Optical Coherence Tomography in Schizophrenia Spectrum Disorders: A Systematic Review and Meta-analysis

Genetic susceptibility to schizophrenia through neuroinflammatory pathways associated with retinal thinness

Schizophrenia is associated with structural and functional changes in the central nervous system, including the most distal part of it, the retina. However, the question of whether retinal atrophy is present before individuals develop schizophrenia or is a secondary consequence of the disorder remains unanswered. Here we address this question by examining the association between polygenic risk scores for schizophrenia and retinal morphologies in individuals without a schizophrenia diagnosis. We used population data for 34,939 white British and Irish individuals from the UK Biobank. Our robust regression results show that higher polygenic risk scores for schizophrenia were associated with thinner overall maculae, while controlling for confounding factors (b = -0.17, P = 0.018). Similarly, we found that greater polygenic risk scores for schizophrenia specific to neuroinflammation gene sets were associated with thinner ganglion cell inner plexiform layers (b = -0.10, self-contained P = 0.014, competitive P = 0.02). These results provide new evidence for genetic factors that could predispose individuals to heightened neuroinflammatory responses. Over time, these responses could contribute to neurodegenerative processes such as retinal thinning.

Thinning of central foveal thickness in the retina of patients with schizophrenia

The neural retina shares a common embryonic origin with the brain and yields pathological changes like that in the brain in various neuropsychiatric disorders, including schizophrenia. Non-invasive examination by optical coherence tomography (OCT) revealed retinal structure abnormalities in patients with schizophrenia. This study investigated retina structures in 29 patients with schizophrenia and 25 healthy controls in a Chinese Han ethnic population with spectral domain OCT. Measurements of central foveal thickness (CFT) as well as other retinal structures in macular and peripapillary subregions were performed. Associations between OCT parameters and clinical features, including severity of positive and negative symptoms, disease duration and antipsychotic dosage were analyzed. With controlling for age and sex, patients showed significantly thinner CFT, thinner central macular thickness, and thinner total retinal thickness in subregions of the central, inner superior, inner temporal, and inner nasal macula of both eyes, thinner ganglion cell complex in a subregion of the left eye, as well as larger cup volume in the peripapillary region of the right eye. In addition, CFT also negatively correlated with severity of negative symptoms. These findings suggest that CFT has the potential to be a disease biomarker of schizophrenia.

Retinal structure and its relationship with premorbid, clinical, and cognitive variables in young Spanish patients with early course schizophrenia spectrum disorders

Emerging evidence suggests that retinal structural alterations are present in schizophrenia spectrum disorders (SSD), potentially reflecting broader neurodevelopmental and neurodegenerative processes. This cross-sectional study investigates retinal thickness and its clinical correlations in a sample of early-course SSD patients compared to healthy controls (HCs). One hundred-two eyes from 26 SSD cases and 25 age- and sex-matched HCs were included. Retinal structure was evaluated using Spectral-Domain Optical Coherence Tomography (SD-OCT), focusing on the peripapillary retinal nerve fiber layer (pRNFL), macular volume/thickness, and ganglion cell-inner plexiform layer (GCL+IPL) thickness. Although SSD cases showed increased peripapillary retinal nerve fiber layer (pRNFL) thickness in specific quadrants, most retinal parameters did not differ significantly between groups. Preliminary associations were observed between retinal measures, premorbid adjustment, DUP, and cognitive performance. These findings, while suggesting the potential of retinal imaging as a tool for early detection and monitoring of psychotic disorders, must be interpreted with caution. Further longitudinal and multimodal research is warranted to explore the association between these retinal changes and neuroinflammation, neurodegeneration, and overall brain health in SSD patients.

Optical coherence tomography (OCT) and OCT angiography: Technological development and applications in brain science

Brain diseases are a leading cause of disability and death worldwide. Early detection can lead to earlier intervention and better outcomes for patients. In recent years, optical coherence tomography (OCT) and OCT angiography (OCTA) imaging have been widely used in stroke, traumatic brain injury (TBI), and brain cancer due to their advantages of in vivo, unlabeled, and high-resolution 3D microvessel imaging at the capillary resolution level. This review summarizes recent advances and challenges in living brain imaging using OCT/OCTA, including technique modality, types of diseases, and theoretical approach. Although there may still be many limitations, with the development of lasers and the advances in artificial intelligence are expected to enable accurate detection of deep cerebral hemodynamics and guide intraoperative tumor resection in vivo in the future.

On the improvement of schizophrenia detection with optical coherence tomography data using deep neural networks and aggregation functions

Schizophrenia is a serious mental disorder with a complex neurobiological background and a well-defined psychopathological picture. Despite many efforts, a definitive disease biomarker has still not been identified. One of the promising candidates for a disease-related biomarker could involve retinal morphology , given that the retina is a part of the central nervous system that is known to be affected in schizophrenia and related to multiple illness features. In this study Optical Coherence Tomography (OCT) data is applied to assess the different layers of the retina. OCT data were applied in the process of automatic differentiation of schizophrenic patients from healthy controls. Numerical experiments involved applying several individual 1D Convolutional Neural Network-based models as well as further using the aggregation of classification results to improve the initial classification results. The main goal of the study was to check how methods based on the aggregation of classification results work in classifying neuroanatomical features of schizophrenia. Among over 300, 000 different variants of tested aggregation operators, a few versions provided satisfactory results.

Genetic susceptibility to schizophrenia through neuroinflammatory pathways is associated with retinal thinning: Findings from the UK-Biobank

The human retina is part of the central nervous system and can be easily and non-invasively imaged with optical coherence tomography. While imaging the retina may provide insights on central nervous system-related disorders such as schizophrenia, a typical challenge are confounders often present in schizophrenia which may negatively impact retinal health. Here, we therefore aimed to investigate retinal changes in the context of common genetic variations conveying a risk of schizophrenia as measured by polygenic risk scores. We used population data from the UK Biobank, including White British and Irish individuals without diagnosed schizophrenia, and estimated a polygenic risk score for schizophrenia based on the newest genome-wide association study (PGC release 2022). We hypothesized that greater genetic susceptibility to schizophrenia is associated with retinal thinning, especially within the macula. To gain additional mechanistic insights, we conducted pathway-specific polygenic risk score associations analyses, focusing on gene pathways that are related to schizophrenia. Of 65484 individuals recruited, 48208 participants with available matching imaging-genetic data were included in the analysis of whom 22427 (53.48%) were female and 25781 (46.52%) were male. Our robust principal component regression results showed that polygenic risk scores for schizophrenia were associated with retinal thinning while controlling for confounding factors (b = -0.03, p = 0.007, pFWER = 0.01). Similarly, we found that polygenic risk for schizophrenia specific to neuroinflammation gene sets revealed significant associations with retinal thinning (b = -0.03, self-contained p = 0.041 (reflecting the level of association), competitive p = 0.05 (reflecting the level of enrichment)). These results go beyond previous studies suggesting a relationship between manifested schizophrenia and retinal phenotypes. They indicate that the retina is a mirror reflecting the genetic complexities of schizophrenia and that alterations observed in the retina of individuals with schizophrenia may be connected to an inherent genetic predisposition to neurodegenerative aspects of the condition. These associations also suggest the potential involvement of the neuroinflammatory pathway, with indications of genetic overlap with specific retinal phenotypes. The findings further indicate that this gene pathway in individuals with a high polygenic risk for schizophrenia could contribute through acute-phase proteins to structural changes in the retina.