Biological Clock Dysfunction in Optic Nerve Hypoplasia

Background: Optic Nerve Hypoplasia (ONH) is a leading cause of blindness in children. For unclear reasons, the incidence of ONH is increasing, with ONH affecting about 1 in 10,000 live-born infants. In addition to visual deficits, ONH is associated with varying degrees of hypopituitarism, developmental delay, brain malformations and obesity. Although genetic mutations have been rarely observed to result in ONH, the causes of ONH are largely not known. In limited anatomical observations, the suprachiasmatic nuclei (SCN) located in the anterior hypothalamus, which generate circadian rhythms, have been observed to be abnormal in children with ONH. Thus, children with ONH may have biological clock dysfunction. In collaborative studies with Dr. Mark Borchert of Childrens Hospital Los Angeles (CHLA), we have recently discovered that one-half of children with ONH have grossly abnormal sleep-wake patterns, as assessed by actigraphy. Although not known for children with ONH, abnormal sleep-wake patterns have been observed to be associated with neurocognitive impairment and obesity. We also observe that nocturnal melatonin administration can improve abnormal sleep-wake cycles in these children, raising the possibility that it will be possible to treat abnormal rhythmicity in children with ONH.