Ganglion cell loss in relation to visual disability in multiple sclerosis

The Study of Remyelinating Therapies in Multiple Sclerosis: Visual Outcomes as a Window Into Repair

INTRODUCTION

Amelioration of disability in multiple sclerosis requires the development of complementary therapies that target neurodegeneration and promote repair. Remyelination is a promising neuroprotective strategy that may protect axons from damage and subsequent neurodegeneration.

METHODS

A review of key literature plus additional targeted search of PubMed and Google Scholar was conducted.

RESULTS

There has been a rapid expansion of clinical trials studying putative remyelinating candidates, but further growth of the field is limited by the lack of consensus on key aspects of trial design. We have not yet defined the ideal study population, duration of therapy, or the appropriate outcome measures to detect remyelination in humans. The varied natural history of multiple sclerosis, coupled with the short time frame of phase II clinical trials, requires that we develop and validate biomarkers of remyelination that can serve as surrogate endpoints in clinical trials.

CONCLUSIONS

We propose that the visual system may be the most well-suited and validated model for the study potential remyelinating agents. In this review, we discuss the pathophysiology of demyelination and summarize the current clinical trial landscape of remyelinating agents. We present some of the challenges in the study of remyelinating agents and discuss current potential biomarkers of remyelination and repair, emphasizing both established and emerging visual outcome measures.

Sample size estimation for AQP4-IgG seropositive optic neuritis: Retinal damage detection by optical coherence tomography

We recruited four aquaporin-4 seropositive optic neuritis patients (five eyes) who received glucocorticoid treatment and underwent optical coherence tomography examination. Baseline medians of the macular ganglion cell layer plus inner plexiform layer (mGCIPL) thickness and volume for the eye of interest were 79.67 µm (73.664 ± 18.497 µm) and 0.58 mm3 (0.534 ± 0.134 mm3), respectively. At 2 months, the medians of the mGCIPL thickness and volume were 60.00 µm (51.576 ± 12.611 µm) and 0.44 mm3 (0.376 ± 0.091 mm3), respectively. At 6 months, the medians of the mGCIPL thickness and volume were 59.55 µm (46.288 ± 11.876 µm) and 0.44 mm3 (0.336 ± 0.084 mm3), respectively. Sample size estimate was achieved using two methods based on the mGCIPL thickness and volume data, with five effect sizes considered. The estimate based on the mGCIPL volume showed that 206 patients were needed at the 6-month follow-up; the power was 80% and effect size was 20%. In conclusion, this study detected retinal damage in aquaporin-4 seropositive optic neuritis patients by optical coherence tomography, and estimated the sample size for two-sample parallel designed clinical trials using two methods.

Trans-Synaptic Degeneration in the Visual Pathway in Patients With Myelin Oligodendrocyte Glycoprotein Antibody-Associated Disease

BACKGROUND AND OBJECTIVES

We aimed to assess the presence of retinal neurodegeneration independent of optic neuritis (ON) in myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD) and to investigate the development of trans-synaptic anterograde degeneration in these patients after ON.

METHODS

Cross-sectional, retrospective study of 34 adult patients with MOGAD and 23 healthy controls (HC). Clinical, optical coherence tomography (OCT), and MRI data were collected. Peripapillary retinal nerve fiber layer (pRNFL) and ganglion cell inner plexiform layer (GCIPL) were obtained using Heidelberg Spectralis. FreeSurfer7 was used to obtain the lateral geniculate nucleus (LGN), occipital volume fractions (to total estimated intracranial volume), and occipital cortical thickness. For the anterior visual pathway, the analysis was conducted using eyes, classified based on the history of ON (Eye-ON and Eye-NON) and compared with Eye-HC. The analysis of OCT and brain volumetric measures was conducted comparing MOGAD-ON, MOGAD-NON, and HC groups. The analysis of covariance with a Bonferroni-adjusted post hoc test was used to test differences between groups and linear regression analysis to evaluate OCT/MRI associations; age and sex were considered as covariates.

RESULTS

24 (70.5%) patients had a prior ON. Median pRNFL and GCIPL thickness (um) was significantly reduced in Eye-ON vs EyeNON and HC (pRNFL: 69.4 (17.3), 89.6 (13.7), 98.2 (11.7), p < 0.001; GCIPL: 55.8 (8.7), 67.39 (8.7), 72.6 (4.5), p < 0.001). pRNFL and GCIPL thickness had a negative correlation with the number of ON episodes (p = 0.025 and p = 0.031, respectively). LGN volume fraction was significantly lower in patients with MOGAD-ON than in HC (0.33 (0.05) vs 0.39 (0.04), p = 0.002). The occipital cortical thickness was lower in MOGAD-ON compared with MOGAD-NON and HC (p = 0.010). In patients with MOGAD-ON, pRNFL correlated with LGN volume (p = 0.006), occipital thickness (p = 0.002), and the medial occipital cortex (p = 0.002), but not the lateral occipital lobe.

DISCUSSION

Compared with HC, MOGAD-ON exhibits reduced retinal thickness, primarily influenced by the presence and the number of prior ON episodes. Moreover, MOGAD-ON demonstrates significant atrophy in the retinal, subcortical, and cortical regions of the visual pathway, distinguishing them from MOGAD-NON and HC. These findings suggest that in patients with MOGAD neurodegeneration is tightly correlated with damage to the involved pathway.

Low-contrast visual acuity test is associated with central inflammation and predicts disability development in newly diagnosed multiple sclerosis patients

Introduction

The visual system is a prominent site of damage in MS since the earliest phases of the disease. Altered low-contrast visual acuity (LCVA) test has been associated with visual impairment and retinal degeneration, predicting medium- and long-term disability. However, it is unclear whether LCVA may also represent a reliable measure of neuroinflammation and a predictor of disease evolution in the very early stages of MS.

Methods

We explored in a group of 76 consecutive newly diagnosed relapsing-remitting MS (RR-MS) patients without visual impairment or altered visual evoked potentials, the association between LCVA scores at 2.5% and 1.25% and clinical characteristics, including prospective disability evaluated after 1- and 2 years of follow-up. Associations between LCVA and the CSF levels of IL-10 at diagnosis were also analyzed.

Results

A negative correlation was found between LCVA at 2.5% and Expanded Disability Status Scale (EDSS) evaluated at first (Spearman's Rho = -0.349, p = 0.005, n = 62) and second year (Spearman's Rho = -0.418, p < 0.001, n = 62) of follow-up, and negative correlations were found with Multiple Sclerosis Severity Score (MSSS) at first (Spearman's Rho = -0.359, p = 0.004, n = 62) and second year (Spearman's Rho = -0.472, p < 0.001, n = 62). All the data were confirmed by a mixed effect model, considering other clinical variables. A positive correlation was found between the CSF concentrations of IL-10 and LCVA at 2.5% (Spearman's Rho = 0.272, p = 0.020, n = 76), and 1.25% (Spearman's Rho, = 0.276, p = 0.018, n = 76), also evidenced in a linear regression.

Discussion

In MS patients at diagnosis, altered LCVA may be associated with CSF inflammation and represent a useful parameter to identify patients with worse disease course.

Visual outcome measures in clinical trials of remyelinating drugs

One of the most promising approaches to delay, prevent or reverse disability progression in multiple sclerosis (MS) is to enhance endogenous remyelination and limit axonal degeneration. In clinical trials of remyelinating drugs, there is a need for reliable, sensitive and clinically relevant outcome measures. The visual pathway, which is frequently affected by MS, provides a unique model system to evaluate remyelination of acute and chronic MS lesions in vivo and non-invasively. In this review, we discuss the different measures that have been used and scrutinise visual outcome measure selection in current and future remyelination trials.

Co-assessment of OCT-A and choroidal vascularity index data in multiple sclerosis patients

OBJECTIVE

To evaluate optical coherence tomography-angiography (OCT-A) findings and choroidal vascular index (CVI) in patients with multiple sclerosis (MS).

METHODS

113 patients, including multiple sclerosis patients with optic neuritis attack (MSON+) and no optic neuritis attack (MSON-) and healthy control group (HCG), participated in this cross-sectional study. OCT-A images of all patients were taken and CVI was calculated.

RESULTS

Superior flow (SF), deep flow (DF), foveal, and parafoveal superior vascular density (sVD) were decreased in the MSON+ group compared to HCG (p < 0.05). Optic disk flow (ODF) and optic disk head density (ONHD) values decreased in the MS group (p < 0.05). CVI was decreased in the MSON+ group compared to HCG (p < 0.05). There is a correlation between CVI and foveal and parafoveal sVD.

CONCLUSION

Non-invasive diagnostic tools such as OCT-A and CVI can be used for early diagnosis and follow-up of microvascular pathologies in inflammatory diseases such as MS.

