Intraocular Pressure Elevation in Keratoconus with Coexisting Pseudoexfoliation Glaucoma: How Important is the Method of Measurement?

Objective In this report, we investigated the association between the intraocular pressure (IOP) values by two different measurement methods and the corneal biomechanical properties in a patient with keratoconus and secondary glaucoma due to pseudoexfoliation syndrome who developed a marked elevation of intraocular pressure in the right eye. Methods IOP was measured over a period of 3 days with Goldmann applanation tonometry (GAT) and dynamic contour tonometry (Pascal tonometry, DCT). Corneal hysteresis (CH) and corneal resistance factor (CRF) were estimated with the aid of an ocular response analyzer (ORA). Results CH and CRF were significantly reduced in the right eye compared to the left eye throughout the period of observation (paired t-test, p < 0.001). The difference between both methods of IOP measurement in the right eye was statistically significant for IOP < 30mmHg by GAT (Wilcoxon test, p = 0.004). For IOP values > 30mmHg by GAT, there was no statistically significant difference between DCT and GAT (Wilcoxon test, p = 0.0625). Conclusions This observation supports the clinical hypothesis that a significant decrease in CH translates to a decreased correlation of CH and IOP recordings by GAT and, furthermore, suggests that after a critical point of CH reduction, the impact of CH on GAT may be comparable to that on DCT.