The frequency and type of sleep disorders in 77 blind children, from 3 to 18 years of age, were compared with 79 matched controls, using a 42-item questionnaire in a study at the Stanford University Sleep Disorders Center, Stanford, CA, and the Laboratoire du Sommeil, Centre Hospitalier Universitaire de l’Hotel-Dieu a Paris, France. Questions were derived from the DSM-IV and the ICSD-90, and were answered by the child alone or with parental help. None had mental retardation nor any chronic illness aside from blindness. Only 8% had a circadian rhythm disorder (dyschronosis). Blindness occurred in perinatal life in 75% and after 1 year of life in 25%.
Mean total sleep time was similar in both groups; it was 526+/-61 minutes on weekdays and 600 min on weekends. A significantly greater proportion of blind children (17%) slept less than 7 hours per night on weekdays compared to controls (2.6%), and blind subjects had more sleep complaints (difficulty in getting to sleep, awakening too early, poor quality sleep, sleepwalking, bruxism). Daily episodic involuntary sleepiness occurred in 13% of blind children compared to 1.3% of controls. Age of onset of blindness and presence or absence of light perception had no influence on the complaints of insomnia. 
COMMENT. Insomnia is more common in blind children than controls, with early awakening particularly on school days. The resultant daytime sleepiness may have an adverse effect on learning.
Melatonin treatment of insomnia in children is reviewed from the University of British Columbia, Vancouver, Canada . The light-dark cycle is the strongest “zeitgeber”, an entraining factor that adjusts the function of the suprachiasmatic nucleus of the anterior hypothalamus and the endogenous circadian brain rhythms by environmental stimuli. Circadian disturbances can result from psychiatric and neurologic disorders, environmental factors, and use of drugs which interfere with pineal melatonin (MLT) secretion. Lack of appreciation of environmental zeitgebers may occur in mentally retarded or blind children, although the incidence was low in the Stanford study. Chronic disabilities may alter the perception of cues for synchronizing sleep with the environment, leading to sleep-wake cycle disorders. Abnormal endogenous MLT secretion has been reported in blind children with sleep disorders, especially those with cortical visual impairment, and in patients with cerebral palsy, or brain tumors involving the hypothalamus, optic chiasma, pineal, or prefrontal cortex. Patients with ocular visual loss are less affected.
The pineal produces MLT in the evening, reaching a peak at 3 am. Newborns have no MLT until 3 months, levels increase in the first year and remain stable until early puberty, when they begin to decline. MLT for the treatment of sleep-wake cycle disorders in children is discussed at length in this review article. Fast-release MLT is effective for about 5 hours; time-release MLT may last up to 9 hours. MLT should not be taken at the same time as other drugs or vitamins. Anticonvulsants and food alter the absorption of MLT. The dose recommended by researchers is dependent on age and the cause of the sleep disorder. Low doses (0.3 to 0.5 mg) are sometimes successful, but larger amounts are usually required: 1 to 3 mg in toddlers and 2.5 to 5 mg for older children. Sleep induction occurs within half an hour. Environmental changes to strengthen zeitgebers and foster healthy sleep habits are required to reset the circadian rhythm. The MLT assists in learning better sleep habits, and cognitive functioning and behavior improve. Once the desired effect is achieved, the MLT may be withdrawn, usually after some months, but depending on the underlying cause of the sleep disorder. Although no serious side effects are reported, the indiscriminate use of MLT is discouraged.