Prevalence and determinants of glaucoma : an epidemiologic approach (The Rotterdam Study)

Glaucoma is an eye disease characterized by damage to the optic nerve head and related visual field defects, often accompanied by elevated intraocular pressure. Glaucoma is an important cause of blindness, particularly in the elderly. One may divide glaucoma in primary glaucoma without known preceding cause, and secundary glaucoma. Primary glaucoma may be genetically determined. The term secundary glaucoma refers to glaucoma caused by some known antecedent or concomitant ocular disease. Furthermore, primary glaucoma can be classified on anatomic basis into four major divisions: open-angle glaucoma, angle closure glaucoma, mixed glaucoma and congenital glaucoma. Primary open-angle is the most frequent type of glaucoma, but its pathogenesis is not well understood. In former times, the presence of an elevated intraocular pressure was considered necessary and sufficient to make a diagnosis of glaucoma. Nowadays solitary elevated intraocular pressure is called ocular hypertension and for the diagnosis primary open-angle glaucoma the emphasis lies on glaucomatous visual field defects even without elevated intraocular pressures. It is unknown whether the sensitivity of the eye for a certain level of intraocular pressure is decisive for the development of glaucomatous visual field defects, and whether glaucoma with normal intraocular pressures is a different disease entity from glaucoma with elevated intraocular pressures. Studies on risk factors for primary open-angle glaucoma, with and without elevated intraocular pressures, have been inconclusive. This thesis focuses on epidemiologic studies on primary open-angle glaucoma. The main part is devoted to the relation of putative risk factors with primary open-angle glaucoma and intraocular pressure whereby a distinction was made between glaucoma with elevated and normal intraocular pressures, respectively. In chapter 2 the current epidemiologic knowledge on primary open-angle glaucoma has been reviewed. The following four chapters are based on the Rotterdam Study, a population-based study of subjects aged 55 years and over. Chapter 3 deals with the distribution of primary open-angle glaucoma and relating characteristics in the Rotterdam Study. In chapter 4,5 and 6 putative risk factors, including diabetes mellitus and systemic blood pressure, are discussed in relation to primary open-angle glaucoma, intraocular pressure and optic disc parameters. Chapter 7 deals with a reproducibility study of intraocular pressure measurement. In chapter 8, some methodological considerations are given in relation to the previous studies, with a review of the results of these studies and some suggestions for further research.