The Canadian Glaucoma Study

• Status: Terminated
• Trial end date: 1995-06-01
• Target enrollment: 0
• Participant gender: All

Summary

Glaucoma is a disease which affects between one and two percent of all individuals aged over 40 years. According to recent Canadian National Institute for the Blind figures, it is the second largest specific cause of blindness in this country. The most common form of glaucoma, open-angle glaucoma, is incipient and typically results in a progressive loss of vision without symptoms due to damage to a structure inside the eye called the optic nerve head. Although the most important known risk factor for the development of open-angle glaucoma is high intraocular pressure (the pressure within the eyeball), a number of researchers have shown that a sizeable proportion of patients continue to lose vision in spite of successful treatment to lower their intraocular pressure. This finding suggests that there may be additional risk factors involved. Ocular vasospasm (the inability of certain blood vessels to dilate and increase blood flow according to the needs the eye) and vascular disease are among other factors implicated but their roles have not yet been fully investigated. The Canadian Glaucoma Study Group proposes to investigate the role of risk factors, including vasospasm and vascular disease, involved in the progression of open-angle glaucoma. We will recruit 410 patients with open-angle glaucoma across 4 centres (Halifax, Vancouver, Montreal and Toronto) who will be treated by experienced investigative ophthalmologists according to a uniform standard protocol to ensure that all patients are managed in the same manner. The patients will be followed meticulously with the most modern and accurate tests available every four months for a period of 5 years to determine whether progression has taken place. Visual function will be measured using two techniques called conventional perimetry and blue-on-yellow perimetry, and optic nerve heads will be examined with a special scanner capable of three-dimensional imaging. By defining both the ocular and systemic profiles of patients who progress and do not progress, we may be able to identify which patients will benefit from the standard treatment of intraocular pressure reduction, such as that prescribed in the study. More importantly, we will identify the characteristics of patients who do not benefit from standard treatment, so that alternative ones may be developed. Such studies are clearly necessary, but have not yet been conducted. We believe that the proposed study will increase our knowledge of open-angle glaucoma and reduce its impact on blindness and visual disability.

• Phase: N/A
• Accepts Healthy Volunteers?: No

Details

• Lead Sponsor: Dalhousie University
• Collaborators: Allergan; Canadian National Institute for the Blind; Glaucoma Research Society of Canada; Merck Frosst Canada Ltd.; Pfizer

Criteria

Inclusion Criteria:

1. Best corrected visual acuity of at least 6/9.

2. Previous visual field examinations showing nerve fibre bundle visual field defects characteristic of open-angle glaucoma and/or previous optic nerve head photographs showing cupping or notching characteristic of open-angle glaucoma.

3. Total visual field damage [in the eligibility visual field (see Section 6.1)] of between 2 and 10 dB using the visual field index Mean Deviation.46

4. Access to patient's previous ocular history and availability of initial untreated intraocular pressure (minimum of three readings).

(d) Normal non-closable angles by gonioscopy. (e) Willingness to participate in the study and to give informed consent.

Exclusion Criteria:

1. Non-glaucomatous ocular disease.

2. Systemic disease known to affect the visual field or ability to participate in the study.

3. Systemic beta-blockers.

4. Chronic ocular medication other than for glaucoma.

5. Previous incisional ocular surgery.

(e) Distance refraction exceeding 6.00 diopters equivalent sphere or 2.50 diopters of astigmatism.

(f) Aphakia or pseudophakia. (g) Contact lens wear.