Original articles
The advanced glaucoma intervention study (AGIS): 7. the relationship between control of intraocular pressure and visual field deterioration

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Abstract

PURPOSE: To investigate the association between control of intraocular pressure after surgical intervention for glaucoma and visual field deterioration.

METHODS: In the Advanced Glaucoma Intervention Study, eyes were randomly assigned to one of two sequences of glaucoma surgery, one beginning with argon laser trabeculoplasty and the other trabeculectomy. In the present article we examine the relationship between intraocular pressure and progression of visual field damage over 6 or more years of follow-up. In the first analysis, designated Predictive Analysis, we categorize 738 eyes into three groups based on intraocular pressure determinations over the first three 6-month follow-up visits. In the second analysis, designated Associative Analysis, we categorize 586 eyes into four groups based on the percent of 6-month visits over the first 6 follow-up years in which eyes presented with intraocular pressure less than 18 mm Hg. The outcome measure in both analyses is change from baseline in follow-up visual field defect score (range, 0 to 20 units).

RESULTS: In the Predictive Analysis, eyes with early average intraocular pressure greater than 17.5 mm Hg had an estimated worsening during subsequent follow-up that was 1 unit of visual field defect score greater than eyes with average intraocular pressure less than 14 mm Hg (P = .002). This amount of worsening was greater at 7 years (1.89 units; P < .001) than at 2 years (0.64 units; P = .071). In the Associative Analysis, eyes with 100% of visits with intraocular pressure less than 18 mm Hg over 6 years had mean changes from baseline in visual field defect score close to zero during follow-up, whereas eyes with less than 50% of visits with intraocular pressure less than 18 mm Hg had an estimated worsening over follow-up of 0.63 units of visual field defect score (P = .083). This amount of worsening was greater at 7 years (1.93 units; P < .001) than at 2 years (0.25 units; P = .572).

CONCLUSIONS: In both analyses low intraocular pressure is associated with reduced progression of visual field defect, supporting evidence from earlier studies of a protective role for low intraocular pressure in visual field deterioration.

Section snippets

Materials and methods

The Advanced Glaucoma Intervention Study design and methods, described in detail elsewhere,16, 17, 18 are summarized here. Appropriate institutional review boards approved the Advanced Glaucoma Intervention Study protocol, and all enrolled patients provided informed consent.

To be eligible for the Advanced Glaucoma Intervention Study, patients had to be 35 to 80 years old and have open-angle glaucoma that could no longer be adequately controlled by medications alone. Eligible eyes had to be

Results

Table 2presents some baseline characteristics for each of the defined intraocular pressure groups for the 738 eyes in the Predictive Analysis. Some characteristics differ by assigned intervention sequence: the majority of eyes with intraocular pressure averaged over the first three 6-month visits of less than 14 mm Hg were in the trabeculectomy–argon laser trabeculoplasty–trabeculectomy sequence, and a majority of eyes in the 14 to 17.5 mm Hg and greater than 17.5 mm Hg groups were in the argon

Discussion

We undertook the present analyses to determine whether the achievement of low levels of intraocular pressure after surgical intervention in eyes of Advanced Glaucoma Intervention Study patients is associated with a slowing of visual field deterioration. We found from both the Predictive Analysis and Associative Analysis that low postintervention intraocular pressure is associated with reduced progression of visual field defect. Moreover, the association became stronger as follow-up lengthened.

Advanced Glaucoma Intervention Study Centers and Investigators: participating institutions, current investigators, and former investigators who participated for two or more years

Study Co-chairmen: Douglas E. Gaasterland, MD; Fred Ederer, MA, FACE

Acknowledgements

The authors thank Paul F. Palmberg, MD, PhD, Bascom-Palmer Eye Institute and member of the Advanced Glaucoma Intervention Study Policy and Treatment Effects Monitoring Board, for suggesting this investigation and for helpful comments on a draft of the manuscript.

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    This study was supported by grants from the National Eye Institute (grant numbers 2 UI0 EY06824 through 2 U10 EY06827, 2 U10 EY06830 through 2 U10 EY06835, 2 U10 EY07057, and 7 U10 EY09640) and the Office of Research on Minority Health. The two agencies are part of the National Institutes of Health, U.S. Department of Health and Human Services, Bethesda, Maryland.

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    The writing team members for this paper are: Paul C. VanVeldhuisen, MS, Fred Ederer, MA, FACE, Douglas E. Gaasterland, MD, E. Kenneth Sullivan, PhD, Allen Beck, MD, Bruce E. Prum, Jr, MD, Marshall N. Cyrlin, MD, and Howard Weiss, MD, MPH. A complete list of participants in the Advanced Glaucoma Intervention Study appears at the end of this article.

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    [email protected]

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