The relationship between retinal neurodegenerative changes and overactive bladder syndrome in multiple sclerosis

INTRODUCTION

This study aimed to compare the neuroaxonal damage of the optic nerve and retina in multiple sclerosis (MS) patients with and without overactive bladder (OAB).

PATIENTS AND METHODS

We included patients with MS, divided into two groups, based on the severity of OAB symptoms, as evaluated by the OAB-V8 questionnaire. The groups were compared in terms of each dial of the Expanded Disability Status Scale (EDSS), best-corrected visual acuity, intraocular pressure, peripapillary retinal nerve fiber layer (pRNFL) thickness, macular thickness, and macular ganglion cell-inner plexiform layer (mGCIPL) thickness.

RESULTS

The study involved a total of 120 eyes, 78 eyes from 43 female patients, and 42 from 22 male patients. There were 86 eyes (Group 1) with OAB-V8 score under 8 and there were 34 eyes (Group 2) with OAB-V8 score of 8 or over. EDSS median value was 1 (0-2) for Group 1 and 2 (0.8-3.3) for Group 2 (p = 0.004). A comparison of pRNFL thicknesses showed statistically significant lower average, superior, and inferior median values in Group 2. A comparison of mGCIPL thicknesses showed statistically significant lower values in Group 2 for superior, superonasal, inferotemporal, and superotemporal quadrants CONCLUSION: This study revealed, for MS patients without optic neuritis attacks, there was a higher incidence of OAB when the EDSS score was higher. There was a statistically significant relationship between the existence of OAB and thinning in both mGCIPL and pRNFL. The most relevant factor for OAB was found to be pRFNL inferior quadrant thinning.

Reduced Cone Density Is Associated with Multiple Sclerosis

Purpose

Multiple sclerosis (MS) is an inflammatory neurodegenerative disease of the central nervous system. Recent evidence suggests that degeneration of the inner layers of the retina occurs in MS. This study aimed to examine whether there are outer retinal changes in patients living with MS.

Design

This was a single center, cross-sectional study.

Participants

Sixteen patients with MS and 25 controls (volunteers without diagnosed MS) were recruited for the study.

Methods

We acquired volumetric spectral domain-OCT scans of the macula and a circular scan around the optic nerve head (ONH). We also captured adaptive optics (AO) images at 0° (centered on the foveola), 2°, 4°, and 6° temporal to the fovea.

Main Outcome Measures

We calculated the thickness of the different retinal layers in the macula and around the ONH using the inbuilt software of the OCT. We evaluated changes in cone photoreceptors by calculating cone density and spacing by the inbuilt AO automatic segmentation algorithm with manual correction. We compared patients with and without optic neuritis and controls.

Results

We found significant thinning of the inner retina and a thickening of the outer retina in the eye with a history of optic neuritis (eyes of patients with MS with a history of optic neuritis; mean difference [MD]: -11.13 ± 3.61 μm, P = 0.002 and MD: 2.86 ± 0.89 μm, P = 0.001; respectively). We did not observe changes in retinal layers without optic neuritis in eyes of patients with MS without a history of optic neuritis. However, regional differences were detected in the peripapillary retinal nerve fiber layer. Analyzing AO images revealed a significantly lower cone outer-segment density at all eccentricities in all patients compared with control eyes (P < 0.05), independent of optic neuritis history.

Conclusions

Our results showed that all MS cases were associated with decreased cone densities. Future longitudinal studies will help to elucidate whether this is a specific and sensitive method to detect and monitor the development and progression of MS.

Financial Disclosures

Proprietary or commercial disclosure may be found after the references.

The Heterogeneous Multiple Sclerosis Lesion: How Can We Assess and Modify a Degenerating Lesion?

Multiple sclerosis (MS) is a heterogeneous disease of the central nervous system that is governed by neural tissue loss and dystrophy during its progressive phase, with complex reactive pathological cellular changes. The immune-mediated mechanisms that promulgate the demyelinating lesions during relapses of acute episodes are not characteristic of chronic lesions during progressive MS. This has limited our capacity to target the disease effectively as it evolves within the central nervous system white and gray matter, thereby leaving neurologists without effective options to manage individuals as they transition to a secondary progressive phase. The current review highlights the molecular and cellular sequelae that have been identified as cooperating with and/or contributing to neurodegeneration that characterizes individuals with progressive forms of MS. We emphasize the need for appropriate monitoring via known and novel molecular and imaging biomarkers that can accurately detect and predict progression for the purposes of newly designed clinical trials that can demonstrate the efficacy of neuroprotection and potentially neurorepair. To achieve neurorepair, we focus on the modifications required in the reactive cellular and extracellular milieu in order to enable endogenous cell growth as well as transplanted cells that can integrate and/or renew the degenerative MS plaque.

Identifying Optical Coherence Tomography Markers for Multiple Sclerosis Diagnosis and Management

BACKGROUND

Multiple sclerosis (MS) is a common neurological disease affecting the optic nerve, directly or indirectly, through transsynaptic axonal degeneration along the visual pathway. New ophthalmological tools, arguably the most important being optical coherence tomography (OCT), could prove paramount in redefining MS diagnoses and shaping their follow-up protocols, even when the optic nerve is not involved.

METHODS

A prospective clinical study was conducted. In total, 158 eyes from patients previously diagnosed with relapsing remitting MS (RRMS)-with or without optic neuritis (ON), clinically isolated syndrome (CIS) with or without ON, and healthy controls were included. Each patient underwent an ophthalmologic exam and OCT evaluation for both eyes (a posterior pole analysis (PPA) and the optic nerve head radial circle protocol (ONH-RC)).

RESULTS

The macular retinal thickness (the 4 × 4, respectively, 2 × 2 grid) and thickness of the peripapillary retinal nerve fiber layer (pRNFL) were investigated. Various layers of the retina were also compared. Our study observed significant pRNFL thinning in the RRMS eyes compared to the control group, the pRNFL atrophy being more severe in the RRMS-ON eyes than the RRMS-NON eyes. In the ON group, the macular analysis showed statistically significant changes in the RRMS-ON eyes when compared only to the CIS-ON eyes, regarding decreases in the inner plexiform layer (IPL) thickness and inner nuclear layer (INL) on the central 2 × 2 macular grid. The neurodegenerative process affected both the inner retina and pRNFL, with clinical damage appearing for the latter in the following order: CIS-NON, CIS-ON, RRMS-NON, and RRMS-ON. In the presence of optic neuritis, SMRR patients presented an increase in their outer retina thickness compared to CIS patients.

CONCLUSIONS

To differentiate the MS patients from the CIS patients, in the absence of optic neuritis, OCT Posterior Pole Analysis could be a useful tool when using a central 2 × 2 sectors macular grid. Retinal changes in MS seem to start from the fovea and spread to the posterior pole. Finally, MS could lead to alterations in both the inner and outer retina, along with pRNFL.

Retinal Neurodegeneration and Visual Acuity Decline in Patients with Chronic Kidney Disease

INTRODUCTION

Chronic kidney disease (CKD) has been associated with accelerated retinal neurodegeneration. The purpose of this study is to evaluate the association between retinal neurodegeneration and the best-corrected visual acuity (BCVA) decline in patients with CKD.

METHODS

Post hoc analysis of two prospective studies. Patients with CKD stage ≥ 3 were enrolled. Macular thickness, peripapillary retinal nerve fiber layer (pRNFL) thickness, and macular ganglion cell complex (GCC) thickness were measured by optical coherence tomography. Eyes were classified into three groups: Group 1, no GCC defect; Group 2, GCC defect confined to parafoveal area; and Group 3, GCC defects extending beyond the parafoveal area. Each group was matched for age, sex, axial length, lens status, and cataract grading.

RESULTS

A total of 120 eyes (40 eyes in each group) from 120 patients (age 63.0 ± 10.3 years) were included. The logMAR BCVA was 0.076 ± 0.101, 0.100 ± 0.127, and 0.196 ± 0.191 in Group 1, 2, and 3, respectively. Group 3, but not Group 2, had a significantly worse BCVA than Group 1. In simple linear regression, parafoveal inner retinal thickness, pRNFL thickness, presence of pRNFL defect, GCC thickness, GCC global loss volume, GCC focal loss volume, and GCC defect extending beyond parafoveal area were associated with BCVA. Central subfield retinal thickness (CRT), parafoveal full retinal thickness, and parafoveal outer retinal thickness were not associated with BCVA. In backward stepwise linear regression, age and GCC defects extending beyond the parafoveal area were factors associated with BCVA. Moreover, GCC defect extending beyond parafoveal area was connected with worse BCVA in both phakic and pseudophakic subgroups.

CONCLUSIONS

GCC defect extending beyond parafoveal area could be an independent biomarker associated with decreased BCVA in patients with CKD. However, macular thinning measured by CRT or parafoveal full retinal thickness might have low discriminative power in determining BCVA.

