Corneal Thickness as a Risk Factor for Visual field Loss in Patients with Glaucomatous Optic Neuropathy

Abstract

Abstract: : Purpose: To determine whether central corneal thickness (CCT) is a risk factor for visual field loss development among patients diagnosed with glaucomatous optic neuropathy (GON). Methods: This longitudinal observational study included 98 eyes of 98 patients with glaucomatous optic neuropathy, with a mean follow-up time of 5.1 ± 3.0 years. Diagnosis of GON was based on masked assessment of optic disc stereophotographs. All patients had normal standard automated perimetry visual fields at baseline. Criteria for visual field abnormality were derived from a prior study¹. Several clinical factors (CCT, intraocular pressure (IOP), vertical cup-to-disc ratio, age, sex, 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 central corneal thickness (adjusted HR = 1.62 per 40µm thinner; P = 0.023; 95% CI: 1.07 to 2.43), higher baseline IOP (adjusted HR = 1.07 per mmHg; P = 0.022; 95% CI: 1.01 to 1.13) and larger baseline vertical cup-to-disc ratio (adjusted HR = 1.63 per 0.1 larger; P = 0.009; 95% CI: 1.13 to 2.35). The mean ± SD CCT of GON patients who developed visual field loss was 543 ± 36 µm as compared to 565 ± 35 µm of those who did not develop visual field abnormalities (P=.004, Student’s t test). Conclusions: CCT is a risk factor for development of visual field loss among patients diagnosed with glaucomatous optic neuropathy. It is important to consider CCT when establishing target intraocular pressure of patients with glaucomatous optic neuropathy. 1. Johnson CA, Sample PA, Cioffi GA, Liebmann JR, Weinreb RN. Structure and function evaluation (SAFE): I. criteria for glaucomatous visual field loss using standard automated perimetry (SAP) and short wavelength automated perimetry (SWAP). Am J Ophthalmol 2002; 134:177-185.

Keywords: clinical (human) or epidemiologic studies: ris • visual fields