Better glycemic control, interventions improved visual impairment in patients with type 1 diabetes

People recently diagnosed with type 1 diabetes had a lower prevalence for visual impairment — which may be caused by the diminishing incidence of proliferative diabetic retinopathy and clinically significant macular edema, according to new study findings.

The Wisconsin Epidemiologic Study of Diabetic Retinopathy included 955 people (3,719 participant visits) aged 4 to 80 years at baseline who were diagnosed with type 1 diabetes before age 30.

A total of five eye examination visits took place during 1980 to 1982, 1984 to 1986, 1990 to 1992, 1995 to 1996 and 2005 to 2007. Participants were grouped according to age of diagnosis of type 1 diabetes: before 1960, 1960 to 1969, 1970 to 1974 and 1975 to 1979.

Researchers measured the best-corrected visual acuity with a modification of the Early Treatment Diabetic Retinopathy protocol; best-corrected visual acuity in the better eye of 20/40 or worse defined visual impairment.

Those who had later examinations were older, had lower HbA1c levels, higher systolic blood pressure, lower diastolic BP and higher frequency of proliferative diabetic retinopathy and macular edema when compared with those with earlier examinations. Later examination was also associated with hypertension, higher education level and photocoagulation for proliferative diabetic retinopathy or macular edema.

Visual impairment

Researchers reported a lower prevalence of visual impairment among those with more recent periods of diagnosis of diabetes (95% CI, 0.88–0.93) — this remained after controlling for related factors such as HbA1c and BP. Annualized incidence rates of any visual impairment decreased from 1.19% in the first follow-up interval to 0.3% in the fourth follow-up interval.

The prevalence of visual impairment in those with 15 to 19-year durations of type 1 diabetes at the time of examination was 13% for those diagnosed between 1960 and 1969, 2% for those diagnosed between 1970 and 1974 and 4% for those diagnosed between 1975 and 1979. For those with 30 to 34-year durations of type 1 diabetes, visual impairment at the time of examination was 16% among those diagnosed between 1922 and 1959, 15% among those diagnosed between 1960 and 1969 and 9% among those diagnosed between 1970 and 1974.

The researchers concluded that it may be “observed differences in health care over the 25 years of the study that may explain, in part, some of these findings.”

Klein R. Opthalmology. 2009;116:1937-1942.