Heritability of retinal vascular fractals: A twin study

Research output: Contribution to journalArticle


PURPOSE. To determine the genetic contribution to the pattern of retinal vascular branching expressed by its fractal dimension. METHODS. This was a cross-sectional study of 50 monozygotic and 49 dizygotic, same-sex twin pairs aged 20 to 46 years. In 50º, disc-centered fundus photographs, the retinal vascular fractal dimension was measured using the box-counting method and compared within monozygotic and dizygotic twin pairs using Pearson correlation coefficients. Falconer’s formula and quantitative genetic models were used to determine the genetic component of variation. RESULTS. The mean fractal dimension did not differ statistically significantly between monozygotic and dizygotic twin pairs (1.505 vs. 1.495, P = 0.06), supporting that the study population was suitable for quantitative analysis of heritability. The intrapair correlation was markedly higher (0.505, P = 0.0002) in monozygotic twins than in dizygotic twins (0.108, P = 0.46), corresponding to a heritability h2 for the fractal dimension of 0.79. In quantitative genetic models, dominant genetic effects explained 54% of the variation and 46% was individually environmentally determined. CONCLUSIONS. In young adult twins, the branching pattern of the retinal vessels demonstrated a higher structural similarity in monozygotic than in dizygotic twin pairs. The retinal vascular fractal dimension was mainly determined by genetic factors, which accounted for 54% of the variation. The genetically predetermination of the retinal vasculature may affect the retinal response to potential vascular disease in later life.


  • Anna Stage Vergmann
  • Rebecca Broe
  • Line Kessel
  • Jesper Leth Hougaard
  • Sören Möller Christensen, Sören
  • Kirsten Ohm Kyvik
  • Michael Larsen
  • Inger Christine Munch
  • Jakob Grauslund
External organisations
  • University of Southern Denmark
  • Odense University Hospital
  • Copenhagen University Hospital
  • University of Copenhagen
  • Zealand University Hospital
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Ophthalmology


  • Dizogotic, Heredity, Monozygotic, Retinal vascular fractal dimension, Twin
Original languageEnglish
Pages (from-to)3997-4002
Number of pages6
JournalInvestigative Ophthalmology and Visual Science
Issue number10
Publication statusPublished - 2017
Publication categoryResearch