Association of Retinal Nerve Fiber Layer Thickness, an Index of Neurodegeneration, With Depressive Symptoms Over Time

Retinal structural alterations in patients with epilepsy taking antiepileptic drugs: A systematic review and meta-analysis of OCT findings

The impact of various neurodegenerative diseases on the retina has been investigated in recent years using optical coherence tomography (OCT). Epilepsy, classified as a neurodegenerative disorder, has been indicated to affect the structural integrity of the retina. Moreover, there is ongoing debate regarding the relative contribution of the disease pathogenesis and the consumption of anti-epileptic drugs (AEDs) to these retinal changes. The lack of systematic reviews has hindered our understanding of the true effects of epilepsy and AEDs on retinal health, as well as the efficacy of OCT in detecting these alterations. To comprehensively review the impact of epilepsy and AEDs on the structure of retina, we thoroughly searched the PubMed, EMBASE, and Web of Science databases to identify relevant articles published until July 7, 2024, and performed a meta-analysis. We updated our search in November, 2024. Random effect models have been used to calculate pooled effect estimates. Nineteen studies with a total number of 1851 eyes were identified. Adult patients showed significant reduction with respect of retinal nerve fiber layer (RNFL) thickness; average, as well as all quadrants. Significant reductions were also detected in all quadrants of ganglion cell complex (GCC). Conversely, average GCC and central macular thickness did not differ significantly between cases and controls. Additionally, in terms of various volume measurements in the retina, significant losses were observed in macular RNFL, ganglion cell-inner plexiform layer and total macula volumes in adult patients. In contrast, the inner nuclear layer volume remained comparable between the 2 groups. In pediatric patients with epilepsy receiving valproic acid, significant reductions was observed in the average RNFL thickness, as well as in the nasal and inferior quadrants; however, there were no significant changes in the thickness of the superior and temporal quadrants of RNFL, nor in foveal thickness. The analysis of pediatric patients receiving levetiracetam indicated no significant changes in retinal structural measurements across various RNFL categories, or in foveal thickness. This meta-analysis revealed the structural retinal alterations following AEDs administration in patients with epilepsy (PwE). OCT appears to be a reliable device that reflects retinal toxicity with AED consumption in PwE.

Neurovascular dysfunction in psychiatric disorders: Underlying mechanisms and therapeutic approaches

BACKGROUND

Neurovascular interfaces, specifically the blood-brain barrier (BBB) and blood-retinal barrier (BRB), play pivotal roles in maintaining the homeostasis of the central nervous system (CNS). For a long time, these structures were seen only as a way of protection, but we currently know that they have a critical role in CNS (dys)function. Several studies have identified neurovascular alterations in early stages of brain and eye diseases, contributing to the pathophysiology of such conditions. More recently, interesting data have also highlighted the importance of neurovasculature in psychiatric disorders.

METHODS

Using the PubMed database, we brought together the evidence concerning the changes in BBB and BRB under psychiatric conditions, with a focus on anxiety, major depressive disorder (MDD), attention-deficit/hyperactivity disorder (ADHD) and drug abuse, specifically related with methamphetamine (METH) and cocaine consumption.

RESULTS

We summarized the main findings obtained from in vitro and animal studies, as well as clinical research that has been undertaken to identify neurovascular abnormalities upon such neuropsychiatric disorders. The drivers of barrier alterations were examined, namely the role of neuroinflammation, while reporting putative barrier-associated biomarkers of these disorders.

CONCLUSION

This review underscores the critical need for a deeper understanding of BBB and BRB function in neuropsychiatric conditions and their potential as therapeutic targets while elucidating the key players involved. The innovative approaches to managing these complex disorders are also addressed while bridging the gap concerning what is currently known regarding the association between neuropsychiatric conditions and their vascular implications.

