Retinal Layer Abnormalities as Biomarkers of Schizophrenia

Specific association between retinal neural layer thinning and neurological soft signs in schizophrenia

There is growing evidence of disproportionate retinal thinning in schizophrenia, but doubts are still raised regarding its significance in the context of the neurobiology of the disease. Therefore, we examined whether these abnormalities are significantly associated with neurological soft signs (NSS) which are closely related to the risk of schizophrenia. This cross-sectional study analyzing linear correlations between variables involved 56 schizophrenia inpatients and 60 controls. The results confirmed such relationships, and only in the patient sample. In addition, retinal abnormalities and NSS were significantly correlated with duration of illness. These findings provide further evidence for linked neurodevelopmental and neurodegenerative aspects of schizophrenia.

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.

Oculomics: A Crusade Against the Four Horsemen of Chronic Disease

Chronic, non-communicable diseases present a major barrier to living a long and healthy life. In many cases, early diagnosis can facilitate prevention, monitoring, and treatment efforts, improving patient outcomes. There is therefore a critical need to make screening techniques as accessible, unintimidating, and cost-effective as possible. The association between ocular biomarkers and systemic health and disease (oculomics) presents an attractive opportunity for detection of systemic diseases, as ophthalmic techniques are often relatively low-cost, fast, and non-invasive. In this review, we highlight the key associations between structural biomarkers in the eye and the four globally leading causes of morbidity and mortality: cardiovascular disease, cancer, neurodegenerative disease, and metabolic disease. We observe that neurodegenerative disease is a particularly promising target for oculomics, with biomarkers detected in multiple ocular structures. Cardiovascular disease biomarkers are present in the choroid, retinal vasculature, and retinal nerve fiber layer, and metabolic disease biomarkers are present in the eyelid, tear fluid, lens, and retinal vasculature. In contrast, only the tear fluid emerged as a promising ocular target for the detection of cancer. The retina is a rich source of oculomics data, the analysis of which has been enhanced by artificial intelligence-based tools. Although not all biomarkers are disease-specific, limiting their current diagnostic utility, future oculomics research will likely benefit from combining data from various structures to improve specificity, as well as active design, development, and optimization of instruments that target specific disease signatures, thus facilitating differential diagnoses.

Signature of Altered Retinal Microstructures and Electrophysiology in Schizophrenia Spectrum Disorders Is Associated With Disease Severity and Polygenic Risk

BACKGROUND

Optical coherence tomography and electroretinography studies have revealed structural and functional retinal alterations in individuals with schizophrenia spectrum disorders (SSDs). However, it remains unclear which specific retinal layers are affected; how the retina, brain, and clinical symptomatology are connected; and how alterations of the visual system are related to genetic disease risk.

METHODS

Optical coherence tomography, electroretinography, and brain magnetic resonance imaging were applied to comprehensively investigate the visual system in a cohort of 103 patients with SSDs and 130 healthy control individuals. The sparse partial least squares algorithm was used to identify multivariate associations between clinical disease phenotype and biological alterations of the visual system. The association of the revealed patterns with individual polygenic disease risk for schizophrenia was explored in a post hoc analysis. In addition, covariate-adjusted case-control comparisons were performed for each individual optical coherence tomography and electroretinography parameter.

RESULTS

The sparse partial least squares analysis yielded a phenotype-eye-brain signature of SSDs in which greater disease severity, longer duration of illness, and impaired cognition were associated with electrophysiological alterations and microstructural thinning of most retinal layers. Higher individual loading onto this disease-relevant signature of the visual system was significantly associated with elevated polygenic risk for schizophrenia. In case-control comparisons, patients with SSDs had lower macular thickness, thinner retinal nerve fiber and inner plexiform layers, less negative a-wave amplitude, and lower b-wave amplitude.

CONCLUSIONS

This study demonstrates multimodal microstructural and electrophysiological retinal alterations in individuals with SSDs that are associated with disease severity and individual polygenic burden.

Assessment of metacognition and retinal optical coherence tomography findings in shift workers

It is known that working in the shift system, especially the night shift, affects physical, mental, and social well-being. We investigated the changes in the inner retinal layers and choroidal layer of the eyes of nurses working night and day shifts using optical coherence tomography (OCT). We also explored the effect of night shift work on metacognition and the relationships between these variables. A total of 79 nurses participated in the study, of whom 40 worked night shifts. The researcher gave the participants sociodemographic information and the Metacognition Questionnaire-30 (MCQ-30) form. Retinal nerve fiber layer (RNFL) thickness, ganglion cell layer (GCL) thickness, inner nuclear layer (INL) thickness, inner plexiform layer (IPL) thickness, central macular thickness (CMT), and subfoveal choroidal thickness (SFCT) were measured with OCT. It was found that the level of metacognitive activity associated with cognitive confidence was higher (p = 0.044) for nurses who worked night shifts and that the level of metacognitive activity associated with cognitive awareness was lower (p = 0.015) for nurses who worked night shifts. RNFL-nasal superior (NS) thickness was lower in night shift workers than the day shift group (p = 0.017). Our study revealed significant relationships between metacognition and the OCT findings among night and day shift workers. Our study revealed that RNFL measurements and metacognitive activity may differ and there may be a relationship between these parameters in nurses who work shifts. Further research is needed to investigate the long-term effects of night shift work on retinal health.

Retina as a potential biomarker in schizophrenia spectrum disorders: a systematic review and meta-analysis of optical coherence tomography and electroretinography

INTRODUCTION

Abnormal findings on optical coherence tomography (OCT) and electroretinography (ERG) have been reported in participants with schizophrenia spectrum disorders (SSDs). This study aims to reveal the pooled standard mean difference (SMD) in retinal parameters on OCT and ERG among participants with SSDs and healthy controls and their association with demographic characteristics, clinical symptoms, smoking, diabetes mellitus, and hypertension.

METHODS

Using PubMed, Scopus, Web of Science, and PSYNDEX, we searched the literature from inception to March 31, 2023, using specific search terms. This study was registered with PROSPERO (CRD4202235795) and conducted according to PRISMA 2020.

RESULTS

We included 65 studies in the systematic review and 44 in the meta-analysis. Participants with SSDs showed thinning of the peripapillary retinal nerve fiber layer (pRNFL), macular ganglion cell layer- inner plexiform cell layer, and retinal thickness in all other segments of the macula. A meta-analysis of studies that excluded SSD participants with diabetes and hypertension showed no change in results, except for pRNFL inferior and nasal thickness. Furthermore, a significant difference was found in the pooled SMD of pRNFL temporal thickness between the left and right eyes. Meta-regression analysis revealed an association between retinal thinning and duration of illness, positive and negative symptoms. In OCT angiography, no differences were found in the foveal avascular zone and superficial layer foveal vessel density between SSD participants and controls. In flash ERG, the meta-analysis showed reduced amplitude of both a- and b-waves under photopic and scotopic conditions in SSD participants. Furthermore, the latency of photopic a-wave was significantly shorter in SSD participants in comparison with HCs.

DISCUSSION

Considering the prior report of retinal thinning in unaffected first-degree relatives and the results of the meta-analysis, the findings suggest that retinal changes in SSDs have both trait and state aspects. Future longitudinal multimodal retinal imaging studies are needed to clarify the pathophysiological mechanisms of these changes and to clarify their utility in individual patient monitoring efforts.

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

Background

Inner retinal atrophy has been demonstrated in schizophrenia spectrum disorder (SSD) using optical coherence tomography (OCT). This systematic review and meta-analysis investigated the role of contemporary Fourier domain OCT devices in SSD.

