Anterior chamber depth and primary angle-closure glaucoma: an evolutionary perspective.

Anterior chamber depth is an inheritable trait which is affected by age, gender and race. Over 30 years ago, Alsbirk proposed that the shallow anterior chamber, which was typical of the Greenlandic Inuit, and which brings the iris in proximity to the cornea, may have evolved as a thermoregulatory adaptation to resist corneal freezing. Here, this hypothesis is revisited. Recent population genetic data which provide evidence for migration patterns of early humans are discussed and the notions of natural selection and ocular adaptation to cold climates are considered. Problems with the hypothesis are examined, but the idea that the shallow anterior chamber has a thermoregulatory role appears sound and suggests that shallow anterior chambers may have evolved in Homo sapiens living in north-east Asia during the last Ice Age.