Fractal dimension of the retinal vasculature: age-related evolution in the general population and effect of cardiovascular health status

Abstract

Purpose : Little is known about the fractal dimension (D_f) in the general population and only a handful studies report on its relationship with age and cardiovascular health. We performed a retrospective, observational clinical study to investigate the age-related evolution of the D_f of the retinal vascular network in a large sample representative of the general population, and to determine the effect of cardiovascular health status on this vascular parameter.

Methods : A total of 890 disc-centered fundus images of 890 individuals (53% female) were collected, aiming at approximately 100 subjects in every 10-year age group between 0 and 99 years. For all participants, available information on ophthalmological and cardiovascular health status was recorded. Mona^TM REVA (VITO NV, Mol, Belgium), software for semi-automated retinal vessel analysis, was used for vessel segmentation and retinal vascular fractal analysis, using the box counting method. The region of interest was the annulus between 1.5 and 4 times the radius of the optic disc, centered on the optic disc.

Results : A mean (± SD) D_f of 1.399 (± 0.038) was observed. First, a significant negative correlation was noted between D_f and aging (p<0.001). The mean values (± SD) of the D_f per age group were 1.452 (± 0.045) in 0-9 years old, 1.421 (± 0.041) in 10-19 years, 1.400 (± 0.031) in 20-29 years, 1.395 (± 0.028) in 30-39 years, 1.395 (± 0.031) in 40-49 years, 1.393 (± 0.031) in 50-59 years, 1.388 (± 0.028) in 60-69 years, 1.388 (± 0.030) in 70-79 years, 1.382 (± 0.032) in 80-89 years and 1.365 (± 0.026) in the 90-99 years age group. Except for the very young (<20 years) and very old (>89 years) individuals, no significant differences were found in D_f between the different age groups, indicating the D_f is a rather robust parameter. Second, a stepwise multivariate linear regression model showed that D_f is significantly correlated with age, BMI, BMI^2 and smoking, while adjusting for gender, arterial hypertension, diabetes, hypercholesterolemia, cardiovascular pathology, neurological pathology and age-related macular degeneration (AMD).

Conclusions : This study demonstrates that the retinal vasculature undergoes age-related rarefaction and that its D_f is a robust parameter over a wide age range (20-89 years). Additionally, this D_f is not only correlated with age, but also with BMI and smoking.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.