Skene Debra J, Arendt Josephine
Centre for Chronobiology, School of Biomedical and Molecular Sciences, University of Surrey, Guildford GU2 7XH, UK.
Sleep Med. 2007 Sep;8(6):651-5. doi: 10.1016/j.sleep.2006.11.013. Epub 2007 Apr 8.
People who are blind, in addition to having to cope with partial or no sight, have an added handicap; the transmission of ocular light from the retina to their circadian clock is impaired. At its worse, for example in people with both eyes enucleated, this lesion results in desynchronisation of the biological clock (located in the hypothalamic suprachiasmatic nuclei) from the 24h day/night environment. While in a desynchronised state, symptoms akin to jet lag are experienced (e.g., daytime sleepiness, poor night sleep, reduced alertness and performance during waking). This is a lifelong condition. Daily administration of exogenous melatonin is the current treatment of choice for this so-called "non-24h sleep/wake disorder". Melatonin has been shown to correct the underlying circadian rhythm abnormality as well as improve sleep and reduce daytime napping. The effectiveness of melatonin therapy depends upon its time of administration relative to the timing of the person's circadian clock. If practicable, assessment of an individual's circadian phase (by measurement of the endogenous melatonin rhythm in plasma, saliva or urine) is recommended prior to commencing treatment to optimise melatonin's effectiveness.
盲人除了要应对部分视力丧失或完全失明外，还有一个额外的障碍；从视网膜到其生物钟的眼部光线传递受损。在最严重的情况下，例如双眼被摘除的人，这种损伤会导致生物钟（位于下丘脑视交叉上核）与24小时昼夜环境不同步。在不同步状态下，会出现类似于时差反应的症状（例如，白天嗜睡、夜间睡眠不佳、清醒时警觉性和表现下降）。这是一种终身疾病。每日服用外源性褪黑素是目前治疗这种所谓“非24小时睡眠/觉醒障碍”的首选方法。褪黑素已被证明可以纠正潜在的昼夜节律异常，改善睡眠并减少白天的小睡。褪黑素疗法的有效性取决于其给药时间与个体生物钟时间的关系。如果可行，建议在开始治疗前评估个体的昼夜节律相位（通过测量血浆、唾液或尿液中的内源性褪黑素节律），以优化褪黑素的疗效。
