Current and future potential of retinal optical coherence tomography in multiple sclerosis with and without optic neuritis

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.

Optical Coherence Tomography in the Differential Diagnosis of Patients with Multiple Sclerosis and Patients with MRI Nonspecific White Matter Lesions

In the differential diagnosis of nonspecific white matter lesions (NSWMLs) detected on magnetic resonance imaging (MRI), multiple sclerosis (MS) should be taken into consideration. Optical coherence tomography (OCT) is a promising tool applied in the differential diagnostic process of MS. We tested whether OCT may be useful in distinguishing between MS and NSWMLs patients. In patients with MS (n = 41) and NSWMLs (n = 19), the following OCT parameters were measured: thickness of the peripapillary Retinal Nerve Fibre Layer (pRNFL) in superior, inferior, nasal, and temporal segments; thickness of the ganglion cell-inner plexiform layer (GCIPL); thickness of macular RNFL (mRNFL); and macular volume (MV). In MS patients, GCIPL was significantly lower than in NSWMLs patients (p = 0.024). Additionally, in MS patients, mRNFL was significantly lower than in NSWMLs patients (p = 0.030). The average segmental pRNFL and MV did not differ between MS and NSWMLs patients (p > 0.05). GCIPL and macular RNFL thinning significantly influenced the risk of MS (18.6% [95% CI 2.7%, 25.3%]; 27.4% [95% CI 4.5%, 62.3%]), and reduced GCIPL thickness appeared to be the best predictor of MS. We conclude that OCT may be helpful in the differential diagnosis of MS and NSWMLs patients in real-world settings.

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.

Association of retinal atrophy with cortical lesions and leptomeningeal enhancement in multiple sclerosis on 7T MRI

BACKGROUND

Retinal atrophy in multiple sclerosis (MS) as measured by optical coherence tomography (OCT) correlates with demyelinating lesions and brain atrophy, but its relationship with cortical lesions (CLs) and meningeal inflammation is not well known.

OBJECTIVES

To evaluate the relationship of retinal layer atrophy with leptomeningeal enhancement (LME) and CLs in MS as visualized on 7 Tesla (7T) magnetic resonance imaging (MRI).

METHODS

Forty participants with MS underwent 7T MRI of the brain and OCT. Partial correlation and mixed-effects regression evaluated relationships between MRI and OCT findings.

RESULTS

All participants had CLs and 32 (80%) participants had LME on post-contrast MRI. Ganglion cell/inner plexiform layer (GCIPL) thickness correlated with total CL volume (r =-0.45, p < 0.01). Participants with LME at baseline had thinner macular retinal nerve fiber layer (mRNFL; p = 0.01) and GCIPL (p < 0.01). Atrophy in various retinal layers was faster in those with certain patterns of LME. For example, mRNFL declined -1.113 (-1.974, -0.252) μm/year faster in those with spread/fill-pattern LME foci at baseline compared with those without (p = 0.01).

CONCLUSION

This study associates MRI findings of LME and cortical pathology with thinning of retinal layers as measured by OCT, suggesting a common link between meningeal inflammation, CLs, and retinal atrophy in MS.

Axonal Degeneration Independent of Inflammatory Activity: Is It More Intense in the Early Stages of Relapsing-Remitting Multiple Sclerosis Disease?

BACKGROUND

This study aimed to investigate whether there are differences in the axonal degeneration rate between patients in the early years of relapsing-remitting multiple sclerosis (RRMS) disease and RRMS patients in their later years.

METHODS

The early-stage RRMS patients (EMS) group had 65 patients whose duration of disease was within 3 years from the date of the first attack. The late-stage RRMS patients (LMS) group had 69 patients whose duration of disease was within the range of 3-10 years from the date of the first attack. In addition, a control group was composed of 32 healthy subjects. Peripapillary retinal nerve fiber layer (RNFL) thickness was monitored with spectral-domain OCT in all included patients for approximately 3 years.

