Population studies of glaucoma provide information that is additive to what can be deduced from studies of persons being treated in clinical offices. For example, we learned from studies of randomly selected persons that half of those with open-angle glaucoma (OAG) have normal intraocular pressure.1 Australian investigators identified 1700 possible OAG cases in Tasmania,2 whose 500 000 inhabitants would be expected to have about 5000 cases of OAG (with OAG defined by reported criteria3). The method of case identification was systematic, but not random, selection. The Tasmanian study suggests that familial cases of glaucoma occur at an earlier age and patients are more severely affected than those with sporadic OAG.
Quigley HA. Chase the Family. Arch Ophthalmol. 2006;124(7):1036-1037. doi:10.1001/archopht.124.7.1036