values, i.e., poorer acuity. There was considerable lack of agreement, with discrepancies of up to 0.2 logMAR when VA was measured around 0.5 logMAR.
Converting decimal VA to logMAR produces overestimation of its true value, especially in lower acuities.
KeywordsCharts Decimal ETDRS Conversion
Compliance with ethical standards
Conflict of interest
Author Asimina Mataftsi declares that she has no conflict of interest.
Author Dimitrios Koutsimpogeorgos declares that he has no conflict of interest.
Author Nikolaos Ziakas declares that he has no conflict of interest.
Author Periklis Brazitikos declared that he had no conflict of interest.
Author Anna-Bettina Haidich declares that she that has no conflict of interest.
All procedures performed in this study involving human participants were in accordance with the ethical standards of the institutional research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.
Informed consent was obtained from all individual participants included in the study.
- 13.NAS-NRC Committee on vision (1980) Recommended standard procedures for the clinical measurement and specification of visual acuity. Adv Ophthalmol 41:103Google Scholar
- 15.Kaiser PK (2009) Prospective evaluation of visual acuity assessment: a comparison of Snellen versus ETDRS charts in clinical practice (an AOS thesis). Trans Am Ophthalmol Soc 107:311–324Google Scholar