The term glaucoma is from the Greek glaukos, which means “watery blue.” It was first mentioned in the Hippocratic Aphorisms around 400 BC. However, it was considered a disease of the crystalline lens for several hundred years following. “The scientific history of glaucoma began the day on which cataracts were put in their correct place” (Albert Terson, 1867-1935). The correct anatomic location of cataracts is credited to Pierre Brisseau (1631-1717) in 1707. Elevation of intraocular pressure (IOP) as a sign of glaucoma was first mentioned in Breviary (1622) by Richard Banister (1570-1626). Discovery of the ophthalmoscope, by Hermann von Helmholtz (1821-1894) in 1851, and its subsequent use by Edward Jaeger (1818-1884) led to the belief that the optic nerve was also involved. Cupping of the optic nerve as a sign of glaucoma was confirmed by anatomist Heinrich Muller in the late 1850s. Von Graefe is credited with having first described contraction of the visual field and paracentral defects in glaucoma in 1856. In recent history, glaucoma had been defined by having an IOP above 21 mm Hg (i.e., more than two standard deviations above the mean IOP from a population-based survey of IOP, 16 ± 2 mm Hg). Later research indicated that the majority of people with IOPs above 21 mm Hg do not develop glaucomatous visual field loss (e.g., Ocular Hypertension Treatment Study). In addition, up to 40% of patients with documented glaucomatous visual field loss never achieve IOPs higher than 21 mm Hg (e.g., Baltimore Eye Survey). Our modern concept of primary open-angle glaucoma (POAG) is a description of the constellation of signs frequently seen in “glaucoma” that incorporate IOP as well as characteristic optic nerve and visual field changes. The hallmark of the diagnosis of glaucoma is progressive change in the optic nerve or visual field, or both, over time. Many glaucoma specialists believe that the syndrome of POAG probably encompasses many diseases with a final common pathway. Our most recent genetic investigations indicate that POAG is polygenic, in which minor alterations of numerous genes contribute to create the syndrome. All genetic mutations that are inherited in a Mendelian
pattern account for less than approximately 10% of all POAGs. Our definition of glaucoma will no doubt continue to evolve as our understanding of the disease increases.