Color vision is strongly associated with retinal thinning in multiple sclerosis

Investigating colour vision and its structural correlates 15 years following a first demyelinating event

BACKGROUND

We investigated the long-term colour and contrast vision outcomes, 15 years after a first demyelinating event, with their structural correlates using optical coherence tomography (OCT) and brain MRI.

METHODS

Patients recruited with their first demyelinating event, were invited~15 years later to undergo clinical assessments, OCT and brain MRI and were clinically classified according to multiple sclerosis (MS) phenotypes. Linear mixed models evaluated associations between visual outcomes, MS phenotypes and OCT measures.

RESULTS

94 patients were evaluated after a median of 14.3 years. 111 eyes affected by optic neuritis and 77 unaffected eyes were studied. Optic neuritis eyes displayed worse colour vision than unaffected eyes. Unaffected eyes showed worse colour vision in relapsing-remitting MS and secondary progressive MS (SPMS) than clinically isolated syndrome, while no similar discriminatory ability was seen for OCT measures. However, ganglion cell inner plexiform layer (GCIPL) was superior to peripapillary retinal nerve fibre layer (pRNFL) in predicting all visual outcomes. Worse colour vision was associated with lower retinal thicknesses and higher brain T2 lesion load; adding MRI volumetrics to macular GCIPL predictors did not improve model prediction of visual outcomes.

CONCLUSIONS

Colour vision was impaired in unaffected eyes, especially in SPMS. GCIPL thinning underpinned this impairment more than pRNFL, suggesting neuroaxonal loss as the pathobiological substrate. The correlation between worse colour vision and increasing T2 lesion load suggests that colour dysfunction reflects overall greater disease burden. Quantitative evaluation of colour vision in addition to OCT may be useful to assess disease severity in patients after a first demyelinating event.

Demyelination and neurodegeneration early in experimental autoimmune encephalomyelitis contribute to functional deficits in the anterior visual pathway

Impaired visual function is a prevalent feature of optic neuritis (ON) in multiple sclerosis (MS). Abnormal visual evoked potential (VEP) findings of increased latencies, reduced amplitudes and abnormal waveforms as well as decreased retinal nerve fiber layer (RNFL) assessed by optical coherence tomography (OCT) are hallmarks of ON-induced visual dysfunction. Here we utilized the experimental autoimmune encephalomyelitis (EAE) mouse model of MS to investigate the functional and pathological progression during early (before any clinical symptoms), peak (initial maximal clinical symptoms), and late (chronic disease for > 3 weeks) disease stages. Demyelination and initial stages of axon damage were observed in early EAE. Significant demyelination, inflammation, increased axon damage and impaired P1/N2 amplitudes and latencies by VEP were seen in middle and late EAE groups. A decrease in RNFL thickness by OCT was observed only during late EAE. NanoString analysis of optic nerves from late EAE indicated elevated inflammation-related genes, reduced myelin-related genes, and changes in axon degeneration-related genes. Early inflammatory demyelination and functional deficits of the visual pathway, if untreated, may lead to severe irrecoverable axon damage in EAE. These studies potentially help explain the progression of visual dysfunction during MS.

Application of the international criteria for optic neuritis in the Acute Optic Neuritis Network

OBJECTIVE

The first international consensus criteria for optic neuritis (ICON) were published in 2022. We applied these criteria to a prospective, global observational study of acute optic neuritis (ON).

METHODS

We included 160 patients with a first-ever acute ON suggestive of a demyelinating CNS disease from the Acute Optic Neuritis Network (ACON). We applied the 2022 ICON to all participants and subsequently adjusted the ICON by replacing a missing relative afferent pupillary defect (RAPD) or dyschromatopsia if magnetic resonance imaging pathology of the optical nerve plus optical coherence tomography abnormalities or certain biomarkers are present.

