BACKGROUND: Diabetic maculopathy (DMP) is a microvascular complication of diabetes that can be responsible for significant visual loss in patients with diabetic retinopathy (DR).
OBJECTIVES: To estimate the incidence rate (IR) of DMP in a cohort of diabetic patients newly diagnosed with DR, overall and by diabetes subtype (type I and type II), in a UK population.
METHODS: We conducted a cohort study using The Health Improvement Network (THIN) database in the UK. A cohort of subjects with a first-ever diagnosis code for DR between January 1st 2000 and December 31st 2008 and without a previous code for DMP, was followed from the day after first DR diagnosis (start date) to first diagnosis of DMP, age 85 years, death or 31 December 2008, whichever occurred first. IR was calculated dividing the total number of patients with DMP by the person-time contributed by all study cohort members.
RESULTS: The study cohort consisted of 7,779 newly diagnosed DR patients, 30 of them were aged 6–15 years. Individuals who were diagnosed with DMP concurrently with retinopathy (n = 430; 2 of them aged 14 and 15 years) were excluded. Among the remaining 7,349 DR patients, we identified 318 individuals (1 aged 15 years) with a diagnosis code of DMP during a mean follow-up time of 2.4 years, resulting in an IR of 18.3 (95% CI:16.4–20.4) per 1,000 person-years. The mean time to develop DMP from DR was 1.7 (range: 5 days to 7.1 years) years, 1.6 years in diabetes type I and 1.7 years in diabetes type II. The IR was 25.7 (95% CI: 12.9–51.5; n = 8 cases) per 1,000 person- years in diabetes type I and 18.1 (95% CI: 16.2–20.3; n = 310 cases) per 1,000 person-years in diabetes type II.
CONCLUSIONS: In UK primary care, the incidence of DMP among diabetic patients affected with DR is high in both type I and II diabetes. Over half of DMP cases were diagnosed concurrently with the retinopathy, suggesting a delay in diagnosis of DR.
