Central corneal thickness and normal tension glaucoma: a cross-sectional study.

BACKGROUND: Recently published evidence has identified thinner central corneal thickness (CCT) as a strong predictive factor for the conversion from ocular hypertension (OHT) to primary open-angle glaucoma (POAG). The association between CCT and development of normal-tension glaucoma (NTG), however, is less clear. Accordingly, we designed this cross-sectional study to further explore the relationship between CCT and NTG. PATIENTS AND METHODS: All patients with a clinical diagnosis of NTG and NTG suspect (NTGS) who were seen from September 2002 through May 2003 at the Albuquerque VA Medical Center eye clinic were identified retrospectively. After eligible subjects were categorized into no, mild, moderate, and advanced visual field loss groups, analysis of variance (ANOVA) and regression analyses were used to determine group differences for several IOP variables, several systemic variables, and CCT. Additional analyses were completed after eligible subjects were recategorized into thin, intermediate, and thick CCT groups. RESULTS: Eighty-four eyes in 84 NTGS subjects and 56 eyes in 56 NTG subjects were studied. Mean CCT was significantly thicker in the no field loss group (NTGS) when compared with all 3 groups with glaucomatous visual field loss (NTG). In multivariate regression analysis, the association between CCT and the presence of NTG-related visual field loss was robust and independent. Conversely, no relationship was found between CCT and severity of NTG-related visual field loss. CONCLUSIONS: In eyes characterized by statistically normal intraocular pressure (IOP) measurements as measured by Goldmann applanation tonometry, we found a significant relationship between CCT and the presence, but not severity, of glaucomatous visual field loss. A prospective study is required to further explore and confirm these relationships.

Relationship between central corneal thickness and severity of glaucomatous visual field loss in a primary care population.

BACKGROUND: Although the ability of central corneal thickness (CCT) to predict development of primary open-angle glaucoma has become increasingly well recognized, the ability of CCT to predict severity of glaucoma remains uncertain. This study was designed to expand the available knowledge about the relationship between CCT and glaucoma severity. METHODS: Retrospective identification of all patients with a clinical diagnosis of either primary open angle glaucoma (POAG) or ocular hypertension who were seen from September 2002 through May 2003 at the Albuquerque VA Medical Center eye clinic was completed. Eligible subjects were segregated into no, mild, moderate, or advanced visual field loss groups based on Advanced Glaucoma Intervention Study (AGIS) visual field scoring criteria. Following statistical analyses comparing the visual field groups, the sample was divided into thin, intermediate, and thick CCT groups, and further analysis was performed. RESULTS: Mean CCT was significantly higher in the no field loss group compared with all 3 groups with glaucomatous visual field loss. Mean CCT was not statistically different, however, between the mild, moderate, and advanced visual field loss groups. In linear regression analyses, no significant relationship was found between CCT and severity of visual field loss. CONCLUSIONS: Although CCT was associated strongly with development of POAG-related visual field loss, CCT was not associated with severity of visual field loss in this study. These findings suggest that glaucoma patients with thinner corneas are just as likely to have advanced levels of field loss as glaucoma patients with thicker corneas. Prospective studies are needed to validate these findings.

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 (IOP) value from measured IOP 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, multivariate logistic regression and correlational analyses were performed to determine relationships between glaucomatous visual-field loss and several glaucoma risk factors, including adjusted IOP values. RESULTS: Multivariate logistic regression analysis did not identify CCT-adjusted IOP 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 IOP and severity of POAG-related visual-field loss, but no other adjusted IOP values significantly correlated with severity of visual-field loss in either POAG or NTG. CONCLUSIONS: Our results suggest that adjusted IOP, as calculated using current algorithms, is not useful within glaucoma risk analysis, since adjusted IOP 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 IOP values using current algorithms.