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Published on: February 18, 2021
Repeatability of mesopic visual acuity measurements using high- and low-contrast ETDRS letter charts
Ana Barrio1, Beatriz Antona, María C Puell
1Applied Vision Research Group, Faculty of Optics and Optometry, Complutense University of Madrid, Av. Arcos de Jalón 118, 28037, Madrid, Spain, arbarrio@ucm.es.
Purpose:
To determine the repeatability of mesopic high-contrast (HC) and low-contrast (LC) visual acuity (VA) measurements made at distance and near in healthy young individuals. While the repeatability of photopic VA is well-known, there is a lack of information with regard to the repeatability of VA measured under low luminance conditions.
Methods:
In two different sessions 1 week apart, best-corrected monocular VA was determined using HC (96 %) and LC (10 %) ETDRS charts under mesopic luminance conditions (0.75 cd/m(2)) at distance (HCD, LCD) and near (HCN, LCN) in 47 healthy subjects aged 22.9 ± 6.8 years. Repeatability was estimated by the Bland and Altman method, whereby the mean difference (MD) and the 95 % limits of agreement were determined as the coefficient of repeatability (COR).
Results:
Mean logMAR VA values were HCD = 0.09, LCD = 0.44, HCN = 0.21, and LCN = 0.57. Mean differences in measurements between sessions 1 and 2 were not significant, and low in clinical terms (≤1 letter). Repeatability was better for the distance measurements at both high and lowcontrast (COR HCD ±0.11 and COR LCD ±0.11 logMAR vs COR HCN ±0.15 and COR LCN ±0.16 logMAR), and MDs were also slightly closer to zero for the distance measurements. Similar repeatability was observed between HC and LC VA, both at distance and near.
Conclusions:
In mesopic conditions, ETDRS charts offer repeatable best-corrected monocular VA measurements. The criterion for a significant change in logMAR VA was 1 line at distance and 1.5 lines at near.
