Myopia, Light and Circadian Rhythms

Myopia has been investigated scientifically for over a century but the search for an effective remedy has been manifestly unsuccessful. The prevalence of myopia in developed societies has now risen to about 30% in USA (Vitale, Sperduto et al. 2009) and up to 70% in some Asian centres (Lin, Shih et al. 2004). In addition to the socio-economic burden of providing optical corrections for myopia, common myopia limits career choice and increases the risk of glaucoma and cataract. High myopia also increases the risk of retinal detachment, chorioretinal degeneration and subsequent visual impairment (Saw, Gazzard et al. 2005). Both genetic and environmental factors have been implicated in the aetiology of myopia. Children with myopic parents have a higher than normal risk of developing myopia (Mutti, Mitchell et al. 2002) and twin studies show a higher level of concordance of common myopia in monozygotic compared to dizygotic twins (Dirani, Chamberlain et al. 2006). However, the rapid rise in myopia prevalence over recent decades argues strongly that changing environmental factors also play an important role in the aetiology of myopia.