Diabetes and the Tortuosity of Vessels of the Bulbar Conjunctiva
Received 13 December 2007; received in revised form 7 February 2008; accepted 12 February 2008. published online 17 April 2008.
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 μm in width or more), whereas increased tortuosity was observed in capillary sized vessels (<25 μm, 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 μm 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 μm 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.
Available online: April 17, 2008.
1Division of Community Health Sciences, St. George's, University of London, London, United Kingdom.
2Southampton Eye Unit, Southampton, United Kingdom.
3School of Computing Information Systems and Mathematics, Kingston University, Kingston-upon-Thames, Surrey, United Kingdom.
4Department of Optometry and Visual Science, City University, London, United Kingdom.
Correspondence to Christopher G. Owen, PhD, Division of Community Health Sciences, St. George's Hospital Medical School, Cranmer Terrace, London SW17 ORE, United Kingdom.
Manuscript no. 2007-1598.
The authors have no financial or any other interest in the automated method of detecting vessels outlined in this article.
ABSTRACT