《老友》专家门诊:我已83岁,左眼因角膜移植后受到排斥反应而失明多年。右眼患中度白内障,视力较差,前不久突然眼前一片漆黑,一点光感都没有了,休息三四分钟后又慢慢地恢复了光感和视力,至今一切如常。请问:这究竟是怎么一回事,今后应如何防范? “Friends” expert clinic: I have 83 years old, the left eye because of corneal rejection after rejection for many years. Right eye suffering from moderate cataracts, poor eyesight, shortly before suddenly a dark, a sense of light are gone, rest three or four minutes and then slowly restored the light perception and visual acuity, so far as usual. Excuse me: What exactly is this matter and how to prevent it in the future?