And it's important to note that they're to scale, so if you stand 20 feet back and you can read between those two black lines, you have 20/20 vision.
值得注意的是 它们和视力表一样是成比例的 也就是说 如果你站在20尺外 能领会到这两行黑字的言外之意 说明你视力正常