[Intraocular pressure and primary open-angle glaucoma. Epidemiologic technics in practice]

It is the object of this paper to familiarize the ophthalmologist with some modern epidemiological techniques and to present examples of their application to a consideration of the influence of the level of intraocular pressure on the development of the type of visual field loss characteristic of primary open angle glaucoma. Epidemiological methods are particularly required in chronic multifactorial diseases such as primary open angle glaucoma and arterial hypertension to obtain reliable guidance on practical measures for their treatment or control. Two basic requirements are reliable uniform data suitable for computer manipulation and epidemiological methods to exploit the data and yield conclusions as free of bias and confounding as possible. An example of a glaucoma data base is described and types of enquiry and the importance of standardising prevalence estimations are discussed. Analyses by the four-fold table, risk ratios, the effect of stratification, sensitivity, specifity and the decision curve are described. Attributable risk (potential for prevention) is indicated as yielding information suitable for public health programmes. The life table method is described when relating initial observations to subsequent progressive visual field loss. The factors to be considered in epidemiological work generally and the inferences concerning the early diagnosis of primary open angle glaucoma are discussed.