Central Corneal Thickness and Measured IOP Response to Topical Ocular Hypotensive Medication in the Ocular Hypertension Treatment Study

EDITOR: WE AGREE WITH BRANDT AND ASSOCIATES 1 THAT GOLDmann applanation tonometry (GAT) yields systematic errors in measurement of intraocular pressure (IOP) attributable significantly to variations in central corneal thickness (CCT). We further agree that “true” IOP is far more complex than can be modeled by a simple linear arithmetic correction. However, there are a few issues related to the study that may be worth further discussion. We would like to point out that two plywoods placed together can bear four times as much weight as one. GAT is based on corneal deformation to external pressure. The relationship between the degree of corneal deformation to external pressure and the corneal thickness is not linear, but exponential. Exponential IOP correction formulas 2,3 are available, and they should give a better estimate of “true” IOP than a simple linear formula. Using the exponential IOP correction formula we developed, we calculated the “true” IOP from the data presented in Table 3 of