Objectives: Diabetes is associated with loss of capillaries and macrovessel dilation in the conjunctiva, similar to well-known vessel changes in the retina. However, little is known about the effect of diabetes on the tortuosity of vessels of the conjunctiva. The authors examined the tortuosity of conjunctival vessels in participants with and without diabetes.
Design: Case-control study.
Participants and controls: Fifty-three patients with diabetes (17 with type 1 diabetes, 36 with type 2 diabetes) and 60 controls (all aged 20-94 years).
Methods: Digital red-free images of conjunctivae were analyzed using an automated computer algorithm to identify vessel axes and to quantify vessel tortuosity. Differences in vessel tortuosity were adjusted for age, gender, blood pressure, and smoking status.
Main outcome measures: Tortuosity was expressed in units of curve energy (the square of the radian angular change between subsequent locations identified by the algorithm, standardized by vessel length).
Results: A longer duration of diabetes was associated with a reduction in overall vessel tortuosity (-2.8%; 95% confidence interval [CI], -4.3% to -1.3% per decade). This inverse association was driven by changes in larger vessels (40 microm in width or more), whereas increased tortuosity was observed in capillary sized vessels (<25 microm, 4.0%; 95% CI, -0.2% to 8.2% per decade). Compared with controls, those with type 1 diabetes (median duration of disease, 26 years) showed a 17.9% increase (95% CI, 4.7% to -31.0%) in capillary tortuosity. Conversely, those with type 1 diabetes showed a 7% decrease (95% CI, -11.8% to -2.3%) in tortuosity among vessels 40 to 80 microm or less in size and a 26.8% decrease (95% CI, -66.2% to 12.7%) in the fewer number of vessels more than 80 microm in size compared with controls. Similar, but smaller differences were seen in those with type 2 diabetes with shorter duration of diabetes (median, 7 years).
Conclusions: Macrovessel dilation associated with diabetes may result in vessel engorgement and straightening, especially among those with longer durations of disease. Increased tortuosity associated with diabetes among conjunctival capillaries mirrors established vessel changes observed in the retina. Conjunctival angiopathy associated with diabetes may contribute to susceptibility to anterior eye disease among patients with diabetes.