Jose R T, Atcherson R M
Am J Optom Physiol Opt. 1977 Sep;54(9):634-8.
We measured the sizes of the test forms (letters, digits, and symbols) on 19 different near-point acuity cards. The results are all expressed in the M notation (1 mm of letter height equals 0.7 M) and are tabled according to the acuity specification system used by the manufacturers--such as, the point-type system, Jaeger notation, equivalent 20-ft Snellen notation, and so on. Our results demonstrate that manufacturer's specifications on near-point acuity cards cannot be used to determine the sizes of test letters. The M system has sufficient advantages over other systems to warrant its universal use for specifying near-point visual acuity.
我们测量了19种不同近点视力卡片上测试图形（字母、数字和符号）的大小。结果均以M表示法（字母高度1毫米等于0.7 M）表示，并根据制造商使用的视力规格系统制成表格，如点型系统、耶格表示法、等效20英尺斯内伦表示法等。我们的结果表明，近点视力卡片上制造商的规格不能用于确定测试字母的大小。M系统相对于其他系统具有足够的优势，值得普遍用于指定近点视力。
