From Imaging the Brain to Imaging the Retina: Optical Coherence Tomography (OCT) in Schizophrenia

Retinal changes in generalized anxiety disorder patients

OBJECTIVE

Optical coherence tomography (OCT) is a method that allows high-resolution cross-sectional imaging of biological tissues. It was suggested that changes in the cranial structure or functions would be reflected in the retina. OCT has been an important method in the diagnosis and follow-up of diseases via morphometric or quantitative retinal measurements. Free radicals, inflammatory processes, and neurotransmission disorders play a role in the etiology of generalized anxiety disorder (GAD). The study aimed to demonstrate the retinal changes in GAD patients due to neurodegeneration based on the comparison of the OCT data of the GAD patients and controls, and the differences between OCT findings of GAD patients and those of controls.

METHODS

The study group included 21 GAD patients. The control group included 21 individuals without any known psychiatric or organic disease, including eye diseases.

RESULTS

There was a statistically significant difference between the macular volumes (MV) of the GAD and control groups, the macular volume was lower in the GAD group. There were positive correlations between BDI scores and MV, GCLT, RNFLT-i, RNFLT-n, between BAE scores and (RNFLT-n), and between the CGI severity scale scores and MV, RNFLT-n, and RNFLT-t.

CONCLUSION

OCT analysis of the GAD patients demonstrated that MV values were lower when compared to the control group. Patients with GAD should be screened for these retinal changes. OCT, a simple, non-invasive, and relatively inexpensive method could be employed as a supplementary method in the follow-up of GAD patients.

Retinal Thinning in Adults with Autism Spectrum Disorder

Since the retina shares its embryological origin with the central nervous system, optical coherence tomography (OCT), an imaging technique frequently employed in ophthalmology to analyze the macula and intraretinal layer thicknesses and volumes, has recently become increasingly important in psychiatric research. We examined 34 autistic and 31 neurotypical adults (NT) using OCT. Autistic adults had reduced overall macular and outer nuclear layer (ONL) thickness and volume compared to NT. Both macular and ONL thickness showed significant inverse associations with the severity of autistic symptoms measured with the Social Responsiveness Scale 2 (SRS-2). Longitudinal studies across different age groups are required to clarify whether retinal changes may represent a possible trait marker.

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.

Association between ADHD and vision problems. A systematic review and meta-analysis

AIM

To conduct the first systematic review and meta-analysis assessing whether attention-deficit/hyperactivity disorder (ADHD) is associated with disorders of the eye, and/or altered measures of visual function.

METHOD

Based on a pre-registered protocol (PROSPERO: CRD42021256352), we searched PubMed, Web of Knowledge/Science, Ovid Medline, Embase and APA PsycINFO up to 16th November 2021, with no language/type of document restrictions. We included observational studies reporting at least one measure of vision in people of any age meeting DSM/ICD criteria for ADHD and in people without ADHD; or the prevalence of ADHD in people with and without vision disorders. Study quality was assessed with the Appraisal tool for Cross-Sectional Studies (AXIS). Random effects meta-analyses were used for data synthesis.

RESULTS

We included 42 studies in the narrative synthesis and 35 studies in the meta-analyses (3,250,905 participants). We found meta-analytic evidence of increased risk of astigmatism (OR = 1.79 [CI: 1.50, 2.14]), hyperopia and hypermetropia (OR = 1.79 [CI: 1.66, 1.94]), strabismus (OR = 1.93 [CI: 1.75, 2.12]), unspecified vision problems (OR = 1.94 [CI: 1.38, 2.73]) and reduced near point of convergence (OR = 5.02 [CI: 1.78, 14.11]); increased lag (Hedge's g = 0.63 [CI: 0.30, 0.96]) and variability (Hedge's g = 0.40 [CI: 0.17, 0.64]) of the accommodative response; and increased self-reported vision problems (Hedge's g = 0.63 [CI: 0.44, 0.82]) in people with ADHD compared to those without ADHD (with no significant heterogeneity). We also found meta-analytic evidence of no differences between people with and without ADHD on retinal nerve fiber layer thickness (Hedge's g = -0.19 [CI: -0.41, 0.02]) and refractive error (Hedge's g = 0.08 [CI: -0.26, 0.42]) (with no significant heterogeneity).