Utility of the visual system to monitor neurodegeneration in multiple sclerosis

Neurodegeneration occurs early in the multiple sclerosis (MS) disease course and is an important driver of permanent disability. Current immunomodulatory therapies do not directly target neuronal health; thus, there is a critical need to develop neuroprotective strategies in MS. Outcome measures in clinical trials primarily evaluate disease activity and clinical disability scores rather than measures of neurodegeneration. The visual system provides a noninvasive correlate of brain atrophy and neuronal function through structural and functional exams. Furthermore, optic nerve axons and their respective neuronal cell bodies in the retina, in addition to their synaptic input to the thalamus, provide a distinct anatomy to investigate neurodegenerative processes. This review discusses the utility of the visual system as an early output measure of neurodegeneration in MS as well as an important platform to evaluate neuroprotective strategies in preclinical models.

Morphological changes of the retinal layers in the central macula in children with anisometropic amblyopia

PURPOSE

The goal of this study was to evaluate the morphological characteristics of the retinal layers in the central macula in children with anisometropic amblyopia.

METHODS

This comparative, observational, prospective study included 28 patients who were diagnosed with anisometropic amblyopia and 30 age- and sex-matched healthy controls. All children were evaluated using the automatic calculation software system available on spectral-domain optical coherence tomography (SD-OCT) for automated segmentation of the macula.

RESULTS

Of the included patients, 18 (64.3%) were male and 10 (35.7%) were female, with a mean age of 10.3±3.4 years. Mean spherical equivalent and best-corrected visual acuity (BCVA) were 4.13±1.95 diopters and 0.707±0.36 logMAR, respectively. The mean axial length was significantly lower in amblyopic eyes compared to fellow eyes (22.1±0.34mm vs. 23.3±0.42mm, P<0.0001), and control eyes (22.1±0.34mm vs. 23.1±0.40mm, P<0.0001). The mean thickness of the outer nuclear layer was significantly lower in amblyopic eyes compared to fellow eyes (79.8±11.9μm vs. 86.8±7.9μm, P=0.007), and healthy controls (79.8±11.9μm vs. 87.4±10.5μm, P=0.012).

CONCLUSION

The results of this study showed that there are quantitative differences in retinal microstructures of the macula in eyes with anisometropic amblyopia compared to fellow eyes and healthy controls. These findings suggest that anisometropic amblyopia may result in abnormal development of macular structure in the inner retinal layer. A detailed analysis of retinal layers may be able to provide a guide to the depth of amblyopia and visual prognosis.

Optical coherence tomography as retinal imaging biomarker of neuroinflammation/neurodegeneration in systemic disorders in adults and children

The retina and the optic nerve are considered extensions of the central nervous system (CNS) and thus can serve as the window for evaluation of CNS disorders. Spectral domain optical coherence tomography (OCT) allows for detailed evaluation of the retina and the optic nerve. OCT can non-invasively document changes in single retina layer thickness and structure due to neuronal and retinal glial cells (RGC) modifications in systemic and local inflammatory and neurodegenerative diseases. These can include evaluation of retinal nerve fibre layer and ganglion cell complex, hyper-reflective retinal spots (HRS, sign of activated microglial cells in the retina), subfoveal neuroretinal detachment, disorganization of the inner retinal layers (DRIL), thickness and integrity of the outer retinal layers and choroidal thickness. This review paper will report the most recent data on the use of OCT as a non invasive imaging biomarker for evaluation of the most common systemic neuroinflammatory and neurodegenerative/neurocognitive disorders in the adults and in paediatric population. In the adult population the main focus will be on diabetes mellitus, multiple sclerosis, optic neuromyelitis, neuromyelitis optica spectrum disorders, longitudinal extensive transverse myelitis, Alzheimer and Parkinson diseases, Amyotrophic lateral sclerosis, Huntington's disease and schizophrenia. In the paediatric population, demyelinating diseases, lysosomal storage diseases, Nieman Pick type C disease, hypoxic ischaemic encephalopathy, human immunodeficiency virus, leukodystrophies spinocerebellar ataxia will be addressed.

Where's the Vision? The Importance of Visual Outcomes in Neurologic Disorders: The 2021 H. Houston Merritt Lecture

Neurologists have long recognized the importance of the visual system in the diagnosis and monitoring of neurologic disorders. This is particularly true because approximately 50% of the brain's pathways subserve afferent and efferent aspects of vision. During the past 30 years, researchers and clinicians have further refined this concept to include investigation of the visual system for patients with specific neurologic diagnoses, including multiple sclerosis (MS), concussion, Parkinson disease (PD), and conditions along the spectrum of Alzheimer disease (AD, mild cognitive impairment, and subjective cognitive decline). This review highlights the visual "toolbox" that has been developed over the past 3 decades and beyond to capture both structural and functional aspects of vision in neurologic disease. Although the efforts to accelerate the emphasis on structure-function relationships in neurologic disorders began with MS during the early 2000s, such investigations have broadened to recognize the need for outcomes of visual pathway structure, function, and quality of life for clinical trials of therapies across the spectrum of neurologic disorders. This review begins with a patient case study highlighting the importance using the most modern technologies for visual pathway assessment, including optical coherence tomography. We emphasize that both structural and functional tools for vision testing can be used in parallel to detect what might otherwise be subclinical events or markers of visual and, perhaps, more global neurologic decline. Such measures will be critical because clinical trials and therapies become more available across the neurologic disease spectrum.

Macular ganglion cell-inner plexiform layer defect patterns in multiple sclerosis patients without optic neuritis: A Spectral-Domain-Optical Coherence Tomography Cross-Sectional, Case-Control, Pilot Study

PURPOSE

Spectral-domain optical coherence tomography (SD-OCT) was used to evaluate, in patients with multiple sclerosis without a history of optic neuritis (MSNON), the proportion of the different macular ganglion cell-inner plexiform layer complex (mGCIP) defect patterns. The results were compared with those of healthy controls (HCs).

METHODS

In this cross-sectional case-control study, 34 eyes of 34 individuals, 17 with MSNON and 17 HCs, were evaluated. All participants underwent mGCIP thickness measurement using SD-OCT (Zeiss Cirrus HD-OCT 4000, macular cube protocol). The mGCIP defect patterns were classified in nine types (minimal, inner, outer, diffuse mild, diffuse severe inferior confined, inferior dominant, superior confined, and superior dominant), according to the shape derived by the deviation map of the instrument, and the proportion of each type was assessed.

RESULTS

A mGCIP defect pattern was detected in 70.5% of MSNON eyes, with an inner type as the most frequent pattern (47%), followed by the outer type (11.7%) and the inferior confined type (11.7%). No defect was found in Hcs.

CONCLUSIONS

A significant thinning of the mGCIP with the frequent presence of an inner defect was seen in MSNON patients. The presence of this defect may serve as a biomarker of subclinical optic nerve involvement in MS patients.

Treatment with MDL 72527 Ameliorated Clinical Symptoms, Retinal Ganglion Cell Loss, Optic Nerve Inflammation, and Improved Visual Acuity in an Experimental Model of Multiple Sclerosis

Multiple Sclerosis (MS) is a highly disabling neurological disease characterized by inflammation, neuronal damage, and demyelination. Vision impairment is one of the major clinical features of MS. Previous studies from our lab have shown that MDL 72527, a pharmacological inhibitor of spermine oxidase (SMOX), is protective against neurodegeneration and inflammation in the models of diabetic retinopathy and excitotoxicity. In the present study, utilizing the experimental autoimmune encephalomyelitis (EAE) model of MS, we determined the impact of SMOX blockade on retinal neurodegeneration and optic nerve inflammation. The increased expression of SMOX observed in EAE retinas was associated with a significant loss of retinal ganglion cells, degeneration of synaptic contacts, and reduced visual acuity. MDL 72527-treated mice exhibited markedly reduced motor deficits, improved neuronal survival, the preservation of synapses, and improved visual acuity compared to the vehicle-treated group. The EAE-induced increase in macrophage/microglia was markedly reduced by SMOX inhibition. Upregulated acrolein conjugates in the EAE retina were decreased through MDL 72527 treatment. Mechanistically, the EAE-induced ERK-STAT3 signaling was blunted by SMOX inhibition. In conclusion, our studies demonstrate the potential benefits of targeting SMOX to treat MS-mediated neuroinflammation and vision loss.

Early predictors of visual and axonal outcomes after acute optic neuritis

Background

Predicting long-term visual outcomes and axonal loss following acute optic neuritis (ON) is critical for choosing treatment. Predictive models including all clinical and paraclinical measures of optic nerve dysfunction following ON are lacking.

Objectives

Using a prospective study method, to identify 1 and 3 months predictors of 6 and 12 months visual outcome (low contrast letter acuity 2.5%) and axonal loss [retinal nerve fiber layer thickness and multifocal evoked potential (mfVEP) amplitude] following acute ON.

