ANSI Z80。21-2020适用于所有临床视力测量系统的视型显示，这些系统使用视型识别，并设计用于一般用途，包括打印在不透明介质上的视型、用于透照的视型、电子生成或投影显示。它不适用于视力的特殊测试，例如低视力或反极性（例如，深色背景上的白色视盘）。

ANSI Z80.21-2020 applies to displays of optotypes for all clinical visual acuity measurement systems that use recognition of 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 reverse polarity (e.g., white optotype on a dark background).