Correlation Between Intraocular Pressure, Central Corneal Thickness, Stage of Glaucoma, and Demographic Patient Data

Abstract

To determine the correlation of central corneal thickness (CCT) to Goldmann applanation tonometry (GAT) and dynamic contour tonometry (DCT, PASCAL®), and to glaucoma stage as assessed by cup-to-disc ratio (CDR). Prospective, cross-sectional tricenter observation study. From three glaucoma specialty practices a sample of 406 independent eyes was included. After ultrasound pachymetry, intraocular pressure was measured using PASCAL® and Goldmann applanation tonometry and cup-to-disc ration was reassessed. Demographic data were included in the multivariate analysis. Mean corneal thickness was 540 μm. African Americans and normal-tension glaucoma patients showed the lowest values (518 μm and 522 μm, respectively). These values were significantly thinner than the central corneal thickness of Caucasians (549 μm) and ocular hypertensives (564 μm). Intraocular pressure assessed by Goldmann applanation tonometry shows a significant correlation with central corneal thickness (r2=0.068, P<0.001), whereas PASCAL® is not significantly associated with central corneal thickness (r2<0.001, P=0.997). Increased IOP is significantly correlated with large ocular pulse amplitudes (r2=0.13, P<0.001), which is predominantly seen in ocular hypertensives. A significant negative correlation was detected between cup-to-disc ratio and central corneal thickness (r2=0.102, P<0.001). Glaucoma patients with thin central corneal thickness are more likely to be found at an advanced stage of the disease and among those with normal-tension glaucoma and black African ancestry. Underestimation of intraocular pressure by Goldmann applanation tonometry could be one causative factor.