Methods

In total, 37 patients of acute ON onset were evaluated within 14 days using between-eye asymmetry of visual acuity, color vision (Ishihara plates), optical coherence tomography, mfVEP, and optic nerve magnetic resonance imaging [magnetic transfer ratio (MTR) and diffusion tensor imaging (DTI)].

Results

Visual outcome at 6 and 12 months was best predicted by Ishihara asymmetry at 1 and 3 months following ON onset. Axonal loss at 6 and 12 months was reliably predicted by Ishihara asymmetry at 1 month. Optic nerve MTR and DTI at 3 months post-acute ON could predict axonal loss at 6 and 12 months.

Conclusions

Simple Ishihara asymmetry testing 1 month after acute ON onset can best predict visual outcome and axonal loss at 6 and 12 months in a clinical or research setting.

Biological Correlations and Confounders for Quantification of Retinal Ganglion Cells by Optical Coherence Tomography Based on Studies of Outbred Mice

Purpose

Despite popularity of optical coherence tomography (OCT) in glaucoma studies, it's unclear how well OCT-derived metrics compare to traditional measures of retinal ganglion cell (RGC) abundance. Here, Diversity Outbred (J:DO) mice are used to directly compare ganglion cell complex (GCC) thickness measured by OCT to metrics of retinal anatomy measured ex vivo with retinal wholemounts and optic nerve histology.

Methods

J:DO mice (n = 48) underwent fundoscopic and OCT examinations, with automated segmentation of GCC thickness. RGC axons were quantified from para-phenylenediamine-stained optic nerve cross-sections and somas from BRN3A-immunolabeled retinal wholemounts, with total inner retinal cellularity assessed by TO-PRO and subsequent hematoxylin staining.

Results

J:DO tissues lacked overt disease. GCC thickness, RGC abundance, and total cell abundance varied broadly across individuals. GCC thickness correlated significantly to RGC somal density (r = 0.58) and axon number (r = 0.44), but not total cell density. Retinal area and nerve cross-sectional area varied widely. No metrics were significantly influenced by sex. In bilateral comparisons, GCC thickness (r = 0.95), axon (r = 0.72), and total cell density (r = 0.47) correlated significantly within individuals.

Conclusions

Amongst outbred mice, OCT-derived measurements of GCC thickness correlate significantly to RGC somal and axon abundance. Factors limiting correlation are likely both biological and methodological, including differences in retinal area that distort sampling-based estimates of RGC abundance.

Translational Relevance

There are significant-but imperfect-correlations between GCC thickness and RGC abundance across genetic contexts in mice, highlighting valid uses and ongoing challenges for meaningful use of OCT-derived metrics.

Optical Coherence Tomography and Optical Coherence Tomography with Angiography in Multiple Sclerosis

Multiple sclerosis (MS) is an inflammatory and neurodegenerative, potentially disabling disease of the central nervous system. OCT (Optical Coherence Tomography) and OCT-A (Optical Coherence Tomography with Angiography) are imaging techniques for the retina and choroid that are used in the diagnosis and monitoring of ophthalmological conditions. Their use has recently expanded the study of several autoimmune disorders, including MS. Although their application in MS remains unclear, the results seem promising. This review aimed to provide insight into the most recent OCT and OCT-A findings in MS and may function as a reference point for future research. According to the current literature, the retinal nerve fibre layer (RNFL) and ganglion cell-inner plexiform complex (GC-IPL) are significantly reduced in people with MS and are inversely correlated with disease duration. The use of OCT might help distinguish between MS and neuromyelitis optica spectrum disorders (NMOSD), as the latter presents with more pronounced thinning in both the RNFL and GC-IPL. The OCT-A findings in MS include reduced vessel density in the macula, peripapillary area, or both, and the enlargement of the foveal avascular zone (FAZ) in the setting of optic neuritis. Additionally, OCT-A might be able to detect damage in the very early stages of the disease as well as disease progression in severe cases.

Structural retinal changes in cerebral small vessel disease

Cerebral small vessel disease (CSVD) is an important contributor to cognitive impairment and stroke. Previous research has suggested associations with alterations in single retinal layers. We have assessed changes of all individual retinal layers in CSVD using high-resolution optical coherence tomography (OCT) for the first time. Subjects with recent magnetic resonance imaging (MRI) underwent macular and peripapillary retinal imaging using OCT for this case-control study. Number and volume ratio index (WMRI) of white matter lesions (WML) were determined on MRI. Data were analyzed using multiple linear regression models. 27 CSVD patients and 9 control participants were included. Ganglion cell layer (GCL) volume was significantly reduced in patients with CSVD compared to age-matched controls (p = 0.008). In patients with CSVD, larger foveal outer plexiform layer (OPL) volume and decreased temporal peripapillary retinal nerve fiber layer (RNFL) thickness were significantly associated with a higher WMRI in linear regression when controlling for age (p ≤ 0.033). Decreased foveal GCL volume and temporal-inferior RNFL thickness at Bruch's membrane opening (MRW), and increased temporal MRW were associated with a higher WML burden (p ≤ 0.037). Thus, we identified alterations in several OCT layers in individuals with CSVD (GCL, OPL, MRW and RNFL). Their potential diagnostic value merits further study.

A multi-regression approach to improve optical coherence tomography diagnostic accuracy in multiple sclerosis patients without previous optic neuritis

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OCT diagnostics for MS improved after combining macular data with compensated peripapillary RNFL.

Background

Optical coherence tomography (OCT) is a retinal imaging system that may improve the diagnosis of multiple sclerosis (MS) persons, but the evidence is currently equivocal. To assess whether compensating the peripapillary retinal nerve fiber layer (pRNFL) thickness for ocular anatomical features as well as the combination with macular layers can improve the capability of OCT in differentiating non-optic neuritis eyes of relapsing-remitting MS patients from healthy controls.

Methods

74 MS participants (n = 129 eyes) and 84 age- and sex-matched healthy controls (n = 149 eyes) were enrolled. Macular ganglion cell complex (mGCC) thickness was extracted and pRNFL measurement was compensated for ocular anatomical factors. Thickness measurements and their corresponding areas under the receiver operating characteristic curves (AUCs) were compared between groups.

Results

Participants with MS showed significantly thinner mGCC, measured and compensated pRNFL (p ≤ 0.026). Compensated pRNFL achieved better performance than measured pRNFL for MS differentiation (AUC, 0.75 vs 0.80; p = 0.020). Combining macular and compensated pRNFL parameters provided the best discrimination of MS (AUC = 0.85 vs 0.75; p < 0.001), translating to an average improvement in sensitivity of 24 percent for differentiation of MS individuals.

Conclusion

The capability of OCT in MS differentiation is made more robust by accounting OCT scans for individual anatomical differences and incorporating information from both optic disc and macular regions, representing markers of axonal damage and neuronal injury, respectively.

Evaluation of progressive retinal degeneration in Bipolar disorder patients over a period of 5 years

PURPOSE

To quantify visual and retinal changes in patients with bipolar disorder (BD) over 5 years, compared with controls.

METHODS

Thirty-eight patients with BD and 122 healthy subjects underwent visual acuity (VA) evaluation, contrast sensitivity vision testing (CSV) with the Pelli Robson and CSV 1000E tests, and retinal thicknesses measurement (ganglion cell layer - GCL- and retinal nerve fiber layer -RNFL-) using Spectralis Optical Coherence Tomography (OCT). All subjects were re-evaluated after 5 years. The relationship between progressive structural changes and disease duration was analysed.

RESULTS

Visual function parameters in BD patients remained unchanged during the follow up period. A progressive decrease affecting macular and peripapillary RNFL thickness (p < 0.050) was observed in patients. Progressive changes in BD were more pronounced when compared with healthy controls (p < 0.050). A significant correlation between GCL thickness changes and disease duration was found (GCL outer temporal, r=-0.680, p = 0.016; GCL central, r=-0.540, p = 0.038).

CONCLUSIONS

Progressive axonal loss was detected in BD patients. Visual function parameters were not affected after the 5-year follow up. Despite observed changes in the neuroretina of patients with BD, axonal degeneration in these patients seemed to be mild and might be slowed down by other factors such as BD treatments.

Retinal imaging biomarkers of neurodegenerative diseases

The timely detection of neurodegenerative diseases is central to improving clinical care as well as enabling the development and deployment of disease-modifying therapies. Retinal imaging is emerging as a method to detect features of a number of neurodegenerative diseases, given the anatomical and functional similarities between the retina and the brain. This review provides an overview of the current status of retinal imaging biomarkers of neurodegenerative diseases including Alzheimer's disease, Parkinson's disease, Lewy body dementia, frontotemporal dementia, Huntington's disease and multiple sclerosis. Whilst research findings are promising, efforts to harmonise study designs and imaging methods will be important in translating these findings into clinical care. Doing so may mean that eye care providers will play important roles in the detection of a variety of neurodegenerative diseases in future.

