Abstract
Purpose: :
Corneal biomechanical properties can influence measurements of intraocular pressure (IOP) obtained with Goldmann applanation tonometry (GAT). The purpose of this study was to assess the influence of race on corneal biomechanical properties and to evaluate the relationship between these properties and GAT IOP measurements.
Methods: :
This was a prospective, observational study. Corneal biomechanical properties were measured using the Ocular Response Analyzer (ORA) in 45 eyes of Caucasian subjects and in 32 eyes of African American (AA) individuals. All participants had normal optic nerves and normal visual field results on standard automated perimetry testing. ORA provided measures of corneal hysteresis (CH), corneal resistance factor (CRF), and corneal compensated intraocular pressure (IOPcc). Central corneal thickness (CCT), axial length, keratometric values and GAT IOP measurements were also obtained for all patients. General linear regression models were used to evaluate differences in ORA parameters and IOP measurements between the two racial groups. One eye from each participant was randomly selected for statistical analysis.
Results: :
Mean ± SD CCT measurements were 530 ± 40 µm and 554 ± 36 µm in AA and Caucasians, respectively (P = 0.01). Corneal hysteresis measurements were significantly lower in AA subjects compared to Caucasians (9.35 ± 1.69 mmHg vs. 10.12 ± 1.46 mmHg; P = 0.03). Measurements of CRF were also significantly lower in AA individuals compared to Caucasians (9.34 ± 1.98 vs. 10.18 ± 1.71; P=0.05). When adjusted for age and CCT, mean values of corneal hysteresis and corneal resistance factor were not statistically significantly different between the two racial groups. GAT IOP measurements were significantly correlated with CCT measurements (r = 0.317; P = 0.04 for Caucasians and r = 0.439; P = 0.012 for AA subjects). IOPcc measurements were not significantly correlated with corneal thickness in any racial group (r = 0.131; P = 0.398 for Caucasians and r = 0.241; P = 0.184 for AA participants).
Conclusions: :
Corneal biomechanical properties, such as corneal hysteresis and corneal resistance factor, were significantly different between African-Americans and Caucasians. However, these differences seem to be mostly related to corneal thickness differences between these two racial groups. ORA IOPcc measurements seem to provide a measurement of intraocular pressure that is less influenced by corneal properties than GAT.
Keywords: intraocular pressure