VISUAL FUNCTION AND RETINAL CHANGES IN PATIENTS WITH BIPOLAR DISORDER

Retinal thickness: A window into cognitive impairment in bipolar disorder

INTRODUCTION

Cognitive impairment (CI) in bipolar disorder (BD) significantly impacts overall functioning and quality of life. A better understanding of the neurobiological mechanisms associated with CI is needed. Studies on neurodegenerative diseases, such as Alzheimer's and Parkinson's diseases, have revealed promising findings related to retinal thickness alterations using optical coherence tomography (OCT). Similarly, retinal differences between healthy controls and individuals with BD or schizophrenia have been described. This study explores the utility of OCT in discerning retinal changes possibly associated with CI in BD to enhance our understanding of the biological markers of BD and provide additional information to neuropsychological testing.

MATERIAL AND METHODS

Optical coherence tomography (OCT) was employed to measure retinal thickness in the macular ganglion cell layer (GCL), inner plexiform layer (IPL), retinal nerve fiber layer (RNFL), and peripapillary RNFL (pRNFL) in 50 individuals with bipolar disorder (BD). Associations with cognitive impairments were analyzed using cross-validated Random Forest models.

RESULTS

The analysis revealed significant associations between retinal thinning in various segments of the macular GCL, IPL, and RNFL and cognitive impairment (CI) in BD, with particular relevance to executive function deficits (AUC>0.8).

CONCLUSIONS

Thinning of the GCL, IPL, and RNFL was significantly associated with worse cognitive performance in individuals with BD. Similar patterns have been observed in schizophrenia, highlighting an innovative and promising field for research and clinical application.

Investigation of optical coherence tomography angiography findings in patients with bipolar disorder

OBJECTIVES

Bipolar Disorder (BD) is an important psychiatric disease that progresses with attacks, can be chronic and causes serious mental problems. In this study, we aimed to identify the retinal vascular pathologies in BD patients by optical coherence tomography angiography (OCTA) imaging.

METHODS

Retinal vascular analysis from 35 BD patients and 30 healthy controls (HCs) were scanned using the OCTA machine. In addition, psychometric tests such as the Young Mania Rating Scale (YMRS) and Clinical Global Impression Scale (CGI-S) were applied to BD patients to assess the severity of the disease and determine the patient's level of functionality.

RESULTS

As a result of OCTA scans, there were significant differences between the groups as following; Deep retinal vessel density (VD) in the total, parafoveal and perifoveal area, Macular thickness in the inner parafoveal area, VD of retinal capillary plexuses in the inside disk and the Choroidal thickness (p < 0.05). Furthermore, according to the results of Pearson correlation analysis between OCTA scans and YMRS and CGI-S scores, it was determined that there was no significant relationship in any measurement (p > 0.05).

CONCLUSION

In our study, it was determined that there were general differences in deep retinal vascular density and inner macular thickness in BD patients. These findings demonstrate that the deep and inner zone of the retina is affected in BD patients.

Retinal Optical Coherence Tomography in Bipolar Disorder: A Scoping Review

BACKGROUND

Bipolar disorder (BD) is a psychiatric condition with significant health implications due to its comorbidities, premature mortality, and functional impairments. Despite extensive research on treatment and rehabilitation, gaps remain in diagnosis and monitoring. Therefore, there is a need for biomarkers to identify individuals at risk for disease progression or exacerbation. Developmentally part of the central nervous system, the retina represents a possible marker for observing BD-related structural and functional alterations in the brain.

SUMMARY

The retina's structure can be assessed through optical coherence tomography (OCT), a noninvasive and cost-effective method. Retinal alterations, particularly in the retinal nerve fiber layer (RNFL) and ganglion cell layer (GCL), have been associated with neurodegenerative and psychiatric disorders in cross-sectional OCT studies. This scoping review discusses findings on retinal changes in BD as well as their association with disease characteristics like symptom severity and illness duration and highlights OCT as a potential diagnostic tool in BD treatment.

KEY FINDINGS

The majority of studies indicate RNFL and GCL thinning in BD patients, which was found to correlate with clinical characteristics in some studies. Although the data are currently limited, there is a possibility that retinal biomarkers could facilitate monitoring of BD, but more research needs to be conducted to observe the relationship between these parameters and BD. Moreover, other factors (e.g., treatment, metabolic and inflammatory conditions) may impact retinal changes, which highlights the need for longitudinal studies to clarify these relationships. Further research should focus on replicating current findings, understanding the role of inflammation, and differentiating between retinal regions affected by BD.

BACKGROUND

Bipolar disorder (BD) is a psychiatric condition with significant health implications due to its comorbidities, premature mortality, and functional impairments. Despite extensive research on treatment and rehabilitation, gaps remain in diagnosis and monitoring. Therefore, there is a need for biomarkers to identify individuals at risk for disease progression or exacerbation. Developmentally part of the central nervous system, the retina represents a possible marker for observing BD-related structural and functional alterations in the brain.

SUMMARY

The retina's structure can be assessed through optical coherence tomography (OCT), a noninvasive and cost-effective method. Retinal alterations, particularly in the retinal nerve fiber layer (RNFL) and ganglion cell layer (GCL), have been associated with neurodegenerative and psychiatric disorders in cross-sectional OCT studies. This scoping review discusses findings on retinal changes in BD as well as their association with disease characteristics like symptom severity and illness duration and highlights OCT as a potential diagnostic tool in BD treatment.

KEY FINDINGS

The majority of studies indicate RNFL and GCL thinning in BD patients, which was found to correlate with clinical characteristics in some studies. Although the data are currently limited, there is a possibility that retinal biomarkers could facilitate monitoring of BD, but more research needs to be conducted to observe the relationship between these parameters and BD. Moreover, other factors (e.g., treatment, metabolic and inflammatory conditions) may impact retinal changes, which highlights the need for longitudinal studies to clarify these relationships. Further research should focus on replicating current findings, understanding the role of inflammation, and differentiating between retinal regions affected by BD.