DISCUSSION

ADHD is associated with some self-reported and objectively ascertained functional vision problems, but not with structural alterations of the eye. Further studies should clarify the causal relationship, if any, between ADHD and problems of vision.

TRIAL REGISTRATION

PROSPERO registration: CRD42021256352.

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.

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.

Retinal Nerve Fiber Layer Thickness and Its Relationship With Executive Functions in Adult Attention Deficit Hyperactivity Disorder Patients

OBJECTIVE

The aim of this study was to compare the thickness of the retinal nerve fiber layer (RNFL) with controls in individuals with attention deficit hyperactivity disorder (ADHD) and to examine the relationship between RNFL thickness and the level of performance in disease severity and executive function tests in ADHD cases.

METHODS

The study included 38 volunteer patients diagnosed with ADHD and 30 healthy volunteers. Adult ADHD self-report scale was used for ADHD symptom severity. Executive functions were evaluated by Digit Span Test, Verbal Fluency Test, Stroop Test, and Trail Making Test. RNFL thickness of all participants was evaluated using optical coherence tomography (OCT).

RESULTS

In the comparison of RNFL values, it was found that right mean, right temporal, right temporal inferior, left mean, left nasal, and left nasal inferior quadrant values were statistically thinner in ADHD cases compared to the control group (p<0.05). There was no statistically significant correlation between the mean RNFL thickness values of the right and left eyes of ADHD cases and the symptom severity and performance levels in executive function tests.

CONCLUSION

This study is a guide in terms of being the first study investigating the relationship between RNFL thickness, symptom severity, and various neuropsychological tests in adults with ADHD.

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.

Jiaotai Pill () Alleviates Insomnia through Regulating Monoamine and Organic Cation Transporters in Rats

OBJECTIVE

To reveal the effect and mechanism of Jiaotai Pill (, JTP) on insomniac rats.

METHODS

The insomniac model was established by intraperitoneal injection of p-chlorophenylalanine (PCPA). In behavioral experiments, rats were divided into control, insomniac model, JTP [3.3 g/(kg•d)], and diazepam [4 mg/(kg•d)] groups. The treatment effect of JTP was evaluated by weight measurement (increasement of body weight), open field test (number of crossings) and forced swimming test (immobility time). A high performance liquid chromatography-electrochemical detection (HPLC-ECD) method was built to determine the concentration of monoamine transmitters in hypothalamus and peripheral organs from normal, model, JTP, citalopram [30 mg/(kg•d)], maprotiline [40 mg/(kg•d)] and bupropion [40 mg/(kg•d)] groups. Expressions of serotonin transporter (SERT), dopamine transporter (DAT), and norepinephrine transporter (NET) were analyzed by quantitative polymerase chain reaction (qPCR) and Western blot in normal, model and JTP groups. A high performance liquid chromatography-electrospray ionization mass spectrometry (HPLC-ESI-MS/MS) method was established to determine the pharmacokinetics, urine cumulative excretion of metformin in vivo, and tissue slice uptake in vitro, which were applied to assess the activity of organic cation transporters (OCTs) in hypothalamus and peripheral organs.

RESULTS

Compared with the insomniac model group, the body weight and spontaneous locomotor were increased, and the immobility time was decreased after treatment with JTP (P<0.01). Both serotonin and dopamine contents in hypothalamus and peripheral organs were increased (P<0.01). The norepinephrine content was increased in peripheral organs and decreased in hypothalamus (P<0.05 or P<0.01). At the same time, SERT, DAT, OCT1, OCT2, and OCT3 were down-regulated in hypothalamus and peripheral organs (P<0.05). NET was down-regulated in peripheral organs and up-regulated in hypothalamus (P<0.05 or P<0.01). Moreover, the activity of OCTs in hypothalamus and peripheral organs was inhibited (P<0.05).

CONCLUSION

JTP alleviates insomnia through regulation of monoaminergic system and OCTs in hypothalamus and peripheral organs.