RESULTS

According to the 2022 ICON, 80 (50%) patients were classified as definite ON, 12 (7%) patients were classified as possible ON, and 68 (43%) as not ON (NON). The main reasons for classification as NON were absent RAPD (52 patients, 76%) or dyschromatopsia (49 patients, 72%). Distribution of underlying ON etiologies was as follows: 78 (49%) patients had a single isolated ON, 41 (26%) patients were diagnosed with multiple sclerosis, 25 (16%) patients with myelin oligodendrocyte glycoprotein antibody-associated disease, and 15 (9%) with neuromyelitis optica spectrum disorder. The application of the adjusted ON criteria yielded a higher proportion of patients classified as ON (126 patients, 79%).

INTERPRETATION

According to the 2022 ICON, almost half of the included patients in ACON did not fulfill the requirements for classification of definite or possible ON, particularly due to missing RAPD and dyschromatopsia. Thorough RAPD examination and formal color vision testing are critical to the application of the 2022 ICON.

Evolution of retinal degeneration and prediction of disease activity in relapsing and progressive multiple sclerosis

Retinal optical coherence tomography has been identified as biomarker for disease progression in relapsing-remitting multiple sclerosis (RRMS), while the dynamics of retinal atrophy in progressive MS are less clear. We investigated retinal layer thickness changes in RRMS, primary and secondary progressive MS (PPMS, SPMS), and their prognostic value for disease activity. Here, we analyzed 2651 OCT measurements of 195 RRMS, 87 SPMS, 125 PPMS patients, and 98 controls from five German MS centers after quality control. Peripapillary and macular retinal nerve fiber layer (pRNFL, mRNFL) thickness predicted future relapses in all MS and RRMS patients while mRNFL and ganglion cell-inner plexiform layer (GCIPL) thickness predicted future MRI activity in RRMS (mRNFL, GCIPL) and PPMS (GCIPL). mRNFL thickness predicted future disability progression in PPMS. However, thickness change rates were subject to considerable amounts of measurement variability. In conclusion, retinal degeneration, most pronounced of pRNFL and GCIPL, occurs in all subtypes. Using the current state of technology, longitudinal assessments of retinal thickness may not be suitable on a single patient level.

Macular OCT's Proficiency in Identifying Retrochiasmal Visual Pathway Lesions in Multiple Sclerosis-A Pilot Study

Optical coherence tomography (OCT) is a non-invasive imaging technique based on the principle of low-coherence interferometry that captures detailed images of ocular structures. Multiple sclerosis (MS) is a neurodegenerative disease that can lead to damage of the optic nerve and retina, which can be depicted by OCT. The purpose of this pilot study is to determine whether macular OCT can be used as a biomarker in the detection of retrochiasmal lesions of the visual pathway in MS patients. We conducted a prospective study in which we included 52 MS patients and 27 healthy controls. All participants underwent brain MRI, visual field testing, and OCT evaluation of the thicknesses of the peripapillary retinal nerve fiber layer (pRNFL), macular ganglion cell layer (GCL), and macular inner plexiform layer (IPL). OCT measurements were adjusted for optic neuritis (ON). VF demonstrated poor capability to depict a retrochiasmal lesion identified by brain MRI (PPV 0.50). In conclusion, the OCT analysis of the macula appears to excel in identifying retrochiasmal MS lesions compared to VF changes. The alterations in the GCL and IPL demonstrate the most accurate detection of retrochiasmal visual pathway changes in MS patients.

Retinal transcriptome profiling identifies novel candidate genes associated with visual impairment in a mouse model of multiple sclerosis

