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

Retinal layers and symptoms and inflammation in schizophrenia

Schizophrenia is a neurodevelopmental disorder that affects brain structure and function. The retina, as well as the brain, consists of neuronal and glial cells packed in layers. Cortical volume and brain thickness are associated with inflammatory biomarkers, however, no study has been performed associating inflammatory biomarkers and retina in schizophrenia. our study aims to compare the retinal macular thickness and volume and peripapillary thickness in patients with schizophrenia and controls, and associate it to symptoms of schizophrenia, to interleukin-6 (IL-6) and C Reactive Protein (CRP) levels. Optical coherence tomography was performed to assess retinal layer thickness and volume, and CRP and IL-6 levels were measured in patients with schizophrenia and controls. Positive, negative, and general symptoms of schizophrenia were measured with the Positive and Negative Syndrome Scale (PANSS). A linear regression controlling for confounding factors was performed. 70 subjects were included, 35 patients, and 35 controls matched for sex and age. Patients with schizophrenia presented a significantly lower macular volume (p < 0.05) and thickness (< 0.05) than controls. PANSS positive, general and total scores were associated with retinal nerve fiber layer (RNFL) thickness (p < 0.05). There was no association between inflammatory markers (CRP and IL-6) levels and the retinal layer. A reduction in macular volume and thickness was found in patients with schizophrenia. The severity of schizophrenia symptoms was associated with RNFL thickness. CRP and IL-6 are not associated with retinal thickness/volume in schizophrenia or controls.

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.

Quantitative assessments of retinal macular structure among rural-dwelling older adults in China: a population-based, cross-sectional, optical coherence tomography study

OBJECTIVES

To quantitatively assess and compare retinal macular structures of rural-dwelling older adults in China using two different optical coherence tomography (OCT) scanners and to examine their associations with demographic, lifestyle, clinical and ocular factors.

DESIGN, SETTING AND PARTICIPANTS

This population-based, cross-sectional study included 971 participants (age ≥60 years) derived from the Multimodal Interventions to Delay Dementia and Disability in Rural China study. We collected data on demographics, lifestyle factors, clinical conditions (eg, cardiovascular disease (CVD)) and ocular factors (eg, visual acuity and spherical equivalent). We used two models of spectral-domain OCT to measure macular parameters in nine Early Treatment Diabetic Retinopathy Study subfields. Data were analysed using the multiple general linear models.

RESULTS

Spectralis OCT demonstrated higher macular thickness but a lower macular volume than Primus 200 OCT (p<0.05). Nasal quadrant of the inner and outer subfields was the thickest, followed by superior quadrant. Adjusting for multiple potential confounding variables, older age was significantly correlated with lower average inner and outer macular thicknesses and overall macular volume. Men had higher macular parameters than women. The presence of CVD was correlated with lower central macular thickness (β=-6.83; 95% CI: -13.08 to -0.58; p=0.032). Middle school or above was associated with higher average inner macular thickness (β=7.85; 95% CI: 1.14 to 14.55; p=0.022) and higher spherical equivalent was correlated with lower average inner macular thickness (β=-1.78; 95% CI: -3.50 to -0.07; p=0.042).

CONCLUSIONS

Macular thickness and volume assessed by Spectralis and Primus 200 OCT scanners differ. Older age and female sex are associated with lower macular thickness and volume. Macular parameters are associated with education, CVD and spherical equivalent.

TRIAL REGISTERATION NUMBER

MIND-China study (ChiCTR1800017758).

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.

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.

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.

Normative Data and Conversion Equation for Spectral-Domain Optical Coherence Tomography in an International Healthy Control Cohort

BACKGROUND

Spectral-domain (SD-) optical coherence tomography (OCT) can reliably measure axonal (peripapillary retinal nerve fiber layer [pRNFL]) and neuronal (macular ganglion cell + inner plexiform layer [GCIPL]) thinning in the retina. Measurements from 2 commonly used SD-OCT devices are often pooled together in multiple sclerosis (MS) studies and clinical trials despite software and segmentation algorithm differences; however, individual pRNFL and GCIPL thickness measurements are not interchangeable between devices. In some circumstances, such as in the absence of a consistent OCT segmentation algorithm across platforms, a conversion equation to transform measurements between devices may be useful to facilitate pooling of data. The availability of normative data for SD-OCT measurements is limited by the lack of a large representative world-wide sample across various ages and ethnicities. Larger international studies that evaluate the effects of age, sex, and race/ethnicity on SD-OCT measurements in healthy control participants are needed to provide normative values that reflect these demographic subgroups to provide comparisons to MS retinal degeneration.

