Factors Associated with Intraocular Pressure before and during 9 Years of Treatment in the Collaborative Initial Glaucoma Treatment Study
Presented in part at: Association for Research in Vision and Ophthalmology Annual Meeting, May 2006, Fort Lauderdale, Florida, and Fourth U.S. Symposium on Ocular Epidemiology, January 2007, Sarasota, Florida.
Received 2 March 2007; received in revised form 1 August 2007; accepted 6 August 2007. published online 26 October 2007.
Purpose
To evaluate, both at initial glaucoma diagnosis and during treatment, the role of demographic and clinical factors on intraocular pressure (IOP).
Design
Cohort study of patients enrolled in a randomized clinical trial.
Participants
Six hundred seven patients with newly diagnosed open-angle glaucoma (OAG) were enrolled at 14 centers in the United States.
Methods
After randomization to initial surgery or medications, patients were followed at 6-month intervals. Intraocular pressure was measured by Goldmann applanation tonometry. Predictive factors for IOP at baseline and during follow-up were analyzed using linear mixed models.
Main Outcome Measure
Intraocular pressure at baseline and during follow-up.
Results
The mean baseline IOP was 27.5 mmHg (standard deviation, 5.6 mmHg). Predictive factors for higher baseline IOP included younger age (0.7 mmHg per 10 years), male gender (2.4 mmHg higher than females), pseudoexfoliative glaucoma (5.4 mmHg higher than primary OAG), and pupillary defect (2.2 mmHg higher than those without a defect). During 9 years of follow-up, both surgery and medications dramatically reduced IOP from baseline levels, but the extent of IOP reduction was consistently greater in the surgery group. Over follow-up years 2 through 9, mean IOP was 15.0 versus 17.2 mmHg for surgery versus medicine, respectively. Predictive associations with higher IOP during follow-up included higher baseline IOP (P<0.0001), worse baseline visual field (mean deviation; P<0.0001), and lower level of education (P = 0.0019). Treatment effect was modified by smoking status: nonsmokers treated surgically had lower IOP than smokers treated surgically (14.6 vs. 16.7 mmHg, respectively; P = 0.0013). Clinical center effects were significant (P<0.0001) in both the baseline and follow-up models.
Conclusions
In this large cohort of newly diagnosed glaucoma patients, predictors of pretreatment IOP and IOP measurements over 9 years of follow-up were identified. Our findings lend credence to the postulate that sociodemographic, economic, compliance, or other environmental influences play a role in IOP control during treatment.
Available online: October 26, 2007.
1Department of Ophthalmology and Visual Sciences, Medical School, University of Michigan, Ann Arbor, Michigan.
2Department of Epidemiology, School of Public Health, University of Michigan, Ann Arbor, Michigan.
3Department of Biostatistics, School of Public Health, University of Michigan, Ann Arbor, Michigan.
4Department of Ophthalmology, Wake Forest University Baptist Medical Center, Winston-Salem, North Carolina.
5Greensboro Ophthalmology Associates, Greensboro, North Carolina.
Correspondence to David C. Musch, PhD, MPH, Department of Ophthalmology and Visual Sciences, Kellogg Eye Center, University of Michigan, 1000 Wall Street, Ann Arbor, MI 48105.
Manuscript no. 2007-296.
Supported by the National Eye Institute, Bethesda, Maryland (grant nos. EY015860, EY09148), and an unrestricted grant from Allergan, Inc., Irvine, California.
No author has a financial or proprietary interest in any product named.
ABSTRACT