Methods

MEDLINE, PubMed, Scopus, Embase, PsycInfo, PYSNDEX, World Health Organization, and Cochrane databases were searched from inception until May 2022. All peer-reviewed adult SSD case-control studies using Fourier domain OCT were included. Ocular pathologies known to affect retinal OCT scans were excluded. Search, data appraisal, and summary data extraction were independently performed by 2 authors.

Results

The review criteria was met by k = 36 studies, with k = 24 studies (1074 cases, 854 controls) suitable for meta-analysis. The SSD group exhibited a thinner global peripapillary retinal nerve fiber layer (-3.26 μm, 95% CI, -5.07 to -1.45, I2 = 64%, k = 21), thinner average macular layer (-7.88 μm, 95% CI, -12.73 to -3.04, I2 = 65%, k = 11), and thinner macular ganglion cell-inner plexiform sublayer (-2.44 μm, 95% CI, -4.13 to -0.76, I2 = 30%, k = 8) compared with the control group. Retinal nerve fiber layer findings remained significant after exclusion of metabolic disease, low quality, outlier, and influential studies. Studies involving eye examinations to exclude eye disease were associated with greater atrophy in SSD. Except for cardiometabolic disease, most studies did not report clinically significant covariate data known to influence retinal thickness.

Conclusions

Individuals with SSD generally exhibited retinal atrophy, possibly paralleling reduced brain volumes documented in clinical imaging. Prospective longitudinal studies that collect clinical data, including various illness phases, and control for confounders will be necessary to evaluate retinal atrophy as a biomarker in SSD.

Clinical and biological correlates of optical coherence tomography findings in schizophrenia

There is a growing body of evidence indicating retinal layer thinning in schizophrenia. However, neuropathological processes underlying these retinal structural changes and its clinical correlates are yet to be known. Here, we aim to investigate the clinical and biological correlates of OCT findings in schizophrenia. 50 schizophrenia patients and 40 healthy controls were recruited. Retinal nerve fiber layer (RNFL), ganglion cell layer (GCL), inner plexiform layer (IPL), and macular and choroidal thicknesses were recorded. A comprehensive battery of neuropsychological tests was applied. Fasting glucose, triglycerides and HDL-cholesterol levels, TNF-α, IL-1β and IL-6 levels were measured. Right IPL was significantly thinner in patients than the controls after controlling for various confounders (F = 5.42, p = .02). Higher IL-6, IL-1β, and TNF-α levels were associated with decreased left macular thickness (r =  - 0.26, p = .027, r =  - 0.30, p = 0.012, and r =  - 0.24, p = .046, respectively) and higher IL-6 was associated with thinning of right IPL (r =  - 0.27, p = 0.023) and left choroid (r =  - 0.23, p = .044) in the overall sample. Thinning of right IPL and left macula were also associated with worse executive functioning (r = 0.37, p = 0.004 and r = 0.33, p = 0.009) and attention (r = 0.31, p = 0.018 and r = 0.30, p = 0.025). In patients with schizophrenia, IPL thinning was associated with increased BMI (r =  - 0.44, p = 0.009) and decreased HDL levels (r = 0.43, p = 0.021). Decreased TNF-α level was related to IPL thinning, especially in the left eye (r = 0.40, p = 0.022). These findings support the hypothesis that OCT might provide the opportunity to establish an accessible and non-invasive probe of brain pathology in schizophrenia and related disorders. However, future studies investigating retinal structural changes as a biological marker for schizophrenia should also consider the metabolic state of the subjects.

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.

Vitamin A and vitamin D3 protect the visual apparatus during the development of dopamine-2 receptor knockout mouse model of Parkinsonism

OBJECTIVES

Dopamine-related movement disorders are associated with a loss of visual acuity. Studies have shown that chemical stimulation of the vitamin D3 receptor (VDR) ameliorates movement disorders; however, the chemical stimulation is not effective when there is a deficiency of vitamin A in the cells. In the study, we examine the role of VDR and its interplay with vitamin A in impaired visual function in the dopamine deficit model.

METHODS

Thirty (30) male mice with an average weight of 26 g ± (2) were divided into six group (NS,-D2,-D2 + VD D2 + VD, -D2 + VA, -D2 + (VD + VA) and -D2 + D2 groups). Dopamine deficit models of movement disorders were created using 15 mg/kg of haloperidol (-D2) injected intraperitoneally daily for 21 days. In the -D2 + (VD + VA) group, 800 IU/day of vitamin D3 (VD) and 1000 IU/day of vitamin A were concurrently used, while in the -D2 + D2 group, bromocriptine (+D2) was used as the standard treatment of the model. At the end of the treatment phase, the animals were subjected to visual water box test for visual acuity. The level of oxidative stress was measured using Superoxide dismutase (SOD) and malondialdehyde (MDA) in the retina and visual cortex. The level of cytotoxicity in these tissues was measured using Lactate dehydrogenase (LDH) assay, while the structural integrity of these tissues was assessed using a light microscope by assessing slide mounted sections that were stained with haematoxylin and eosin.

RESULTS

A significant decline in time taken to reach the escape platform in the visual water box test was observed in the -D2 (p<0.005) and -D2 + D2 (p<0.05) group. In the retina and the visual cortex, a significant increase in LDH, MDA and the density of degenerating neurons was observed in the -D2 and -D2 + D2 groups. LDH level in the retina was also found to be significantly increased in (-D2 + VD, -D2 + VA, -D2 + (VD + VA). A Significant decrease in SOD was found in the retina and visual cortex of -D2 and -D2 + D2 group. In the histology of the retina, thinning of the retina, retinal fold, distortion and retinal detachment were all seen in the -D2 group. These structural alterations were not seen in other groups. Histological hallmarks of degeneration were observed in the visual cortex of the mice from the -D2 (p<0.001), -D2 + D2 (p<0.005) and -D2 + VD (p<0.05) groups only.

CONCLUSIONS

Dopamine-deficient models of movement disorders are associated with loss of visual functions, especially due to thinning of the retina, retinal fold, retinal detachment, and neurodegeneration in the visual cortex. Supplementation during the development of the model with vitamin D3 and vitamin A prevented the deterioration of the retina and visual cortex by reducing the degree of oxidative stress and cytotoxicity.

Differentiation of the retinal morphology aging trajectories in schizophrenia and their associations with cognitive dysfunctions

Previous studies evaluating the morphology of the selected retinal layers in schizophrenia showed abnormalities regarding macular thickness, retinal nerve fiber layer (RNLF), and ganglion cell complex (GCC). Concurrently, accumulating neuroimaging results suggest that structural alterations of the brain in this disease might be an effect of accelerated aging. Referring to these findings, we aimed to determine whether the thinning of the retinal layers assessed with the optic coherence tomography (OCT) in a group of schizophrenia patients (n = 60) presents a significant age-related decrease exceeding potential changes noted in the control group (n = 61). Samples of patients and controls were divided into three age subgroups, namely, younger, middle-aged, and older participants. OCT outcomes, such as macular thickness and volume, macular RNFL, peripapillary RNFL, and GCC, were analyzed concerning a diagnosis status (controls vs. patients) and age subgroups. Additionally, associations between retinal parameters, age, and selected cognitive functions were evaluated. post-hoc tests revealed that macular thickness and volume in patients undergo significant age-dependent thinning, which was not observed in the control group. Regression analyses confirmed the association between macular morphology and age. Selected speed-dependent cognitive functions in patients decreased significantly with age, and these features were also significantly associated with some OCT outcomes also after controlling for antipsychotic treatment. Our results suggest that reduced measures of retinal structure detected in schizophrenia may be an effect of accelerated aging; however, further research is needed using computational solutions derived from brain imaging studies based on large datasets covering representatives of all age groups.