Neuroprotective Effects of Novel Treatments on Acute Optic Neuritis—A Meta-Analysis

Optic neuritis, inflammation of the optic nerve, can cause visual impairment through retinal nerve fiber layer (RNFL) degeneration. Optical coherence tomography could serve as a sensitive noninvasive tool for measuring RNFL thickness and evaluating the neuroprotective effects of treatment. We conducted a meta-analysis to compare RNFL loss between novel add-on treatments and corticosteroid therapy at least 3 months after acute optic neuritis. The outcome measures were mean differences (MDs) in (1) RNFL thickness compared with the baseline in the affected and unaffected eye and (2) LogMAR visual acuity (VA). Seven studies involving five novel agents (memantine, erythropoietin, interferon-beta, phenytoin, and clemastine) were analyzed. When compared with the baseline RNFL thickness of the affected eye, the neuroprotective effects of novel add-on treatments could not be demonstrated. The difference in visual outcomes was also not significant between the two treatment groups. One study revealed that phenytoin has the potential to alleviate RNFL loss when the baseline thickness of the unaffected eye is considered. Larger randomized controlled trials with suitable outcome measures are warranted to evaluate the neuroprotective effects of novel treatments. Further studies should also tailor therapies to specific patient populations and investigate a more targeted treatment for acute optic neuritis.

Optical Coherence Tomography Identifies Visual Pathway Involvement Earlier than Visual Function Tests in Children with MRI-Verified Optic Pathway Gliomas

Simple Summary

Retrograde degeneration of the eye’s retinal ganglion cells, causing visual loss and even blindness, is a feared consequence of optic pathway gliomas. Optical coherence tomography (OCT) is a patient-friendly, high-resolution imaging technique enabling objective measurements of the integrity of the retinal ganglion cell layer. Children with optic pathway glioma unable to complete formal visual field testing and/or reliable visual acuity testing, may undergo OCT, providing objective information about visual loss and potential clinical progression. By combining visual functional measurements with OCT findings, the clinical examination will be safer and more reliable. By improving the clinical follow-up of the tumor, the treatment choices can be optimized thereby preventing further visual loss and, in the worst case, blindness.

Abstract

This study investigates whether optical coherence tomography (OCT) could add useful information in the examination of children with optic pathway glioma (OPG) at high risk of developing vision loss. For this purpose, the relationship between ganglion cell-inner plexiform layer (GC-IPL) thickness and visual function, evaluated with tests of visual acuity (VA) and visual field (VF), as well as tumor site according to magnetic resonance imaging (MRI), were examined in a geographically defined group of children with OPG. Methods: Children aged <18 years with OPG underwent ophthalmic examination including VA, VF (Zeiss HFA perimetry) and OCT imaging (Zeiss Cirrus HD-OCT). Results: Out of 51 patients included, 45 provided 77 eyes with MRI-verified OPG, and 19 patients provided 25 eyes without OPG. Significant correlations were found between GC-IPL, VF and VA (p < 0.001). The GC-IPL pattern loss corresponded in 95% to VF defects and in 92% to MRI findings. Conclusions: Our study indicates that GC-IPL measures could serve as an early marker of vision-threatening changes related to OPG and as a valuable link between MRI and visual function tests. Thinning of GC-IPL and differences in topography between eyes are strong indicators of and predictive of vision loss related to OPG.

Leveraging Visual Outcome Measures to Advance Therapy Development in Neuroimmunologic Disorders

The visual system offers unparalleled precision in the assessment of neuroaxonal damage. With the majority of patients with multiple sclerosis (MS) experiencing afferent and efferent visual dysfunction, outcome measures capturing these deficits provide insight into neuroaxonal injury, even in those with minimal disability. Ideal for use in clinical trials, visual measures are generally inexpensive, accessible, and reproducible. Quantification of visual acuity, visual fields, visual quality of life, and electrophysiologic parameters allows assessment of function, whereas optical coherence tomography (OCT) provides reliable measures of the structural integrity of the anterior afferent visual pathway. The technology of oculomotor biometrics continues to advance, and discrete measures of fixation, smooth pursuit, and saccadic eye movement abnormalities are ready for inclusion in future trials of MS progression. Visual outcomes allow tracking of neuroaxonal injury and aid in distinguishing MS from diseases such as neuromyelitis optica spectrum disorder (NMOSD) or myelin oligodendrocyte glycoprotein antibody-associated diseases (MOGAD). OCT has also provided unique insights into pathophysiology, including the identification of foveal pitting in NMOSD, possibly from damage to Müller cells, which carry an abundance of aquaporin-4 channels. For some study designs, the cost-benefit ratio favors visual outcomes over more expensive MRI outcomes. With the next frontier of therapeutics focused on remyelination and neuroprotection, visual outcomes are likely to take center stage. As an international community of collaborative, committed, vision scientists, this review by the International MS Visual System Consortium (IMSVISUAL) outlines the quality standards, informatics, and framework needed to routinely incorporate vision outcomes into MS and NMOSD trials.

Correlation Between Retrograde Trans-Synaptic Degeneration of Ganglion Cells and Optical Coherence Tomography Angiography Following Ischemic Stroke

Objective Following nerve injury, the projection of posterior visual pathway lesions into the macular ganglion cell layer (GCL) region indicates retrograde trans-synaptic degeneration (RTSD) as a mechanism of functional damage. Our purpose is to assess GCL damage and the impacts of ischemic brain lesions affecting the visual pathway on macular microvascularization in patients with stroke. Methods In a case-control study, we examined 15 ischemic stroke patients who showed visual field defects and 50 healthy controls using the high-resolution optical coherence tomography (OCT) techniques such as spectral domain-OCT (SD-OCT) to measure retinal nerve fiber layer (RNFL) and GCL thicknesses, and OCT angiography (OCTA) to assess damage to the macular microvasculature. Results In the cases, the correlation was detected among the site of vascular damage, visual field defect, retinal GCL thinning, and normal RNFL thickness. Further observations were significant reductions in macular thickness, GCL thickness, outer retinal layer vascular density, and vascular area in deeper retinal layers (p < 0.05). Conclusion Our findings suggest that ocular microvasculature abnormalities could serve as diagnostic and/or prognostic markers in patients with stroke and support the described use of GCL thickness as an image marker of visual pathway RTSD after brain injury.

Clinical and neuroimaging findings in MOGAD-MRI and OCT

Myelin oligodendrocyte glycoprotein antibody-associated disorders (MOGAD) are rare in both children and adults, and have been recently suggested to be an autoimmune neuroinflammatory group of disorders that are different from aquaporin-4 autoantibody-associated neuromyelitis optica spectrum disorder and from classic multiple sclerosis. In-vivo imaging of the MOGAD patient central nervous system has shown some distinguishing features when evaluating magnetic resonance imaging of the brain, spinal cord and optic nerves, as well as retinal imaging using optical coherence tomography. In this review, we discuss key clinical and neuroimaging characteristics of paediatric and adult MOGAD. We describe how these imaging techniques may be used to study this group of disorders and discuss how image analysis methods have led to recent insights for consideration in future studies.

AxonDeep: Automated Optic Nerve Axon Segmentation in Mice With Deep Learning

Purpose

Optic nerve damage is the principal feature of glaucoma and contributes to vision loss in many diseases. In animal models, nerve health has traditionally been assessed by human experts that grade damage qualitatively or manually quantify axons from sampling limited areas from histologic cross sections of nerve. Both approaches are prone to variability and are time consuming. First-generation automated approaches have begun to emerge, but all have significant shortcomings. Here, we seek improvements through use of deep-learning approaches for segmenting and quantifying axons from cross-sections of mouse optic nerve.

Methods

Two deep-learning approaches were developed and evaluated: (1) a traditional supervised approach using a fully convolutional network trained with only labeled data and (2) a semisupervised approach trained with both labeled and unlabeled data using a generative-adversarial-network framework.

Results

From comparisons with an independent test set of images with manually marked axon centers and boundaries, both deep-learning approaches outperformed an existing baseline automated approach and similarly to two independent experts. Performance of the semisupervised approach was superior and implemented into AxonDeep.

Conclusions

AxonDeep performs automated quantification and segmentation of axons from healthy-appearing nerves and those with mild to moderate degrees of damage, similar to that of experts without the variability and constraints associated with manual performance.

Translational Relevance

Use of deep learning for axon quantification provides rapid, objective, and higher throughput analysis of optic nerve that would otherwise not be possible.

