Primary Open Angle Glaucoma: Is It Just One Disease?

Purpose of Review: This article reviews evidence from the literature suggesting that primary open angle glaucoma (POAG) represents a group of heterogeneous diseases with varying clinical features rather than a single disease. Recent Findings: A growing body of evidence has been made available recently indicating that POAG behaves differently in different subpopulations. Although normal tension glaucoma has long been regarded as a diagnosis distinct from POAG, a considerable degree of overlap exists in their pathophysiology and clinical characteristics and suggests that intraocular pressure alone is not a reliable means of separating POAG into different subtypes. Meanwhile, POAG patients with initial paracentral visual field defects rather than early peripheral defects more often exhibit systemic vascular dysregulation, regardless of whether their intraocular pressures are high or low. Patients of African and Afro-Caribbean heritage develop a subtype of POAG that manifests at an earlier age, displays a more rapid disease course, and leads to blindness more frequently than do patients of European descent. Summary: Recognizing the existence of various POAG subtypes differentiated by factors other than intraocular pressure alone will allow clinicians to diagnose glaucoma more accurately and provide more individualized care.