A systematic review and meta-analysis of optical coherence tomography studies in schizophrenia, bipolar disorder and major depressive disorder

Abstract

Objectives: Due to the common neurodevelopmental origin and easy accessibility, the retina serves as a surrogate marker for changes in the brain. Hence, Optical Coherence Tomography (OCT), a tool to examine the neuronal layers of retina has gained importance in investigating psychiatric disorders. Several studies in the last decade have reported retinal structural alterations in schizophrenia (SCZ), bipolar disorder (BD), and major depressive disorder (MDD). However, the findings are inconsistent. Hence, we conducted a meta-analysis to investigate alterations in OCT parameters in patients with SCZ, BD and MDD. Methods: We searched electronic databases for studies that examined OCT parameters in patients with SCZ, BD and MDD published up to January 2023. The primary outcome measures were thickness and volumes of the retinal Nerve Fibre Layer (RNFL). We conducted meta-analysis using a random effects model. Results: The searches yielded 2638 publications of which 43 studies were included in the final analysis across all disorders. Compared to controls, the RNFL was thinner in SCZ patients (SMD ¼ À0.37, p ¼ <0.001) and BD patients (SMD ¼ À0.67, p ¼ < 0.001), but not in MDD patients (SMD ¼ À0.08, p ¼ 0.54). On quadrant wise analysis, temporal quadrant RNFL was thinner in SCZ but not in BD, while all other quadrants were thinner in both SCZ and BD. Conclusion: We found significant reductions in RNFL thickness in SCZ and BD, but not in MDD. The differential involvement in various quadrants and parameters across the disorders has potential implications for using retinal parameters as a diagnostic biomarker.

Retinal electrophysiology in central nervous system disorders. A review of human and mouse studies

“…These may explain the localized mfERG functional differences reported in schizophrenia, with normal PERGs that are summed over a larger macular area and are not sensitive enough to be altered by foveal changes ( Bernardin et al, 2021 ). Nonetheless there is promise that structural and functional changes may help to diagnose and monitor individuals with schizophrenia ( Silverstein et al, 2020 ; Prasannakumar, 2023 ) as well as helping to identify individuals at risk of developing schizophrenia ( Demmin et al, 2018 ; Hosak et al, 2018 ; Hébert et al, 2020 ; Komatsu et al, 2022 ; Maziade et al, 2022 ; Moreau et al, 2022 ; Peredo et al, 2022 ). Taken together, these functional and structural findings suggest that retinal biomarkers will become a useful clinical tool in the identification of individuals at risk of and with schizophrenia to improve management and early diagnosis.…”

Investigating light sensitivity in bipolar disorder (HELIOS-BD)

“…Research has shown that people with bipolar disorder (or bipolar disorder traits) exhibit altered, state-dependent pupillary responses to light ( Bullock et al , 2019 ; Madsen et al , 2021 ) and reduced colour discrimination ( Fernandes et al , 2017 ; Fernandes et al , 2022 ; Garcia-Martin et al , 2019 ) and visual processing ( Fernandes et al , 2019 ), indicative of alterations in retinal sensitivity. Further to these functional changes, retinal imaging studies have found structural changes to the vasculature and retinal layers in individuals with bipolar disorder ( Appaji et al , 2019 ; Garcia-Martin et al , 2019 ; Prasannakumar et al , 2023 ). It is not known whether, and how, these structural and visual function changes relate to non-visual responses in bipolar disorder.…”

Linking physiology and demographics, non‐ocular pathology and pharmaceutical drug use to standard OCT measures of the inner retina: The PPP project

“…4,5 These standard clinical normative databases, however, are typically constrained to age-and race/ ethnicity-adjustment, overlooking many other potentially confounding factors. In the emerging field of oculomics, which studies the interplay between the eye and the body, 4,5 much attention has been directed towards the relationship between retinal measures and systemic diseases, particularly including metabolic, 6 mental, 7,8 nervous system [9][10][11] and cardiovascular factors. 12,13 Thus far, the literature has largely ignored the interaction between the retina and other body systems, as well as other potential interactions with physiology, demographics and pharmaceutical drug use.…”