Effects of Central Corneal Stromal Thickness and Epithelial Thickness on Intraocular Pressure Using Goldmann Applanation and Non-Contact Tonometers

Abstract

PURPOSE: To investigate whether corneal thickness parameters measured by optical coherence tomography (OCT), such as central corneal thickness (CCT), central corneal stromal thickness (CCST), and central corneal epithelial thickness (CCET), influence the intraocular pressure (IOP) difference measured by Goldmann applanation tonometry (GAT) and non-contact tonometry (NCT). METHODS: In total, 50 eyes from 50 subjects without glaucomatous defects were included in this retrospective, cross-sectional study. We measured IOP using GAT and NCT and calculated the difference between the two methods. CCT was measured by a Cirrus HD-OCT device using anterior segment imaging. The basement membrane of the epithelium, which was seen as a high-reflection line in the OCT image, was taken as a reference line to measure CCST and CCET. RESULTS: The mean IOP measured by GAT and NCT was 16.7 +/- 3.0 and 18.1 +/- 3.8 mmHg, respectively. The mean IOP difference was 1.5 +/- 1.7 mmHg, and the IOP measured by NCT was 8.4% +/- 11.3% higher than that measured by GAT. The CCET and CCST were 57.9 +/- 5.6 and 501.7 +/- 33.8 mum, respectively. CCT showed a positive correlation with both GAT IOP (r = 0.648, P < 0.001) and NCT IOP (r = 0.676, P < 0.001). Although CCST showed a significant correlation with GAT IOP and NCT IOP, CCET did not. The difference between GAT IOP and NCT IOP increased with CCT (r = 0.333, P = 0.018), and CCET was positively correlated with the IOP difference between GAT and NCT (r = 0.435, P = 0.002). CONCLUSIONS: IOP increased with greater CCT, and CCST seemed to have a more important role than CCET. CCET also increased with greater CCT, and this may be a possible explanation for the increasing difference in IOP between GAT and NCT with increasing CCT.