Visual impairment is occasionally observed in multiple sclerosis (MS) and its animal model, experimental autoimmune encephalomyelitis (EAE). Although uveitis and optic neuritis have been reported in MS and EAE, the precise mechanisms underlying the pathogenesis of these visual impairments remain poorly understood. This study aims to identify differentially expressed genes (DEGs) in the retinas of mice with EAE to identify genes that may be implicated in EAE-induced visual impairment. Fourteen adult mice were injected with myelin oligodendrocyte glycoprotein35-55 to induce the EAE model. Transcriptomes of retinas with EAE were analyzed by RNA-sequencing. Gene expression analysis revealed 347 DEGs in the retinas of mice with EAE: 345 were upregulated, and 2 were downregulated (adjusted p-value < 0.05 and absolute log2 fold change > 1). Gene ontology (GO) analysis showed that the upregulated genes in the retinas of mice with EAE were primarily related to immune responses, responses to external biotic stimuli, defense responses, and leukocyte-mediated immunity in the GO biological process. The expression of six upregulated hub genes (c1qb, ctss, itgam, itgb2, syk, and tyrobp) from the STRING analysis and the two significantly downregulated DEGs (hapln1 and ndst4) were validated by reverse transcription-quantitative polymerase chain reaction. In addition, gene set enrichment analysis showed that the negatively enriched gene sets in EAE-affected retinas were associated with the neuronal system and phototransduction cascade. This study provides novel molecular evidence for visual impairments in EAE and indicates directions for further research to elucidate the mechanisms of these visual impairments in MS.

B cell-dependent EAE induces visual deficits in the mouse with similarities to human autoimmune demyelinating diseases

BACKGROUND

In the field of autoimmune demyelinating diseases, visual impairments have extensively been studied using the experimental autoimmune encephalomyelitis (EAE) mouse model, which is classically induced by immunization with myelin oligodendrocyte glycoprotein peptide (MOG35-55). However, this model does not involve B cells like its human analogs. New antigens have thus been developed to induce a B cell-dependent form of EAE that better mimics human diseases.

METHODS

The present study aimed to characterize the visual symptoms of EAE induced with such an antigen called bMOG. After the induction of EAE with bMOG in C57BL/6J mice, visual function changes were studied by electroretinography and optomotor acuity tests. Motor deficits were assessed in parallel with a standard clinical scoring method. Histological examinations and Western blot analyses allowed to follow retinal neuron survival, gliosis, microglia activation, opsin photopigment expression in photoreceptors and optic nerve demyelination. Disease effects on retinal gene expression were established by RNA sequencing.

RESULTS

We observed that bMOG EAE mice exhibited persistent loss of visual acuity, despite partial recovery of electroretinogram and motor functions. This loss was likely due to retinal inflammation, gliosis and synaptic impairments, as evidenced by histological and transcriptomic data. Further analysis suggests that the M-cone photoreceptor pathway was also affected.

CONCLUSION

Therefore, by documenting visual changes induced by bMOG and showing similarities to those seen in diseases such as multiple sclerosis and neuromyelitis optica, this study offers a new approach to test protective or restorative ophthalmic treatments.

Dyschromatopsia in multiple sclerosis reflects diffuse chronic neurodegeneration beyond anatomical landmarks

To formulate and validate a dyschromatopsia linear regression model in patients with multiple sclerosis (MS). 64 MS patients (50 to formulate the model and 14 for its validation) underwent neurological (Expanded Disability Status Scale, EDSS), color vision (Farnsworth D15 test), and peripapillary retinal nerve fiber layer (pRNFL) and retinal evaluation with spectral-domain optical coherence tomography (SD-OCT). Neuroradiological examination permitted to obtain brain parenchymal fraction (BPF) and cervical spinal cord volume (SC). Ophthalmic parameters were calculated as the average of both non-optic neuritis (ON) eyes, and in case the patient had previous ON, the value of the fellow non-ON eye was taken. The influence of sex, age, disease duration, and history of disease-modifying treatment (first- or second-line DMT) was tested as covariables that could influence color perception. Color confusion index (log CCI) correlated with pRNFL (r =  - 0.322, p = 0.009), ganglion cell layer (GCL, r =  - 0.321, p = 0.01), BPF (r =  - 0.287, p = 0.021), SC volume (r =  - 0.33, p = 0.008), patients' age (r = 0.417, p = 0.001), disease duration (r = 0.371, p = 0.003), and EDSS (r = 0.44, p = 0.001). The following CCI equation was obtained: log (CCI) = 0.316-0.224 BPF - 0.187 SC volume (mm3) + 0.226 age (years) + 0.012 disease duration (years) - 0.372 GCL (µm). CCI correlates with MS clinical and paraclinical established biomarkers suggesting chronic diffuse neurodegeneration in MS operates at brain, SC, and retina linking all three compartments. Color vision outcome can be calculated through the aforementioned variables for clinical and research purposes.

