Original Articles
Comparison of glaucomatous progression between untreated patients with normal-tension glaucoma and patients with therapeutically reduced intraocular pressures

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Abstract

PURPOSE: To determine if intraocular pressure plays a part in the pathogenic process of normal-tension glaucoma.

METHODS: One eye of each eligible subject was randomized either to be untreated as a control or to have intraocular pressure lowered by 30% from baseline. Eyes were randomized if they met criteria for diagnosis of normal-tension glaucoma and showed documented progression or high-risk field defects that threatened fixation or the appearance of a new disk hemorrhage. The clinical course (visual field and optic disk) of the group with lowered intraocular pressure was compared with the clinical course when intraocular pressure remained at its spontaneous untreated level.

RESULTS: One hundred-forty eyes of 140 patients were used in this study. Sixty-one were in the treatment group, and 79 were untreated controls. Twenty-eight (35%) of the control eyes and 7 (12%) of the treated eyes reached end points (specifically defined criteria of glaucomatous optic disk progression or visual field loss). An overall survival analysis showed a statistically significant difference between the two groups (P < .0001). The mean survival time ±SD of the treated group was 2,688 ± 123 days and for the control group, 1,695 ± 143 days. Of 34 cataracts developed during the study, 11 (14%) occurred in the control group and 23 (38%) in the treated group (P = .0075), with the highest incidence in those whose treatment included filtration surgery.

CONCLUSIONS: Intraocular pressure is part of the pathogenic process in normal-tension glaucoma. Therapy that is effective in lowering intraocular pressure and free of adverse effects would be expected to be beneficial in patients who are at risk of disease progression.

Section snippets

Patients and methods

Two hundred and thirty patients from 24 centers were enrolled in the study. The study was approved by the ethics committees of all the participating centers, and all patients signed written consent forms after the study was explained. A monitoring and safety committee regularly inspected the data for statistically significant outcomes and possible adverse events.

To be included, patients had to have unilateral or bilateral normal-tension glaucoma with optic disk abnormalities and visual field

Results

Two hundred and thirty eyes were enrolled in the study. All 145 eyes of 145 patients meeting the randomization criteria by virtue of showing progression as defined or having a threat to fixation at the time of recruitment were randomized. Five eyes in the treatment group were randomized but withdrew from the study before their intraocular pressure stabilized and therefore provided no information for this part of the study. They are, however, included in the subsequent intent-to-treat analysis.

Discussion

Shortly after the introduction of the ophthalmoscope, when the cupping of the optic nerve head was recognized as a feature of glaucomatous optic neuropathy, von Graefe20 recognized the existence of optic nerve head abnormality, with disturbances of vision, with digitally estimated normal intraocular pressure. His colleagues so severely criticized this concept that he later recanted but continued to stress that different optic nerves might have different susceptibilities to intraocular pressure.

Collaborative normal-tension glaucoma study group

Statistical design, consultation and analysis was carried out by Michael Schulzer, MD, PhD. Departments of Medicine & Biostatistics, University of British Columbia.

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    The study was generously funded by the Glaucoma Research Foundation, with special grants from the Oxnard Foundation and the Edward J. Daly Foundation, San Francisco, California.

    The members of the Collaborative Normal-Tension Glaucoma Study Group are listed at the end of the article.

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    [email protected]

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