The relationship between corneal biomechanical properties and intraocular pressure

Abstract

AbstractPurpose To determine the relationship between the biomechanical properties and the intraocular pressure (IOP) measured with the Goldmann applanation Tonometer (GAT) and a noncontact tonometer (NCT). Repeatability of corneal biomechanical properties was also assessed.Methods One randomly selected eye of 106 healthy subjects was assessed using the Ocular Response Analyzer (ORA), a noncontact tonometer, an ultrasound pachymeter and the Goldmann tonometer, on two separate days. The order of measurement was randomized between the ORA and the NCT, followed by measurements of central corneal thickness (CCT) and IOP with the GAT. The main outcome measures were corneal hysteresis (CH), corneal resistance factor (CRF), central corneal thickness (CCT) & IOP.Results The Pearson correlation coefficients between the GAT IOP on one hand and CH, CRF & CCT on the other, respectively, were: 0.323(P < 0.0001), 0.579 (p < 0.0001), & 0.421 (P < 0.0001) in session 1. The corresponding values for the NCT were: 0.565 (P < 0.0001), 0.772 (P < 0.0001) & 0.681 (P < 0.0001) respectively. The highest correlation coefficients obtained (with both tonometers) when IOP was plot against ‘CCT + CRF’, were: 0.562 (P<0.001) and 0.788 (P<0.0001), for the GAT and the NCT, respectively in session 1. Repeatability indices in the first session were ±2.91mmHg, ±2.51mmHg, and ±0.01μm, respectively, for CH, CRF, & CCT. Reproducibility indices were ±3.11mmHg, ±2.78mmHg and ±0.03μm for CH, CRF and CCT, respectively.Conclusion CH, CRF, and CCT are all significantly correlated with IOP, more so when the IOP is measured with a NCT. When plot together, CCT &CRF were best able to explain the variation of IOP. All three corneal biomechanical properties showed good repeatability and reproducibility indices.