Primary open-angle glaucoma in a population associated with high prevalence of primary angle-closure glaucoma: the Kumejima Study.

PURPOSE: To evaluate the prevalence of and risk factors for primary open-angle glaucoma (POAG) in a rural population of southwestern Japan.

DESIGN

Population-based cross-sectional study.

PARTICIPANTS

All residents 40 years of age and older in Kumejima, Okinawa, Japan.

METHODS

Of the eligible 4632 residents 40 years of age and older, 3762 subjects (participant rate, 81.2%) underwent screening examinations, including visual acuity (VA) measurement, slit-lamp examination, Goldmann applanation tonometry, gonioscopy, undilated stereoscopic fundus photographs, autorefractometry, noncontact specular microscopy, pachymetry, and visual field (VF) testing using frequency-doubling technology. If glaucoma or other related ocular disorders were suspected, subjects were referred for definitive examinations including VF testing with the Humphrey Field Analyzer. The diagnosis of POAG was based on the criteria of the International Society for Geographical and Epidemiological Ophthalmology.

MAIN OUTCOME MEASURES: Prevalence and risk factors of POAG.

RESULTS

The prevalence of POAG was 4.0% (95% confidence interval [CI], 3.4%-4.7%); 82% of patients had an intraocular pressure (IOP) less than 22 mmHg, resulting in a prevalence of 3.3% (95% CI, 2.8%-3.9%). Because of POAG, 3 subjects had a VA worse than 20/400 in only 1 eye, and 1 subject had VA loss of worse than 20/400 bilaterally. The average IOP values (mean ± standard deviation) were 14.9 ± 3.2 and 14.6 ± 3.3 mmHg in the right and left eyes, respectively; the IOP values were higher in patients with POAG (15.4 ± 3.3 and 15.2 ± 3.3 mmHg, respectively) than in subjects without glaucoma (14.8 ± 3.1 and 14.4 ± 3.1 mmHg, respectively; P<0.045, Student t test). Multivariate analysis showed that male gender (P = 0.003), older age (P<0.001), higher IOP (P<0.001), longer axial length (P<0.001), and thinner central cornea (P = 0.006) were associated with POAG.

CONCLUSIONS

High prevalence rates of POAG (4.0%) and POAG with normal IOP levels (3.3%), which were comparable with those on the Japanese mainland, were found in a southwestern rural island of Japan, where the prevalence of primary angle-closure glaucoma (previously reported as 2.2%) was considerably higher than on the Japanese mainland (0.6% in the Tajimi Study) or other countries. The risk factors for POAG included male gender, older age, higher IOP, myopia, and a thinner cornea.