Glucocorticoid-Dependent Retinal Degeneration and Vision Impairment in Mice Susceptible to Prenatal Stress-Induced Behavioral Abnormalities

Chronic exposure to prenatal stress can impair neurogenesis and lead to irreversible cognitive and neuropsychiatric abnormalities in offspring. The retina is part of the nervous system; however, the impacts of prenatal stress on retinal neurogenesis and visual function remain unclear. This study examined how elevated prenatal glucocorticoid levels differentially affect retinal development in the offspring of pregnant mice exposed to chronic unpredictable mild stress (CUMS). Offspring were classified into control, stress-resilient, and stress-susceptible groups based on behavioral tests assessing spatial memory and depression-like behaviors. The stress-susceptible group exhibited significantly altered synaptogenesis, reduced ganglion cell development, decreased retinal thickness, and visiual impairment. These mice also showed a pervasive transformation of retinal astrocytes into a proinflammatory A1-like reactive state, evidenced by increased GFAP and decreased STAT3 expression levels. This astrocyte phenotype shift coincided with disruptions in neurogenesis and synaptic formation. Furthermore, prenatal exposure to exogenous corticosterone confirmed that the effects of prenatal stress are mediated by glucocorticoid-induced retinal neurodegeneration. Our findings suggest that elevated prenatal glucocorticoid levels trigger a series of neurodevelopmental disturbances leading to retinal neurodegeneration and vision impairment. This research highlights the impact of prenatal stress on retinal development and visual health, suggesting new avenues for understanding and potentially mitigating the negative effects of early-life stress on neurodevelopment.

Retinal microvascular function and incidence and trajectories of clinically relevant depressive symptoms: the Maastricht Study

BACKGROUND

Cerebral microvascular dysfunction may contribute to depression via disruption of brain structures involved in mood regulation, but evidence is limited. We investigated the association of retinal microvascular function, a proxy for microvascular function in the brain, with incidence and trajectories of clinically relevant depressive symptoms.

METHODS

Longitudinal data are from The Maastricht Study of 5952 participants (59.9 ± 8.5 years/49.7% women) without clinically relevant depressive symptoms at baseline (2010-2017). Central retinal arteriolar equivalent and central retinal venular equivalent (CRAE and CRVE) and a composite score of flicker light-induced retinal arteriolar and venular dilation were assessed at baseline. We assessed incidence and trajectories of clinically relevant depressive symptoms (9-item Patient Health Questionnaire score ⩾10). Trajectories included continuously low prevalence (low, n = 5225 [87.8%]); early increasing, then chronic high prevalence (early-chronic, n = 157 [2.6%]); low, then increasing prevalence (late-increasing, n = 247 [4.2%]); and remitting prevalence (remitting, n = 323 [5.4%]).

RESULTS

After a median follow-up of 7.0 years (range 1.0-11.0), 806 (13.5%) individuals had incident clinically relevant depressive symptoms. After full adjustment, a larger CRAE and CRVE were each associated with a lower risk of clinically relevant depressive symptoms (hazard ratios [HRs] per standard deviation [s.d.]: 0.89 [95% confidence interval (CI) 0.83-0.96] and 0.93 [0.86-0.99], respectively), while a lower flicker light-induced retinal dilation was associated with a higher risk of clinically relevant depressive symptoms (HR per s.d.: 1.10 [1.01-1.20]). Compared to the low trajectory, a larger CRAE was associated with lower odds of belonging to the early-chronic trajectory (OR: 0.83 [0.69-0.99]) and a lower flicker light-induced retinal dilation was associated with higher odds of belonging to the remitting trajectory (OR: 1.23 [1.07-1.43]).

CONCLUSIONS

These findings support the hypothesis that cerebral microvascular dysfunction contributes to the development of depressive symptoms.

