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R. Klein, K. E. Lee, R. E. Gangnon, M. D. Knudtson, B. E. K. Klein; The 25-Year Cumulative Incidence of Visual Impairment and Associated Risk Factors in Type 1 Diabetes Mellitus (T1DM). The Wisconsin Epidemiologic Study of Diabetic Retinopathy. Invest. Ophthalmol. Vis. Sci. 2009;50(13):3900.
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To examine the 25-year cumulative incidence of visual impairment (VI), its relation to various risk factors and whether the prevalence of VI was lower in more recently diagnosed cohorts.
Persons with T1DM were examined at baseline (1980-1982) and in at least 1 of the 4 follow-up exams over a 25 year period. Best corrected visual acuity (VA) was measured using a modification of the ETDRS protocol. VI was defined as best corrected VA in the better eye of 20/40 or worse. Incidence and relative risk were calculated using models that account for censoring and competing events. Cohort relationships for prevalent VI were examined categorizing period of diagnosis of T1DM as <1960, 1960-1969, 1970-1974, and 1975-1979.
The 25-year cumulative incidence of VI (accounting for competing risk of death) was 13%. Multivariate models showed increased risk of VI (Relative Risk, 95% Confidence Interval, and P-value) with more severe baseline retinopathy (1.24, 1.10-1.39, P<.001), higher glycosylated hemoglobin (1.24 per %, 1.12-1.38, P<.001), presence of hypertension (1.99, 1.15-3.45, P=.01), and currently smoking (vs. never smoked, 1.83, 1.10-3.05, P=.02) but not proteinuria. Cohort differences in prevalence of VI were observed. While controlling for duration of T1DM, there was a lower prevalence of VI for more recent periods of diagnosis of T1DM (per period of diagnosis category, 0.91, 0.88-0.93; P <.001).
These data show a relatively high 25-year cumulative incidence of VI and show that persons diagnosed most recently had lower risk of prevalent VI independent of duration of diabetes. This is likely due to the diminishing incidence of proliferative diabetic retinopathy (PDR) and clinically significant macular edema (CSME) due to better glycemic control and more timely interventions with photocoagulation for CSME and PDR in those with more recently diagnosed T1DM.
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