Irreversible Primary Visual Cortex Impairment in a Mouse Model of High-Risk Schizophrenia

PURPOSE

Although visual deficits can be observed at any stage of schizophrenia, few studies have focused on visual cortex alterations in individuals at high risk of schizophrenia. This study aimed to investigate the pathological changes of the primary visual cortex in a prenatal mouse model of MK801-induced high-risk schizophrenia.

METHODS

The high-risk schizophrenia model was generated by MK801 injection into pregnant mice. The male offspring without schizophrenia-like behaviors in early adulthood were defined as the high-risk mouse model of schizophrenia (HRMMS) and divided into two groups. One HRMMS group received the antipsychotic agent risperidone beginning at postnatal week 4 and another group did not receive any treatment. After treatment for 4 weeks, in vivo two-photon calcium imaging was performed to characterize the primary visual cortex activity. The novel object recognition test and the prepulse inhibition apparatus test were also implemented to assess the cognitive and behavioral performance, respectively.

RESULTS

Both groups of HRMMS mice, with or without antipsychotic treatment, had decreased neuronal calcium activity, demonstrating primary visual cortex impairment. More notably, antipsychotic treatment did not normalize the impaired neuronal activities in the primary visual cortex. Correspondingly, the treatment did not improve the cognitive or behavioral impairment.

CONCLUSION

Visual cortex impairment might be a prominent feature of individuals at high risk of schizophrenia that cannot be normalized by early treatment with antipsychotic medication, indicating the presence of independent regulatory pathways for visual perception disturbance in schizophrenia. Thus, visual system impairment in schizophrenic patients must be further studied.

[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.

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.

Electroretinographic Abnormalities and Sex Differences Detected with Mesopic Adaptation in a Mouse Model of Schizophrenia: A and B Wave Analysis

Purpose

Mesopic flash electroretinography (fERG) as a tool to identify N-methyl-d-aspartate receptor (NMDAR) hypofunction in subjects with schizophrenia shows great potential. We report the first fERG study in a genetic mouse model of schizophrenia characterized by NMDAR hypofunction from gene silencing of serine racemase (SR) expression (SR-/-), an established risk gene for schizophrenia. We analyzed fERG parameters under various background light adaptations to determine the most significant variables to allow for early identification of people at risk for schizophrenia, prior to onset of psychosis. SR is a risk gene for schizophrenia, and negative and cognitive symptoms antedate the onset of psychosis that is required for diagnosis.

Methods

The scotopic, photopic, and mesopic fERGs were analyzed in male and female mice in both SR-/- and wild-type (WT) mice and also analyzed for sex differences. Amplitude and implicit time of the a- and b-wave components, b-/a-wave ratio, and Fourier transform analysis were analyzed.

Results

Mesopic a- and b-wave implicit times were significantly delayed, and b-wave amplitudes, b/a ratios, and Fourier transform were significantly decreased in the male SR-/- mice compared to WT, but not in female SR-/- mice. No significant differences were observed in photopic or scotopic fERGs between genotype.

Conclusions

The fERG prognostic capability may be improved by examination of background light adaptation, a larger array of light intensities, considering sex as a variable, and performing Fourier transform analyses of all waveforms. This should improve the ability to differentiate between controls and subjects with schizophrenia characterized by NMDAR hypofunction.

Assessment of intraocular pressure, macular thickness, retinal nerve fiber layer, and ganglion cell layer thicknesses: ocular parameters and optical coherence tomography findings in attention-deficit/hyperactivity disorder

Objective:

To compare intraocular pressure (IOP) and macular, retinal nerve fiber layer (RNFL), and ganglion cell layer (GCL) thicknesses in treatment-naive children with attention-deficit/hyperactivity disorder (ADHD), children with ADHD on regular methylphenidate (MPH) treatment for at least 3 months, and healthy controls.

Methods:

A total of 58 treatment-naive children with ADHD, 45 children with ADHD on regular MPH treatment, and 44 healthy controls were enrolled in this study. All participants underwent a comprehensive eye examination. Optical coherence tomography (OCT) was used to assess global RNFL thickness, central macular thickness, and GCL thickness in both eyes.

