Applanation Tonometry in the Diagnosis and Treatment of Glaucoma

Introduction Despite the increasing accuracy and availability of other methods and the ultimate dependence upon perimetry, the early detection of glaucoma and the evaluation of its therapy are still largely dependent on routine tonometry. However, Schiotz determinations of intraocular pressure may be in error because of deviations from the assumed average value for scleral rigidity. In a patient with increased scleral rigidity, this error leads to a falsely high estimate of intraocular pressure when measured with a Schiotz tonometer. Fortunately, in practice a high scleral rigidity alone in an otherwise normal eye rarely results in an assumed intraocular pressure high enough to make a false diagnosis of glaucoma. 1 A much more serious error occurs in instances of lower than average scleral rigidity. With a decreased rigidity, the Schiotz readings suggest an intraocular pressure lower than actually exists. In such eyes the presence of glaucoma may be overlooked. In addition,