当眼睛因外伤或疾病而引起视力减退,假使需要评定其外伤残废等级或视力损失程度,通常首先要确定它的视效率(Visual efficiency)。视效率是包括视力、视野、眼球运动等多方面的,其中以中心视力视效率的计算比较复杂。以往都沿用美国医学会制订的远近视力的视效率分级标准(表1)。表中第1项为分数记录的远视力(检距是20叹),第2项为 When the eye causes vision loss due to trauma or illness, if its level of disability or visual impairment needs to be assessed, its visual efficiency is usually first determined. The visual efficiency is including vision, visual field, eye movement and many other aspects, of which the central visual acuity efficiency is more complicated. In the past, according to the American Medical Association to develop visual acuity rating criteria (Table 1). The first item in the table is the fractional recorded distance vision (20 sighs) and the second item is