Older adults, diabetes mellitus and visual acuity: a community-based case-control study

Main objectives: to screen for impaired distance visual acuity in older adults living at home, both with and without diabetes mellitus to determine whether diabetes increases the likelihood of visual impairment and to identify associated factors. Design: case-control study. Settings: three districts of Wales: North Clwyd, Powys and South Glamorgan, with assessments in subjects' homes. Subjects: 385 with diabetes mellitus and 385 age- and sex-matched controls. Main outcome measures: visual acuity measures, short form (SF)-36 quality of life scores Results: we observed impairment of visual acuity in 40% of those with diabetes mellitus and 31% of controls. Diabetes was associated with an increased risk of visual impairment [odds ratio 1.50 (95% confidence interval 1.09-2.05), P = 0.013]. The pinhole test identified uncorrected refractive error in 11% of the 63 patients with diabetes and 12% of the 49 controls who wore glasses, and in 51% of the 91 patients and 84% of the 69 controls who did not wear glasses (P < 0.001). Increasing age (P < 0.001) and female sex (P = 0.014) were significantly associated with visual impairment in both groups, whilst history of foot ulceration (P = 0.001), duration of diabetes (P = 0.018) and treatment with insulin (P < 0.001) were significantly associated with visual impairment in subjects with diabetes. We observed a significant association between impaired visual acuity and five domains of the SF-36 (physical and social functioning, mental health, vitality, and health perceptions; P < 0.01 in each case). Conclusion: older adults living at home have a high prevalence of uncorrected visual impairment. Diabetes mellitus is associated with significantly increased risk of visual loss. This impairment is associated with detriments in health-related quality of life. We recommend earlier use of optometry services and assessment of visual acuity by clinicians.