Comparison of the Ocular Response Analyzer and the Goldmann Applanation Tonometer for Measuring Intraocular Pressure after Deep Anterior Lamellar Keratoplasty

Abstract

To compare intraocular pressure (IOP) measured using the Ocular Response Analyzer (ORA; Reichert Ophthalmic Instruments, Buffalo, NY) with that measured using the Goldmann applanation tonometer (GAT) in keratoconic eyes after deep anterior lamellar keratoplasty (DALK) and evaluate the influence of central graft thickness (CGT), corneal astigmatism, corneal hysteresis (CH), and corneal resistance factor (CRF) on the IOP measurements. IOP using the GAT (IOP(GAT)), CH, CRF, Goldmann-correlated IOP (IOP(g)), cornea-compensated IOP (IOP(cc)) using the ORA, and CGT were measured in 23 keratoconic eyes undergoing DALK. Bland-Altman plots were used to evaluate agreement between the tonometers. The correlation between refraction, CH, CRF, and CGT with IOP readings was investigated using multivariate regression analysis. Mean patient age was 27.2 ± 6.5 years. Mean CGT, CH, and CRF were 547.0 ± 42.6 μm, 9.6 ± 2.1 mm Hg, and 9.4 ± 2.1 mm Hg, respectively. Mean IOP(GAT), IOP(g), and IOP(cc) were 11.3 ± 2.9, 14.1 ± 2.4, and 15.6 ± 2.6 mm Hg, respectively (P < 0.001). The 95% limit of agreement for IOP(g) and IOP(GAT) was between -2.61 and 8.19 mm Hg and for IOP(cc) and IOP(GAT) it was between -0.69 and 9.21 mm Hg. CH and CRF were significantly associated with IOP(GAT). No significant association was found between CGT and IOP readings obtained using either the ORA or GAT. IOP readings by the ORA were significantly greater than those by the GAT, and CH and CRF play a more important role in post-DALK IOP readings by both GAT and ORA than other graft characteristics including curvature and central thickness.