RESULTS

The annual RNFL atrophy rate (aRNFLr) in the EMS group was -1.246 ± 0.778 μm/year, the aRNFLr in the LMS group was -0.898 ± 0.536 μm/year, and the aRNFLr was -0.234 ± 0.154 μm/year in the control group (p < 0.001). The aRNFLr in the EMS group was significantly higher than the aRNFLr in the LMS group (p = 0.01). The aRNFLr was not associated with MRI activity or the condition of having an attack. There was a correlation between Expanded Disability Status Scale (EDSS) progression and aRNFLr in both the EMS and LMS patient groups (r = -0.471, p < 0.001, and r = -0.567, p < 0.001, respectively).

CONCLUSION

The axonal degeneration rate is faster in RRMS patients in the first years of the disease than in later years. In addition, axonal degeneration occurs independently of inflammatory activity. Axonal degeneration is correlated with disability progression, but not with inflammatory findings, such as clinical episodes and MRI activity.

Optical coherence tomography angiography findings of multiple sclerosis with or without optic neuritis

Objective: Nowadays, retinal microvascular structures can be investigated using optical coherence tomography angiography (OCTA). We aimed to evaluate the probable vascular changes in the foveal and peripapillary regions of patients with multiple sclerosis (MS).Methods: A total of 20 patients with relapsing remitting multiple sclerosis (RRMS) and 24 healthy controls were recruited in this study. All participants' superficial and deeper retinal and peripapillary layers were evaluated using OCTA after a total ophthalmologic examination.Results: In the superficial plexus, the whole image (49.53 ± 3.9% and 51.83 ± 2.1%, p = 0.009), superior hemisphere (49.44 ± 4.11% and 51.63 ± 2.3%, p = 0.018), inferior hemisphere (49.75 ± 3.9% and 52.03 ± 2.2%, p = 0.012), parafoveal (51.87 ± 3.9% and 53.08 ± 3.46%, p = 0.048) and perifoveal (50.41 ± 3.86% and 52.76 ± 2.1%, p = 0.007) vascular densities were statistically significant lesser in patients with RRMS than in controls. In the optic disc OCTA parameters, the vessel density of the inferior (50.15 ± 6.99% and 53.04 ± 3.63% p = 0.043) and temporal sector (48.09 ± 5.47% and 50.85 ± 5.24%, p = 0.045) were statistically significantly lesser in patients with RRMS than in controls.Conclusion: The reductions in vessel density of the retinal or peripapillary area of patients with RRMS shown in this study should be investigated further to determine whether it is a secondary lesion to optic neuritis (ON) or a primary vasculopathic condition of MS.

Macular ganglion cell complex parameters by optical coherence tomography in cases of multiple sclerosis without optic neuritis compared to healthy eyes

Purpose:

To compare different macular thickness parameters and peripapillary retinal nerve fiber layer (RNFL) thickness between recently diagnosed cases of multiple sclerosis (MS) without optic neuropathy (ON) and healthy individuals.

Methods:

This cross-sectional study was performed between June 2014 and June 2015. All subjects underwent ocular and retinal examination. Spectral domain optical coherence tomography (SD-OCT) was used to measure the thickness of different layers of the retina at macular and peripapillary regions and at different quadrants. Between groups comparison was performed with P < 0.05 indicating statistical significance.

Results:

There were 32 eyes in the MS group and 74 eyes in the control group. The MS group was significantly younger than the control group (P < 0.001). The mean ganglion cell complex (GCL++) thickness in superior macular area was 64.1 ± 8.9 μ in the MS group and 71.1 ± 5.9 μ in the control group. The thickness of the RNFL did not statistically differ in each of the quadrants between groups. Despite controlling for age, the macular thickness parameters were significantly thinner in eyes with MS compared to healthy eyes (P < 0.01).

