Blindness and visual impairment in an urban West African population: the Tema Eye Survey.

OBJECTIVE: To determine the prevalence, causes, and risk factors of blindness and visual impairment among persons aged 40 years or older residing in an urban West African location. DESIGN: Population-based, cross-sectional study. PARTICIPANTS: A total of 5603 participants residing in Tema, Ghana. METHODS: Proportionate random cluster sampling was used to select participants aged 40 years or older living in the city of Tema. Presenting distance visual acuity (VA) was measured at 4 and 1 m using a reduced logarithm of the minimum angle of resolution tumbling E chart and then with trial frame based on autorefraction. A screening examination was performed in the field on all participants. Complete clinical examination by an ophthalmologist was performed on participants with best-corrected visual acuity (BCVA) <20/40 or failure of any screening test. MAIN OUTCOME MEASURES: Age- and gender-specific prevalence, causes, and risk factors for blindness (VA of <20/400 in the better eye, World Health Organization definition) and visual impairment (VA of <20/40 in the better eye). RESULTS: A total of 6806 eligible participants were identified, of whom 5603 (82.3%) participated in the study. The mean age (± standard deviation) of participants was 52.7 ± 1 0.9 years. The prevalence of visual impairment and blindness was 17.1% and 1.2%, respectively. After refraction and spectacle correction, the prevalence of visual impairment and blindness decreased to 6.7% and 0.75%, respectively, suggesting that refractive error is the major correctable cause of visual impairment and blindness in this population. Of 65 subjects with a VA <20/400, 22 (34%) were correctable with refraction, 21 to the level of visual impairment and 1 to normal. The remaining 43 patients (66%) had underlying pathology (cataract in 19, glaucoma in 9, nonglaucomatous optic neuropathy in 3, corneal opacities in 3, retinal disease in 3, and undetermined in 5) that prevented refractive correction. Increased age was a significant risk factor for blindness and visual impairment. CONCLUSIONS: There is a high prevalence of blindness and visual impairment among those aged ≥ 40 years in Tema, Ghana, West Africa. Refractive error is a major cause of blindness and visual impairment in this population, followed by cataract, glaucoma, and corneal disease.

Interobserver agreement and intraobserver reproducibility of the subjective determination of glaucomatous visual field progression.

PURPOSE: To determine the extent of interobserver agreement and intraobserver reproducibility of the subjective determination of visual field progression with achromatic automated static perimetry in eyes with glaucoma, and to determine the impact of access to Glaucoma Progression Analysis (GPA) data on interobserver agreement. DESIGN: Retrospective, observational case series. PARTICIPANTS: Five glaucoma subspecialists from 5 different academic medical centers. METHODS: Five visual field tests from each of 100 eyes of 83 patients being monitored for glaucoma were retrospectively identified and subjectively and independently evaluated by the 5 glaucoma subspecialists. Each set of visual fields was classified regarding progression as "none," "questionable," "probable," or "definite." More than 1 month later, the same expert observers reevaluated the same sets of visual field tests to allow determination of intraobserver reproducibility. A final subjective evaluation regarding progression was performed 3 months later, at which time the expert observers had access to the GPA printout. MAIN OUTCOME MEASURES: The level of interobserver agreement and intraobserver reproducibility was estimated using kappa statistics on the raw classification data and also on dichotomized data in which "none" and "questionable" progression were reclassified together as nonprogressed and " probable" and "definite" were reclassified as progressed. RESULTS: Intraobserver reproducibility was good to excellent (kappa = 0.62-0.78) for the raw data and moderate to good (kappa = 0.58-0.71) for the dichotomized data. Interobserver agreement was moderate (kappa = 0.45; 95% confidence interval [CI], 0.35-0.55) for the raw classification data and also for dichotomized data (kappa = 0.55; 95% CI, 0.46-0.64). Access to the GPA printout did not significantly change the level of interobserver agreement. CONCLUSIONS: Five glaucoma experts had good to excellent reproducibility of the determination of visual field progression compared with earlier evaluation of the same field sets. Agreement among the experts with each other was only moderate, and did not improve when each had access to GPA results. .