Retinal Abnormalities May Be Biomarkers for Schizophrenia, Bipolar Disorder

Relative to healthy controls, individuals with schizophrenia and bipolar disorder (BD) display peripapillary and macular structural retinal abnormalities, according to results from a systematic review and meta-analysis published in Schizophrenia Bulletin.

Patients with schizophrenia and BD often report visual processing deficits, including impaired contrast sensitivity, visual acuity, and motion discrimination. Accordingly, some researchers have proposed that optical coherence tomography (OCT) may be a useful noninvasive, high-resolution tool to evaluate neurodegenerative pathologies and potential biomarkers of schizophrenia and BD.

To assess retinal and macular changes in schizophrenia and BD, investigators from Beth Israel Deaconess Medical Center conducted a systematic review and meta-analysis. The investigators searched publication databases for OCT-based studies of schizophrenia and BD (confirmed using Diagnostic and Statistical Manual of Mental Disorders [DSM] criteria) published between 2012 and 2022.

A total of 39 studies were included in the analysis, which comprised 1802 healthy controls, 1084 patients with schizophrenia, and 770 patients with BD.

The investigators found that the probands of the patient groups showed thinner peripapillary retinal nerve fiber layer (RNFL) thickness (standardized mean difference [SMD], -0.43; P <.001) and thinner subregional thickness in the superior (SMD, -0.28; P =.0012), inferior (SMD, -0.31; P <.0001), nasal (SMD, -0.18; P =.0130), and temporal (SMD, -0.19; P =.0022) regions relative to controls.

The funnel plots for the comparisons showed asymmetry. After trim-and-fill analyses, results remained significant for peripapillary RNFL in probands among both patient groups, superior regional thickness in probands among patients with BD, inferior regional thickness in probands among both patient groups, and temporal regional thickness in probands.

In the macula, patient probands displayed thinning in the retina (SMD, -0.60; P =.0009); fovea (SMD, -0.36; P =.0370); inner superior (SMD, -0.40; P <.0001), inner inferior (SMD, -0.38; P =.0002), inner nasal (SMD, -0.40; p =.0013), inner temporal (SMD, -0.47; P =.0003), outer superior (SMD, -0.48; P =.0002), outer inferior (SMD, -0.29; P =.0095), outer nasal (SMD, -0.39; P =.0039), and outer temporal (SMD, -0.28; P =.0099) regions; ganglion cell layer-inner plexiform layer (SMD, -0.28; P <.0001); ganglion cell complex (SMD, -0.42; P =.0349); inner plexiform layer (IPL; SMD, -0.26; P =.0032); outer nuclear layer (ONL; SMD, -0.52; P =.0372); and retinal pigmented epithelium (RPE; SMD, -0.37; P =.0018) thicknesses as well as a decreased macular volume (SMD, -0.34; P =.0060) relative to controls.

These comparisons also exhibited asymmetry. After trim-and-fill analyses, group differences remained significant for inner superior and inferior macular regions in probands among both patient groups, inner nasal and temporal regions in probands among patients with BD, outer inferior region in probands among patients with schizophrenia, and outer nasal and temporal regions, IPL, ONL, and RPE in probands.

The investigators observed significant moderating effects with illness duration, Newcastle Ottawa Scale (NOS) score, smoking status, age, cardiometabolic disease, symptom scores, OCT device, and/or gender for multiple peripapillary and macular outcomes.

The investigators concluded, “This study builds upon existing literature on the pathology of [schizophrenia] and BD patients, identifies potential biomarkers for diagnosis and patient screening and monitoring for neurodegeneration (including cognitive decline), and serves as a foundation for further clinical research to develop more targeted treatments for [schizophrenia] and BD.”

The major limitation of the present analysis was that OCT outcomes were averaged between the left and right eyes or came from only one eye, depending on the study.

This article originally appeared on Psychiatry Advisor