Retina in Clinical High-Risk and First-Episode Psychosis

BACKGROUND AND HYPOTHESIS

Abnormalities in the retina are observed in psychotic disorders, especially in schizophrenia.

STUDY DESIGN

Using spectral-domain optical coherence tomography, we investigated structural retinal changes in relatively metabolic risk-free youth with clinical high-risk (CHR, n = 34) and first-episode psychosis (FEP, n = 30) compared with healthy controls (HCs, n = 28).

STUDY RESULTS

Total retinal macular thickness/volume of the right eye increased in FEP (effect sizes, Cohen's d = 0.69/0.66) and CHR (d = 0.67/0.76) compared with HCs. Total retinal thickness/volume was not significantly different between FEP and CHR. Macular retinal nerve fiber layer (RNFL) thickness/volume of the left eye decreased in FEP compared with HCs (d = -0.75/-0.66). Peripapillary RNFL thickness was not different between groups. The ganglion cell (GCL), inner plexiform (IPL), and inner nuclear (INL) layers thicknesses/volumes of both eyes increased in FEP compared with HCs (d = 0.70-1.03). GCL volumes of both eyes, IPL thickness/volume of the left eye, and INL thickness/volume of both eyes increased in CHR compared with HCs (d = 0.64-1.01). In the macula, while central sector thickness/volume decreased (d = -0.62 to -0.72), superior outer (peri-foveal) sector thickness/volume of both eyes increased (d = 0.81 to 0.86) in FEP compared with HCs.

CONCLUSIONS

The current findings suggest that distinct regions and layers of the retina may be differentially impacted during the emergence and early phase of psychosis. Consequently, oculomics could play significant roles, not only as a diagnostic tool but also as a mirror reflecting neurobiological changes at axonal and cellular levels.

Investigating light sensitivity in bipolar disorder (HELIOS-BD)

Many people with bipolar disorder have disrupted circadian rhythms. This means that the timing of sleep and wake activities becomes out-of-sync with the standard 24-hour cycle. Circadian rhythms are strongly influenced by light levels and previous research suggests that people with bipolar disorder might have a heightened sensitivity to light, causing more circadian rhythm disruption, increasing the potential for triggering a mood switch into mania or depression. Lithium has been in clinical use for over 70 years and is acknowledged to be the most effective long-term treatment for bipolar disorder. Lithium has many reported actions in the body but the precise mechanism of action in bipolar disorder remains an active area of research. Central to this project is recent evidence that lithium may work by stabilising circadian rhythms of mood, cognition and rest/activity. Our primary hypothesis is that people with bipolar disorder have some pathophysiological change at the level of the retina which makes them hypersensitive to the visual and non-visual effects of light, and therefore more susceptible to circadian rhythm dysfunction. We additionally hypothesise that the mood-stabilising medication lithium is effective in bipolar disorder because it reduces this hypersensitivity, making individuals less vulnerable to light-induced circadian disruption. We will recruit 180 participants into the HELIOS-BD study. Over an 18-month period, we will assess visual and non-visual responses to light, as well as retinal microstructure, in people with bipolar disorder compared to healthy controls. Further, we will assess whether individuals with bipolar disorder who are being treated with lithium have less pronounced light responses and attenuated retinal changes compared to individuals with bipolar disorder not being treated with lithium. This study represents a comprehensive investigation of visual and non-visual light responses in a large bipolar disorder population, with great translational potential for patient stratification and treatment innovation.

Can retinal nerve fiber layer (RNFL) thickness be a marker for distinguishing bipolar depression from unipolar depression?

OBJECTIVE

We aimed to compare retinal nerve fiber layer (RNFL) thickness and ganglion cell complex (GCC) thickness in bipolar disorder (BD) and major depressive disorder (MDD).

METHOD

The study included thirty MDD, thirty-two BD participants in depressive episode, and thirty-seven controls matched according to age, gender, body mass index (BMI), and smoking status. Optic coherence tomography (OCT) measurements were performed for both participants and controls. The RNFL and GCC thickness were measured and recorded automatically by a spectral OCT device. Participants were also subjected to Hamilton Depression Rating Scale (HAM-D).

RESULTS

RNFL superior thickness was significantly lower in BD participants, compared to the MDD participants and controls (p = 0.001). GCC inferior (p = 0.022) and inferonasal (p = 0.005) thickness were detected lower in BD group, compared to the control groups. In the BD group, HAM-D scores were negatively correlated with RNFL-temporal (p = 0.049, r= -0.357), GCC inferotemporal (p = 0.02, r= -0.416) and superotemporal thickness (p = 0.002, r= -0.546).

CONCLUSIONS

RNFL thickness were lower in BD participants compared to the MDD and controls and, GCC thickness were lower in BD participants compared to the controls. Our findings support the hypothesis that neurodegeneration is part of the pathogenesis of BD. Future research are needed to confirm the lack of RNFL thickness in MDD, which could have immediate therapeutic consequences as well as implications for distinguishing BD from MDD.

Optical coherence tomography angiography in patients with bipolar disorder and major depressive disorder

BACKGROUND

Cerebral microvascular dysfunction is a promising area for research into the pathogenesis of major depressive disorder (MDD) and bipolar disorder (BD). Despite the scientific and clinical potential of studying microvascular dysfunction, progress in this area has long been hampered by the lack of methods to study microvessels intravitally.

AIMS

The aim of the present study was to search for potential optical coherence tomography (OCT) and OCT-angiography (OCTA) biomarkers of BD and MDD.

METHODS

One hundred and five consecutive patients with a current depressive episode were enrolled in the study (39 - BD and 66 - MDD). In addition, forty-one generally healthy subjects were enrolled as a control group. Only the right eye was examined in all subjects. Structural OCT and OCTA scans with signal strength ≥7 were included.

RESULTS

Structural OCT measurements showed no significant differences between the groups. OCTA measurements of foveal avascular zone (FAZ), area and skeleton density showed a decrease in the retinal capillary bed in BD patients, whereas OCTA values in MDD patients did not differ from the control group. Several significant differences were found between the BD and control groups. In the BD group, the FAZ of the deep capillary plexus was increased, reflecting a reduction in capillary perfusion in the central subfield of this plexus.