Conclusion:

The macular ganglion cell complex (mGCC) parameters were significantly reduced in recently diagnosed cases of MS as compared to healthy individuals.

Discriminative power of intra-retinal layers in early multiple sclerosis using 3D OCT imaging

OBJECTIVE

To evaluate volumetric changes and discriminative power of intra-retinal layers in early-stage multiple sclerosis (MS) using a 3D optical coherence tomography (OCT) imaging method based on an in-house segmentation algorithm.

METHODS

3D analysis of intra-retinal layers was performed in 71 patients with early-stage MS (mean disease duration 2.2 ± 3.5 years) at baseline and 40 healthy controls (HCs). All patients underwent a follow-up OCT scan within 23 ± 9 months. Patients with a clinical episode of optic neuritis (ON) more than 6 months prior to study entrance were compared with patients who never experienced clinical symptoms of an ON episode (NON).

RESULTS

Significantly decreased total retinal volume (TRV), macular retinal nerve fiber layer (mRNFL) and ganglion cell-inner plexiform layer (GCIPL) volumes were detected in ON patients compared to NON patients (all p values < 0.05) at baseline. Each parameter on its own allowed identification of prior clinical ON based on a discriminative model (ROC analysis). Over time, TRV decreased in both ON (p = 0.013) and NON patients (p = 0.002), whereas mRNFL volume (p = 0.028) decreased only in ON and GCIPL volume (p = 0.003) decreased only in NON patients.

CONCLUSION

Our 3D-OCT data demonstrated that TRV, mRNFL and GCIPL allow discrimination between ON and NON patients in a cross-sectional analysis. However, the subsequent retinal atrophy pattern diverges in the initial phase of MS: Prior ON promotes sustained axonal thinning over time indicated by mRNFL loss, whereas longitudinal measurement of GCIPL volume better depicts continuous retrograde neurodegeneration in NON patients in early-stage MS.

Multiple retinal anomalies in schizophrenia

INTRODUCTION

In addition to being a critical component of the visual system, the retina provides the opportunity for an accessible and noninvasive probe of brain pathology in neuropsychiatric disorders. Several studies have reported various retinal abnormalities in schizophrenia, some primary and others iatrogenic. There is now increasing evidence supporting the existence of retinal anomalies in schizophrenia across structural, neurochemical and physiological parameters. Here, we review the types of retinal pathology in schizophrenia and discuss how these findings may provide novel insights for future research into the neurodevelopmental neurobiology of this syndrome, and possibly as useful biomarkers.

METHODS

Using the keywords schizophrenia, retina, pathology, electroretinogram (ERG), and/or optical coherence tomography (OCT) on PubMed, all studies using the English language within 30years were reviewed. Methods were examined, and common themes were identified, tabulated, and discussed.

RESULTS

We classified the reports of retinal pathology into primary and secondary. The major secondary retinal pathology is related to the iatrogenic effects of a once widely prescribed first generation antipsychotic (thioridazine), which was found to be associated with retinal pigment deposits, decreased visual acuity, and suppression of dark adapted ERG responses. The primary retinal findings were obtained via different measures primarily using ERG, OCT, and microvascular imaging. The most consistent findings were 1) decreased ERG wave amplitudes, 2) reduced macular volume, 3) thinning of retinal nerve fiber layer, and 4) widened venule caliber.

CONCLUSION

The abnormal pathobiological findings of the retina in schizophrenia may represent an important avenue for elucidating some of the neurodevelopmental aberrations in schizophrenia. The well replicated retinal anomalies could serve as biomarkers for schizophrenia and perhaps an endophenotype that may help identify at-risk individuals and to facilitate early intervention.

The clinical perspective: How to personalise treatment in MS and how may biomarkers including imaging contribute to this?

BACKGROUND

Multiple sclerosis (MS) is a highly heterogeneous disease, both in its course and in its response to treatments. Effective biomarkers may help predict disability progression and monitor patients' treatment responses.

