The relationship between central corneal thickness-adjusted intraocular pressure and glaucomatous visual-field loss

Background Although measurement of central corneal thickness (CCT) is increasingly becoming an important component of glaucoma risk analysis, significant controversy exists regarding the benefit of calculating a corrected intraocular pressure (I0P) value from measured I0P and CCT data. Methods Three hundred forty-four male subjects were identified from a VA eye clinic with one of the following clinical diagnoses: ocular hypertension (OHT), primary open-angle glaucoma (POAG), normal tension glaucoma (NTG), and normal tension glaucoma suspect (NTGS). Using one eye per subject, multi-variate logistic regression and correlational analyses were performed to determine relationships between glaucomatous visual-field loss and several glaucoma risk factors, including adjusted I0P values. Results Multivariate logistic regression analysis did not identify CCT-adjusted I0P values as independent risk factors for development of either NTG or POAG-related glaucomatous visual-field loss. CCT, however, was found to be strongly associated with both NTG and POAG-related visual-field loss. Correlational analysis revealed a weak correlation between Ehlers-adjusted pre-treatment I0P and severity of POAG-related visual-field loss, but no other adjusted I0P values significantly correlated with severity of visual-field loss in either POAG or NTG. Conclusions Our results suggest that adjusted I0P, as calculated using current algorithms, is not useful within glaucoma risk analysis, since adjusted I0P was unable to predict either presence or severity of glaucomatous visual-field loss in this study. CCT, conversely, was found to be a robust and independent predictor of glaucomatous visual-field loss. These findings, while supporting routine CCT measurements for all glaucoma suspects, do not support routine clinical computation of adjusted I0P values using current algorithms.