CONCLUSIONS

OCTA measurements of FAZ, area and skeleton density showed a decrease in the retinal capillary bed in BD patients, whereas OCTA values in MDD patients did not differ from the control group.

Neuroretinal Alterations in Schizophrenia and Bipolar Disorder: An Updated Meta-analysis

Schizophrenia (SZ) and bipolar disorder (BD) are characterized by major symptomatic, cognitive, and neuroanatomical changes. Recent studies have used optical coherence tomography (OCT) to investigate retinal changes in SZ and BD, but their unique and shared changes require further evaluation. Articles were identified using PubMed and Google Scholar. 39 studies met the inclusion criteria. Diagnostic groups were proband (SZ/BD combined), SZ, BD, and healthy control (HC) eyes. Meta-analyses utilized fixed and random effects models when appropriate, and publication bias was corrected using trim-and-fill analysis ("meta" package in R). Results are reported as standardized mean differences with 95% CIs. Data from 3145 patient eyes (1956 SZ, 1189 BD) and 3135 HC eyes were included. Studies identified thinning of the peripapillary retinal nerve fiber layer (pRNFL, overall and in 2 subregions), m-Retina (overall and all subregions), mGCL-IPL, mIPL, and mRPE in SZ patients. BD showed thinning of the pRNFL (overall and in each subregion), pGCC, and macular Retina (in 5 subregions), but no changes in thickness or volume for the total retina. Neither SZ nor BD patients demonstrated significant changes in the fovea, mRNFL, mGCL, mGCC, mINL, mOPL, mONL, or choroid thicknesses. Moderating effects of age, illness duration, and smoking on retinal structures were identified. This meta-analysis builds upon previous literature in this field by incorporating recent OCT studies and examining both peripapillary and macular retinal regions with respect to psychotic disorders. Overall, this meta-analysis demonstrated both peripapillary and macular structural retinal abnormalities in people with SZ or BD compared with HCs.

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

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 = -0.37, p = <0.001) and BD patients (SMD = -0.67, p = < 0.001), but not in MDD patients (SMD = -0.08, p = 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.

Choroidal Structural Alterations and Choroidal Vascularity Index in Bipolar Disorder Patients

PURPOSE

The aim of this study was to compare bipolar disorder (BD) patients with age- and sex-matched healthy individuals in order to assess the choroidal structural alterations, retinal nerve fiber layer (RNFL) thickness, and retinal changes in BD patients using encanhed depth imaging optic coherence tomography (EDI-OCT).

METHOD

For this research, 39 eyes of BD patients and 36 eyes of age-matched healthy volunteers were used. Five locations were used to assess the choroidal thickness (CT): subfoveal, 500 µm nasal and 1500 µm nasal to the fovea, 500 µm temporal and 1500 µm temporal to the fovea. Image-J was used to determine the total choroidal area (TCA), luminal area (LA), and choroidal vascularity index (CVI). The Spectralis-OCT device was used to evaluate the central macular thickness (CMT), retinal nerve fiber layer (RNFL), and ganglion cell layer (GCL). The data were statistically compared.

RESULTS

BD patients had significantly decreased subfoveal, nasal, and temporal CTs than controls (for all three, p = 0.0001). The results of CMT and GCL were found to be thinner than controls. (for all p=0.0001) In comparison to the controls, the mean TCA and LA were decreased in the BD group. (p=0.0001, p=0.0001  respectively,).  Between the RNFL and CVI values in the BD and control groups, there was no statistically significant difference (p>0.05).

CONCLUSION

The results of this investigation showed that the retina and choroid of patients with BD had considerable anatomical changes.

Optical coherence tomography angiography in patients with euthymic bipolar disorder

OBJECTIVE

The number of studies conducted on the evaluation of retinal microvascularity in patients with Bipolar Disorder (BD) is very few. Therefore, in the present study it was aimed to provide a significant diagnostic support and to better understand the relationship between BD and vascular changes by making vascular measurements with Optical Coherence Tomography Angiography (OCTA).

METHOD

The statistical analysis was performed by comparing OCTA measurements of 48 eyes of 48 euthymic patients followed up with a diagnosis of BD and in remission for at least 6 months, and 45 eyes of 45 age-matched healthy volunteers in the control group. Among the OCTA measurements compared were retinal vessel density analysis, foveal avascular zone measurements, retinal nerve fiber layer, radial peripapillary capillary plexus, ganglion cell-inner plexiform layer values.

RESULTS

In the multivariate regression model, such variables as nasal quadrant of retinal nerve fiber layer, inferior and nasal quadrants of radial peripapillary capillary plexus and superficial vessel density variables were determined to have a significant and independent effect in differentiating patients with BD from the participants in the healthy control group.

CONCLUSION

In the present study, for the first time, the OCTA method was used to compare both retinal neurodegeneration and vascularization measurements in those in the BD and the healthy groups. That the effects of drugs other than mood stabilizers were not taken into account is among the limitations of our study.

Berberis dictyophylla F. inhibits angiogenesis and apoptosis of diabetic retinopathy via suppressing HIF-1α/VEGF/DLL-4/Notch-1 pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Xiao Bopi (XBP, སྐྱེར་བའི་བར་ཤུན།), as a classical Tibetan medicinal plant in China, which derived from the stem bark of Berberis dictyophylla F., has the function of "clearing heat and decreasing mKhris-pa". And it traditionally is utilized to treat the diabetes mellitus and its complications, such as diabetic retinopathy (DR). However, its underlying mechanisms remain unclear.

AIM OF THE STUDY

The purpose of this study aimed to explore the microvascular protection of water extract of XBP against the spontaneous retinal damage of db/db mice. Meanwhile, the underlying mechanisms of XBP on angiogenesis and apoptosis were further interpreted.