Retinal Oxygen Metabolism and Haemodynamics in Patients With Multiple Sclerosis and History of Optic Neuritis

Vascular changes and alterations of oxygen metabolism are suggested to be implicated in multiple sclerosis (MS) pathogenesis and progression. Recently developed in vivo retinal fundus imaging technologies provide now an opportunity to non-invasively assess metabolic changes in the neural retina. This study was performed to assess retinal oxygen metabolism, peripapillary capillary density (CD), large vessel density (LVD), retinal nerve fiber layer thickness (RNFLT) and ganglion cell inner plexiform layer thickness (GCIPLT) in patients with diagnosed relapsing multiple sclerosis (RMS) and history of unilateral optic neuritis (ON). 16 RMS patients and 18 healthy controls (HC) were included in this study. Retinal oxygen extraction was modeled using O₂ saturations and Doppler optical coherence tomography (DOCT) derived retinal blood flow (RBF) data. CD and LVD were assessed using optical coherence tomography (OCT) angiography. RNFLT and GCIPLT were measured using structural OCT. Measurements were performed in eyes with (MS+ON) and without (MS-ON) history for ON in RMS patients and in one eye in HC. Total oxygen extraction was lowest in MS+ON (1.8 ± 0.2 μl O₂/min), higher in MS-ON (2.1 ± 0.5 μl O₂/min, p = 0.019 vs. MS+ON) and highest in HC eyes (2.3 ± 0.6 μl O₂/min, p = 0.002 vs. MS, ANOVA p = 0.031). RBF was lower in MS+ON (33.2 ± 6.0 μl/min) compared to MS-ON (38.3 ± 4.6 μl/min, p = 0.005 vs. MS+ON) and HC eyes (37.2 ± 4.7 μl/min, p = 0.014 vs. MS+ON, ANOVA p = 0.010). CD, LVD, RNFLT and GCIPL were significantly lower in MS+ON eyes. The present data suggest that structural alterations in the retina of RMS patients are accompanied by changes in oxygen metabolism, which are more pronounced in MS+ON than in MS-ON eyes. Whether these alterations promote MS onset and progression or occur as consequence of disease warrants further investigation. Clinical Trial Registration: ClinicalTrials.gov registry, NCT03401879.

Neuroprotective Effects of Fingolimod in a Cellular Model of Optic Neuritis

Visual dysfunction resulting from optic neuritis (ON) is one of the most common clinical manifestations of multiple sclerosis (MS), characterized by loss of retinal ganglion cells, thinning of the nerve fiber layer, and inflammation to the optic nerve. Current treatments available for ON or MS are only partially effective, specifically target the inflammatory phase, and have limited effects on long-term disability. Fingolimod (FTY) is an FDA-approved immunomodulatory agent for MS therapy. The objective of the current study was to evaluate the neuroprotective properties of FTY in the cellular model of ON-associated neuronal damage. R28 retinal neuronal cell damage was induced through treatment with tumor necrosis factor-α (TNFα). In our cell viability analysis, FTY treatment showed significantly reduced TNFα-induced neuronal death. Treatment with FTY attenuated the TNFα-induced changes in cell survival and cell stress signaling molecules. Furthermore, immunofluorescence studies performed using various markers indicated that FTY treatment protects the R28 cells against the TNFα-induced neurodegenerative changes by suppressing reactive oxygen species generation and promoting the expression of neuronal markers. In conclusion, our study suggests neuroprotective effects of FTY in an in vitro model of optic neuritis.

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.

Targeted deletion of PAC1 receptors in retinal neurons enhances neuron loss and axonopathy in a model of multiple sclerosis and optic neuritis

Chronic inflammation drives synaptic loss in multiple sclerosis (MS) and is also commonly observed in other neurodegenerative diseases. Clinically approved treatments for MS provide symptomatic relief but fail to halt neurodegeneration and neurological decline. Studies in animal disease models have demonstrated that the neuropeptide pituitary adenylate cyclase-activating polypeptide (PACAP, ADCYAP1) exhibits anti-inflammatory, neuroprotective and regenerative properties. Anti-inflammatory actions appear to be mediated primarily by two receptors, VPAC1 and VPAC2, which also bind vasoactive intestinal peptide (VIP). Pharmacological experiments indicate that another receptor, PAC1 (ADCYAP1R1), which is highly selective for PACAP, provides protection to neurons, although genetic evidence and other mechanistic information is lacking. To determine if PAC1 receptors protect neurons in a cell-autonomous manner, we used adeno-associated virus (AAV2) to deliver Cre recombinase to the retina of mice harboring floxed PAC1 alleles. Mice were then subjected to chronic experimental autoimmune encephalomyelitis (EAE), a disease model that recapitulates major clinical and pathological features of MS and associated optic neuritis. Unexpectedly, deletion of PAC1 in naïve mice resulted in a deficit of retinal ganglionic neurons (RGNs) and their dendrites, suggesting a homeostatic role of PAC1. Moreover, deletion of PAC1 resulted in increased EAE-induced loss of a subpopulation of RGNs purported to be vulnerable in animal models of glaucoma. Increased axonal pathology and increased secondary presence of microglia/macrophages was also prominently seen in the optic nerve. These findings demonstrate that neuronal PAC1 receptors play a homeostatic role in protecting RGNs and directly protects neurons and their axons against neuroinflammatory challenge. SIGNIFICANCE STATEMENT: Chronic inflammation is a major component of neurodegenerative diseases and plays a central role in multiple sclerosis (MS). Current treatments for MS do not prevent neurodegeneration and/or neurological decline. The neuropeptide pituitary adenylate cyclase-activating polypeptide (PACAP) has been shown to have anti-inflammatory, neuroprotective and regenerative properties but the cell type- and receptor-specific mechanisms are not clear. To test whether the protective effects of PACAP are direct on the PAC1 receptor subtype on neurons, we delete PAC1 receptors from neurons and investigate neuropathologigical changes in an animal model of MS. The findings demonstrate that PAC1 receptors on neurons play a homeostatic role in maintaining neuron health and can directly protect neurons and their axons during neuroinflammatory disease.

Optical coherence tomography monitoring and diagnosing retinal changes in multiple sclerosis

This study explores the use of optical coherence tomography (OCT) to monitor and diagnose multiple sclerosis (MS). The analysis of reduced total macular volume and peripapillary retinal nerve fiber layer thinning are shown. The severity of these defects increases as MS progresses, reflecting the progressive degeneration of nerve fibers and retinal ganglion cells. The OCT parameters are noninvasive, sensitive indicators that can be used to assess the progression of neurodegeneration and inflammation in MS.

Clinical and Paraclinical Biomarkers and the Hitches to Assess Conversion to Secondary Progressive Multiple Sclerosis: A Systematic Review

Conversion to secondary progressive (SP) course is the decisive factor for long-term prognosis in relapsing multiple sclerosis (MS), generally considered the clinical equivalent of progressive MS-associated neuroaxonal degeneration. Evidence is accumulating that both inflammation and neurodegeneration are present along a continuum of pathologic processes in all phases of MS. While inflammation is the prominent feature in early stages, its quality changes and relative importance to disease course decreases while neurodegenerative processes prevail with ongoing disease. Consequently, anti-inflammatory disease-modifying therapies successfully used in relapsing MS are ineffective in SPMS, whereas specific treatment for the latter is increasingly a focus of MS research. Therefore, the prevention, but also the (anticipatory) diagnosis of SPMS, is of crucial importance. The problem is that currently SPMS diagnosis is exclusively based on retrospectively assessing the increase of overt physical disability usually over the past 6–12 months. This inevitably results in a delay of diagnosis of up to 3 years resulting in periods of uncertainty and, thus, making early therapy adaptation to prevent SPMS conversion impossible. Hence, there is an urgent need for reliable and objective biomarkers to prospectively predict and define SPMS conversion. Here, we review current evidence on clinical parameters, magnetic resonance imaging and optical coherence tomography measures, and serum and cerebrospinal fluid biomarkers in the context of MS-associated neurodegeneration and SPMS conversion. Ultimately, we discuss the necessity of multimodal approaches in order to approach objective definition and prediction of conversion to SPMS.

Measuring Treatment Response in Progressive Multiple Sclerosis-Considerations for Adapting to an Era of Multiple Treatment Options

Disability in multiple sclerosis accrues predominantly in the progressive forms of the disease. While disease-modifying treatment of relapsing MS has drastically evolved over the last quarter-century, the development of efficient drugs for preventing or at least delaying disability in progressive MS has proven more challenging. In that way, many drugs (especially disease-modifying treatments) have been researched in the aspect of delaying disability progression in patients with a progressive course of the disease. While there are some disease-modifying treatments approved for progressive multiple sclerosis, their effect is moderate and limited mostly to patients with clinical and/or radiological signs of disease activity. Several phase III trials have used different primary outcomes with different time frames to define disease progression and to evaluate the efficacy of a disease-modifying treatment. The lack of sufficiently sensitive outcome measures could be a possible explanation for the negative clinical trials in progressive multiple sclerosis. On the other hand, even with a potential outcome measure that would be sensitive enough to determine disease progression and, thus, the efficacy or failure of a disease-modifying treatment, the question of clinical relevance remains unanswered. In this systematic review, we analyzed outcome measures and definitions of disease progression in phase III clinical trials in primary and secondary progressive multiple sclerosis. We discuss advantages and disadvantages of clinical and paraclinical outcome measures aiming for practical ways of combining them to detect disability progression more sensitively both in future clinical trials and current clinical routine.