Present and Future Modeling of Human Psychiatric Connectopathies With Brain Organoids

Brain organoids derived from human pluripotent stem cells are emerging as a powerful tool to model cellular aspects of neuropsychiatric disorders, including alterations in cell proliferation, differentiation, migration, and lineage trajectory. To date, most contributions in the field have focused on modeling cellular impairment of the cerebral cortex, with few studies probing dysfunction in local network connectivity. However, it is increasingly more apparent that these psychiatric disorders are connectopathies involving multiple brain structures and the connections between them. Therefore, the lack of reproducible anatomical features in these 3-dimensional cultures represents a major bottleneck for effectively modeling brain connectivity at the micro(cellular) level and at the macroscale level between brain regions. In this perspective, we review the use of current organoid protocols to model neuropsychiatric disorders with a specific emphasis on the potential and limitations of the current strategies to model impairments in functional connectivity. Finally, we discuss the importance of adopting interdisciplinary strategies to establish next-generation, multiregional organoids that can model, with higher fidelity, the dysfunction in the development and functionality of long-range connections within the brain of patients affected by psychiatric disorders.

Investigation of the Relationship Between Cognitive Functions and Retinal Findings From Spectral Optical Coherence Tomography in Patients With Schizophrenia and Their Healthy Siblings

OBJECTIVE

Retinal structural changes which were investigated by optical coherence tomography (OCT) have been reported in schizophrenia. Since cognitive dysfunction is a core feature of schizophrenia, the correlations between retinal findings and cognitive functions of patients and their healthy siblings may provide insight into the pathophysiological processes of the disorder. We aimed to investigate the relationship between neuropsychiatric tests and retinal changes in schizophrenia patients and their healthy siblings.

METHODS

We measured OCT parameters and cognitive performance (via Trail Making Tests, verbal fluency tests, and The Digit Span Tests) of 72 participants (36 patients with schizophrenia and 36 healthy siblings) and disease severity (with Positive and Negative Syndrome Scale, Global Assessment of Functioning, and Clinical Global Impression scales) in patients with schizophrenia and evaluated the relationship between retinal findings and clinical parameters, especially neurocognitive tests.

RESULTS

We found decreased ganglion cell layer-inner plexiform layer thickness and macular volume in the patient group. There were strong correlations between neurocognitive tests and OCT findings in both groups. On the other hand, there was not any correlation between retinal findings and disease parameters.

CONCLUSION

The cognitive symptoms of schizophrenia may be more closely related to structural changes in the retina.

Cognitive Impairment Associated with Schizophrenia: From Pathophysiology to Treatment

Cognitive impairment is a core feature of schizophrenia and a major contributor to poor functional outcomes. Methods for assessment of cognitive dysfunction in schizophrenia are now well established. In addition, there has been increasing appreciation in recent years of the additional role of social cognitive impairment in driving functional outcomes and of the contributions of sensory-level dysfunction to higher-order impairments. At the neurochemical level, acute administration of N-methyl-d-aspartate receptor (NMDAR) antagonists reproduces the pattern of neurocognitive dysfunction associated with schizophrenia, encouraging the development of treatments targeted at both NMDAR and its interactome. At the local-circuit level, an auditory neurophysiological measure, mismatch negativity, has emerged both as a veridical index of NMDAR dysfunction and excitatory/inhibitory imbalance in schizophrenia and as a critical biomarker for early-stage translational drug development. Although no compounds have yet been approved for treatment of cognitive impairment associated with schizophrenia, several candidates are showing promise in early-phase testing.

Perceptual Functioning

Perceptual disorders are not part of the diagnosis criteria for schizophrenia. Yet, a considerable amount of work has been conducted, especially on visual perception abnormalities, and there is little doubt that visual perception is altered in patients. There are several reasons why such perturbations are of interest in this pathology. They are observed during the prodromal phase of psychosis, they are related to the pathophysiology (clinical disorganization, disorders of the sense of self), and they are associated with neuronal connectivity disorders. Perturbations occur at different levels of processing and likely affect how patients interact and adapt to their surroundings. The literature has become very large, and here we try to summarize different models that have guided the exploration of perception in patients. We also illustrate several lines of research by showing how perception has been investigated and by discussing the interpretation of the results. In addition to discussing domains such as contrast sensitivity, masking, and visual grouping, we develop more recent fields like processing at the level of the retina, and the timing of perception.

A comparative study of retinal layer changes among patients with schizophrenia and healthy controls

AIM

This study aimed to evaluate the retinal nerve fibre layer changes among different group of patients with schizophrenia and compare it with healthy controls by using swept-source optical coherence tomography.

METHODOLOGY

Patients with first-episode schizophrenia (n = 21) in remission (n = 35) or with treatment-resistant schizophrenia (TRS) (n = 35) and 36 healthy controls were evaluated for retinal thickness.

RESULTS

Patients with psychotic illnesses had significantly lower sub-foveal choroidal thickness (effect size 0.84-0.86), when compared to the healthy controls. When patients with first-episode schizophrenia were compared with patients with TRS, TRS patients had significant lower sub-foveal choroidal thickness (left eye) when the various confounders (such as age, gender, duration of treatment, smoking, current medications, body mass index, waist circumference, blood pressure, fasting glucose, HbA1c, presence or absence of metabolic syndrome) were taken into account. When the patients with TRS were compared with healthy controls, initially significant differences were observed for the macular volume (left and right) and the ganglion cell thickness (right eye) but these differences disappeared after controlling for the various covariates.

CONCLUSIONS

Compared to healthy controls, patients with schizophrenia, psychotic illnesses have thinning of the retina, especially in the sub-foveal choroidal thickness.

Structural and functional retinal alterations in patients with paranoid schizophrenia

Ophthalmological methods have increasingly raised the interest of neuropsychiatric specialists. While the integrity of the retinal cell functions can be evaluated with the electroretinogram (ERG), optical coherence tomography (OCT) allows a structural investigation of retinal layer thicknesses. Previous studies indicate possible functional and structural retinal alterations in patients with schizophrenia. Twenty-five patients with paranoid schizophrenia and 25 healthy controls (HC) matched for age, sex, and smoking status participated in this study. Both, ERG and OCT were applied to obtain further insights into functional and structural retinal alterations. A significantly reduced a-wave amplitude and thickness of the corresponding para- and perifoveal outer nuclear layer (ONL) was detected in patients with paranoid schizophrenia with a positive correlation between both measurement parameters. Amplitude and peak time of the photopic negative response (PhNR) and thickness of the parafoveal ganglion cell layer (GCL) were decreased in patients with schizophrenia compared to HC. Our results show both structural and functional retinal differences between patients with paranoid schizophrenia and HC. We therefore recommend the comprehensive assessment of the visual system of patients with schizophrenia, especially to further investigate the effect of antipsychotic medication, the duration of illness, or other factors such as inflammatory or neurodegenerative processes. Moreover, longitudinal studies are required to investigate whether the functional alterations precede the structural changes.

Retinal layers and associated clinical factors in schizophrenia spectrum disorders: a systematic review and meta-analysis

INTRODUCTION

The retina shares structural and functional similarities with the brain. Furthermore, structural changes in the retina have been observed in patients with schizophrenia spectrum disorders (SSDs). This systematic review and meta-analysis investigated retinal abnormalities and their association with clinical factors for SSD.

METHODS

Studies related to retinal layers in SSD patients were retrieved from PubMed, Scopus, Web of Science, Cochrane Controlled Register of Trials, International Clinical Trials Registry Platform, and PSYNDEX databases from inception to March 31, 2021. We screened and assessed the eligibility of the identified studies. EZR ver.1.54 and the metafor package in R were used for the meta-analysis and a random-effects or fixed-effects model was used to report standardized mean differences (SMDs).

