Eye Exam as a Predictor of Risk for Bipolar Disorder
In this small study, a test called an electroretinography (ERG) was used to examine the retina and how well it functions. The retina is part of the central nervous system and is located at the back of the eye. It contains two types of light sensory: rods and cones. Rods see black and white and are important for sight in low light conditions and for peripheral vision. Cones, on the other hand, see color. Electroretinography provides a measurement of the rods and cones in the retina. Although researchers already knew that retinal abnormalities were detected in people diagnosed with bipolar disorder and schizophrenia, the effects of the illness and the medication used to treat it made those findings not usable for research purposes. This is why, in this study, researchers examined the retinas of healthy young adults (average age was 20) who were at a high genetic risk for developing bipolar disorder or schizophrenia, due to having one parent with either bipolar disorder or schizophrenia. The retina exams of these healthy offspring were then compared with a control group whose families did not have a history of those illnesses. Results revealed that in the high genetic risk group, the ability of light to activate the rods was significantly reduced, as compared to the control group. This result remained significant even when the investigators of the study controlled for age, gender, and the season of testing. There was no difference in the cones’ responses between the two groups.
What Do These Results Mean?
It suggests that the response of the retina’s rods may serve as an early biomarker of risk for developing bipolar disorder or schizophrenia. This knowledge may be helpful in future genetic testing and prevention research. That being said, the authors of the study note that coming up with a precise explanation for why there was a rod function reduction in the high genetic risk offspring is difficult. Based on prior animal studies, they suggest a potential abnormality in the production or receptor sensitivity of certain brain chemicals (called neurotransmitters) like dopamine or serotonin. Another theory that may explain this finding is that there is an abnormal developmental process in the brains of children born into a family with a strong history of bipolar disorder or schizophrenia. Remember, the retina is part of the brain, connected to it by the optic nerve, so it serves as a window into the brain. Finally, you may wonder whether a diminished response of the rods leads to actual perceptual problems in bipolar disorder and schizophrenia? It’s possible, as people with these psychiatric illnesses may have a slight but significant problem with how they perceive the world. This may contribute to their functional impairment.
A Word From Verywell
It’s important to note that other studies have found ERG anomalies in people with psychiatric disorders like seasonal affective disorder, autism, drug addiction, and major depression disorder. This only supports the bigger picture—that a change in how a retina functions (as measured by ERG) may one day aid in diagnosing a psychiatric illness.