MATERIALS AND METHODS

We firstly used high-performance liquid chromatography to detected the representative chemical ingredients in the water extract of XBP. The DR model of db/db mice was then randomly divided into five groups: model group, calcium dobesilate (0.23 g/kg) group, and the water extract of XBP (0.375, 0.75 and 1.5 g/kg, respectively) groups. After 8 weeks of continuous administration, the parameters including body weight, fasting blood glucose, oral glucose tolerance test and insulin tolerance test were measured. The pathological changes and abnormal angiogenesis of the retina were detected by optical coherence tomography, HE, periodic acid-Schiff staining and transmission electron microscopy. Simultaneously, molecular docking was used to predict the potential connections between representative ingredients in XBP and angiogenesis/apoptosis-related proteins. The level of angiogenesis-related proteins and gene hypoxia-inducible factor-1α (HIF-1α), vascular endothelial growth (VEGF), delta-like ligand 4 (DLL-4) and Notch-1 were estimated by immunofluorescence analyses and real time-PCR. Further, TUNEL staining and immunofluorescence analyses were performed to investigate the apoptotic phenomenon and the expression of Bax, Bcl-2, Apaf-1, Cyto-c and cleaved caspase-3 and cleaved caspase-9 in the retina.

RESULTS

Phytochemical analysis revealed that magnoflorine, jatrorrhizine, palmatine and berberine were principally representative ingredients in XBP. The results demonstrated that XBP effectively increased glucose tolerance and insulin sensitivity, whereas no effect on body weight of DR mice. Moreover, retinal thickening, pathological and retinal ultrastructure changes in DR mice were evidently ameliorated by XBP. The molecular docking results demonstrated that the main components of XBP and the protein of angiogenesis and apoptosis had a potential bind. XBP restrained the gene and protein levels of HIF-1α, VEGF, DLL-4 and Notch-1 in retina. Additionally, the TUNEL-positive cell rate and the down-regulated proteins of Bax, Apaf-1, Cyto-c, cleaved Caspase-3 and cleaved Caspase 9 and increased Bcl-2 level were revised by XBP.

CONCLUSIONS

To sum up, the results suggested that XBP against DR could attribute to alleviating angiogenesis and apoptosis by suppressing the HIF-1α/VEGF/DLL-4/Notch-1 pathway. This evidence sheds a new light on the potential mechanisms of XBP in the treatment of DR.

[Chronobiological aspects of bipolar disorder]

BACKGROUND

Numerous symptoms of bipolar disorder are regulated by the circadian rhythm. Because of this association it is assumed that disruption of the circadian rhythm may be part of the pathomechanism of bipolar disorder.

OBJECTIVES

A comparison and subsequent critical discussion of the current data situation on chronobiological aspects of bipolar disorder are presented.

METHODS

A narrative literature search was carried out and the main findings are presented in a summarized form.

RESULTS

There are a large number of animal and human studies investigating the connection between disorders of the circadian rhythm and bipolar disorder. Especially chronotype, the environmental factor light and sleep disorders seem to be associated with the development of bipolar disorder.

CONCLUSIONS

The neurobiology of bipolar disorder shows numerous chronobiological aspects. There is evidence for a direct connection of disruption of the circadian rhythm and development and progression of bipolar disorder; however, at present there is no proof for the specificity of these findings for bipolar disorder. Future studies should consolidate the evidence on the impact of disorders of the circadian rhythm on the pathomechanism of bipolar disorder.

Retinal changes in bipolar disorder as an endophenotype candidate: Comparison of OCT-detected retinal changes in patients, siblings, and healthy controls

Optical coherence tomography (OCT) is a non-invasive imaging technique that detects retinal changes reflecting neurodegeneration. In recent studies in patients with bipolar disorder (BD) abnormal OCT findings have shown. In this study, we aimed to investigate the retinal changes in BD patients and their healthy siblings (HS) by comparing them with the healthy control (HC) group and to explore these findings as potential endophenotype candidates. 31 patients with BD, 31 age-matched HSs and 46 HCs were included and peripapillary retinal nerve fiber layer (RNFL), ganglion cell layer (GCL)+inner plexiform layer (IPL) and macular volume (MV) thicknesses were measured by OCT. The relationship between disease severity parameters, functionality and OCT measurements in the patient group was also investigated. In results, the mean RNFL thicknesses did not differ between groups. All GCL+IPL thicknesses were found to be significantly lower in the patient and sibling groups compared to the HCs. GCL+IPL thicknesses were significantly correlated with functionality of patients and severity of the disorder. Our findings suggest that analysis of retinal layers with OCT may be a beneficial indicator to show neuronal changes in BD and GCL+IPL may be a suitable endophenotype candidate.

Objective Diagnosis of Fibromyalgia Using Neuroretinal Evaluation and Artificial Intelligence

Background/Objective

This study aims to identify objective biomarkers of fibromyalgia (FM) by applying artificial intelligence algorithms to structural data on the neuroretina obtained using swept-source optical coherence tomography (SS-OCT).

Method

The study cohort comprised 29 FM patients and 32 control subjects. The thicknesses of complete retina, 3 retinal layers [ganglion cell layer (GCL+), GCL++ (between the inner limiting membrane and the inner nuclear layer boundaries) and retinal nerve fiber layer (RNFL)] and choroid in 9 areas around the macula were obtained using SS-OCT. Discriminant capacity was evaluated using the area under the curve (AUC) and the Relief algorithm. A diagnostic aid system with an automatic classifier was implemented.

Results

No significant difference (p ≥ .660) was found anywhere in the choroid. In the RNFL, a significant difference was found in the inner inferior region (p = .010). In the GCL+, GCL++ layers and complete retina, a significant difference was found in the 4 regions defining the inner ring: temporal, superior, nasal and inferior. Applying an ensemble RUSBoosted tree classifier to the features with greatest discriminant capacity achieved accuracy = .82 and AUC = .82.

Conclusions

This study identifies a potential novel objective and non-invasive biomarker of FM based on retina analysis using SS-OCT.

Ganglion cell complex thickness changes in patients with different states of bipolar disorder

OBJECTIVES

Neuroimaging studies in patients with bipolar disorder have suggested that a neuropathological process may be effective in this disease. Neurodegenerative changes in the retina can be followed by optical coherence tomography, a non-invasive imaging method that allows in vivo visualization of the retinal layers. The aim of this study was to investigate the possible differences in optical coherence tomography parameters during euthymic, manic, and depressive episodes in patients diagnosed with bipolar disorder.

