A population-based perspective on low-tension and classic primary open-angle glaucoma: The Baltimore Eye Survey

Although intraocular pressure (IOP) is a strong and consistent risk factor for primary open-angle glaucoma (POAG), a large proportion of the disease occurs in patients with IOPs within the normal range. Data from the population-based Baltimore Eye Survey were used to examine this relationship in unselected cases of POAG and controls. More than 5300 adults underwent comprehensive screening and definitive evaluation, if appropriate; 161 were diagnosed with POAG. The proportion of POAG cases classified as low tension ranged from 16 percent to more than 50 percent, depending on the criteria used to define low-tension glaucoma. No differences between high- and low-tension POAG in terms of patients' prior knowledge of their diagnosis or treatment status were noted. Demographic patterns for these two types of POAG were also similar. If the etiologic heterogeneity of POAG is accepted, there is little justification to divide POAG on the basis of IOP alone.