Depression and Eye Disease-A Narrative Review of Common Underlying Pathophysiological Mechanisms and their Potential Applications

Background: Depression has been shown to be associated with eye diseases, including dry eye disease (DED), cataracts, glaucoma, age-related macular degeneration (AMD), and diabetic retinopathy (DR). This narrative review explores potential pathophysiological connections between depression and eye disease, as well as its potential correlations with ocular parameters. Methods: A literature search was conducted in August 2022 in PUBMED, EMBASE, and PsycINFO. Published articles related to the subject were consolidated and classified according to respective eye diseases and pathophysiological mechanisms. Results: The literature reviewed suggests that common pathophysiological states like inflammation and neurodegeneration may contribute to both depression and certain eye diseases, while somatic symptoms and altered physiology, such as disruptions in circadian rhythm due to eye diseases, can also influence patients' mood states. Grounded in the shared embryological, anatomical, and physiological features between the eye and the brain, depression is also correlated to changes observed in non-invasive ophthalmological imaging modalities, such as changes in the retinal nerve fibre layer and retinal microvasculature. Conclusions: There is substantial evidence of a close association between depression and eye diseases. Understanding the underlying concepts can inform further research on treatment options and monitoring of depression based on ocular parameters.

Association of Retinal Neurovascular Impairment with Disease Severity in Patients with Major Depressive Disorder: An Optical Coherence Tomography Angiography Study

Background

Identifying the fundus objective biomarkers for the major depressive disorders (MDD) may help promote mental health. The aim of this study was to evaluate retinal neurovascular changes and further investigate their association with disease severity in MDD.

Methods

This cross-sectional study conducted in the hospital enrolled patients with MDD and healthy controls.The retinal neurovascular parameters for all subjects, including vessel density (VD), thickness of ganglion cell complex (GCC) and retinal nerve fiber layer (RNFL), and optic nerve head (ONH) eg are automatically calculated by the software in optical coherence tomography angiography (OCTA). The severity of MDD including depressive symptoms, anxiety, cognition, and insomnia was assessed by Hamilton Depression Rating Scale (HAMD), Hamilton Anxiety Scale (HAMA), Montreal Cognitive Assessment (MoCA), and Insomnia Severity Index (ISI) respectively.

Results

This study included 74 MDD patients (n=74 eyes) and 60 healthy controls (HCs) (n=60 eyes). MDD patients showed significantly decreased VD of superficial and deep capillary plexus, thickness of GCC and RNFL, and volume of ONH (all p<0.05) and increased vertical cup-to-disc ratio and global loss volume (GLV) (all p<0.05) compared to HCs. Positive associations were found between HAMD scores and cup area (r=0.30, p=0.035), cup volume (r=0.31, p=0.029), and disc area (r=0.33, p=0.020) as well as ISI scores and RNFL thickness (r=0.34, p=0.047).

Conclusion

We found the retinal neurovascular impairment and its association with disease severity in MDD patients. OCTA showed promise as a potential complementary assessment tool for MDD.

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.

Childhood Social Isolation as a Predictor of Retinal Neuronal Thickness in Middle Age: A Lifecourse Birth Cohort Study

OBJECTIVE

We investigated whether childhood social isolation was associated with retinal neural layer changes in adulthood, and whether this association was independent of other childhood or adulthood risk factors, including adult social isolation.

METHODS

Participants were members of the Dunedin Multidisciplinary Health and Development Study, a longitudinal population-based birth cohort from Aotearoa New Zealand ( n = 1037), born 1972 to 1973 and followed until age 45 years, with 94% of the living cohort still participating. Social isolation was recorded prospectively at ages 5, 7, 9, and 11 years, from teacher and parent report. Retinal nerve fiber layer (RNFL) and ganglion cell-inner plexiform layer thicknesses were measured via optical coherence tomography at age 45 years.

RESULTS

Childhood social isolation was associated with thinner average RNFL ( B = -0.739, p = .02), nasal RNFL ( B = -1.118, p = .005), and inferior RNFL ( B = -1.524, p = .007), although only nasal RNFL remained significant after adjustment. These associations were not fully explained by other psychosocial or physical health risk factors in childhood or adulthood, nor were they mediated by adult loneliness or social support.