Novel Foveal Features Associated With Vision Impairment in Multiple Sclerosis

Purpose

To characterize scattering and hyperreflective features in the foveal avascular zone of people with multiple sclerosis (MS) using adaptive optics scanning laser ophthalmoscopy (AOSLO) and to evaluate their relationship with visual function and MS disease characteristics.

Methods

Twenty subjects with MS underwent confocal reflectance and non-confocal split-detection AOSLO foveal imaging. Peripapillary retinal nerve fiber layer thickness was measured using optic nerve optical coherence tomography. Blood pressure, intraocular pressure (IOP), and best-corrected high-contrast visual acuity (HCVA) and low-contrast visual acuity (LCVA) were measured. AOSLO images were graded to determine the presence and characteristics of distinct structures.

Results

Two distinct structures were seen in the avascular zone of the foveal pit. Hyperreflective puncta, present in 74% of eyes, were associated with IOP and blood pressure. Scattering features, observed in 58% of eyes, were associated with decreased HCVA and LCVA, as well as increased MS duration and disability, but were not associated with retinal nerve fiber layer thickness. Hyperreflective puncta and scattering features were simultaneously present in 53% of eyes.

Conclusions

Hyperreflective puncta were associated with parameters affecting ophthalmic perfusion, but they were not associated with MS disease parameters. Scattering features were associated with parameters corresponding to advanced MS, suggesting that they may be related to disease progression. Scattering features were also correlated with reduced visual function independent from ganglion cell injury, suggesting the possibility of a novel ganglion cell–independent mechanism of impaired vision in people with MS.

Macular ganglion cell complex injury in different stages of anterior ischemic optic neuropathy

BACKGROUND

Anterior ischemic optic neuropathy (AION) is a group of ophthalmic diseases in which the optic nerve is injured causing blindness. However, the pathogenesis, clinical manifestations, and clinical treatments of AION are yet elusive. Only a few related experimental or clinical reports are available on the disease. In this study, spectral domain optical coherence tomography (SD-OCT) was used to examine the morphology of thickness swelling and atrophic changes of macular ganglion cell complex (mGCC) in the different stages of AION that were then compared with the visual fields. Thus, the clinical value of mGCC examination was alleged to be similar to that of the visual field.

AIM

To explore the mGCC injury at different stages in AION and the clinical significance.

METHODS

Cases with AION were analyzed in a retrospective study. SD-OCT was used to analyze the correlation between mGCC and peripapillary retinal nerve fiber layer thicknesses at different stages of AION and the changes in the corresponding stages of visual fields.

RESULTS

A total of 21 cases (28 eyes) presented AION. The onset time of AION was defined as early stage (within 3 wk of onset), middle stage (from 3 wk to 2 mo), and late stage (disease span > 2 mo). In the early stage, the mGCC thickness of SD-OCT was within the normal high limit, and the perioptic nerve fibers thickness was more than the normal. The changes in the visual field in early stage were not consistent with the swelling changes in mGCC and peri-disc nerve fibers. In addition, atrophy and thinning appeared in mGCC, and the perioptic nerve fibers were swollen. However, the thickness was lower in the middle period than that in the early stage. The change in visual field was consistent with that of mGCC in this period. In the late stage, mGCC shrank and thinned, and the thickness of the nerve fibers around the optic disc in the corresponding region shrank and thinned.

CONCLUSION

The changes in mGCC thickness in patients with AION showed early, middle, and late stages of development by SD-OCT. Although the early stage visual field changes of AION were not consistent with the swelling changes of mGCC, the horizontal delimitation or annular atrophy of mGCC was consistent with that in the middle and late stage of the disease. The atrophy of peripheral nerve fibers was later than that of the mGCC atrophy.

Past, present and future role of retinal imaging in neurodegenerative disease

Retinal imaging technology is rapidly advancing and can provide ever-increasing amounts of information about the structure, function and molecular composition of retinal tissue in humans in vivo. Most importantly, this information can be obtained rapidly, non-invasively and in many cases using Food and Drug Administration-approved devices that are commercially available. Technologies such as optical coherence tomography have dramatically changed our understanding of retinal disease and in many cases have significantly improved their clinical management. Since the retina is an extension of the brain and shares a common embryological origin with the central nervous system, there has also been intense interest in leveraging the expanding armamentarium of retinal imaging technology to understand, diagnose and monitor neurological diseases. This is particularly appealing because of the high spatial resolution, relatively low-cost and wide availability of retinal imaging modalities such as fundus photography or OCT compared to brain imaging modalities such as magnetic resonance imaging or positron emission tomography. The purpose of this article is to review and synthesize current research about retinal imaging in neurodegenerative disease by providing examples from the literature and elaborating on limitations, challenges and future directions. We begin by providing a general background of the most relevant retinal imaging modalities to ensure that the reader has a foundation on which to understand the clinical studies that are subsequently discussed. We then review the application and results of retinal imaging methodologies to several prevalent neurodegenerative diseases where extensive work has been done including sporadic late onset Alzheimer's Disease, Parkinson's Disease and Huntington's Disease. We also discuss Autosomal Dominant Alzheimer's Disease and cerebrovascular small vessel disease, where the application of retinal imaging holds promise but data is currently scarce. Although cerebrovascular disease is not generally considered a neurodegenerative process, it is both a confounder and contributor to neurodegenerative disease processes that requires more attention. Finally, we discuss ongoing efforts to overcome the limitations in the field and unmet clinical and scientific needs.

Detecting retinal cell stress and apoptosis with DARC: Progression from lab to clinic

DARC (Detection of Apoptosing Retinal Cells) is a retinal imaging technology that has been developed within the last 2 decades from basic laboratory science to Phase 2 clinical trials. It uses ANX776 (fluorescently labelled Annexin A5) to identify stressed and apoptotic cells in the living eye. During its development, DARC has undergone biochemistry optimisation, scale-up and GMP manufacture and extensive preclinical evaluation. Initially tested in preclinical glaucoma and optic neuropathy models, it has also been investigated in Alzheimer, Parkinson's and Diabetic models, and used to assess efficacy of therapies. Progression to clinical trials has not been speedy. Intravenous ANX776 has to date been found to be safe and well-tolerated in 129 patients, including 16 from Phase 1 and 113 from Phase 2. Results on glaucoma and AMD patients have been recently published, and suggest DARC with an AI-aided algorithm can be used to predict disease activity. New analyses of DARC in GA prediction are reported here. Although further studies are needed to validate these findings, it appears there is potential of the technology to be used as a biomarker. Much larger clinical studies will be needed before it can be considered as a diagnostic, although the relatively non-invasive nature of the nasal as opposed to intravenous administration would widen its acceptability in the future as a screening tool. This review describes DARC development and its progression into Phase 2 clinical trials from lab-based research. It discusses hypotheses, potential challenges, and regulatory hurdles in translating technology.

Identification of posterior visual pathway lesions and MRI burden in people with Multiple Sclerosis

OBJECTIVES

This review systematically identifies posterior visual pathway lesions and MRI burden in people with multiple sclerosis (MS).

METHODS

The articles were searched through Web of Science, Medline, and Embase databases on January 2020, for English language articles from 2000 to 2019.

RESULTS

This review presents summary measures if related to MRI assessment to an overall measure of MS and visual pathway lesions. A total of 44 articles fulfilled all inclusion criteria, covering the period 2000-2019. Different atypical outcomes reveal a low risk for subsequent clinically predefined MS development, specifically in the presence of normal brain MRI. Several impairments related to quality of life have been identified as a result of the effect of retinal nerve fiber layer, ganglion cell layer, and inner plexiform layer.

CONCLUSION

The afferent visual system in MS offers unique accessibility and structure-related functions with further understanding offered by electrophysiology, considering vision as a useful framework for examining new multiple sclerosis therapies.

Deletion of arginase 2 attenuates neuroinflammation in an experimental model of optic neuritis

Vision impairment due to optic neuritis (ON) is one of the major clinical presentations in Multiple Sclerosis (MS) and is characterized by inflammation and degeneration of the optic nerve and retina. Currently available treatments are only partially effective and have a limited impact on the neuroinflammatory pathology of the disease. A recent study from our laboratory highlighted the beneficial effect of arginase 2 (A2) deletion in suppressing retinal neurodegeneration and inflammation in an experimental model of MS. Utilizing the same model, the present study investigated the impact of A2 deficiency on MS-induced optic neuritis. Experimental autoimmune encephalomyelitis (EAE) was induced in wild-type (WT) and A2 knockout (A2-/-) mice. EAE-induced cellular infiltration, as well as activation of microglia and macrophages, were reduced in A2-/- optic nerves. Axonal degeneration and demyelination seen in EAE optic nerves were observed to be reduced with A2 deletion. Further, the lack of A2 significantly ameliorated astrogliosis induced by EAE. In conclusion, our findings demonstrate a critical involvement of arginase 2 in mediating neuroinflammation in optic neuritis and suggest the potential of A2 blockade as a targeted therapy for MS-induced optic neuritis.

