Pfoff D S, Werner J S
J Cataract Refract Surg. 1994 Nov;20(6):620-5. doi: 10.1016/s0886-3350(13)80650-5.
The effect of cataract surgery was assessed in 103 patients whose visual acuity, as measured in dim light and with high contrast Snellen letters, was 20/50 or better. The patients desired cataract surgery. They complained of glare symptoms, had given up driving at night, or both. Contrast sensitivity was measured under simulated night conditions with a calibrated Vistech MCT 8000 device. No patient who had a contrast sensitivity of less than 27 at 6 cycles per degree (20/70 "equivalent acuity") had cataract surgery. The mean preoperative contrast sensitivity function showed abnormally low values for all frequencies (cycles/degree) tested. Postoperatively the values returned to normal. Of 99 patients who answered a postoperative questionnaire, 41 (41%) had been driving at night preoperatively and 80 (80%) were driving at night postoperatively. A control group of 24 noncataractous patients (48 eyes) was in the normal range of the test device used. These results support the view that the benefits of cataract surgery are not well predicted by Snellen acuity, even though functional vision may be significantly reduced.
对103例患者的白内障手术效果进行了评估，这些患者在暗光下使用高对比度斯内伦视力表测量的视力为20/50或更好。患者希望接受白内障手术。他们抱怨有眩光症状，或者已经放弃夜间驾驶，或两者皆有。使用校准后的Vistech MCT 8000设备在模拟夜间条件下测量对比敏感度。在每度6周（20/70“等效视力”）时对比敏感度低于27的患者均未接受白内障手术。术前平均对比敏感度函数在所有测试频率（周/度）下均显示出异常低的值。术后这些值恢复正常。在回答术后问卷的99例患者中，41例（41%）术前夜间驾驶，80例（80%）术后夜间驾驶。24例非白内障患者（48只眼）的对照组处于所用测试设备的正常范围内。这些结果支持这样一种观点，即即使功能性视力可能显著降低，斯内伦视力也不能很好地预测白内障手术的益处。