RESULTS

Twenty-three studies (2079 eyes of patients and 1571 eyes of controls) were included in the systematic review and meta-analysis. The average peripapillary retinal nerve fiber layer (pRNFL) thickness, average macular thickness (MT), and macular ganglion cell layer-inner plexiform layer (GCL-IPL) thickness were significantly lower in patients than in controls (n = 14, 6, and 3, respectively; SMD = -0.33, -0.49, and -0.43, respectively). Patients also had significantly reduced macular volume (MV) compared to controls (n = 7; SMD = -0.53). The optic cup volume (OCV) was significantly larger in patients than in controls (n = 3; SMD = 0.28). The meta-regression analysis indicated an association between several clinical factors, such as duration of illness and the effect size of the pRNFL, macular GCL-IPL, MT, and MV.

CONCLUSION

Thinning of the pRNFL, macular GCL-IPL, MT, and MV and enlargement of the OCV in SSD were observed. Retinal abnormalities may be applicable as state/trait markers in SSDs. The accumulated evidence was mainly cross-sectional and requires verification by longitudinal studies to characterize the relationship between OCT findings and clinical factors.

Optical coherence tomography reveals retinal thinning in schizophrenia spectrum disorders

BACKGROUND

Schizophrenia spectrum disorders (SSDs) are presumed to be associated with retinal thinning. However, evidence is lacking as to whether these retinal alterations reflect a disease-specific process or are rather a consequence of comorbid diseases or concomitant microvascular impairment.

METHODS

The study included 126 eyes of 65 patients with SSDs and 143 eyes of 72 healthy controls. We examined macula and optic disc measures by optical coherence tomography (OCT) and OCT angiography (OCT-A). Additive mixed models were used to assess the impact of SSDs on retinal thickness and perfusion and to explore the association of retinal and clinical disease-related parameters by controlling for several ocular and systemic covariates (age, sex, spherical equivalent, intraocular pressure, body mass index, diabetes, hypertension, smoking status, and OCT signal strength).

RESULTS

OCT revealed significantly lower parafoveal macular, macular ganglion cell-inner plexiform layer (GCIPL), and macular retinal nerve fiber layer (RNFL) thickness and thinner mean and superior peripapillary RNFL in SSDs. In contrast, the applied OCT-A investigations, which included macular and peripapillary perfusion density, macular vessel density, and size of the foveal avascular zone, did not reveal any significant between-group differences. Finally, a longer duration of illness and higher chlorpromazine equivalent doses were associated with lower parafoveal macular and macular RNFL thickness.

CONCLUSIONS

This study strengthens the evidence for disease-related retinal thinning in SSDs.

Mapping Retinal Abnormalities in Psychosis: Meta-analytical Evidence for Focal Peripapillary and Macular Reductions

BACKGROUND

Several studies have suggested that the retina structure is affected in schizophrenia spectrum disorders (SSD). We aimed to investigate the location and size of the potential differences between patients and healthy controls (HC) in several thickness and volume measures across the retina.

STUDY DESIGN

We included cross-sectional studies comparing peripapillary retinal nerve fiber layer (pRNFL) thickness, macular volume, macular thickness (MT), foveal thickness, ganglion cell and inner plexiform layer thickness (GCL+IPL), cup volume, and cup/disc ratio (C/D) in the right and/or left eyes and/or the pRNFL and MT quadrants between patients with SSD and HC. Search databases were MEDLINE, Web of Science, PsycINFO, Cochrane Central, and medrxiv.org. Risk of bias was assessed with the Newcastle-Ottawa Scale. Standardized mean differences (SMD), subgroup analysis, and meta-regression with several variables were computed using the dmetar package in R. PROSPERO: CRD42021287873.

STUDY RESULTS

Data from 22 reports (942 patients, 742 HC) were included. We found a retinal thinning in pRNFL (-0.30; 95% CI: -0.46, -0.14), macula (-0.37; 95% CI: -0.61, -0.13), and GCL+IPL (-0.33; 95% CI: -0.57, -0.10). The retinal thinning was especially pronounced in the superior and inferior quadrants of the inner ring of the macula. We also observed a decrease of macular volume (-0.44; 95% CI: -0.68, -0.20) and an increase in C/D ratio (0.35; 95% CI: 0.03, 0.67).

CONCLUSIONS

Current evidence demonstrates retinal thinning in SSD, affecting both axonal and cellular structures, specially focused in the inner ring of the macula.

Comparing retinal changes measured by optical coherence tomography in patients with schizophrenia and their siblings with healthy controls: Are retinal findings potential endophenotype candidates?

AIM

The aim of our study is to examine whether differences in retinal structure may reflect endophenotypes for schizophrenia by comparing thicknesses of retinal layers between patients with schizophrenia, their unaffected siblings, and healthy control groups and investigating the relationship between OCT findings and disease parameters.

MATERIAL AND METHODS

46 patients with schizophrenia, their 46 healthy siblings, and 46 age and gender-matched healthy controls were enrolled in the study and underwent spectral domain OCT (examinations to assess differences in peripapillary retinal nerve fiber layer (RNFL) thickness, ganglion cell layer (GCL)+ inner plexiform layer (IPL) thicknesses and macular volumes (MV) in both eyes). Clinical variables were also recorded in the patient group.

RESULTS

There was no difference between the groups in terms of RNFL thicknesses. The GCL+IPL thicknesses of the siblings are between the patients and controls but according to post hoc comparisons the GCL+IPLs of the patients were only thinner than controls. Additionally, MVs were significantly lower in the patient group compared to the sibling group. There was no correlation between any clinical parameters and the GCL+IPLs of all groups, however there were some correlations between RNFL and clinical features especially in the patients group.

CONCLUSION

GCL+IPL values do not seem to be affected by the disease parameters or the factors like body mass index or nicotine use. On the other hand, further studies are needed to determine whether GCL+IPL could be an endophenotype candidate.

Schizophrenia in Translation: Why the Eye?

Schizophrenia is increasingly recognized as a systemic disease, characterized by dysregulation in multiple physiological systems (eg, neural, cardiovascular, endocrine). Many of these changes are observed as early as the first psychotic episode, and in people at high risk for the disorder. Expanding the search for biomarkers of schizophrenia beyond genes, blood, and brain may allow for inexpensive, noninvasive, and objective markers of diagnosis, phenotype, treatment response, and prognosis. Several anatomic and physiologic aspects of the eye have shown promise as biomarkers of brain health in a range of neurological disorders, and of heart, kidney, endocrine, and other impairments in other medical conditions. In schizophrenia, thinning and volume loss in retinal neural layers have been observed, and are associated with illness progression, brain volume loss, and cognitive impairment. Retinal microvascular changes have also been observed. Abnormal pupil responses and corneal nerve disintegration are related to aspects of brain function and structure in schizophrenia. In addition, studying the eye can inform about emerging cardiovascular, neuroinflammatory, and metabolic diseases in people with early psychosis, and about the causes of several of the visual changes observed in the disorder. Application of the methods of oculomics, or eye-based biomarkers of non-ophthalmological pathology, to the treatment and study of schizophrenia has the potential to provide tools for patient monitoring and data-driven prediction, as well as for clarifying pathophysiology and course of illness. Given their demonstrated utility in neuropsychiatry, we recommend greater adoption of these tools for schizophrenia research and patient care.