METHODS

A total of 150 patients with bipolar disorder were included in the study, divided into three groups (50 patients in a euthymic state, 50 patients in a manic state, and 50 patients in a depressive state) and compared with 50 healthy controls. Ganglion cell complex thickness was measured with automated macular segmentation software of spectral-domain optical coherence tomography.

RESULTS

Ganglion cell complex thicknesses were thicker in all quadrants in patient groups than the control group but the differences were significant in perifoveal superior and perifoveal inferior quadrants (p < 0.001, p < 0.001). There were no differences in ganglion cell complex thickness among the patient groups (p > 0.05).

CONCLUSION

The evaluation of ganglion cell complex thickness by spectral-domain optical coherence tomography may give a clue for monitoring neurodegenerative changes in patients with bipolar disorder.

Neurobiological and behavioral mechanisms of circadian rhythm disruption in bipolar disorder: A critical multi-disciplinary literature review and agenda for future research from the ISBD task force on chronobiology

AIM

Symptoms of bipolar disorder (BD) include changes in mood, activity, energy, sleep, and appetite. Since many of these processes are regulated by circadian function, circadian rhythm disturbance has been examined as a biological feature underlying BD. The International Society for Bipolar Disorders Chronobiology Task Force (CTF) was commissioned to review evidence for neurobiological and behavioral mechanisms pertinent to BD.

METHOD

Drawing upon expertise in animal models, biomarkers, physiology, and behavior, CTF analyzed the relevant cross-disciplinary literature to precisely frame the discussion around circadian rhythm disruption in BD, highlight key findings, and for the first time integrate findings across levels of analysis to develop an internally consistent, coherent theoretical framework.

RESULTS

Evidence from multiple sources implicates the circadian system in mood regulation, with corresponding associations with BD diagnoses and mood-related traits reported across genetic, cellular, physiological, and behavioral domains. However, circadian disruption does not appear to be specific to BD and is present across a variety of high-risk, prodromal, and syndromic psychiatric disorders. Substantial variability and ambiguity among the definitions, concepts and assumptions underlying the research have limited replication and the emergence of consensus findings.

CONCLUSIONS

Future research in circadian rhythms and its role in BD is warranted. Well-powered studies that carefully define associations between BD-related and chronobiologically-related constructs, and integrate across levels of analysis will be most illuminating.

Evaluation of progressive retinal degeneration in Bipolar disorder patients over a period of 5 years

PURPOSE

To quantify visual and retinal changes in patients with bipolar disorder (BD) over 5 years, compared with controls.

METHODS

Thirty-eight patients with BD and 122 healthy subjects underwent visual acuity (VA) evaluation, contrast sensitivity vision testing (CSV) with the Pelli Robson and CSV 1000E tests, and retinal thicknesses measurement (ganglion cell layer - GCL- and retinal nerve fiber layer -RNFL-) using Spectralis Optical Coherence Tomography (OCT). All subjects were re-evaluated after 5 years. The relationship between progressive structural changes and disease duration was analysed.

RESULTS

Visual function parameters in BD patients remained unchanged during the follow up period. A progressive decrease affecting macular and peripapillary RNFL thickness (p < 0.050) was observed in patients. Progressive changes in BD were more pronounced when compared with healthy controls (p < 0.050). A significant correlation between GCL thickness changes and disease duration was found (GCL outer temporal, r=-0.680, p = 0.016; GCL central, r=-0.540, p = 0.038).

CONCLUSIONS

Progressive axonal loss was detected in BD patients. Visual function parameters were not affected after the 5-year follow up. Despite observed changes in the neuroretina of patients with BD, axonal degeneration in these patients seemed to be mild and might be slowed down by other factors such as BD treatments.

Risk of retinal disease in patients with bipolar disorder: A nationwide cohort study

AIMS

Patients with brain diseases have been associated with several retinal abnormalities. This study aimed to assess the risk of retinal diseases in patients with bipolar disorder (BD).

METHODS

This nationwide cohort of 73,271 patients with BD was enrolled between 2001 and 2009. To identify newly diagnosed retinal diseases, the patients were followed to the end of 2011. The control group included 293,084 patients, matched for demographic characteristics and medical and ophthalmological comorbidities. The Kaplan-Meier method was used to estimate incidence rates of retinal diseases. Cox regression was applied to calculate the hazard ratios (HRs) with 95% confidence intervals (CIs) after adjusting for confounders.

RESULTS

Patients with BD had higher incidence rates of any retinal disease than the controls (1.27% vs 0.48%, P < 0.001), and retinal diseases were diagnosed at a young age (54.23 years [±12.68 years] vs 57.01 years [±13.12 years], P < 0.001). After adjusting for demographic characteristics, physical and ophthalmological comorbidities, and medications, the HR was 3.24 (95% CI, 2.18-4.82) for retinal detachment, 2.35 (95% CI, 1.83-3.03) for primary retinopathy, 2.26 (95% CI, 1.91-2.68) for diabetes retinopathy, 2.39 (95% CI, 1.49-3.82) for hypertensive retinopathy, and 3.46 (95% CI, 2.45-4.89) for retinal vascular complications in patients with BD vs controls. The cumulative daily dose of bipolar medications was not associated with the incidence of any retinal disease.

CONCLUSION

Patients with BD were associated with a higher risk of retinal detachment, primary retinopathy, diabetes retinopathy, hypertensive retinopathy, and retinal vascular complications than the controls. Further studies are needed to examine the mechanisms mediating these retinal diseases in patients with BD.

