scope:

This standard applies to displays of optotypes for all clinical visual acuity measurement systems that use recognition of high-contrast optotypes and that are designed for general use including optotypes printed on opaque media, those intended for transillumination, electronically generated or projected displays. It does not apply to special testing of visual acuity, e.g., low-vision or low-contrast charts.

Purpose

The principles of standardized visual acuity testing are presented in standards adopted by the National Academy of Sciences and the Consilium Ophthalmologicum Universal as referenced below. Due to practical design considerations and physical limitations of most general-purpose clinical visual acuity measurement systems, the chart design features specified in these reference standards can only be met for a limited range of acuity presentations. Specialized charts are often required for special clinic visual acuity measurements - such as for low-vision patients. The purpose of this standard is to provide for standardized visual acuity charts for general measurement, which will enable the measurement of visual acuity over a limited, but clinically useful, range of acuities according to the principles contained in the reference standards.