Results:

Separate univariate analysis of covariance (ANCOVA) on the outcome variables revealed a significant difference among the research groups with respect to IOP in the left eye. Post-hoc univariate analyses indicated that left IOP was significantly higher in children with ADHD under MPH treatment than among healthy controls. However, global RNFL thickness, central macular thickness, and GCL thickness of both eyes, as well as IOP in the right eye, were not significantly different across groups.

Conclusion:

Further longitudinal follow-up studies are needed to determine whether MPH treatment has any effect on IOP or OCT findings.

Functionality and Neurocognition in Patients With Bipolar Disorder After a Physical-Exercise Program (FINEXT-BD Study): Protocol of a Randomized Interventionist Program

Introduction: Recent studies have shown that symptoms of psychiatric illness, functionality, and cognitive function improve with exercise. The aim of this study will be to investigate whether the implementation of an individualized exercise program will improve the functional status of patients with bipolar disorder (BD). Methods: This longitudinal, interventional, randomized, controlled, simple-blind clinical trial will include 80 patients aged 18-65 years, all of them with BD diagnosis. Patients will be randomly assigned to a physical exercise intervention + Treatment-As-Usual (TAU) group and a non-intervention + TAU group. Patients will be assessed by an extensive battery of clinical tests, physical parameters (e.g., brain structure changes measured by optical coherence tomography, cardiorespiratory fitness) and biological parameters (inflammation, oxidative stress and neurotrophic factors) at baseline, after a 4-month intervention period, and 6-month follow-up. Discussion: This is an innovative study aimed at gaining a deeper understanding of the physiopathology of BD and determining whether the prognosis and evolution of the disease can be improved through modifiable areas of the patient's lifestyle. Clinical Trial Registration: NCT04400630. NCT clinicaltrials.gov. Date of registration in primary registry 22 May 2020. clinicaltrials.gov.

Retinal Changes in Schizophrenia: A Systematic Review and Meta-analysis Based on Individual Participant Data

BACKGROUND

Retinal assessment has indicated the presence of neuronal loss in neurodegenerative disorders, but its role in schizophrenia remains unclear. We sought to synthesize the available evidence considering 3 noninvasive modalities: optical coherence tomography, electroretinography, and fundus photography, and examine their diagnostic accuracy based on unpublished individual participant data, when provided by the primary study authors.

METHODS

We searched MEDLINE, SCOPUS, clinicaltrials.gov, PSYNDEX, Cochrane Controlled Register of Trials (CENTRAL), WHO International Clinical Trials Registry Platform, and Google Scholar, up to October 30, 2018. Authors were contacted and invited to share anonymized participant-level data. Aggregate data were pooled using random effects models. Diagnostic accuracy meta-analysis was based on multiple cutoffs logistic generalized linear mixed modeling. This study was registered with PROSPERO, number CRD42018109344.

RESULTS

Pooled mean differences of peripapillary retinal nerve fiber layer thickness in micrometer between 694 eyes of 432 schizophrenia patients and 609 eyes of 358 controls, from 11 case-control studies, with corresponding 95% confidence intervals (CIs) by quadrant were the following: -4.55, 95% CI: -8.28, -0.82 (superior); -6.25, 95% CI: -9.46, -3.04 (inferior); -3.18, 95% CI: -5.04, -1.31 (nasal); and -2.7, 95% CI: -4.35, -1.04 (temporal). Diagnostic accuracy, based on 4 studies, was fair to poor, unaffected by age and sex; macular area measurements performed slightly better.

CONCLUSION

The notion of structural and functional changes in retinal integrity of patients with schizophrenia is supported with current evidence, but diagnostic accuracy is limited. The potential prognostic, theranostic, and preventive role of retinal evaluation remains to be examined.

