Age-related changes in the fractal dimension of the retinal microvasculature, effects of cardiovascular risk factors and smoking behaviour

Acta Ophthalmol. 2022 Aug;100(5):e1112-e1119. doi: 10.1111/aos.15047. Epub 2021 Nov 7.

Abstract

Purpose: This cross-sectional study investigates the association between retinal vessel complexity and age and studies the effects of cardiovascular health determinants.

Methods: Retinal vessel complexity was assessed by calculating the box-counting fractal dimension (Df ) from digital fundus photographs of 850 subjects (3-97 years). All photographs were labelled as 'non-pathological' by the treating ophthalmologist.

Results: Statistical models showed a significantly decreasing relationship between age and Df (linear: R-squared = 0.1897, p < 0.0001; quadratic: R-squared = 0.2343, p < 0.0001; cubic: R-squared = 0.2721, p < 0.0001), with the cubic regression model offering the best compromise between accuracy and model simplicity. Multivariate cubic regression showed that age, spherical equivalent and smoking behaviour have an effect (p < 0.0001) on Df . A significantly increasing effect of the number of pack-years on Df was observed (effect: 0.0004, p = 0.0017), as well as a significantly decreasing effect of years since tobacco abstinence (effect: -0.0149, p < 0.0001).

Conclusion: We propose using a cubic trend with age, refractive error and smoking behaviour when interpreting retinal vessel complexity.

Keywords: age; cardiovascular health; fractal dimension; refractive error; retinal vasculature; smoking.

MeSH terms

  • Cardiovascular Diseases* / etiology
  • Cross-Sectional Studies
  • Fractals*
  • Heart Disease Risk Factors
  • Humans
  • Microvessels
  • Retinal Vessels
  • Risk Factors
  • Smoking / adverse effects