Alleviation of extensive visual pathway dysfunction by a remyelinating drug in a chronic mouse model of multiple sclerosis

Visual deficits are among the most prevalent symptoms in patients with multiple sclerosis (MS). To understand deficits in the visual pathway during MS and potential treatment effects, we used experimental autoimmune encephalomyelitis (EAE), the most commonly used animal model of MS. The afferent visual pathway was assessed in vivo using optical coherence tomography (OCT), electroretinography (ERG), and visually evoked cortical potentials (VEPs). Inflammation, demyelination, and neurodegeneration were examined by immunohistochemistry ex vivo. In addition, an immunomodulatory, remyelinating agent, the estrogen receptor β ligand chloroindazole (IndCl), was tested for its therapeutic potential in the visual pathway. EAE produced functional deficits in visual system electrophysiology, including suppression of ERG and VEP waveform amplitudes and increased signal latencies. Therapeutic IndCl rescued overall visual system latency by VEP but had little impact on amplitude or ERG findings relative to vehicle. Faster VEP conduction in IndCl-treated mice was associated with enhanced myelin basic protein signal in all visual system structures examined. IndCl preserved retinal ganglion cells (RGCs) and oligodendrocyte density in the prechiasmatic white matter, but similar retinal nerve fiber layer thinning by OCT was noted in vehicle and IndCl-treated mice. Although IndCl differentially attenuated leukocyte and astrocyte staining signal throughout the structures analyzed, axolemmal varicosities were observed in all visual fiber tracts of mice with EAE irrespective of treatment, suggesting impaired axonal energy homeostasis. These data support incomplete functional recovery of VEP amplitude with IndCl, as fiber tracts displayed persistent axon pathology despite remyelination-induced decreases in latencies, evidenced by reduced optic nerve g-ratio in IndCl-treated mice. Although additional studies are required, these findings demonstrate the dynamics of visual pathway dysfunction and disability during EAE, along with the importance of early treatment to mitigate EAE-induced axon damage.

Dynamics of Central Remyelination and Treatment Evolution in a Model of Multiple Sclerosis with Optic Coherence Tomography

The need for remyelinating drugs is essential for healing disabling diseases such as multiple sclerosis (MS). One of the reasons for the lack of this class of therapies is the impossibility to monitor remyelination in vivo, which is of utmost importance to perform effective clinical trials. Here, we show how optical coherence tomography (OCT), a cheap and non-invasive technique commonly used in ophthalmology, may be used to assess remyelination in vivo in MS patients. Our pioneer approach validates OCT as a technique to study remyelination of the optic nerve and reflects what is occurring in non-accessible central nervous system (CNS) structures, like the spinal cord. In this study we used the orally bioavailable small molecule VP3.15, confirming its therapeutical potential as a neuroprotective, anti-inflammatory, and probably remyelinating drug for MS. Altogether, our results confirm the usefulness of OCT to monitor the efficacy of remyelinating therapies in vivo and underscore the relevance of VP3.15 as a potential disease modifying drug for MS therapy.

Binocular Vision in Patients with Multiple Sclerosis

PURPOSE

Oculomotor disorders have been reported in multiple sclerosis (MS) in up to 80% of cases. There have been studies evaluating binocular vision in several neurological diseases, but not in MS. Considering that a high percentage of eye-movement anomalies have been reported, the aim of this study was to analyze binocular vision in these subjects.