Overexpression of Neuregulin-1 Type III Has Impact on Visual Function in Mice

Schizophrenia is associated with several brain deficits, including abnormalities in visual processes. Neuregulin-1 (Nrg1) is a family of trophic factors containing an epidermal growth factor (EGF)-like domain. It is thought to play a role in neural development and has been linked to neuropsychiatric disorders. Abnormal Nrg1 expression has been observed in schizophrenia in clinical studies. Moreover, in schizophrenia, there is more and more evidence found about pathological changes of the retina regarding structural, neurochemical and physiological parameters. However, mechanisms of these changes are not well known. To investigate this, we analysed the function of the visual system using electroretinography (ERG) and the measurement of visual evoked potentials (VEP) in transgenic mice overexpressing Nrg1 type III of three different ages (12 weeks, 24 weeks and 55 weeks). ERG amplitudes tended to be higher in transgenic mice than in control mice in 12-week old mice, whereas the amplitudes were almost similar in older mice. VEP amplitudes were larger in transgenic mice at all ages, with significant differences at 12 and 55 weeks (p values between 0.003 and 0.036). Latencies in ERG and VEP measurements did not differ considerably between control mice and transgenic mice at any age. Our data show for the first time that overexpression of Nrg1 type III changed visual function in transgenic mice. Overall, this investigation of visual function in transgenic mice may be helpful to understand corresponding changes that occur in schizophrenia, as they may find use as biomarkers for psychiatric disorders as well as a potential tool for diagnosis in psychiatry.

Analysis of the Thickness of the Outer Retinal Layer Using Optical Coherence Tomography - A Predictor of Visual Acuity in Schizophrenia

BACKGROUND

The aim of this study was to evaluate the thickness of the outer retinal layer (ORL) together with macular thickness and changes in the retinal nerve fiber layer (RNFL) in patients with schizophrenia in comparison with healthy controls.

METHODS

This study included 114 eyes of 57 patients diagnosed with schizophrenia and 114 eyes of 57 healthy controls. Central foveal thickness (CFT), central macular thickness (CMT), and ORL thickness were measured in both groups via the images obtained by spectral-domain optical coherence tomography (SD-OCT). RNFL was also assessed in four quadrants (inferior, superior, temporal, nasal). CMT measurements were presented as the average thickness of the macula in the central 1 mm area on the Early Treatment Diabetic Retinopathy Study (ETDRS) grid. The ORL thickness was defined as the distance between the external limiting membrane and retinal pigment epithelium at the center of the foveal pit.

RESULTS

The mean age of 57 patients was 37 ± 10 years, of whom 34 (60%) were male and 23 (40%) female. No statistically significant difference was found between groups in terms of age and gender (p = 0.8 for age, p = 0.9 for gender). There was no statistically significant difference in the mean CMT between the two groups (p = 0.1). The mean ORL thickness in the two groups was 99.8 ± 8.3 and 103.7 ± 6.2, respectively, and was significantly decreased in the schizophrenia group (p = 0.005). RNFL analysis demonstrated significant thinning in the inferior and superior quadrants compared to healthy controls (p < 0.001 and p = 0.017, respectively).

CONCLUSIONS

SD-OCT findings - especially ORL and RNFL thickness - may be related to the neurodegenerational changes in schizophrenia.

Early-stage visual perception impairment in schizophrenia, bottom-up and back again

Visual perception is one of the basic tools for exploring the world. However, in schizophrenia, this modality is disrupted. So far, there has been no clear answer as to whether the disruption occurs primarily within the brain or in the precortical areas of visual perception (the retina, visual pathways, and lateral geniculate nucleus [LGN]). A web-based comprehensive search of peer-reviewed journals was conducted based on various keyword combinations including schizophrenia, saliency, visual cognition, visual pathways, retina, and LGN. Articles were chosen with respect to topic relevance. Searched databases included Google Scholar, PubMed, and Web of Science. This review describes the precortical circuit and the key changes in biochemistry and pathophysiology that affect the creation and characteristics of the retinal signal as well as its subsequent modulation and processing in other parts of this circuit. Changes in the characteristics of the signal and the misinterpretation of visual stimuli associated with them may, as a result, contribute to the development of schizophrenic disease.

Quantifying Retinal Microvascular Morphology in Schizophrenia Using Swept-Source Optical Coherence Tomography Angiography

BACKGROUND

Retinovascular changes are reported on fundus imaging in schizophrenia (SZ). This is the first study to use swept-source optical coherence tomography angiography (OCT-A) to comprehensively examine retinal microvascular changes in SZ.

METHODS

This study included 30 patients with SZ/schizoaffective disorder (8 early and 15 chronic) and 22 healthy controls (HCs). All assessments were performed at Beth Israel Deaconess Medical Center and Massachusetts Eye and Ear. All participants underwent swept-source OCT-A of right (oculus dextrus [OD]) and left (oculus sinister [OS]) eye, clinical, and cognitive assessments. Macular OCT-A images (6 × 6 mm) were collected with the DRI Topcon Triton for superficial, deep, and choriocapillaris vascular regions. Microvasculature was quantified using vessel density (VD), skeletonized vessel density (SVD), fractal dimension (FD), and vessel diameter index (VDI).

RESULTS

Twenty-one HCs and 26 SZ subjects were included. Compared to HCs, SZ patients demonstrated higher overall OD superficial SVD, OD choriocapillaris VD, and OD choriocapillaris SVD, which were primarily observed in the central, central and outer superior, and central and outer inferior/superior, respectively. Early-course SZ subjects had significantly higher OD superficial VD, OD choriocapillaris SVD, and OD choriocapillaris FD compared to matched HCs. Higher bilateral (OU) superficial VD correlated with lower Positive and Negative Syndrome Scale (PANSS) positive scores, and higher OU deep VDI was associated with higher PANSS negative scores.

CONCLUSIONS AND RELEVANCE

These results suggest the presence of microvascular dysfunction associated with early-stage SZ. Clinical associations with microvascular alterations further implicate this hypothesis, with higher measures being associated with worse symptom severity and functioning in early stages and with lower symptom severity and better functioning in later stages.

Altered central vision and amacrine cells dysfunction as marker of hypodopaminergic activity in treated patients with schizophrenia

BACKGROUND

Retinal dysfunction is widely documented in schizophrenia using flash (fERG) and pattern electroretinograms (PERG), but the role of dopamine transmission has seldom been explored.

METHODS

We explored the role of dopamine transmission by evaluating the spatial location of retinal anomalies using multifocal ERG (mfERG) in photopic condition and the oscillatory potentials (OPs) extracted from fERG measured in scotopic condition in 29 patients with schizophrenia and 29 healthy controls.

RESULTS

With the mfERG, our main results revealed reduced amplitudes in the center of the retina: P1 (p < .005) and N2 amplitudes (p < .01) in the <2° region, N1 (p < .0005) and P1 amplitudes (p < .001) in the 2-5° region and P1 amplitude (p < .05) in the 5-10° region. For OPs, our results showed a decrease in the O1 (p < .005), O2 (p < .005), O3 (p < .05) and overall O1, O2, O3 index amplitudes (p < .005) in patients with schizophrenia.

CONCLUSIONS

Both the central location of retinal dysfunctions of the mfERG and OPs results could reflect a hypodopaminergic effect in patients with schizophrenia. In future studies, OPs should be considered as a measure to evaluate the hypodopaminergy in patients.

Assessment of Optical Coherence Tomography Findings in Adults with Attention Deficit Hyperactivity Disorder: A Case-Control Study

Background

To assess retinal nerve fiber layer and ganglion cell-inner plexiform layer thickness using optical coherence tomography in attention deficit hyperactivity disorder adults on regular methylphenidate treatment, comparing them to healthy controls.

Methods

A total of 33 attention deficit hyperactivity disorder adults and 31 healthy subjects, matched for age, gender, and education (control group), were included in this study. Retinal nerve fiber layer and ganglion cell-inner plexiform layer thickness of both eyes were measured using optical coherence tomography, and symptom severity was evaluated using Adult Attention Deficit Hyperactivity Disorder Self-Report Scale and Wender Utah Rating Scale.

Results

There was no significant difference in retinal nerve fiber layer thickness between the attention deficit hyperactivity disorder and control groups (P > .05). Thinner ganglion cell-inner plexiform layer total (P = .044), inferior (P = .012), and inferior nasal quadrant thickness (P = .049) were observed in attention deficit hyperactivity disorder patients as compared to the controls.

