Primary angle-closure glaucoma. Oculometry, epidemiology, and genetics in a high risk population.

The ocular dimensions in patients suffering from primary angle-closure glaucoma (a.c.g.) have been studied in several clinical series, chiefly in Caucasians. The epidemiology and aetiology of a.c.g. are less well known although genetic factors seem to be involved. Eskimos have recently been shown to constitute a high risk population with respect to a.c.g. Consequently, a series of oculometric, epidemiologic, and genetic studies among Greenland Eskimos was undertaken. Besides the immediate purpose, prevention of blindness in this population, the survey had important general aspects and the following main results were obtained: 1a) Ocular dimensions, as well as clinical symptoms, in Eskimo a.c.g. patients correspond closely to those of a.c.g. reports from other ethnic groups and 1b) ocular dimensions of the anterior segment in the general Eskimo population deviate conspicuously towards the low level characteristic of all samples of a.c.g. patients. 2) A.c.g. prevalence rates were estimated at 1.6% in males and 5.1% in females of the general population aged 40 years or more. The epidemiology of a.c.g. seems to reflect closely the variations of axial anterior chamber depth (ACD) according to race (Eskimo, Caucasian), sex and age. Empirical a.c.g. risk estimates, depending on the ACD value, were obtained in elderly females. 3) A relatively shallow chamber was found in 1st and 2nd degree relatives of a.c.g. patients, in close agreement with an earlier study in Caucasians (Törnquist 1953). However, also in the general Eskimo population a pronounced familial resemblance with respect to ACD and corneal diameter was found. Thus the family studies indicate that the size of the anterior chamber shows a mainly genetic determination, which probably constitutes the genetic basis of a.c.g. as well. With this background a hypothesis is discussed, which interprets the small anterior chambers in Eskimos as a result of genetic adaptation to arctic environment. Corneal protection may have been the significant advantage and the a.c.g. load in elderly persons a relatively less important cost.