OBJECTIVE

The aim of this review was to focus on how biomarkers may contribute to treatment individualisation in MS patients.

METHODS

This review reflects the content of presentations, polling results and discussions on the clinical perspective of MS during the first and second Pan-European MS Multi-stakeholder Colloquia in Brussels in May 2014 and 2015.

RESULTS

In clinical practice, magnetic resonance imaging (MRI) measures play a significant role in the diagnosis and follow-up of MS patients. Together with clinical markers, the rate of MRI-visible lesion accrual once a patient has started treatment may also help to predict subsequent treatment responsiveness. In addition, several molecular (immunological, genetic) biomarkers have been established that may play a role in predictive models of MS relapses and progression. To reach personalised treatment decisions, estimates of disability progression and likely treatment response should be carefully considered alongside the risk of serious adverse events, together with the patient's treatment expectations.

CONCLUSION

Although biomarkers may be very useful for individualised decision making in MS, many are still research tools and need to be validated before implementation in clinical practice.

Structure-function relationships in the visual system in multiple sclerosis: an MEG and OCT study

BACKGROUND

We conducted a multi-modal optical coherence tomography (OCT) and magnetoencephalography (MEG) study to test whether there is a relationship between retinal layer integrity and electrophysiological activity and connectivity (FC) in the visual network influenced by optic neuritis (ON) in patients with multiple sclerosis (MS).

METHODS

One hundred and two MS patients were included in this MEG/OCT study. Retinal OCT data were collected from the optic discs, macular region, and segmented. Neuronal activity and FC in the visual cortex was estimated from source-reconstructed resting-state MEG data by computing relative power and the phase lag index (PLI). Generalized estimating equations (GEE) were used to account for intereye within-patient dependencies.

RESULTS

There was a significant relationship for both relative power and FC in the visual cortex with retinal layer thicknesses. The findings were influenced by the presence of MSON, particularly for connectivity in the alpha bands and the outer macular layers. In the absence of MSON, this relationship was dominated by the lower frequency bands (theta, delta) and inner and outer retinal layers.

CONCLUSION

These results suggest that visual cortex FC more than activity alters in the presence of MSON, which may guide the understanding of FC plasticity effects following MSON.

Retinal nerve fiber layer thickness by Stratus and Cirrus OCT in retrobulbar optic neuritis and nonarteritic ischemic optic neuropathy

PURPOSE

To compare retinal nerve fiber layer thickness (RNFLT) measurements by Stratus and Cirrus optical coherence tomography (OCT) and to evaluate agreement between the 2 instruments in retrobulbar optic neuritis (RON), nonarteritic ischemic optic neuropathy (NAION), and healthy controls.

METHODS

A total of 89 eyes with RON, 92 with NAION (6 to 12 months after diagnosis of acute disease), and 159 control eyes were studied. Average RNFLT was measured by Stratus and Cirrus OCTs. Comparisons among groups were performed by analysis of variance. Agreement between the 2 instruments was assessed using intraclass correlation coefficient (ICC) with 95% confidence interval (CI) and Bland-Altman analysis. Statistical significance was set at p≤0.05.

RESULTS

Average RNFLT was lower in NAION eyes than in RON and control ones using both OCT devices (60.0 ± 1.2, 69.9 ± 1.2, and 97.4 ± 0.9 μm, p&lt;0.001 by Cirrus; 49.7 ± 1.5, 65.9 ± 1.9, and 99.2 ± 1.3 μm, p&lt;0.001 by Stratus). The RNFLT values were higher with Cirrus than with Stratus in NAION (+10.30 μm, confidence interval [CI] 7.82-12.79 μm) and RON (+4.01 μm, CI 1.32-6.70 μm) eyes, and slightly lower in control ones (-1.75 μm, CI -3.51 to 0.01 μm). A stronger agreement between the 2 instruments was found in control and RON eyes than in NAION ones (ICC 0.682, CI 0.566-0.771; 0.635, CI 0.467-0.758; 0.321, CI 0.132-0.472, respectively).

