Although elevated intraocular pressure (IOP) is a risk factor for glaucoma, the sensitivity, specificity, and positive predictive value of IOP screening for glaucoma is poor. Up to 50% of all patients with glaucoma may have pressures below 22 mm Hg at any given screening; therefore, glaucoma may remain undetected if these patients are screened on the basis of intraocular pressure alone. Because one-sixth of individuals with glaucoma may have intraocular pressures consistently below 22 mm Hg, an IOP of 22 mm Hg or higher is no longer part of the definition of glaucoma. In the past, a measurement of 21 mm Hg was considered the cutoff point for glaucoma because it is two standard deviations away from the mean IOP for the population in the United States, 16 mm Hg (assuming a normal, ie, Gaussian, distribution).