CONCLUSIONS

Childhood social isolation was an independent predictor of RNFL thickness in middle age. Highlighting prospective links between childhood psychosocial adversity and retinal neuronal measures will help to inform future research into the utility of retinal neuronal thickness as a biomarker for neurodegeneration.

Association of type 2 diabetes according to the number of risk factors within the recommended range with incidence of major depression and clinically relevant depressive symptoms: a prospective analysis

BACKGROUND

Type 2 diabetes is associated with an increased risk of depression, but the extent to which risk factor modification can mitigate this risk is unclear. We aimed to examine the association between the incidence of major depression and clinically relevant depressive symptoms among individuals with type 2 diabetes, according to the number of risk factors within the recommended target range, compared with individuals without diabetes.

METHODS

We did a prospective analysis of population-based data from the UK Biobank and the Maastricht Study. Individuals with type 2 diabetes were categorised according to the number of risk factors within the recommended target range (non-smoking, guideline-recommended levels of glycated haemoglobin (HbA_1c), blood pressure, BMI, albuminuria, physical activity, and diet). The primary outcome, based on data from the UK Biobank, was the incidence of major depression ascertained from hospital records; the secondary outcome, based on data from the UK Biobank and the Maastricht Study, was clinically relevant depressive symptoms based on a score of 10 or higher on the Patient Health Questionnaire (PHQ-9).

FINDINGS

The study population of the UK Biobank comprised 77 786 individuals (9047 with type 2 diabetes and 68 739 without diabetes; median age 59 years [IQR 51-64]; 34 136 [43·9%] women and 43 650 [56·1%] men). A median of 12·7 years (IQR 11·8-13·4) after recruitment (between March 13, 2006, and Oct 1, 2010), 493 (5·5%) of 9047 individuals with type 2 diabetes and 2574 (3·7%) of 68 739 individuals without diabetes developed major depression. Compared with individuals without diabetes, those with type 2 diabetes had a higher risk of major depression (hazard ratio [HR] 1·61 [95% CI 1·49-1·77]). Among individuals with type 2 diabetes, the excess risk of depression decreased stepwise with an increasing number of risk factors within the recommended target range (HR 2·04 [95% CI 1·65-2·52] for up to two risk factors within the recommended target range; 1·95 [1·65-2·30] for three risk factors within the recommended target range; 1·38 [1·16-1·65] for four risk factors within the recommended target range; and 1·34 [1·12-1·62] for five to seven risk factors within the recommended target range). In the UK Biobank dataset, a median of 7·5 years (IQR 6·8-8·2) after the baseline examination, 147 (7·5%) of 1953 individuals with type 2 diabetes and 954 (4·5%) of 21 413 individuals without diabetes had developed clinically relevant depressive symptoms. The study population of the Maastricht Study comprised 4530 individuals (1158 with type 2 diabetes and 3372 without diabetes; median age 60 years [IQR 53-66]; 2244 [49·5%] women and 2286 [50·1%] men). A median of 5·1 years (IQR 4·1-6·1) after recruitment (between Sept 1, 2010, and Dec 7, 2017), 170 (14·7%) of 1158 individuals with type 2 diabetes and 227 (6·7%) of 3372 individuals without diabetes developed clinically relevant depressive symptoms. Similarly, in both the UK Biobank dataset and the Maastricht Study cohort, among individuals with type 2 diabetes, the excess risk of clinically relevant depressive symptoms decreased stepwise with an increasing number of risk factors within the recommended target range.

INTERPRETATION

Among individuals with type 2 diabetes, the excess risk of major depression and clinically relevant depressive symptoms decreased stepwise with an increasing number of risk factors within the recommended target range. This study provides further evidence to promote risk factor modification strategies in individuals with type 2 diabetes and to encourage the adoption of a healthy lifestyle.

FUNDING

ZonMW, Hartstichting, and Diabetes Fonds.

Association Between Retinal Nerve Fiber Layer Thickness and Incident Dementia in the European Prospective Investigation into Cancer in Norfolk Cohort

BACKGROUND

Retinal nerve fiber layer (RNFL) thickness may reflect cerebral status.