CONCLUSIONS

Both Stratus and Cirrus OCT can identify RNFLT reduction in previous RON and NAION. Absolute RNFLT values differ between the 2 instruments; hence they are not to be considered interchangeable.

Evaluation of Retinal Nerve Fiber Layer and Ganglion Cell Complex in Patients with Optic Neuritis or Neuromyelitis Optica Spectrum Disorders Using Optical Coherence Tomography in a Chinese Cohort

We evaluate a cohort of optic neuritis and neuromyelitis optica (NMO) spectrum disorders patients in a territory hospital in China. The peripapillary retinal nerve fiber layer (RNFL) and macular ganglion cell complex (GCC) were measured using spectral-domain OCT after 6 months of acute onset. The results showed that both the peripapillary RNFL and macular GCC were significantly thinner in all optic neuritis subtypes compared to controls. In addition, the recurrent optic neuritis and NMO groups showed more severe damage on the RNFL and GCC pattern.

Glia-Mediated Retinal Neuroinflammation as a Biomarker in Alzheimer's Disease

Alzheimer's disease (AD) is the most common type of dementia worldwide; it is characterized by a progressive decline in cognitive functions and memory, resulting from synaptic and cell loss, and accompanied by a strong neuroinflammatory response. Besides the vast progress in the understanding of the pathophysiology of AD in the past decades, there is still no effective treatment. Moreover, the diagnosis occurs usually at an advanced stage of the disease, where the neurological damage has already occurred. The identification of biomarkers that would allow an early diagnosis of this disease is a major goal that would also help managing AD progression. Due to its cellular and physiological resemblances with the brain, the retina has long been regarded as a window to the brain. Several brain manifestations have been associated with retinal alterations. In AD patients, some structural and functional alterations in the retina can be associated with disease onset. However, only a few studies have focused on the alterations in retinal glial cells associated with AD. This review aims at giving an overview of the AD-associated retinal alterations, particularly in glial cells. The documented alterations in retinal glia will be discussed concerning their potential to predict the brain alterations occurring in AD.

Retinal nerve fiber layer and macular thickness in patients with schizophrenia: Influence of recent illness episodes

Optical coherence tomography (OCT) has been recently used to investigate neuropsychiatric disorders. We aimed to study retinal OCT measures of patients with schizophrenia with respect to healthy controls, and to evaluate possible differences between recent illness episode (RIE) and non-recent illness episode (NRIE) patients. Thirty schizophrenia patients were classified as RIE (n=10) or NRIE (n=20), and compared with 30 matched controls. Statistical analyses included linear mixed-effects models to study the association between OCT measures and group membership. Multivariate models were used to control for potential confounders. In the adjusted linear mixed-effects regression model, patients had a significantly thinner retinal nerve fiber layer (RNFL) in overall measurements, and in the nasal, superior and inferior quadrants. Macular inner ring thickness and macular volume were also significantly smaller in patients than controls. Compared with controls, in the adjusted model only NRIE (but not RIE) patients had significantly reduced RNFL overall measures, superior RNFL, nasal RNFL, macular volume, and macular inner ring thickness. No significant correlation was found between illness duration and retinal measurements after controlling for age. In conclusion, retinal parameters observed using OCT in schizophrenia patients could be related to clinical status and merit attention as potential state biomarkers of the disorder.

Optical coherence tomography indicates disease activity prior to clinical onset of central nervous system demyelination

BACKGROUND

Establishing biomarkers for predicting disease activity in demyelinating disease of the central nervous system is crucial for designing appropriate disease modifiying treatment strategies.

OBJECTIVE

To investigate retinal findings and disease activity in patients with radiologically isolated and clinically isolated syndromes.