Conclusion

Findings detected thinner ganglion cell-inner plexiform layer in some quadrants of attention deficit hyperactivity disorder adults, indicating an early disorder in retinal structure development. Whether retinal structures are sensitive attention deficit hyperactivity disorder biomarkers should be supported and investigated in future multimodal studies.

Antipsychotics With Different Chemical Structures Cause Different Degrees of Functional Impairments in the Primary Visual Cortex in a Murine Model: A Pilot Study

Background

Antipsychotic medications can impair vision in patients with schizophrenia. However, little is known regarding the pharmacodynamics of antipsychotics in the primary visual cortex. We aimed to study the pharmacodynamics of antipsychotics in the visual cortex in a murine model.

Methods

We used an adapted 2-photon imaging technique to observe changes in calcium dynamics induced by 4 antipsychotics (olanzapine, risperidone, aripiprazole, and amisulpride) in the primary visual cortex of healthy and schizophrenic C57BL/6 mice. Visual function was further assessed by using a novel object recognition test.

Results

All 4 antipsychotics decreased calcium activity in the primary visual cortex and reduced visual recognition test scores in healthy and schizophrenic mice. The most potent drug was olanzapine, followed by risperidone, aripiprazole, and amisulpride. All drugs showed significant differences between groups.

Conclusion

Our pilot study demonstrated that antipsychotics impair visual cortical function. This finding underscores the importance of monitoring for visual adverse events in patients receiving antipsychotic medications to treat schizophrenia.

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.

Patients with first-episode untreated schizophrenia who experience concomitant visual disturbances and auditory hallucinations exhibit co-impairment of the brain and retinas-a pilot study

There are limited structural brain and retina alteration data from schizophrenia patients who experience visual disturbances (VDs) with or without auditory hallucinations (AHs). We compared brain and retina alterations between first-episode untreated schizophrenia patients with VDs (FUSCH-VDs) with versus without AHs, and between patients and healthy controls (HCs)(N = 30/group). VDs, AHs, gray matter volumes (GMVs), and retinal thicknesses were evaluated with the Bonn Scale for Assessment of Basic Symptoms (BSABS) scale, the Auditory Hallucinations Rating Scale (AHRS), magnetic resonance imaging (MRI), and optical coherence tomography (OCT), respectively. Compared to HCs, FUSCH-VDs had reduced GMVs, mainly in dorsal V3/V3A and V5 regions, the fusiform gyrus, and ventral V4 and V8 regions. Most FUSCH-VDs (85.0%; 51/60) had primary visual cortex-retina co-impairments. FUSCH-VDs with AHs had more serious and larger scope GMV reductions than FUSCH-VDs without AHs. FUSCH-VDs with AHs had significant retinal thickness reductions compared to HCs. Primary visual cortex-retina co-impairments were found to be more common, and more pronounced when present, in FUSCH-VDs with AHs than in FUSCH-VDs without AHs. The present findings support the notion that VDs and AHs may have reciprocal deteriorating actions in patients with schizophrenia.

Neuroretinal Biomarkers for Schizophrenia Spectrum Disorders

Purpose

We evaluated the patient-control differences and predictive value of the retina as potential biomarkers for schizophrenia.

Methods

The institutional study included both eyes of 58 schizophrenia spectrum disorder (SSD) patients (age 37.2 ± 12.3 years) and 35 controls (age 41.1 ± 15.2 years). Retinal nerve fiber layer (RNFL), ganglion cell–inner plexiform layer, outer retinal photoreceptor complex, and total macula thicknesses were measured by optical coherence tomography (OCT). Anterior segment parameters including central corneal thickness, anterior chamber depth, and axial length were measured to rule out confounds on the retinal measures.

Results

The peripapillary RNFL was overall significantly thinner in SSD relative to controls (F = 3.97, P = 0.049), most pronounced in the temporal (5.2 µm difference, F = 6.95, P = 0.010) and inferior quadrants (12.1 µm difference, F = 7.32, P = 0.009). There were no significant group differences in thickness for the macular RNFL, ganglion, or photoreceptor cell related measures (P > 0.05). Peripapillary RNFL, central macula, and outer photoreceptor complex thicknesses were together able to classify SSD patients with 80% sensitivity and 71% specificity; area under the curve = 0.82 (95% confidence interval, 0.75–0.88).

Conclusions

SSD patients exhibited significant RNFL thinning relative to controls. Notably, retinal thickness measures including both peripapillary and macular data exhibited improved diagnostic accuracy for SSD as compared to these regions alone.

Translational Relevance

This is the first study to evaluate the predictive value of both the inner and outer retina in SSD. OCT retinal thickness measures including peripapillary data in conjunction with macular data may provide an informative, noninvasive in vivo ocular biomarker for schizophrenia.

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.

Reduction of Retinal Thickness Ipsilateral to Hippocampal Sclerosis in Epilepsy

Objectives: Reductions in the peripapillary retinal nerve fiber layer (pRNFL) have been reported in epilepsy, namely in drug-resistant people. Hippocampal sclerosis (HS) is the most frequent cause of drug-resistant epilepsy in tertiary care centers. We aimed to evaluate the likelihood and characteristic of RNFL loss in individuals with epilepsy having HS.

Methods: Fifty-five adults diagnosed with unilateral HS (mean age of 25 years; 42 female) by magnetic resonance imaging were included in this observational cross-sectional study, 58 age-matched individuals with epilepsy with no detectable structural brain abnormality were included as non-HS, and 55 people without neurological diseases were included as healthy controls. pRNFL of both eyes was measured by optical coherence tomography (OCT). In each individual disease related information was recorded.

Results: Among the 55 individuals with unilateral HS, one (1.82%) and ten (18.18%) had significant or borderline abnormal thinning of the pRNFL of the ipsilateral eye to the HS. The average pRNFL ipsilateral to the side of HS was significantly thinner than people with epilepsy non-HS (p = 0.013) and healthy controls (p = 0.000), especially in the inferior quadrants. Only age was significantly correlated with the average and inferior quadrant pRNFL thickness of the ipsilateral eye to the HS (R = −0.286, p = 0.035; R = −0.353, p = 0.008 respectively).

Conclusion: These preliminary findings suggest that retinal abnormalities associated with HS may have a specific pattern. Further studies need to confirm this finding and to unravel the underlying mechanism.

Exploring the role of macular thickness as a potential early biomarker of neurodegeneration in acute schizophrenia

OBJECTIVE

The retina has been investigated as a gateway to assess the neurodegenerative changes in the brain. Schizophrenia is also conceptualized as a neurodegenerative disorder like Alzheimer's and Parkinson's disease. The current literature suggests reduced retinal nerve fibre layer (RNFL) thickness and macular thickness (MT), as a marker of neurodegeneration, in patient suffering from chronic schizophrenia. This study aims to compare RNFL thickness and MT in acute schizophrenic patients with age and sex matched healthy controls.

METHODS

Twenty acutely ill schizophrenic patients and 20 normal controls were included in the study after proper informed consent. RNFL thickness and MT was measured using spectral domain Optical Coherence Tomography after clinical psychological assessment and ocular examination.

RESULTS

The two groups were comparable in terms of socio-demographic variables. The average RNFL thickness of patients and healthy controls was 102.11 ± 29.18 µm and 105.14 ± 27.35 µm, respectively. Central macular thickness was 181.12 ± 13.63 µm in patients and 234.58 ± 10.71 µm in controls. There was a statistically significant reduction in thickness of macula (p < 0.05) but not for RNFL (p = 0.339).

CONCLUSION

The study concludes that macular thinning rather than reduced RNFL is an early manifestation in acute schizophrenia patients and can be considered as a potential early biomarker of neurodegeneration in schizophrenia.

