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[The new standard for diagnostic near reading charts-DIN EN ISO 7921:2024]
Wolfgang Radner1,2,3,4, Rainer Kirchhübel5,6,7, Frank Müller5,7,8
1Karl Landsteiner Privatuniversität für Gesundheitswissenschaften GmbH, Dr. Karl-Dorrek-Str. 30, 3500, Krems, Österreich. vienormous@outlook.com.
Background:
With the publication of the DIN EN ISO 7921:2024 standard, an international standard for medical near reading charts has been introduced for the first time. This standard enables the determination of a valid and internationally comparable threshold for near visual performance, i.e., the reading acuity.
Material And Methods:
This article reports on the central contents and scientific background of this standard. It describes the definition of print size based on the x‑height, the geometric (logarithmic) progression of print sizes, standard testing distances and requirements regarding illumination, contrast and typefaces.
Results:
The standard defines the calculation principles for print sizes in their geometric (logarithmic) progression, including the permissible tolerances as well as conditions such as test distance, illumination and contrast. The standard notation logRAD is used because it precisely represents the geometric scaling of print sizes and is well established in scientific practice. Other geometric notations are not excluded for clinical use. The typefaces specified are Helvetica and Times New Roman or typefaces similar to these.
Conclusion:
Diagnostic reading charts are class I medical devices. DIN EN ISO 7921:2024 establishes, for the first time, an internationally uniform basis for diagnostic reading charts and thereby enables comparable and reproducible measurements of reading acuity. Together with the mandatory registration of medical devices in EUDAMED since 2026, this standard strengthens the validity, comparability and traceability of reading acuity measurements in clinical and scientific use and thus also enhances legal reliability.
