Tonography and projection perimetry. Relationship according to receiver operating characteristic curves

G. L. Portney and M. Krohn

Previous large scale tonographic studies revealed a significant overlap of coefficient of outflow (C) values for normal and glaucomatous eyes, but their differential diagnosis rested primarily on tangent screen visual field tests. To determine whether projection perimetry would make a difference in the correlation of outflow coefficients with glaucoma, 434 eyes from normal, ocular hypertensive (those without scotomas but with elevated intraocular pressure) and glaucomatous categories were evaluated. Results support the conclusions of earlier work concerning C value overlap and demonstrate the relatively better specificity of the initial intraocular pressure over one coefficient of outflow (Po/C) in distinguishing normal from glaucomatous eyes. It also shows that ocular hypertensives as a group are no different from glaucoma patients with regard to their aqueous outflow. Tonographic tests are, therefore, useful in identifying those eyes that need to be watched closely for the development of glaucomatous change.