Revealing Retinal Changes
A new study shows: indications of an increased risk of schizophrenia can already be detected in the retina. This could contribute to better early detection in the future.
The retina is part of the central nervous system and therefore part of the brain.
Changes in the brain may therefore also be detectable in the eye. An international research team led by the University of Zurich and the Psychiatric University Hospital Zurich has taken up this idea: in their study, the researchers examined whether altered nerve connections in the retina are linked to the genetic risk for schizophrenia. This is particularly relevant because disturbances in neuronal information processing are considered a central feature of schizophrenia.
Previous studies have shown that people with schizophrenia are not only affected by deficits in the grey matter of the brain, but also exhibit minimal tissue loss in the retina. However, it has so far been unclear whether these changes are a cause or a consequence of schizophrenia. The illness itself could also influence the retina — for example through lifestyle, medication, or accompanying diabetes.
Large volumes of data from healthy individuals analysed
«To investigate whether the risk of developing schizophrenia already affects the central nervous system, we examined tens of thousands of healthy individuals,» says Finn Rabe, lead author of the study and postdoctoral researcher at the University of Zurich. «We then calculated their schizophrenia risk using a genetic score.»
The team was able to draw on extensive retinal data and genetic information from the so-called UK Biobank. This data from a national cohort study involving more than half a million people is publicly accessible. «It is fair to say that the UK Biobank has revolutionised biomedical research through the scope of its data,» said Rabe.
Higher risk associated with thinner retina
The study showed that a higher genetic risk for schizophrenia is indeed associated with a thinner retina. However, the effects are small, and therefore large studies like this one are necessary to demonstrate them reliably. The advantage of this finding: such retinal changes — unlike those in the brain — can be detected using simple, non-invasive and cost-effective eye measurements. Thanks to optical coherence tomography, a kind of ultrasound of the eye, the thickness of the retina can be measured within a few minutes.
This is promising for prevention. “Our study demonstrates the potential of using optical coherence tomography in clinical routine. However, large long-term studies are still needed to clarify its benefit in prevention,” says Finn Rabe.
Perspectives for new therapies
Another key finding of the study concerns genetic variants associated with inflammatory processes in the brain. These could also contribute to structural changes in the retina. In doing so, the study supports the so-called inflammation hypothesis of schizophrenia — that is, the idea that inflammatory processes contribute to the onset or progression of the disease. “If this hypothesis is correct, inflammation could be interrupted by medication, potentially allowing the disease to be treated even more effectively in the future,” explains Rabe.
