How Retinal Imaging Can Reveal Your Overall Health

The retina is a complex tissue that forms part of the central nervous system and is responsible for converting light into neural signals that are sent to the brain. The retina has multiple layers, each with a specific function and structure. The thickness of these layers can be measured non-invasively using a technique called optical coherence tomography (OCT), which produces high-resolution images of the retina.

A recent study, published in Science Translational Medicine¹, used OCT images from 44,823 UK Biobank participants to explore the links between retinal layer thickness and human health. The researchers performed phenome- and genome-wide analyses, meaning that they examined the associations between retinal thickness and a large number of phenotypes (observable traits or characteristics) and genotypes (genetic variants).

The phenome-wide analysis involved correlating retinal thickness with 1866 incident conditions (diseases or events that occurred during the follow-up period of 10 years) and 88 quantitative traits and blood biomarkers. The researchers found that thinner retinal layers were associated with higher risk of mortality, as well as ocular, neuropsychiatric, cardiometabolic, and pulmonary conditions. For example, thinner photoreceptor segments (the layer that contains the light-sensitive cells) were associated with higher risk of age-related macular degeneration (AMD), a leading cause of blindness, and poorer cardiometabolic and pulmonary function. Thinner ganglion cell complex (the layer that contains the nerve cells that transmit visual information to the brain) was associated with higher risk of glaucoma, a condition that damages the optic nerve and can lead to vision loss.

The genome-wide analysis involved identifying genetic variants that influence retinal layer thickness. The researchers discovered 259 unique loci (regions of the genome) that were associated with retinal thickness, many of which were novel or had not been previously linked to retinal or ocular traits. Some of these loci were also associated with systemic conditions, such as diabetes, hypertension, and COPD, suggesting a shared genetic basis between retinal and systemic health.

The researchers also performed a comparative analysis of the phenome- and genome-wide associations, to identify potential causal relationships between retinal layer thickness and ocular and systemic conditions. They used a method called Mendelian randomization, which uses genetic variants as natural experiments to infer causality. They found evidence for causal links between thinner retinal nerve fiber layer and glaucoma, thinner photoreceptor segments and AMD, and poorer cardiometabolic and pulmonary function and thinner photoreceptor segments.

The study demonstrates the power of retinal imaging as a tool to reveal insights into human health and disease. The findings could have implications for the prevention, diagnosis, and treatment of various ocular and systemic conditions, as well as for the development of new therapies that target the retina. The study also highlights the potential of integrating phenotypic and genotypic data to uncover the complex interactions between the retina and the rest of the body.