Most near reading charts in community clinics deviate from ISO size standards

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medRxiv Published April 8, 2026 Medically reviewed April 26, 2026 Study authors: Murphy, T. I.; Chen, J.; Leung, M. DOI ↗ By Dr. Lars van Dijk, PhD · Surgical, Procedural & Diagnostic

Key Takeaway

Consider that most near reading charts deviate from ISO size standards, affecting measurement comparability.

A measurement study evaluated 19 internationally available near reading charts used in community optometry clinics against ISO standards. The primary outcome was how these charts compared to international requirements for text size, font type, line spacing, contrast, and surface finish.

Only 1 of 19 charts (5.26%) had all text sizes within ISO tolerance. Font type variability was substantial: 12 charts (63.2%) used serif fonts, while 7 charts (36.8%) used sans-serif fonts. Serif charts tended to be smaller than required (mean deviation -9.63%), while sans-serif charts tended to be larger (mean deviation +4.96%). All charts met line spacing and minimum contrast requirements, but some were printed on laminated or satin plastic surfaces that do not meet the matte surface standard. Interrater agreement for measurements was perfect (ICC(2,1) = 1.00).

Safety and tolerability data were not reported. Key limitations include the small sample size of 19 charts and lack of information about funding or conflicts of interest. The findings suggest that most commercially available near reading charts deviate from ISO size standards, with systematic differences based on font type. For clinical practice, this means measurements obtained from different charts may not be directly comparable, particularly when monitoring progressive vision changes or in shared care models where multiple charts might be used.

Study Details

EvidenceLevel 5

PublishedApr 2026

View Original Abstract ↓

Purpose Measuring near vision provides clinicians with valuable insight into visual function. There is limited information on the accuracy of available reading charts frequently used in community practice. This study aimed to measure internationally available reading charts to determine how they compare to international standards. Methods Commercially and device manufacturer-provided reading charts available in community optometry clinics were scanned at 600 dots per inch. Gaussian adaptive threshold was used to facilitate repeatable measurements. X-heights of letters were measured independently by three researchers. Contrast levels and line spacing were also estimated. Results for each chart were compared with ISO Standards. Intraclass correlation coefficient was used to assess intergrader agreement. Results Of the 19 reading charts that were measured, only one chart (5.26%) had text sizes that were all within tolerance. There was high variability in size observed between charts. Twelve charts (63.2%) used serif fonts and seven used sans-serif (36.8%). Text on serif charts tended to be smaller than required ({micro}=-9.63%) compared to sans-serif ({micro}=+4.96%). All charts met the line spacing requirements and minimum required contrast level; however, some charts were printed on laminated or satin plastic which does not meet the standard of using a matte surface. There was high interrater agreement (ICC(2,1) = 1.00), indicating a highly repeatable measurement technique. Conclusion This study found that the tested reading charts displayed significant variability in text size. Although some charts had more lines of text within size tolerances than others, none met all the requirements of the International Standard. Clinicians and researchers should take care when interpreting changes in near reading acuity when multiple charts have been used, especially as part of shared care models or when monitoring progressive vision changes. A free UC/UWA Reading Chart has been developed as a result of this study, which conforms to the ISO Standard.