# Longitudinal Retinal and Choroidal Image Analysis in a Set of Monozygotic Twins

## TL;DR

This study used retinal and choroidal imaging to compare healthy identical twins over five years, finding that some eye structures are more influenced by genetics while others are shaped by environment.

## Contribution

The study provides new insights into the relative roles of genetics and environment in retinal and choroidal structure and microvasculature.

## Key findings

- Up to 11% variation in OCT and OCTA variables was observed within subjects over five years.
- Subfoveal choroidal thickness and foveal avascular zone area showed larger environmental influence.
- Genetic factors appear to influence the parafoveal superficial capillary plexus and retinal layer thicknesses.

## Abstract

We analyzed multimodal retinal and choroidal imaging, including optical coherence tomography (OCT) and OCT angiography (OCTA), to assess differences and characterize variations in the retinal and choroidal structure and microvasculature between healthy monozygotic twins without ocular or systemic pathology over a five-year period. Retinal imaging of both subjects revealed normal age-related changes. There was up to an 11% difference in OCT and OCTA variables within the subjects, both at baseline and at five years, and there was up to an 18% difference in OCT and OCTA parameters between the subjects for both time points. Larger changes in subfoveal choroidal thickness and foveal avascular zone area were observed. Our observations suggest that the parafoveal superficial capillary plexus, choroidal vascularity index, central subfield thickness, retinal nerve fiber layer thickness, and ganglion cell-inner plexiform layer thickness may be more heavily influenced by genetic, rather than environmental, factors. In contrast, subfoveal choroidal thickness and the foveal avascular zone area may be more heavily influenced by environmental factors. The environmental impact on retinal and choroidal structure and microvasculature is increasingly important to characterize, as such imaging parameters are being explored as potential biomarkers of systemic disease. These differences, as seen in these identical twin subjects, may be important considerations in supporting the security of biometric identifiers.