Bipolar disorders and retinal electrophysiological markers (BiMAR): Study protocol for a comparison of electroretinogram measurements between subjects with bipolar disorder and a healthy control group

BACKGROUND

Bipolar disorders (BD) is a common, chronic and disabling psychiatric condition. In addition to being characterized by significant clinical heterogeneity, notable disturbances of sleep and cognitive function are frequently observed in all phases of the disease. Currently, there is no readily available biomarker in current clinical practice to help diagnose or predict the disease course. Thus, identification of biomarkers in BD is today a major challenge. In this context, the study of electrophysiological biomarkers based on electroretinogram (ERG) measurements in BD seems highly promising. The BiMAR study aims to compare electrophysiological data measured with ERG between a group of euthymic patients with BD and a group of healthy control subjects. Secondarily, we will also describe the existing potential relationship between clinical, sleep and neuropsychological phenotypes of patients and electrophysiological data.

METHODS

The BiMAR study is a comparative and monocentric study carried out at the Expert Center for BD in Nancy, France. In total, 70 euthymic adult patients with BD and 70 healthy control subjects will be recruited. Electrophysiological recordings with ERG and electroencephalogram (EEG) will be performed with a virtual reality headset after a standardized clinical evaluation to all participants. Then, an actigraphic monitoring of 21 consecutive days will be carried out. At the end of this period a neuropsychological evaluation will be performed during a second visit. The primary outcome will be electrophysiological measurements with ERG flash and pattern. Secondary outcomes will be EEG data, sleep settings, clinical and neuropsychological assessments. For patients only, a complementary ancillary study, carried out at the University Hospital of Nancy, will be proposed to assess the retinal structure and microvascularization using Optical Coherence Tomography. Recruitment started in January 2022 and will continue until the end of July 2023.

DISCUSSION

The BiMAR study will contribute to identifying candidate ERG electrophysiological markers for helping the diagnosis of BD and identify subgroups of patients with different clinical profiles. Eventually, this would allow earlier diagnosis and personalized therapeutic interventions.

CLINICAL TRIAL REGISTRATION

The study is registered at Clinicaltrials.gov, NCT05161546, on 17 December 2021 (https://clinicaltrials.gov/ct2/show/NCT05161546).

The relation of optical coherence tomography findings with oxidative stress parameters in patients with bipolar disorder and unaffected first-degree relatives

BACKGROUND

We aimed to evaluate the optical coherence tomography(OCT) findings and oxidative stress parameters in patients with bipolar disorder(BD) and their unaffected first-degree relatives(FDRs) and to explore OCT findings and oxidative stress parameters as potential endophenotype candidates.

METHODS

Fifty patients with BD, 40 FDRs of BD, and 50 healthy controls(HCs) were included. OCT was performed to measure peripapillary retinal nerve fiber layer(RNFL), ganglion cell layer(GCL), inner plexiform layer(IPL), central macular, and minimum foveal thicknesses(CMT and MFT), choroidal thickness(ChT). 4-hydroxy-2-nonenal(HNE), total thiol(TT), native thiol(NT), total oxidant status(TOS), total antioxidant status(TAS), disulfide(DIS) and oxidative stress index(OSI) were measured from serum samples.

RESULTS

TOS was higher patients with BD and FDRs than HCs (p < .001 and p = .012, respectively). OSI, DIS, HNE levels were higher patients with BD and FDRs than HCs (p < .001). TAS, TT, NT levels were lower patients and FDRs than HCs (p < .001). MFT of patients was thinner than HCs (p = .001). CMT of patients was thinner than HCs (p = .006); the same trend was observed in FDRs but did not reach the statistical significance level (p = .07). The groups did not differ on RNFL and choroidal thickness or GCL and IPL volume.

LIMITATIONS

Evaluation of only a few retinal layers.

CONCLUSIONS

TOS, TAS, OSI, TT, NT, DIS, HNE can be useful endophenotype biomarkers in BD. Among the OCT findings, CMT was determined as the closest parameter to being an endophenotype biomarker. Our study corroborates that oxidative stress parameters are more effective than OCT findings in endophenotype studies.

Analysis of the Peripapillary and Macular Regions Using OCT Angiography in Patients with Schizophrenia and Bipolar Disorder

PURPOSE

To measure RNFL and vasculature around the optic disc and in the macula in patients with schizophrenia (SZ) and bipolar disorder (BD) using optical coherence tomography angiography (OCTA).

METHODS

24 eyes of patients with SZ and 16 eyes of patients with BD as well as 30 eyes of healthy subjects were examined with OCTA. The radiant peripapillary capillary (RPC) density and RNFL thickness were measured in the peripapillary area. Moreover, macular thickness and vessel density were measured in both superficial and deep layers.

RESULTS

Significantly decreased values of vessel density in the macular deep vascular complex were found in the eyes of patients with SZ, compared to BD and the control group. The macular thickness in the whole vascular complex and in the fovea was significantly lower in SZ and BD group than in the control group. The radiant peripapillary vascular density and RNFL thickness were similar across groups.

CONCLUSIONS

The retinal microvascular dysfunction occurs in the macula in patients with SZ and BD, but not around optic disc. OCTA can become an essential additional diagnostic tool in detection of psychiatric disorders.

Automatic Diagnosis of Bipolar Disorder Using Optical Coherence Tomography Data and Artificial Intelligence

Background: The aim of this study is to explore an objective approach that aids the diagnosis of bipolar disorder (BD), based on optical coherence tomography (OCT) data which are analyzed using artificial intelligence. Methods: Structural analyses of nine layers of the retina were analyzed in 17 type I BD patients and 42 controls, according to the areas defined by the Early Treatment Diabetic Retinopathy Study (ETDRS) chart. The most discriminating variables made up the feature vector of several automatic classifiers: Gaussian Naive Bayes, K-nearest neighbors and support vector machines. Results: BD patients presented retinal thinning affecting most layers, compared to controls. The retinal thickness of the parafoveolar area showed a high capacity to discriminate BD subjects from healthy individuals, specifically for the ganglion cell (area under the curve (AUC) = 0.82) and internal plexiform (AUC = 0.83) layers. The best classifier showed an accuracy of 0.95 for classifying BD versus controls, using as variables of the feature vector the IPL (inner nasal region) and the INL (outer nasal and inner inferior regions) thickness. Conclusions: Our patients with BD present structural alterations in the retina, and artificial intelligence seem to be a useful tool in BD diagnosis, but larger studies are needed to confirm our findings.