METHODS

A total of 59 participants with MS - 21 with monocular optic neuritis, eleven with binocular optic neuritis, and 27 without optic neuritis - and 26 age-matched controls were enrolled. Binocular vision was analyzed using near point of convergence (NPC), positive and negative fusional vergence for far and near distance, measurement of heterophoria at both distances with cover and modified Thorington tests, and random-dot stereoscopy.

RESULTS

The percentage of subjects with abnormal NPC values was highest in the MS group, followed by the MSONm (MS with optic neuritis in one eye), MSONb (MS with optic neuritis in both eyes), and control groups. MS patients showed an esophoric trend at near distance. Positive fusional vergence showed no significant differences between control and MS groups, but higher variability in recovery was found in MS groups. Negative fusional vergence at near distance showed significant differences between the control group and the two MS groups, with optic neuritis for both break-point and recovery values. A high percentage of patients with MS had alterations on stereopsis.

CONCLUSION

Alterations in binocular vision were present in MS, with divergence at near distance and stereopsis the most affected parameters. Likewise, MS patients with optic neuritis showed worse binocular vision.

Ocular fixation and macular integrity by microperimetry in multiple sclerosis

PURPOSE

To characterize the fixation and macular integrity of subjects with multiple sclerosis (MS) with and without previous optic neuritis (ON) using microperimetry (MP).

METHODS

Fifty-five eyes of MS patients, subdivided into three groups (28 eyes without ON, 16 with previous ON, and 11 eyes with previous ON in the contralateral eye), and 43 healthy eyes were enrolled (January-November 2018). All cases were evaluated using the MAIA microperimeter (Centervue), analyzing the following parameters: average macular threshold (AT), fixation indexes (P1 and P2), bivariate contour ellipse area (BCEA) for 95% and 63% of points, and horizontal (H) and vertical (V) axes of the ellipse of fixation.

RESULTS

All MS groups showed a significant reduced AT compared with the control group (p < 0.001). This reduction was more representative (p < 0.001) in eyes with previous ON. No statistically significant differences were found between MS patients with and without previous ON (p > 0.05). Mean AT was correlated with the examination time in all three groups (between ρ = - 0.798 p < 0.001 and ρ = - 0.49 p < 0.001). Significant differences in fixation parameters were only found between control and MS with ON groups (p < 0.02). The ratio of the disease showed a significant correlation with fixation parameters in MS groups (p < 0.02), but not with AT.

CONCLUSIONS

In MS patients, macular sensitivity is altered, especially in eyes with previous ON. Likewise, a fixational instability is present in MS patients with ON, with more increase of the V axis of the fixation area than of the H. The ratio of the disease also affects the patient fixation pattern.

Functional Evaluation of the Visual Pathway in Patients with Multiple Sclerosis Using a Multifunction Stimulator Monitor

Objectives

To assess the capability of the vision monitor unit Monpack One of detecting visual function alterations in patients with multiple sclerosis (MS) and to evaluate the correlation between structural retinal parameters and functional measurements obtained with this device.

Methods

Forty-eight patients with MS and 46 healthy controls were included in a cross-sectional study. All participants underwent a complete functional evaluation of the visual pathway, which included low-contrast visual acuity (LCVA), contrast sensitivity vision (CSV), automated perimetry, multifocal visual evoked potentials (mfVEPs), and pattern electroretinogram (ERG). All tests were performed using the vision monitor unit Monpack One (Metrovision, France), a multifunction stimulator device. Retinal structural measurements were obtained in all subjects using Triton swept source optical coherence tomography (Topcon, Japan).

Results

Patients with MS presented reduced low-contrast VA (p < 0.001) and reduced CSV at medium (p=0.001, p=0.013) and low (p=0.001, p=0.002) spatial frequencies. All visual field parameters were found to be altered in MS patients compared with controls (≤0.001). Patients with MS presented lower amplitude of the P100 waveform of the mfVEP in areas corresponding to central (p < 0.001), inferonasal (p=0.001), and inferotemporal (p=0.003) retina. The pattern ERG did not show significant differences. Significant correlations were observed between structural retinal measurements and functional parameters, especially between the inner macular areas and measurements corresponding to contrast sensitivity and perimetry indexes.

