Extensive lit. review links retinal changes to brain pathology in schizophrenia.
Individuals with schizophrenia have trouble with social interactions and in recognizing what is real. Past research has suggested that, in schizophrenia, abnormalities in the way the brain processes visual information contribute to these problems by making it harder to track moving objects, perceive depth, draw contrast between light and dark or different colors, organize visual elements into shapes, and recognize facial expressions. Surprisingly though, there has been very little prior work investigating whether differences in the retina or other eye structures contribute to these disturbances.
Now, an extensive literature review from researchers at Mount Sinai and Rutgers University has found that schizophrenia is associated with structural and functional alterations of the visual system, including specific structural changes in the eye. The team state that tracking such changes may provide new measures for risk of, and progression of the disease and their analysis of many studies suggests that measuring retinal changes may help doctors in the future to adjust schizophrenia treatment for each patient. The opensource study is published in the journal Schizophrenia Research: Cognition.
Previous studies show that the link between vision problems and schizophrenia is well established, with as many as 62 percent of adult patients with schizophrenia experience visual distortions involving form, motion, or color. One past study found that poorer visual acuity at four years of age predicted a diagnosis of schizophrenia in adulthood, and another that children who later develop schizophrenia have elevated rates of strabismus, or misalignment of the eyes, compared to the general population.
The current literature review examined the results of approximately 170 existing studies and grouped the findings into multiple categories, including changes in the retina vs. other parts of the eye, and changes related to dopamine vs. other neurotransmitters, key brain chemicals associated with the disease. The newly published review found multiple, replicated, indicators of eye abnormalities in schizophrenia. One of these involves widening of small blood vessels in the eyes of schizophrenia patients, and in young people at high risk for the disorder, perhaps caused by chronic low oxygen supply to the brain.
The lab hypothesize that this could explain several key vision changes and serve as a marker of disease risk and worsening. They go on to note that what is also important in this regard was thinning of the retinal nerve fiber layer in schizophrenia, which is known to be related to the onset of hallucinations and visual acuity problems in patients with Parkinson’s disease. In addition, earlier studies indicate abnormal electrical responses by retinal cells exposed to light (as measured by electroretinography) suggest cellular-level differences in the eyes of schizophrenia patients, and may represent another useful measure of disease progression, according to the group.
In addition, the new review highlighted the potentially detrimental effects of dopamine receptor-blocking medications on visual function in schizophrenia (secondary to their retinal effects), and the need for further research on effects of excessive retinal glutamate on visual disturbances in the disorder.
Interestingly, the team note that the analysis found that there are no reports of people with schizophrenia who were born blind, suggesting that congenital blindness may completely or partially protect against the development of schizophrenia. They go on to add that because congenitally blind people tend to have cognitive abilities in certain domains (e.g., attention) that are superior to those of healthy individuals, understanding brain re-organization after blindness may have implications for designing cognitive remediation interventions for people with schizophrenia.
The researchers explain that the retina develops from the same tissue as the brain, so retinal changes may parallel or mirror the integrity of brain structure and function. They hypothesize that when present in children, these changes may suggest an increased risk for schizophrenia in later life. The team note that additional research is needed to clarify these relationships, with the goals of better predicting emergence of schizophrenia, and of predicting relapse and treatment response and people diagnosed with the condition.
The lab surmise that vision has been understudied in schizophrenia and studies of the retina and other ocular structures in the disorder are in their infancy. However, they go on to conclude, that because it is much faster and less expensive to obtain data on retinal structure and function, measures of retinal and ocular structure and function may have an important role in both future research studies and the routine clinical care of people with schizophrenia.
Source: The Mount Sinai Health System