Canadian Glaucoma Study: 1. Study design, baseline characteristics, and preliminary analyses

Abstract

Background: The Canadian Glaucoma Study is a multicentered, prospective longitudinal study designed to study a variety of systemic risk factors for the progression of open-angle glaucoma under a standardised interventional protocol for intraocular pressure (IOP) control.

Methods: Newly or previously diagnosed patients with early to moderate open-angle glaucoma were recruited consecutively from 5 hospital-based university departments. Baseline parameters, including an assessment of peripheral vasospasm, haematologic, coagulation, and immunopathologic variables were obtained. Newly diagnosed patients were targeted for a >or=30% reduction in IOP, whereas previously diagnosed patients entered the study at a physician-defined target IOP. After baseline examinations, patients were followed at 4-month intervals with standard automated perimetry, short-wavelength automated perimetry, and confocal scanning laser tomography, and at 28-32-month intervals with stereo disc photography. If the patient had visual field progression with standard automated perimetry, a further >or=20% reduction in IOP was mandated. A standardized IOP treatment protocol, ranging from topical monotherapy to filtration surgery, was implemented.

Results: A total of 258 patients (131 [corrected] men and 127 [corrected] women, median age 65.0 years) were enrolled. Baseline median values for visual acuity, visual field mean deviation, untreated IOP, and refractive error were 0.10 logMAR, -4.04 dB, 25.0 mm Hg, and 0.00 D, respectively. Approximately 30% of the patients were hypertensive, 16% had cardiovascular disease, 9% thyroid disease, 9% diabetes, 14% migraine, and 19% were smokers. The median follow-up was 5.3 years, with 148 (57.0%) and 51 (19.8%) patients completing >or=5 and >or=7 years follow-up, respectively. The cumulative visual field progression rate at 2, 4, 6, and 8 years was 11.3%, 21.5%, 33.1%, and 43.5%, respectively.

Interpretation: We describe the study design and baseline patient characteristics of the Canadian Glaucoma Study and present some preliminary results. This long and close follow-up of a large group of patients will reveal the importance of several systemic factors for the progression of glaucoma.