The Phenomenology and Neurobiology of Visual Distortions and Hallucinations in Schizophrenia: An Update

Schizophrenia is characterized by visual distortions in ~60% of cases, and visual hallucinations (VH) in ~25-50% of cases, depending on the sample. These symptoms have received relatively little attention in the literature, perhaps due to the higher rate of auditory vs. visual hallucinations in psychotic disorders, which is the reverse of what is found in other neuropsychiatric conditions. Given the clinical significance of these perceptual disturbances, our aim is to help address this gap by updating and expanding upon prior reviews. Specifically, we: (1) present findings on the nature and frequency of VH and distortions in schizophrenia; (2) review proposed syndromes of VH in neuro-ophthalmology and neuropsychiatry, and discuss the extent to which these characterize VH in schizophrenia; (3) review potential cortical mechanisms of VH in schizophrenia; (4) review retinal changes that could contribute to VH in schizophrenia; (5) discuss relationships between findings from laboratory measures of visual processing and VH in schizophrenia; and (6) integrate findings across biological and psychological levels to propose an updated model of VH mechanisms, including how their content is determined, and how they may reflect vulnerabilities in the maintenance of a sense of self. In particular, we emphasize the potential role of alterations at multiple points in the visual pathway, including the retina, the roles of multiple neurotransmitters, and the role of a combination of disinhibited default mode network activity and enhanced state-related apical/contextual drive in determining the onset and content of VH. In short, our goal is to cast a fresh light on the under-studied symptoms of VH and visual distortions in schizophrenia for the purposes of informing future work on mechanisms and the development of targeted therapeutic interventions.

Relationships Among Retinal Nerve Fiber Layer Thickness, Vascular Endothelial Growth Factor, and Cognitive Impairment in Patients with Schizophrenia

BACKGROUND

Studies have suggested retinal nerve fiber layer (RNFL) involvement in the pathogenesis of schizophrenia. Additionally, research has shown that vascular endothelial growth factor (VEGF) potentially contributes to the pathophysiology of psychiatric disorders. Therefore, this study aimed to investigate VEGF, RNFL, and correlations with cognitive impairments in schizophrenia patients.

METHODS

Patients with schizophrenia (n = 138) were compared to healthy controls (n = 160). RNFLs were measured with optical coherence tomography (OCT). The Stroop color and word test (SCWT) was used to evaluate neurocognition. Blood samples were collected to measure VEGF. SPSS 20.0 was used to perform analysis of covariance, t-tests, partial correlation analysis, and linear regression.

RESULTS

Thinner RNFLs were found in schizophrenia patients (p < 0.001). RNFL showed a significant correlation with SCWT scores (all p < 0.05). Serum level of VEGF was lower in patients with schizophrenia (p = 0.010). Total and inferior RNFL thicknesses of right eyes were positively correlated to VEGF level (RNFL total thickness p = 0.032, inferior thickness p = 0.014).Total RNFL thicknesses were shown to be reduced following a prolonged duration of illness (both p < 0.01).

CONCLUSION

These findings suggest that patients with schizophrenia have degeneration with RNFL thickness following illness duration, which may contribute to neurocognitive impairments observed in schizophrenia. VEGF is speculated to play some important role on RNFL degeneration with schizophrenia patients.

THE USE OF ELECTRORETINOGRAPHY AND OPTICAL COHERENCE TOMOGRAPHY IN PATIENTS WITH SCHIZOPHRENIA

The use of electroretinography (ERG) and optical coherence tomography (OCT) has currently expanded beyond ophthalmology alone. The aim of this review is to present the results and knowledge acquired by these two methods in patients suffering from schizophrenia. Reviewing the studies applying ERG and OCT methods in the field of psychiatry, one can conclude that results of the research imply morphological and functional changes of retina in patients with schizophrenia that are not consistent. However, in most studies there was reduction of the amplitude and changes in the implicit time related parameters on ERG and thinning of the retinal nerve fiber layer on OCT. Neurons in the eye use the same neurotransmitters as neurons in the basal brain structures that are most affected in schizophrenia, according to the dopamine hypothesis of schizophrenia. Unlike neurons in the basal brain structures, the neurons in the eye are in vivo available to ERG. Using the aforementioned tests together with clinical diagnostic criteria of schizophrenia, the subgroups with different prognostic and therapeutic specificities within schizophrenia as a group of diseases might be identified more precisely.

Structural imaging of the retina in psychosis spectrum disorders: current status and perspectives

PURPOSE OF REVIEW

Structural changes of the retina in schizophrenia and other psychotic disorders seem plausible as these conditions are accompanied by widespread morphological abnormalities of the brain. Advances in structural retinal imaging have led to the possibility of precise quantification of individual retinal layers, using optical coherence tomography (OCT) scanners.

RECENT FINDINGS

The aggregation of information related to OCT findings in schizophrenia has resulted in three metaanalyses, which are currently described. Areas where retinal changes were reported include retinal nerve fiber layer (RNFL), ganglion cell layer complex (GCC), macular volume, and macular thickness, but findings on affected retinal segments vary to some extent across studies. Discrepancies in individual studies could be because of small samples, heterogeneity within schizophrenia (phase of the illness, illness duration, predominant symptomatology), inconsistent reporting of antipsychotic therapy, insufficient control of confounding variables (somatic comorbidities, smoking, and so on), and use of the different types of OCT scanners.

SUMMARY

Exploration of potential disturbances in retinal architecture could provide new insights into neuronal changes associated with psychosis spectrum disorders, with potential to elucidate the nature and timing of developmental, progressive, inflammatory, and degenerative aspects of neuropathology and pathophysiology, and to assist with characterizing heterogeneity and facilitating personalized treatment approaches.

Association of retinal nerve fiber abnormalities with serum CNTF and cognitive functions in schizophrenia patients

BACKGROUND

Recent studies have reported reductions in retinal nerve fiber layers (RNFL) in schizophrenia. Ciliary neurotrophic factor (CNTF) has shown protective effects on both the neurogenesis and retina. This study aimed at investigating retinal abnormalities and establishing their correlation with serum CNTF and cognitive impairments in schizophrenic Chinese patients.

METHODS

In total, 221 patients diagnosed with schizophrenia and 149 healthy controls were enrolled. Serum CNTF and clinical features of patients were investigated. Cognitive functions were evaluated with Repeatable Battery for the Assessment of Neuropsychology Status (RBANS). RNFL thickness and macular thickness (MT) of both eyes were measured with optical coherence tomography (OCT). T-tests and analysis of covariance were used to compare the variables between the patient and control groups, while multiple linear regression analysis was performed to determine the associations of RNFL thickness, CNTF and cognitive impairments.

RESULTS

RNFL was found thinner in patients than in healthy controls (right: 88.18 ± 25.84 µm vs.102.13 ± 14.32 µm, p = 0.001; left: 92.84 ± 13.54 µm vs.103.71 ± 11.94 µm, p < 0.001). CNTF was lower in the schizophrenia group (1755.45 ± 375.73 pg/ml vs. 1909.99 ± 368.08 pg/ml, p = 0.001). Decline in RNFL thickness was found correlated with course of illness and serum CNTF in patients (all p < 0.05). Similarly, cognitive functions such as immediate memory and visuospatial functions were also found correlated with decline in RNFL thickness.

CONCLUSION

Decline in RNFL thickness was associated with cognitive impairments of schizophrenia and CNFT serum concentration. The possibility of reduction in RNFL thickness as a biomarker for schizophrenia needs to be further examined.

