[Intraocular pressure measurements after penetrating keratoplasty using the ocular response analyzer versus goldmann applanation tonometer]

ABSTRACT

To compare intraocular pressure [IOP] readings measured by the Ocular Response Analyzer [ORA] with those measured by the Goldmann applanation tonometer [GAT] in keratoconic eyes following penetrating keratoplasty [PKP] and to evaluate the influence of anatomical and biomechanical properties of the grafts on IOP measurements. This cross-sectional study was conducted on 45 keratoconic eyes undergoing PKP. IOP was measured using the GAT [IOP GAT]; corneal hysteresis [CH], corneal resistance factor [CRF], Goldmannrelated IOP [IOPg], and cornea-compensated IOP [IOPcc] were obtained using the ORA; central graft thickness [CGT] was measured by ultrasonic pachymetry. Bland-Altman and mountain plots were used to evaluate agreement between the tonometers. The correlation of graft curvature and astigmatism; central graft thickness [CGT]; and corneal biomechanical properties with IOP readings was investigated using multivariate regression analysis. Mean patient age was 29.8 +/- 6.1 years and mean follow up was 91.2 +/- 35.4 months. Mean CH, CRF, and CGT were 10.2 +/- 2.1 mmHg, 10.1 +/- 2.2 mmHg, and 565.4 +/- 37.7 mm, respectively. Mean IOP GAT, IOPg, and IOPcc were 12.2 +/- 2.4, 15.1 +/- 3.5, and 15.8 +/- 3.3 mmHg, respectively [P<0.001]. The 95% limit of agreement between IOP GAT and IOPg ranged from -3.6 to 9.3 mmHg. CH and CRF, but not CGT or keratometric astigmatism were significantly associated with IOP GAT, IOPg, and IOPcc. Graft biomechanics had more influence on IOP values as compared to anatomical features. In comparison to GAT, the ORA seem to overestimate IOP in post-PKP eyes