Retinal structural changes in mood disorders: The optical coherence tomography to better understand physiopathology?

BACKGROUND

Mood disorders are particularly common, disabling conditions. Diagnosis can be difficult as it may involve different pathophysiological assumptions. This could explain why such disorders are resistant to treatment. The retina is part of the central nervous system and shares a common embryonic origin with the brain. Optical coherence tomography (OCT) is an imaging technique for analysing the different layers of the retina. We reviewed studies that examined the retina with OCT in mood disorders.

METHODS

We conducted Pubmed search and additional manual research based on the bibliography in each of selected articles. We found and analysed 11 articles relevant to our subject.

RESULTS

This literature review confirms that it is possible to use OCT to detect neurodegeneration and neuroinflammation in mood disorders. Their impact is thought to depend on the duration and severity of the disease, and whether it is in acute or chronic stage. The differences seen in studies dealing with depression and those looking at bipolar disorder may reflect the particular characteristics of each disorder. A number of OCT parameters can be proposed as biomarkers of active or chronic inflammation and neurodegeneration. Markers of predisposition to an at-risk mental state are also suggested.

LIMITATIONS

The main limitation is selection bias, studies including more varied population would help to confirm and precise these results.

CONCLUSION

OCT is thus a particularly promising tool for evaluating some of the etiopathogenetic mechanisms involved in mood disorders. The combination with other approaches could help to find more specific biomarkers.

Ganglion Cell and Retinal Nerve Fiver Layers Correlated with Time Disease of Bipolar Disorder Using 64 Cell Grid OCT Tool

MATERIALS AND METHODS

Twenty-five eyes of 25 patients with bipolar disorder and 74 eyes of 74 healthy controls underwent retinal measurements of retinal nerve fiber layer (RNFL) and ganglion cell layer (GCL) thickness. Measurements were obtained using the Spectralis-OCT device with the new Posterior Pole protocol which assesses the macular area by analyzing retinal thickness in a grid of 64 (8*8) cells.

RESULTS

Significant differences (p < 0.05) in RNFL and GCL thickness were found between BD patients and healthy controls, in parafoveal and perifoveal cells respectively. Significant inverse correlations were found between RNFL and GCL thinning at their thickest location and the duration of bipolar disorder. Several predictive variables were observed with a binary logistic regression for the presence/absence of BD: cell 1.3 RNFL (p = 0.028) and GCL in cells 7.8 (p = 0.012), 2.7 (p = 0.043) and 1.3 (p = 0.047).

CONCLUSION

Posterior Pole OCT protocol is a useful tool to assess changes in the inner retinal layers in bipolar disorder. These observed changes, especially those affecting the GCL, may be associated with disease evolution and may be predictive of the presence of the disease. OCT data could potentially be a useful tool for clinicians to diagnose and monitor BD patients.

The use of optical coherence tomography in the evaluation of patients with bipolar disorder

Bipolar disorder (BD) is a mental disorder characterised by episodes of extremal mood changes. In recent years, some researchers found neurodegeneration in patients with BD using Magnetic Resonance Imaging. Evaluation of the optic nerve and the retinal layers using optical coherence tomography (OCT) has proved to be a useful, non-invasive tool for diagnosis and monitoring of neurodegenerative diseases. Accordingly, a decrease in the retinal nerve fibre layer and the ganglion cell complex measured by OCT was found in patients with BD in different studies, suggesting that BD is a neurodegenerative process in addition to a psychiatric disorder. Therefore, the neuro-ophthalmological evaluation of these patients could be used as a marker for diagnosis of this disease. This work analyses literature on retinal degeneration in bipolar disorder patients, and evaluates the ability of OCT devices in the detection of neuronal degeneration affecting the different retinal layers in these patients, and its possible role in the diagnosis and monitoring of the disease.

Retinal layer abnormalities and their association with clinical and brain measures in psychotic disorders: A preliminary study

Studies utilizing optical coherence tomography (OCT) in psychosis have identified abnormalities in retinal cytoarchitecture. We aim to analyze retinal layer topography in psychosis and its correlation with clinical and imaging parameters. Macular retinal images were obtained via OCT in psychosis probands (n = 25) and healthy controls (HC, n = 15). Clinical, cognitive and structural MRI data were collected from participants. No thinning was noted for the retinal nerve fiber, ganglion cell or inner plexiform layers. We found significant thinning in the right inner temporal, right central, and left inner superior quadrants of the outer nuclear layer (ONL) in probands compared to HC. Thickening of the outer plexiform layer (OPL) was observed in the right inner temporal, left inner superior, and left inner temporal quadrants. The right inner temporal and left inner superior quadrants of both the OPL and ONL showed significant inverse correlations. Retinal pigment epithelium thinning correlated with worse mania symptoms, and thinning in the ONL was associated with worse cognitive function. ONL thinning was also associated with smaller total brain and white matter volume. Our findings suggest that outer retinal layers may provide additional insights into the pathophysiology of psychosis, possibly reflecting synaptic or inflammatory aberrations that lead to retinal pathologies.

Retinal correlates of psychiatric disorders

Diagnosis and monitoring of psychiatric disorders rely heavily on subjective self-reports of clinical symptoms, which are complicated by the varying consistency of accounts reported by patients with an impaired mental state. Hence, more objective and quantifiable measures have been sought to provide clinicians with more robust methods to evaluate symptomology and track progression of disease in response to treatments. Owing to the shared origins of the retina and the brain, it has been suggested that changes in the retina may correlate with structural and functional changes in the brain. Vast improvements in retinal imaging, namely optical coherence tomography (OCT) and electrodiagnostic technology, have made it possible to investigate the eye at a microscopic level, allowing for the investigation of potential biomarkers in vivo. This review provides a summary of retinal biomarkers associated with schizophrenia, bipolar disorder and major depression, demonstrating how retinal biomarkers may be used to complement existing methods and provide structural markers of pathophysiological mechanisms that underpin brain dysfunction in psychiatric disorders.