METHODS

Participants were part of an 11-site collaboration within the International Multiple Sclerosis Visual System (IMSVISUAL) consortium. SD-OCT was performed by a trained technician for healthy control subjects using Spectralis or Cirrus SD-OCT devices. Peripapillary pRNFL and GCIPL thicknesses were measured on one or both devices. Automated segmentation protocols, in conjunction with manual inspection and correction of lines delineating retinal layers, were used. A conversion equation was developed using structural equation modeling, accounting for clustering, with healthy control data from one site where participants were scanned on both devices on the same day. Normative values were evaluated, with the entire cohort, for pRNFL and GCIPL thicknesses for each decade of age, by sex, and across racial groups using generalized estimating equation (GEE) models, accounting for clustering and adjusting for within-patient, intereye correlations. Change-point analyses were performed to determine at what age pRNFL and GCIPL thicknesses exhibit accelerated rates of decline.

RESULTS

The healthy control cohort (n = 546) was 54% male and had a wide distribution of ages, ranging from 18 to 87 years, with a mean (SD) age of 39.3 (14.6) years. Based on 346 control participants at a single site, the conversion equation for pRNFL was Cirrus = -5.0 + (1.0 × Spectralis global value). Based on 228 controls, the equation for GCIPL was Cirrus = -4.5 + (0.9 × Spectralis global value). Standard error was 0.02 for both equations. After the age of 40 years, there was a decline of -2.4 μm per decade in pRNFL thickness ( P < 0.001, GEE models adjusting for sex, race, and country) and -1.4 μm per decade in GCIPL thickness ( P < 0.001). There was a small difference in pRNFL thickness based on sex, with female participants having slightly higher thickness (2.6 μm, P = 0.003). There was no association between GCIPL thickness and sex. Likewise, there was no association between race/ethnicity and pRNFL or GCIPL thicknesses.

CONCLUSIONS

A conversion factor may be required when using data that are derived between different SD-OCT platforms in clinical trials and observational studies; this is particularly true for smaller cross-sectional studies or when a consistent segmentation algorithm is not available. The above conversion equations can be used when pooling data from Spectralis and Cirrus SD-OCT devices for pRNFL and GCIPL thicknesses. A faster decline in retinal thickness may occur after the age of 40 years, even in the absence of significant differences across racial groups.

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.

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.

Sex differences in macular thickness of the retina in patients with psychosis spectrum disorders

INTRODUCTION

Imaging of retinal structure in psychosis spectrum disorders (PSD) is a novel approach to studying effect of this illness class on CNS structure. Studies of optical coherence tomography (OCT) have revealed significant reductions in regarding: retinal nerve fiber layer (RNFL), macular thickness (MT), ganglion cell-inner plexiform layer (GC-IPL) and macular volume (MV). Sex differences in retinal structure in PSD have not been previously explored.

METHODS

This cross-sectional pilot study included 81 participant of age matched patients and controls. There were no differences between genders regarding illness duration and antipsychotic daily dose in the patient group. SD-OCT assessed RNFL, GC-IPL, MT, MV, and optic nerve cup-to-disc (C/D) ratio. In order to assess the main effects of illness, sex, and illness × sex interaction on the retinal parameters, general linear model was performed.

RESULTS

Patients demonstrated abnormalities on all OCT indices. Effects of sex were observed for central subfield MT and C/D ratio, which were lower in females. An illness × sex interaction effect was observed for the left MT, indicating greater thinning in female patients.

CONCLUSION

Sex differences in OCT findings in PSD appear to be most prominent considering macular parameters. These preliminary data may have important implications for the valid interpretation of OCT findings as potential biomarkers for PSD.

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.

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.

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.