Retinal vascular fractals and microvascular and macrovascular complications in type 1 diabetes

Purpose: Fractal analysis is a method to quantify the geometric pattern and complexity of the retinal vessels. This study examined the association of retinal fractal dimension (D(f)) and microvascular and macrovascular complications in a population-based cohort of Danish patients with type 1 diabetes.

Design: Cross-sectional study.

Participants: This was a cross-sectional study of 208 long-term surviving type 1 diabetes patients from a population-based Danish cohort identified in 1973.

Methods: Retinal photographs were obtained at a clinical examination in 2007 or 2008. D(f) was measured with a semiautomatic computer-based program (International Retinal Imaging Software; National University of Singapore, Republic of Singapore; University of Sydney, Sydney, and University of Melbourne, Melbourne, Australia). D(f) of the retinal vasculature was measured within a predefined circular region of 3.5 optic disc radii centered on the optic disc. Line tracing of the vasculature was provided by the program. Any artifacts were removed by the grader, and the box-counting method then was used by the program to calculate D(f).

Main outcome measures: The association of D(f) with proliferative retinopathy, nephropathy, neuropathy, and macrovascular disease (coronary heart disease, stroke, peripheral artery disease) was examined.

Results: Retinal fractals were gradable in at least 1 eye in 178 (86.6%) of 208 patients. Median age and duration of diabetes for these patients were 57.8 years and 42 years, respectively. Median D(f) was 1.4610 (range, 1.3774-1.5188). After adjustments for age, gender, duration of diabetes, systolic blood pressure, and smoking, persons with lower D(f) were more likely to have proliferative retinopathy (odds ratio [OR], 1.45 per standard deviation [SD] decrease in D(f); 95% confidence interval [CI], 1.04-2.03) and neuropathy (OR, 1.42 per SD decrease in D(f); 95% CI, 1.01-2.01). There was also a trend of an association between lower D(f) and nephropathy (OR, 1.39 per SD decrease in D(f); 95% CI, 0.97-2.01) but not macrovascular disease. Furthermore, persons with lower D(f) were older.

Conclusions: This study adds to the evidence that D(f) may have some role as a global measure of retinal vasculature and its association with systemic disease. Prospective studies clarifying this role are needed.

Financial disclosure(s): The author(s) have no proprietary or commercial interest in any materials discussed in this article.