A Meta-analysis of Retinal Cytoarchitectural Abnormalities in Schizophrenia and Bipolar Disorder

BACKGROUND

Schizophrenia (SZ) and bipolar disorder (BD) are characterized by reductions in gray matter and white matter. Limitations in brain imaging have led researchers to use optical coherence tomography (OCT) to explore retinal imaging biomarkers of brain pathology. We examine the retinal layers that may be associated with SZ or BD.

METHODS

Articles identified using PubMed, Web of Science, Cochrane Database. Twelve studies met inclusion for acutely/chronically ill patients. We used fixed or random effects meta-analysis for probands (SZ and BD), SZ or BD eyes vs healthy control (HC) eyes. We adjusted for sources of bias, cross-validated results, and report standardized mean differences (SMD). Statistical analysis performed using meta package in R.

RESULTS

Data from 820 proband eyes (SZ = 541, BD = 279) and 904 HC eyes were suitable for meta-analysis. The peripapillary retinal nerve fiber layer (RNFL) showed significant thinning in SZ and BD eyes compared to HC eyes (n = 12, SMD = -0.74, -0.51, -1.06, respectively). RNFL thinning was greatest in the nasal, temporal, and superior regions. The combined peripapillary ganglion cell layer and inner plexiform layer (GCL-IPL) showed significant thinning in SZ and BD eyes compared to HC eyes (n = 4, SMD = -0.39, -0.44, -0.28, respectively). No statistically significant differences were identified in other retinal or choroidal regions. Clinical variables were unrelated to the RNFL or GCL-IPL thickness by meta-regression.

CONCLUSION

The observed retinal layer thinning is consistent with the classic gray- and white-matter atrophy observed on neuroimaging in SZ and BD patients. OCT may be a useful biomarker tool in studying the neurobiology of psychosis.

Examination of retinal vascular trajectory in schizophrenia and bipolar disorder

AIM

Evidence suggests microvascular dysfunction (wider retinal venules and narrower arterioles) in schizophrenia (SCZ) and bipolar disorder (BD). The vascular development is synchronous with neuronal development in the retina and brain. The retinal vessel trajectory is related to retinal nerve fiber layer thinning and cerebrovascular abnormalities in SCZ and BD and has not yet been examined. Hence, in this study we examined the retinal vascular trajectory in SCZ and BD in comparison with healthy volunteers (HV).

METHODS

Retinal images were acquired from 100 HV, SCZ patients, and BD patients, respectively, with a non-mydriatic fundus camera. Images were quantified to obtain the retinal arterial and venous trajectories using a validated, semiautomated algorithm. Analysis of covariance and regression analyses were conducted to examine group differences. A supervised machine-learning ensemble of bagged-trees method was used for automated classification of trajectory values.

RESULTS

There was a significant difference among groups in both the retinal venous trajectory (HV: 0.17 ± 0.08; SCZ: 0.25 ± 0.17; BD: 0.27 ± 0.20; P < 0.001) and the arterial trajectory (HV: 0.34 ± 0.15; SCZ: 0.29 ± 0.10; BD: 0.29 ± 0.11; P = 0.003) even after adjusting for age and sex (P < 0.001). On post-hoc analysis, the SCZ and BD groups differed from the HV on retinal venous and arterial trajectories, but there was no difference between SCZ and BD patients. The machine learning showed an accuracy of 86% and 73% for classifying HV versus SCZ and BD, respectively.

CONCLUSION

Smaller trajectories of retinal arteries indicate wider and flatter curves in SCZ and BD. Considering the relation between retinal/cerebral vasculatures and retinal nerve fiber layer thinness, the retinal vascular trajectory is a potential marker for SCZ and BD. As a relatively affordable investigation, retinal fundus photography should be further explored in SCZ and BD as a potential screening measure.

Surface-based regional homogeneity in bipolar disorder: A resting-state fMRI study

Surface-based, two-dimensional regional homogeneity (2dReHo) was used in the current study to compare local functional synchronization of spontaneous neuronal activity between patients with bipolar disorder (BD) and healthy controls (HC), rather than volume-based, three-dimensional regional homogeneity (3dReHo) methods that have been previously described. Seventy-one BD patients and 113 HC participated in structural and resting-state fMRI scans. Participants ranged in age from 12 to 54 years. All subjects were rated with the Young Mania Rating Scale and the Hamilton Depression Rating Scale. BD patients showed reduced surface-based ReHo across the cortical surface, both at the global level and in the left ventral visual stream (VVS). Additionally, ReHo value across the cortical surface showed a significant negative correlation with age in both groups at the global level. Abnormal activity in the left VVS cortex may contribute to the pathogenesis of BD. Therefore, surface-based ReHo may be a useful index to explore the pathophysiology of BD.

Could structural changes in the retinal layers be a new biomarker of mental disorders? A systematic review and thematic synthesis

It has recently been suggested that alterations of the layers of the retina could be a biomarker of specific mental disorders since they originate in the same embryonic layer as the brain and both are interconnected through the optic nerve. The purpose of this article is to offer a systematic review of the literature and a thematic synthesis on the current state of the alterations of the retina layers identified by optical coherence tomography in patients with schizophrenia, bipolar disorder and major depression. For this purpose, we performed a bibliographic search, a systematic review of the studies and a thematic synthesis of the reported findings. Patients with schizophrenia have more abnormal findings followed by patients with bipolar disorder, with very few findings in depression. The nerve fiber layer is the retinal layer with more abnormal findings both in schizophrenia and in bipolar disorder, while no study in major depression found alterations in it. Of the clinical parameters, the duration of the illness correlates significantly and inversely with the thickness of the different layers in all disorders. When interpreting these data, it is necessary to take into account the limitations and differences of the studies, especially the mean length of the disorders. Given that this was very different among the 3 disorders (more than doubled in the case of schizophrenia respect to major depression), the differences in the results found could be due more to the effect of the length of illness than to the disorder itself. In summary, optical coherence tomography findings are promising, since they could provide biomarkers of neurodegeneration and/or neuroprogression of both schizophrenia and bipolar disorder.