Measuring intraocular pressure after intrastromal corneal ring segment implantation with rebound tonometry and Goldmann applanation tonometry

Abstract

Purpose: The aim of this study was to compare intraocular pressure (IOP) measurements in patients with ectatic corneas after intrastromal corneal ring segment (ICRS) implantation using the Rebound tonometers (RBTs) Icare and Icare Pro, compared with Goldmann applanation tonometry (GAT) and to assess the influence of central corneal thickness (CCT), corneal curvature (CC), and corneal astigmatism (CA) on IOP. Methods: This prospective cross-sectional study consecutively included 60 eyes of 60 patients with corneal ectasia having ICRS for at least 6 months from January 2011 to December 2013. All subjects underwent GAT, Icare, and Icare Pro IOP measurements in a random order, and CCT, CC, and CA evaluation using a Pentacam. The Bland–Altman method and multivariate regression analysis logistic method were used to assess intertonometer agreement and the influence of corneal variables on IOP measurements. Results: Icare significantly underestimated IOP compared with GAT [GAT - Icare 1.2 ± 3.0 mm Hg, P = 0.002 (95% confidence interval, 0.5–2.0)], whereas Icare Pro showed no statistical differences compared with GAT [GAT - Icare Pro 0.1 ± 3.1 mm Hg, P = 0.853 (95% confidence interval, -0.7 to 0.9)]. Both RBTs presented good concordance with GAT (intraclass coefficient correlation > 0.6). All tonometer measurements were influenced by CCT values and age (P < 0.05); the number of ICRS implanted did not influenced IOP measurement with any of the 3 tonometers. Conclusions: Both RBTs could be an alternative to GAT in patients with corneal ectasia and ICRS; however, Icare Pro shows greater accuracy.