PURPOSE: To assess the myopic shift in refraction caused by incident cataract in the Blue Mountains Eye Study (BMES) population. METHODS: Five-year prospective follow-up of the BMES, initially performed in 1992. After 5 years, 2335 survivors (75.1%) of 3654 baseline BMES participants were re-examined. Refractive change was assessed by age, sex, incident cataract type and baseline refraction. Slit-lamp and retroillumination lens photographs were graded for presence of incident cataract and signs of previous cataract surgery. Objective and subjective refractions were performed. RESULTS: In a multivariate model, age (p < 0.0001), incident nuclear cataract (p < 0.0003), hyperopia (p < 0.0009), incident posterior subcapsular cataract (p < 0.0027) and incident cortical cataract (p < 0.025) were factors associated with a relatively modest myopic refractive shift (0.34 diopters). Baseline myopia and gender were not associated with refractive change over the follow-up period. A myopic shift in refraction occurred most frequently in older (> or = 70 years) than younger (< 70 years) participants. CONCLUSIONS: Older age, baseline hyperopia and all types of incident cataract were principal factors found associated with myopic refractive shift over 5 years in an older population.