PURPOSE: To determine the possible effect of corneal collagen crosslinking (CXL) with riboflavin and ultraviolet A (UVA) on intraocular pressure (IOP) measurements by Goldmann applanation tonometry (GAT).SETTING: Institute of Vision and Optics, Faculty of Medicine, University of Crete, Heraklion, Crete, Greece.DESIGN: Prospective case series.METHODS: This noncomparative study measured IOP by GAT before CXL and 6 months and 12 months after CXL.RESULTS: The study evaluated 55 eyes (55 patients). There was a statistically significant increase in the measured IOP 6 months and 12 months after CXL (both P<.001). The mean measured IOP was 9.95 mm Hg ± 3.01 (SD) before CXL, 11.40 ± 2.89 mm Hg at 6 months, and 11.35 ± 3.38 mm Hg at 12 months. The change in IOP measurements at both postoperative examinations was not correlated with patient age, preoperative pachymetry, or preoperative keratometry readings.CONCLUSION: After riboflavin-UVA CXL in eyes with keratoconus, there was a significant increase in IOP measured by GAT that was probably caused by an increase in corneal rigidity.