Associations between Elevated Intraocular Pressure and Glaucoma, Use of Glaucoma Medications, and 5-Year Incident Cataract: The Blue Mountains Eye Study
Received 26 August 2005; accepted 15 October 2005. published online 03 February 2006.
Purpose
To examine incident relationships between elevated intraocular pressure (IOP), open-angle glaucoma (OAG), and use of glaucoma medications with 5-year incident cataract.
Design
Population-based cohort study.
Participants
The Australian Blue Mountains Eye Study examined 3654 participants ≥50 years old at baseline (82.4% response; 1992–1994); 2335 eligible participants were reexamined after 5 years (75.1% response; 1997–1999).
Methods
A detailed medical and ocular history, including current medications, was taken, and a comprehensive eye examination, including applanation tonometry, automated perimetry, and lens photography, was performed at each examination. The Wisconsin system was used to grade lens photographs in assessing incident nuclear, cortical, and posterior subcapsular cataract (PSC). Data from both eyes were assessed using generalized estimating equation analyses.
Main Outcome Measures
Elevated IOP was defined as ≥21 mmHg. Open-angle glaucoma was diagnosed from typical glaucomatous field loss with matching optic disc cupping, without reference to IOP. Subjects without OAG or secondary or angle-closure glaucoma with IOP > 21 mmHg in either eye were classified as having ocular hypertension (OH), as were non-OAG subjects with IOP < 22 mmHg using glaucoma medications. Wisconsin levels 4 to 5 were graded as nuclear cataract, at least 5% lens involvement was graded as cortical cataract, and any PSC defined its presence.
Results
The 5-year incidence of nuclear cataract was 23.4% (592/2532), or 23.1% (574/2486) after excluding subjects using glaucoma medication. A marginally significant association was found for elevated IOP or OH at baseline and incident nuclear cataract (odds ratio [OR], 1.93 [95% confidence interval (CI), 0.97–3.89], and OR, 1.83 [95% CI, 0.96–3.48], respectively) in subjects not using glaucoma medications, after multivariate adjustment. Age- and gender-adjusted analyses showed similar but statistically significant associations. The association between elevated IOP or OH and nuclear cataract was significant in multivariate analyses (OR, 2.07 [95% CI, 1.04–3.12], and OR, 1.78 [95% CI, 1.05–3.01], respectively). Use of glaucoma medications was associated with nonsignificantly increased adjusted odds for incident nuclear cataract (OR, 1.90 [95% CI, 0.92–3.92]). No associations, however, were found with incident cortical cataract or PSC.
Conclusions
Elevated IOP may increase the risk of nuclear cataract, but not that of other types. The use of glaucoma medications could magnify this risk.
1Centre for Vision Research, Department of Ophthalmology and Westmead Millennium Institute, University of Sydney, Westmead, Australia
2School of Public Health, University of Sydney, Sydney, Australia
Correspondence to Paul Mitchell, MD, PhD, Centre for Vision Research, Department of Ophthalmology, University of Sydney, Westmead Hospital, Hawkesbury Road, Westmead, NSW 2145, Australia.
ABSTRACT