Corneal thickness as a risk factor for visual field loss in patients with preperimetric glaucomatous optic neuropathy

Purpose: To determine whether central corneal thickness (CCT) is a risk factor for visual field loss development among patients diagnosed with preperimetric glaucomatous optic neuropathy (GON). Design: Observational cohort study. Methods: The study included 98 eyes of 98 patients with GON, with a mean follow-up time of 4.3+/-2.7 years. Diagnosis of GON was based on masked assessment of optic disk stereophotographs. All patients had normal standard automated perimetry visual fields at baseline. Criteria for visual field abnormality were derived from a prior study. Several clinical factors (CCT, intraocular pressure, vertical cup-to-disk ratio, refraction, age, gender, family history of glaucoma, high blood pressure, cardiovascular disease, and migraine) were investigated to ascertain whether there is an association with development of repeatable visual field loss. Cox proportional hazards models were used to obtain hazard ratios (HR) and identify factors that predicted which individuals developed glaucomatous visual field loss during the follow-up period. Results: Thirty-four patients (35%) developed repeatable visual field abnormality during follow-up. In multivariate analysis, risk factors that predicted the development of visual field loss were a thinner CCT (adjusted HR=1.62/40 mum thinner; P=.023; 95% confidence interval [CI]: 1.07-2.45), higher baseline intraocular pressure (adjusted HR=1.07/mm Hg; P=.022; 95% CI: 1.01-1.14), and larger baseline vertical cup-to-disk ratio (adjusted HR=1.63/0.1 larger; P=.009; 95% CI: 1.13-2.35). The mean +/- standard deviation CCT of GON patients who developed visual field loss was 543+/-36 mum compared with 565+/-35 mum of those who did not develop visual field abnormalities (P=.005, Student t test). Conclusion: Central corneal thickness is a risk factor for development of visual field loss among patients diagnosed with preperimetric GON. It is important to consider CCT when establishing target intraocular pressure of patients with GON.