Teriflunomide treatment is associated with optic nerve recovery in early multiple sclerosis

Background and aims:

Various attempts have been made to support recovery following optic neuritis (ON), but the respective trials have mostly been negative. The aim of this study was to determine whether disease-modifying treatment (DMT) following ON as first manifestation of relapsing-remitting multiple sclerosis influences long-term outcomes.

Methods:

A total of 79 patients with ON were identified and evaluated at relapse, DMT induction, and 12 months following treatment induction with either glatiramer acetate (GLAT), interferon-beta (IFN), or teriflunomide (TRF). Low-contrast letter acuity (LCLA) and full-field visual-evoked potentials (FF-VEP) were compared between treatment groups using multivariable regression models. The impact of TRF treatment induction compared with IFN or GLAT following relapses outside the optic nerves was evaluated in an independent cohort of 122 patients. Magnetic resonance imaging (MRI) outcomes and rates of confirmed improvement of relapse-related disability were evaluated.

Results:

TRF-treated patients exhibited higher LCLA and lower relative P100 latencies normalized to the fellow-eye. Findings were significant following covariate-adjustment by multivariable analyses. Cranial MRI lesion load as well as disability progression rates were not significantly different between groups. The cohort of patients following relapses other than ON showed no differences in confirmed improvement of disability.

Conclusion:

TRF treatment is associated with favorable outcomes regarding functional optic nerve recovery following ON in early multiple sclerosis.

Association of Spectral-Domain OCT With Long-term Disability Worsening in Multiple Sclerosis

OBJECTIVE

To evaluate whether a retinal spectral-domain optical coherence tomography (SD-OCT) assessment at baseline is associated with long-term disability worsening in people with multiple sclerosis (PwMS), we performed SD-OCT and Expanded Disability Status Scale (EDSS) assessments among 132 PwMS at baseline and at a median of 10 years later.

METHODS

In this prospective, longitudinal study, participants underwent SD-OCT, EDSS, and visual acuity (VA) assessments at baseline and at follow-up. Statistical analyses were performed using generalized linear regression models, adjusted for age, sex, race, multiple sclerosis (MS) subtype, and baseline disability. We defined clinically meaningful EDSS worsening as an increase of ≥2.0 if baseline EDSS score was <6.0 or an increase of ≥1.0 if baseline EDSS score was ≥6.0.

RESULTS

A total of 132 PwMS (mean age 43 years; 106 patients with relapsing-remitting MS) were included in analyses. Median duration of follow-up was 10.4 years. In multivariable models excluding eyes with prior optic neuritis, relative to patients with an average baseline ganglion cell + inner plexiform layer (GCIPL) thickness ≥70 µm (the mean GCIPL thickness of all eyes at baseline), an average baseline GCIPL thickness <70 µm was associated with a 4-fold increased odds of meaningful EDSS worsening (adjusted odds ratio [OR] 3.97, 95% confidence interval [CI] 1.24-12.70; p = 0.02) and an almost 3-fold increased odds of low-contrast VA worsening (adjusted OR 2.93, 95% CI 1.40-6.13; p = 0.04).

CONCLUSIONS

Lower baseline GCIPL thickness on SD-OCT is independently associated with long-term disability worsening in MS. Accordingly, SD-OCT at a single time point may help guide therapeutic decision-making among individual PwMS.

CLASSIFICATION OF EVIDENCE

This study provides Class I evidence that lower baseline GCIPL thickness on SD-OCT is independently associated with long-term disability worsening in MS.

Using Optical Coherence Tomography as a Surrogate of Measurements of Intracranial Pressure in Idiopathic Intracranial Hypertension

Importance

There is an unmet need for noninvasive biomarkers of intracranial pressure (ICP), which manifests as papilledema that can be quantified by optical coherence tomography (OCT) imaging.

Objective

To determine whether OCT of the optic nerve head in papilledema could act as a surrogate measure of ICP.

Design, Setting, and Participants

This longitudinal cohort study used data collected from 3 randomized clinical trials that were conducted between April 1, 2014, and August 1, 2019. Participants who were female and had active idiopathic intracranial hypertension were enrolled from 5 National Health Service hospitals in the UK. Automated perimetry and OCT imaging were followed immediately by ICP measurement on the same day. Cohort 1 used continuous sitting telemetric ICP monitoring (Raumedic Neurovent P-tel device) on 1 visit. Cohort 2 was evaluated at baseline and after 3, 12, and 24 months and underwent lumbar puncture assessment of ICP.

Main Outcomes and Measures

Optical coherence tomography measures of the optic nerve head and macula were correlated with ICP levels, Frisén grading, and perimetric mean deviation. The OCT protocol included peripapillary retinal nerve fiber layer, optic nerve head, and macular volume scans (Spectralis [Heidelberg Engineering]). All scans were validated for quality and resegmented manually when required.

Results

A total of 104 women were recruited. Among cohort 1 (n = 15; mean [SD] age, 28.2 [9.4] years), the range of OCT protocols was evaluated, and optic nerve head central thickness was found to be most closely associated with ICP (right eye: r = 0.60; P = .02; left eye: r = 0.73; P = .002). Subsequently, findings from cohort 2 (n = 89; mean [SD] age, 31.8 [7.5] years) confirmed the correlation between central thickness and ICP longitudinally (12 and 24 months). Finally, bootstrap surrogacy analysis noted a positive association between central thickness and change in ICP at all points (eg, at 12 months, a decrease in central thickness of 50 μm was associated with a decrease in ICP of 5 cm H2O).

Conclusions and Relevance

In this study, optic nerve head volume measures on OCT (particularly central thickness) reproducibly correlated with ICP and surrogacy analysis demonstrated its ability to inform ICP changes. These data suggest that OCT has the utility to not only monitor papilledema but also noninvasively prognosticate ICP levels in idiopathic intracranial hypertension.

Optical coherence tomography (OCT) in neuro-ophthalmology

Optical coherence tomography (OCT) is a non-invasive medical imaging technology that is playing an increasing role in the routine assessment and management of patients with neuro-ophthalmic conditions. Its ability to characterise the optic nerve head, peripapillary retinal nerve fibre layer and cellular layers of the macula including the ganglion cell layer enables qualitative and quantitative assessment of optic nerve disease. In this review, we discuss technical features of OCT and OCT-based imaging techniques in the neuro-ophthalmic context, potential pitfalls to be aware of, and specific applications in more common neuro-ophthalmic conditions including demyelinating, inflammatory, ischaemic and compressive optic neuropathies, optic disc drusen and raised intracranial pressure. We also review emerging applications of OCT angiography within neuro-ophthalmology.

Role for OCT in detecting hemi-macular ganglion cell layer thinning in patients with multiple sclerosis and related demyelinating diseases

OBJECTIVE

Investigations have found associations of homonymous thinning of the macular ganglion cell/ inner-plexiform layer (GCIPL) with demyelinating lesions in the post-chiasmal visual pathway among patients with multiple sclerosis (MS). Retinal thinning may also occur through retrograde trans-synaptic degeneration, a process by which lesions in post-geniculate visual pathway structures lead to thinning of the GCIPL across thalamic synapses. The purpose of our study was to determine the frequency of homonymous hemimacular thinning that occurs in association with post-chiasmal visual pathway demyelinating lesions in patients with MS and other demyelinating diseases.

METHODS

Adult patients with demyelinating diseases (MS, neuromyelitis optica spectrum disorder [NMOSD], myelin oligodendrocyte glycoprotein antibody disease (anti-MOG)) who were participants in an ongoing observational study of visual pathway structure and function were analyzed for the presence of hemimacular GCIPL thinning on OCT scans. Brain MRI scans were examined for the presence of post-geniculate visual pathway demyelinating lesions.

RESULTS

Among 135 participants in the visual pathway study, 5 patients (3.7%) had homonymous hemimacular GCIPL thinning. Eleven patients (8.1%) had a whole+half pattern of GCIPL thinning, characterized by hemimacular thinning in one eye and circumferential macular thinning in the contralateral eye. All but one patient with homonymous hemimacular thinning had demyelinating lesions in the post-geniculate visual pathway; however, these lesions were located in both cerebral hemispheres.

CONCLUSION

Homonymous hemimacular thinning in the GCIPL by OCT is associated with post-chiasmal visual pathway demyelinating lesions but it appears to be a relatively uncommon contributor to GCIPL loss. Patients with this pattern of GCIPL often fail to complain of hemifield visual loss. Future studies with prospective and detailed MR imaging may be able to more closely associate demyelinating lesions in anatomically appropriate regions of the post-chiasmal visual pathways with homonymous hemimacular thinning.