[Retinal investigations in patients with major depressive disorder, bipolar disorder or schizophrenia: A review of the literature]

Major depressive disorder, bipolar disorder and schizophrenia are currently among the most common psychiatric disorders, known to constitute a serious public health issue in terms of morbidity, mortality and functional handicap. Their pathophysiology is still unclear, but there is now increasing evidence supporting the existence of abnormalities of neurotransmission. As the retina is an extension of the central nervous system, it may be an interesting site of study which might provide a better understanding of the pathophysiology of psychiatric disorders. Several studies have demonstrated retinal abnormalities, with abnormal cone and rod responses on electroretinography (ERG), suggesting a process of functional neuronal loss, structurally supported by a decrease in the retinal nerve fiber layer thickness (RNFL) on optical coherence tomography (OCT), which suggests involvement of the molecular signal pathways of neurotransmission. These tests could be useful tools for diagnosing and monitoring psychiatric disorders. This article is an overview of the literature on retinal abnormalities observed in patients with major depressive disorder, bipolar disorder or schizophrenia, and discusses how they could be pathophysiologic markers.

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.

Study of retinal structure and function in patients with major depressive disorder, bipolar disorder or schizophrenia: A review of the literature

Major depressive disorder, bipolar disorder and schizophrenia are currently among the most common psychiatric disorders, known to constitute a serious public health issue in terms of morbidity, mortality and functional handicap. Their pathophysiology is still unclear, but there is now increasing evidence supporting the existence of abnormalities of neurotransmission. As the retina is an extension of the central nervous system, it may be an interesting site of study which might provide a better understanding of the pathophysiology of psychiatric disorders. Several studies have demonstrated retinal abnormalities, with abnormal cone and rod responses on electroretinography (ERG), suggesting a process of functional neuronal loss, structurally supported by a decrease in the retinal nerve fiber layer thickness (RNFL) on optical coherence tomography (OCT), which suggests involvement of the molecular signal pathways of neurotransmission. These tests could be useful tools for diagnosing and monitoring psychiatric disorders. This article is an overview of the literature on retinal abnormalities observed in patients with major depressive disorder, bipolar disorder or schizophrenia, and discusses how they could be pathophysiologic markers.

Schizophrenia and the retina: Towards a 2020 perspective

BACKGROUND

Differences between people with schizophrenia and psychiatrically healthy controls have been consistently demonstrated on measures of retinal function such as electroretinography (ERG), and measures of retinal structure such as optical coherence tomography (OCT). Since our 2015 review of this literature, multiple new studies have been published using these techniques. At the same time, the accumulation of data has highlighted the "fault lines" in these fields, suggesting methodological considerations that need greater attention in future studies.

METHODS

We reviewed studies of ERG and OCT in schizophrenia, as well as data from studies whose findings are relevant to interpreting these papers, such as those on effects of the following on ERG and OCT data: comorbid medical conditions that are over-represented in schizophrenia, smoking, antipsychotic medication, substance abuse, sex and gender, obesity, attention, motivation, and influences of brain activity on retinal function.

RESULTS

Recent ERG and OCT studies continue to support the hypothesis of retinal structural and functional abnormalities in schizophrenia, and suggest that these are relevant to understanding broader aspects of pathophysiology, neurodevelopment, and neurodegeneration in this disorder. However, there are differences in findings which suggest that the effects of multiple variables on ERG and OCT data need further clarification.

CONCLUSIONS

The retina, as the only component of the CNS that can be imaged directly in live humans, has potential to clarify important aspects of schizophrenia. With greater attention to specific methodological issues, the true potential of ERG and OCT as biomarkers for important clinical phenomena in schizophrenia should become apparent.

Schizophrenia and the retina: Towards a 2020 perspective

BACKGROUND

Differences between people with schizophrenia and psychiatrically healthy controls have been consistently demonstrated on measures of retinal function such as electroretinography (ERG), and measures of retinal structure such as optical coherence tomography (OCT). Since our 2015 review of this literature, multiple new studies have been published using these techniques. At the same time, the accumulation of data has highlighted the "fault lines" in these fields, suggesting methodological considerations that need greater attention in future studies.

METHODS

We reviewed studies of ERG and OCT in schizophrenia, as well as data from studies whose findings are relevant to interpreting these papers, such as those on effects of the following on ERG and OCT data: comorbid medical conditions that are over-represented in schizophrenia, smoking, antipsychotic medication, substance abuse, sex and gender, obesity, attention, motivation, and influences of brain activity on retinal function.

RESULTS

Recent ERG and OCT studies continue to support the hypothesis of retinal structural and functional abnormalities in schizophrenia, and suggest that these are relevant to understanding broader aspects of pathophysiology, neurodevelopment, and neurodegeneration in this disorder. However, there are differences in findings which suggest that the effects of multiple variables on ERG and OCT data need further clarification.

CONCLUSIONS

The retina, as the only component of the CNS that can be imaged directly in live humans, has potential to clarify important aspects of schizophrenia. With greater attention to specific methodological issues, the true potential of ERG and OCT as biomarkers for important clinical phenomena in schizophrenia should become apparent.

Retinal single-layer analysis with optical coherence tomography (OCT) in schizophrenia spectrum disorder

BACKGROUND

Volume reductions in brain structures of patients with schizophrenia spectrum disorder (SSD) have repeatedly been found in voxel-based morphometry MRI studies. Hence, an underlying neurodegenerative etiological component of SSD is currently being discussed. In recent years, the imaging method of optical coherence tomography (OCT) has shown its potential in evaluating structural changes in the retina in patients with confirmed neurodegenerative disorders, providing a window into the brain.

METHODS

Twenty-six patients with schizophrenia or schizoaffective disorder and 23 age- and sex-matched healthy controls were examined with the Heidelberg Spectralis OCT system to derive a single-layer analysis of both retinas. The segmentation of retinal layers was manually corrected to minimize artifacts and software imprecisions.

RESULTS

Compared to the control group, SSD patients showed reduced thickness and volume measurements for nearly all retinal layers, and these differences reached significance for macular volume, macular thickness, retinal nerve fiber layer (RNFL) and inner nucleiform layer (INL). Furthermore, a significant correlation between the duration of illness and the total volume of the RNFL was found.

CONCLUSION

Our OCT measurements demonstrate reduced single retinal layer thickness in patients with SSD. In the context of the MRI volume changes, our results provide further evidence that structural changes seen in the brain of patients are also observable in the retina, potentially allowing further insights into the different components of the nervous system that are altered in this highly etiologically complex disorder.

Optical coherence tomography of the retina in schizophrenia: Inter-device agreement and relations with perceptual function

BACKGROUND

Optical coherence tomography (OCT) studies have demonstrated differences between people with schizophrenia and controls. Many questions remain including the agreement between scanners. The current study seeks to determine inter-device agreement of OCT data in schizophrenia compared to controls and to explore the relations between OCT and visual function measures.

METHODS

Participants in this pilot study were 12 individuals with schizophrenia spectrum disorders and 12 age- and sex-matched controls. Spectralis and Cirrus OCT machines were used to obtain retinal nerve fiber layer (RNFL) thickness and macular volume. Cirrus was used to obtain ganglion cell layer + inner plexiform layer (GCL + IPL) thickness. Visual function was assessed with low-contrast visual acuity and the King-Devick test of rapid number naming.

RESULTS

There was excellent relative agreement in OCT measurements between the two machines, but poor absolute agreement, for both patients and controls. On both machines, people with schizophrenia showed decreased macular volume but no difference in RNFL thickness compared to controls. No between-group difference in GCL + IPL thickness was found on Cirrus. Controls showed significant associations between King-Devick performance and RNFL thickness and macular volume, and between low-contrast visual acuity and GCL + IPL thickness. Patients did not show significant associations between OCT measurements and visual function.

CONCLUSIONS

Good relative agreement suggests that the offset between machines remains constant and should not affect comparisons between groups. Decreased macular volume in individuals with schizophrenia on both machines supports findings of prior studies and provides further evidence that similar results may be found irrespective of OCT device.