METHODS

We performed retinal optical coherence tomography and cerebral magnetic resonance imaging in healthy control individuals (n=19), in individuals with non-specific white matter lesions (n=18), and in patients with clinically isolated syndromes (n=18) and radiologically isolated syndromes (n=20).

RESULTS

Reduced volume of retinal nerve fibre layer and increased volume of inner nuclear layer at baseline correlated with subsequent disease activity as measured by an increase in cerebral T2 lesion load in patients with radiologically isolated syndromes. Reduced volume of retinal nerve fibre layer and increased volumes of inner and outer nuclear layer were associated with progression into multiple sclerosis in patients with clinically isolated syndromes.

CONCLUSION

Patients with radiologically and clinically isolated syndromes behave similarly concerning paraclinical disease activity in cerebral magnetic resonance imaging. In both conditions, reduction of retinal nerve fibre layer and increased inner nuclear layer and outer nuclear layer volumes predict disease activity and are associated with progression into multiple sclerosis.

Visual pathway neurodegeneration winged by mitochondrial dysfunction

Objectives

To test for structural and functional contribution of mitochondrial dysfunction to neurodegeneration in multiple sclerosis (MS). A visual pathway model void of MS lesions was chosen in order to exclude neurodegeneration secondary to lesion related axonotmesis.

Methods

A single-centre cohort study (230 MS patients, 63 controls). Spectral domain optical coherence tomography of the retina, 3T magnetic resonance imaging of the brain, spectrophotometric assessment of serum lactate levels. Postmortem immunohistochemistry.

Results

The visual pathway was void of MS lesions in 31 patients and 31 age-matched controls. Serum lactate was higher in MS compared to controls (P = 0.029). High serum lactate was structurally related to atrophy of the retinal nerve fiber layer at the optic disc (P = 0.041), macula (P = 0.025), and the macular ganglion cell complex (P = 0.041). High serum lactate was functionally related to poor color vision (P < 0.01), Expanded Disability Status Scale score (R = 0.37, P = 0.041), Guy's Neurological disability score (R = 0.38, P = 0.037), MS walking scale (R = 0.50, P = 0.009), upper limb motor function (R = 0.53, P = 0.002). Immunohistochemistry demonstrated increased astrocytic expression of a key lactate generating enzyme in MS lesions as well as profound vascular expression of monocarboxylate transporter-1, which is involved in lactate transport.

Interpretation

This study provides structural, functional, and translational evidence for visual pathway neurodegeneration in MS related to mitochondrial dysfunction.

Optical coherence tomography for retinal imaging in multiple sclerosis

Visual disturbances caused by inflammatory and demyelinating processes of the visual system, mainly in the optic nerve, are a common symptom in multiple sclerosis (MS). Optical coherence tomography (OCT) is a tool that is increasingly used for quantifying retinal damage in MS and other neurologic diseases. Based on spectral interferometry, it uses low-coherent infrared light to generate high-resolution spatial images of the retina. The retinal nerve fiber layer (RNFL) consists of unmyelinated axons that form the optic nerve, and thus represents a part of the central nervous system. OCT allows for noninvasive measurements of RNFL thickness in micrometer resolution. With the help of OCT, researchers have managed to demonstrate that eyes of MS patients show distinct RNFL thinning after an event of acute optic neuritis in MS, and even subclinical damage in eyes with no previous optic neuritis. OCT is also a useful tool in terms of providing a differential diagnosis of MS toward, for example, neuromyelitis optica, a disease that usually shows stronger retinal thinning, or Susac syndrome, which is characterized by distinct patchy thinning of the inner retinal layers. RNFL thinning is associated with magnetic resonance imaging-derived measurements of the brain, such as whole-brain atrophy, gray and white matter atrophy, and optic radiation damage. These features suggest that OCT-derived retinal measurements are a complement for measuring central nervous system neurodegeneration in the context of clinical trials – for example, with neuroprotective substances.