OBJECTIVE

This study assessed the relationship between RNFL thickness and incident all-cause dementia in the European Prospective Investigation into Cancer in Norfolk (EPIC-Norfolk) Eye Study.

METHODS

Glaucoma detection with variable corneal compensation (GDx-VCC) and Heidelberg Retinal Tomograph II (HRT II) derived global mean RNFL thickness from dementia-free participants at baseline within the EPIC-Norfolk Eye Study were analyzed. Incident dementia was identified through linkage to electronic medical records. Cox proportional hazard mixed-effects regression models adjusted for key confounders were used to examine the associations between RNFL thickness and incident dementia in four separate models.

RESULTS

6,239 participants were included with 322 cases of incident dementia and mean age of 67.5-years old, with 49.7% women (median follow-up 13.2-years, interquartile range (11.7 to 14.6 years). Greater RNFL thickness (GDx-VCC) was not significantly associated with a lower risk of incident dementia in the full adjusted model [HR per quartile increase 0.95; 95% CI 0.82-1.10]. Similarly, RNFL thickness assessed with HRT II was also not associated with incident dementia in any model (full adjusted model; HR per quartile increase: 1.06; [95% CI 0.93-1.19]. Gender did not modify any associations under study.

CONCLUSION

GDx-VCC and HRT II derived RNFL thickness are unlikely to be useful predictors of incident dementia. Higher resolution optical imaging technologies may clarify whether there are useful relationships between neuro-retinal morphology and brain measures.

Optical Coherence Tomography Retinal Nerve Fibre Layer and Ganglion Cell Complex Measurements in Normal Southern Nigerian Eyes

Introduction Glaucoma is the leading cause of irreversible blindness worldwide. It is more severe in people with African heritage, and intraocular pressure remains the only modifiable risk factor in managing glaucoma. Attempts to improve the diagnosis and monitoring of glaucoma are ongoing. One of those attempts is the development of optical coherence tomography (OCT). However, there is a theoretical possibility of a delayed or wrong diagnosis of glaucoma using the OCT because of racial, age, and sex differences in the RNFL (retina nerve fibre layer), GCL (ganglion cell layer), and GCL+IPL (ganglion cell layer and inner plexiform layer) thickness. Objective This study aims to provide the measurements of RNFL, GCL, and GCL+IPL in normal eyes of southern Nigerian patients and specifically to evaluate the relationship of these measurements to gender, age, intra-eye variability, and the Topcon SD-OCT normative database. Method Three hundred and four eyes of 152 patients who had normal OCT scans using the 6x6 RNFL (four sectors) and Macula scans of the Topcon OCT-1 3D Maestro OCT machine were included for analysis. Parametric tests were used to interrogate the relationship between normally distributed parameters and gender, age, and the Topcon reference database. Non-parametric tests were used for non-normally distributed data. Results The male-to-female ratio was 1:1, and ages ranged between 18 and 71 for both genders. The average RNFL values were 111.49 ± 10.44 (right eye - RE) and 111.96 ± 9.66 (left eye - LE). For the GCL, average values were 66.23 ± 4.4 (RE) and 66.34 ± 4.19 (LE). GCL+IPL values were 104.02 ± 6.71 (RE) and 103.89 ± 6.66 (LE). There was no difference between genders (X² = 56.467; df = 46; p = 0.160), and RNFL, GCL, and GCL+IPL values showed a significant reduction as the age of the respondents increased. There was a significant difference between RNFL, GCL, and GCL+IPL values and the Topcon reference database, p < 0.001. Conclusion Significant differences exist between the Southern Nigerian eyes' RNFL, GCL, and GCL+ IPL values and the Topcon OCT-1 3D Maestro reference database. While randomised control trials and extensive multi-centre studies have not been conducted to determine the possible effects of these differences between measured values and reference databases of the OCTs, they need to be considered while diagnosing and managing glaucoma with the OCT.