Study Population

Details of the Blue Mountains Eye Study population and its methods are reported elsewhere. In brief, the Blue Mountains Eye Study is a population-based cohort study of vision and common eye diseases in an urban older population comprising 2 postcode areas in the Blue Mountains region, west of Sydney, Australia. This geographically well-defined area has a stable population that is reasonably representative of Australia in socioeconomic status and other measures. All residents 49 years of age or older of these 2 postcode areas were eligible and were invited to participate in the survey.

At baseline examinations (1992 through 1994), 4433 eligible residents were identified, of whom 3654 (82.4%) were interviewed and examined. Baseline differences between participants and nonparticipants were reported previously. All surviving participants were invited for re-examination after 5 years (1997 through 1999) and 10 years (2002 through 2004), with 2335 (75.1% of survivors) and 1952 (75.6% of survivors) returning for re-examinations at these times, respectively. Altogether, 2564 participants were followed-up at least once since their baseline examinations.

Comparisons of participants and nonparticipants at each follow-up examination have been reported previously. Nonparticipants were significantly younger ( P < .0001), were more likely to be current smokers ( P < .0001), and were more likely to have been diagnosed with diabetes ( P = .049). They also were more likely to report lower job prestige index ( P = .041) and were less likely to live in their own home ( P = .0006) than those who participated in follow-up examinations.

The study was approved by the University of Sydney and Western Sydney Area Health Service Human Research Ethics Committees. Written informed consent was obtained from all participants.

Procedures

An interviewer-administered questionnaire was used to collect detailed demographic and medical history data at each visit. All participants underwent detailed eye examinations. Slit-lamp lens photographs of each eye were obtained using Ektachrome 200 color film (Kodak, Rochester, New York, USA) on a Topcon SL-7E photograph slit-lamp camera (Topcon, Tokyo, Japan) to assess the presence of nuclear cataract. Retroillumination lens photographs were obtained using a Neitz CT-R cataract camera (Neitz Instruments, Tokyo, Japan) to assess the presence of cortical cataract and posterior subcapsular (PSC) cataract.

Presence of pseudoexfoliation was recorded at baseline eye examination as described previously. After pupil dilatation, a detailed high-magnification slit-lamp assessment of the anterior segment was performed by means of a narrowed slit beam by 1 observer (P.M.) on all participants. The anterior lens surface from each eye was scanned from left to right, looking specifically for early signs of PXS, including pregranular radial lines, as well as established granular deposits. Presence of specific anterior segment abnormalities was recorded, including the presence of exfoliative material on the anterior lens surface or on the pupil margin, with the latter useful in pseudophakic eyes.

Intraocular pressure was measured using applanation tonometry. Glaucoma was diagnosed from characteristic visual field loss combined with optic disc cupping and rim thinning without reference to intraocular pressure. Refractive error was assessed using autorefraction, followed by subjective best-corrected refraction. At the 5-year and 10-year follow-up visits, participants were re-examined in approximately the same order as that at baseline, using the same procedures and equipment.

The Wisconsin Cataract Grading System, first developed in 1990 for use in the Beaver Dam Eye Study, was followed closely in performing masked grading of all lens photographs obtained at each visit. Intergrader and intragrader reproducibility of the lens photograph grading was assessed using quadratic weighted κ statistics and was shown to be within an acceptable range in our study.

Incident cataract was defined as the appearance of nuclear, cortical, or PSC cataract subtypes in bilaterally phakic participants, in which the corresponding cataract subtype was not present in either eye at baseline. Similarly, incident cataract surgery was defined as cataract surgery performed in either eye of participants who were bilaterally phakic at baseline.

Progression of nuclear cataract was defined as an increase of 1.0 or more in the grading score of nuclear opacity. Progression of cortical cataract was defined as an increase of at least 10% of the lens area affected by the cortical cataract. Progression of PSC cataract was defined as an increase of at least 2% of the lens area affected by PSC cataract.

Statistical Analysis

SAS software (SAS Institute, Cary, North Carolina, USA) was used for data analysis. Generalized estimating equation regression models and eye-specific data were used to assess associations between the presence of pseudoexfoliation at baseline and the prevalence and 10-year incidence of cortical, nuclear, and PSC cataract or cataract surgery. Potential confounders adjusted for included age, gender, diabetes, smoking, steroid use, myopia, socioeconomic status, and open-angle glaucoma. Supplemental analyses using competing risk models considering competing event of death also were performed using subject-specific data and the SAS macros function. Findings are presented as odds ratios (ORs) with 95% confidence intervals (CIs).