Natural history of normal-tension glaucoma☆
Section snippets
Methods
Details of the study protocol were documented earlier.3, 4, 7 Pertinent here is that 260 subjects were enrolled from 24 collaborating centers, each with Institutional Review Board approval. To be considered eligible, the protocol called for the inclusion of subjects who had unilateral or bilateral NTG evidenced by glaucomatous cupping of the disc and field loss (as defined) with a median IOP of 20 mmHg or less in 10 baseline measurements. One reading of 23 or 24 mmHg was allowed by the
Characterization of subjects
Sixty-one of the 160 subjects were men and 99 were women. Their mean age and standard deviation were 63.6 ± 9.8 years. The eyes analyzed had a mean IOP at baseline of 16.1 ± 2.1 mmHg, and their baseline mean MD was −5.9 ± 4.2. Baseline data (Table 1) reveal no significant differences among the four subgroups in the distribution of gender, in mean age, or in mean IOP at entry. The MD index at entry was slightly less abnormal in those never randomized (P < 0.001).
The mean duration of the
Analysis of the natural course
In the total group of 160 eyes, 52 end points (four-of-five criteria) occurred. The Kaplan-Meier analysis (Fig 1A) estimated the mean time to end point and standard error (SE) at 2046 ±103 days. As illustrated in Figure 1B, there is no apparent or statistical difference (P = 0.778) between those immediately randomly assigned (group IRC) and the others (group NIR). The estimated mean survival for the IRC group is 1795 days (SE ± 169), for the NIR group 2070 days (SE ± 121), with 15 of 49 end
Discussion
In this multicenter clinical study of NTG, we collected data that made it possible to examine the natural history of the untreated disease in a large group of subjects. We believe that such an analysis has not been done previously.
If the subjects with NTG in some clinical practices differ from those we studied, our results may not apply fully. However, our study was conducted at a large number of centers, we have no reason to suspect that particular types of subjects were selectively included
Collaborating centers
Wallace L. M. Alward, MD, University of Iowa Hospital, Iowa City, Iowa
Frederick Feldman, MD, FRCS (C), Graham Trope, MD, University of Toronto, Ontario, Canada
L. Frank Cashwell, MD, Wake Forest University Medical Center, Winston-Salem, North Carolina
Jacob Wilensky, MD,UIC Eye Center, Chicago, Illinois
H. Caroline Geijssen, MD, Erik Greeve, MD, University of Amsterdam, The Netherlands
Harry Quigley, MD, Henry Jampel, MD, Johns Hopkins Hospital, Baltimore, Maryland
Greg Skuta, MD, Paul R. Lichter,
Data and coordinating center
Tara Steele Glaucoma Research Foundation, San Francisco, California
Statistical center
Michael Schulzer, MD, PhD, Departments of Medicine and Biostatistics, University of British Columbia, Vancouver, British Columbia, Canada
Reading committee
Douglas R. Anderson, MD, Stephen M. Drance, OC, MD
Data and safety monitoring committee
John Clarkson, MD (Chairman, 1989–1995), Steven Litinsky, MD (Chairman, 1995–), Robert Hardy, PhD (1993–1996) Joyce Schiffman, MS, Alvin Rose, PhD, James Neaton, PhD (1996–), Stephen M. Drance, OC, MD, Michael Schulzer, MD, PhD, Douglas R. Anderson, MD, Tara Steele
Steering & writing committee
Douglas R Anderson, MD, Stephen M Drance, OC, MD, Michael Schulzer, MD, PhD
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Funded by the Glaucoma Research Foundation, San Francisco, California, with special grants from the Oxnard Foundation and the Edward J. Daly Foundation, San Francisco, California.