The role of optical coherence tomography in therapeutics and conditions, which primarily have systemic manifestations: a narrative review

Optical coherence tomography is designed to evaluate in vivo qualitative and quantitative changes of the anterior segment, optic nerve and the retina. Initial applications of this technology were confined mainly to ophthalmic diseases. However recently, numerous studies have evaluated its use in systemic conditions and in therapeutics where, optic nerve and retinal architecture can be assessed to monitor progression of systemic conditions and its response to treatment. This is a narrative review aimed at evaluating the debate surrounding the role of spectral domain optical coherence tomography, in systemic conditions where optic nerve affection can be measured and be used in the diagnosis, monitoring and assessment of treatment effect as a non-invasive, quick, novel technique.

Principles of OCTA and Applications in Clinical Neurology

PURPOSE OF REVIEW

The article reviews the recent findings on the use of optical coherence tomography angiography (OCTA) in neurology.

RECENT FINDINGS

OCTA is a new addition to the powerful and complementary technology of the OCT. Due to its noninvasiveness, and reproducibility, it is possible to obtain high-resolution 3D images of the vessels of the human eye. As the vessels of the retina with the presence of endothelial cell's tight junctions resemble the brain vessels, it was hypothesized that the imaging of the retinal vessels might bring insight into brain vessels. OCTA has been effectively used to predict retinal vessel abnormalities in dementia, demyelization, optic disc neuropathies, and inherited degenerative diseases. Most common findings were decrease of vascular density and flow and an increase of avascular zones. Although OCTA is a relative new technology, recent studies show that it can be successfully applied in neurology.

Evaluation of Optical Coherence Tomography Results and Cognitive Functions in Patients with Restless Legs Syndrome

Introduction

The aim of this study was to evaluate whether retinal neural network was impaired and cognitive functions were disturbed in restless legs syndrome (RLS) considering the hypothesis that there may be a dysfunction in dopaminergic pathways in RLS like in Parkinson's disease. Therefore, we evaluated retinal neural network with optical coherence tomography (OCT) and presence of cognitive impairment with Montreal Cognitive Assessment (MOCA).

Methods

OCT evaluations were performed for 30 RLS patients and 30 healthy controls. Ganglion cell complex was segmented to retinal nerve fiber layer (RNFL), ganglion cell layer (GCL), and inner plexiform layer (IPL) automatically by the device, and recorded. Additionally, all the patients and the controls were evaluated using MOCA.

Results

No statistically significant difference was detected between RLS and controls in RNFL, GCL, IPL, and choroidal thicknesses. However, total MOCA score and all of its subscale scores were significantly lower in the RLS patients compared with the controls. No significant correlation was detected between OCT and MOCA parameters.

Conclusion

No degeneration was detected in retinal neurons (RNFL, GCL, and IPL) of RLS patients. However, impairments were seen in MOCA total and subscale scores of these patients. On the other hand, no significant correlation was detected between MOCA scores and RNFL, GCL, or IPL thicknesses. These findings suggest decrease in cognitive functions of RLS patients probably due to dopaminergic dysfunction regardless of anatomical neural degeneration. Longitudinal follow-up studies are warranted to evaluate whether neuronal degeneration will develop.

[Structural endpoints for glaucoma studies]

BACKGROUND

Structural endpoints have been discussed as surrogate endpoints for the approval of neuroprotective drugs in glaucoma.

OBJECTIVE

Is the evidence strong enough to establish structural endpoints as surrogate endpoints?

MATERIAL AND METHODS

Review of current understanding between structure and function in glaucoma.

RESULTS

The introduction of optical coherence tomography has revolutionized imaging in glaucoma patients. Clinically either the nerve fiber layer thickness can be measured along a circle centered in the optic nerve head or the ganglion cell layer thickness can be assessed in the macular region, the latter being quantified in combination with other inner retinal layers. On a microscopic level there is a strong correlation between structural and functional loss but this relation can only partially be described with currently available clinical methods. This is particularly true for longitudinal course of the disease in glaucoma patients. Novel imaging techniques that are not yet used clinically may have the potential to increase our understanding between structure and function in glaucoma but further research in this field is required.

CONCLUSION

The current evidence does not allow the establishment of structural endpoints as surrogate endpoints for phase 3 studies in glaucoma. Neuroprotective drugs have to be approved on the basis of visual field data because this is the patient-relevant endpoint. Structural endpoints can, however, play an important role in phase 2 and proof of concept studies.