Autism Spectrum Disorders (ASD) are a neurodevelopmental disorder. Their prevalence is estimated at around 0.4% of the general population worldwide. Their early onset and chronic nature make them a disabling disorder, all the more so as there is a high prevalence of sleep disorders in these populations, estimated at between 50 and 80%, with many complaints of insomnia in particular. These sleep disorders may result from biological, psychological, social, environmental and family factors. Smith Magenis Syndrome (SMS) is a complex disorder characterized by severe neurological, psychological and behavioral disorders including sleep-wake rhythm disorders. It is a rare disease with a prevalence of 1/25 000. These sleep disorders observed could be the consequence of a general dysregulation of the circadian system, since SMS patients show an inversion of the melatonin secretion profile (with a totally abnormal diurnal peak) and in patients with autism spectrum disorders, an overall reduction in melatonin secretion. These sleep-wake disturbances cycle could play a significant role in learning deficits and in the frequency and severity of behavioral abnormalities observed in SMS and ASD. In this project, investigators propose to study the mechanisms involved in the sleep-wake cycle disorders observed in Smith Magenis and Autism Spectrum children, in particular by evaluating the quality of the pupillary reflex using a pupillometer. The pupillary reflex is a simple and non-invasive method to test light sensitivity and the photobiological mechanisms involved. In this way, investigators want to evaluate the diurnal profile of the pupillary reflex in children with Smith Magenis syndrome and with Autism Spectrum Disorders in relation to the diurnal melatonin profile. Investigators will complete this study by determining the chronobiological profile of these patients by measuring different variables: * Diurnal cortisol and amylase profile * 24h body temperature and heart rate profile * Urinary cortisol and 6-sulfatoxymelatonin (major metabolite of melatonin) profiles * Daytime sleepiness profile measured subjectively by questionnaire and objectively via a waking EEG recording. * Actimetry at home * Polysomnography * A neurocognitive and behavioural assessment