Conclusions

Patients with MS present visual dysfunction detectable with the vision monitor unit Monpack One. This device may be a fast and useful tool to provide a full evaluation of axonal damage in patients with multiple sclerosis.

Color perception impairment following optic neuritis and its association with retinal atrophy

BACKGROUND

Emphasis is often placed on the good recovery of vision following optic neuritis (ON). However, patients continue to perceive difficulties in performing everyday visual tasks and have reduced visual quality of life. This is in addition to documented permanent loss of retinal volume.

METHODS

Seventy-five subjects following monocular ON (> 3 months prior to assessment), were evaluated by the Rabin cone contrast test (CCT). Red, green and blue cone contrast scores were extracted for the affected and fellow eyes. Retinal nerve fiber layer (RNFL) and macular volume (MV) were assessed using optical coherence tomography.

RESULTS

Fifty-seven patients had multiple sclerosis and 17 had clinically isolated syndrome. Median time from ON to evaluation was 47 months. Expanded Disability Status Scale (EDSS) ranged between 0 and 6.5 with average of 2 ± 1.3. Cone contrast scores for red, green and blue in the affected eyes were significantly lower than in the fellow eyes. RNFL thickness and MV were reduced in the affected compared to the fellow eyes. Positive correlations between CCT and RNFL were found in both eyes, but much stronger in the affected eyes (r = 0.72, 0.74, 0.5 and 0.53, 0.58, 0.46 for red green and blue in each eye, respectively). Positive correlations between CCT and MV were found in both eyes, but only modestly stronger in the affected eyes.

CONCLUSIONS

Impaired chromatic discrimination thresholds quantitatively document persistent functional complaints after ON. There is evidence of dysfunction in both the affected eye and the fellow eye.

Color vision testing versus pattern visual evoked potentials and optical coherence tomography parameters in subclinical optic nerve involvement in multiple sclerosis

Acute idiopathic demyelinating optic neuritis is frequently the initial manifestation of multiple sclerosis (MS). We aimed to discuss the value of color vision testing to detect possible optic nerve involvement in patients with MS who had no history of optic neuritis. We evaluated color vision with Farnsworth-Munsell 100 (FM-100) hue test. Total error scores (TES), partial error scores for the red-green axis (RGS) and blue-yellow axis (BYS) were calculated. Topographic optic disc parameters (RNFL, RA, DA, CV, RV, and vertical C/D ratio), total macular volume (TMV), central macular thickness (CMT), and retinal ganglion cell layer (RGCL) were determined using spectral domain optical coherence tomography (SD-OCT). Choroidal thickness (CT) was measured using enhanced depth imaging optical coherence tomography (EDI-OCT). Pattern visual evoked potentials (PVEP) were also performed. Twenty-eight patients with RRMS (56 eyes) and 25 healthy controls (50 eyes) were included. P100 latencies were significantly delayed and P100 amplitudes were significantly reduced in the patient group compared with the controls (p ≤ 0.05). Statistically significant thinning was found in temporal quadrant in the patient group compared with the controls (p = 0.002). TES RGS, and BYS were all increased in the patient group but this was not statistically significant. We found no correlation between TES, RGS, BYS, and P100 latencies or OCT parameters. In our investigation as to whether color vision testing could be a simple biomarker for showing neurodegeneration of the anterior visual pathway regardless of optic neuritis, PVEP and OCT-assessed RNFL thickness seemed to be a more valuable biomarker than color vision testing.

Retinal nerve fiber layer and ganglion cell layer changes on optical coherence tomography in early multiple sclerosis and optic neuritis cases

PURPOSE

To study the retinal nerve fiber layer (RNFL) and ganglion cell layer (GCL) changes on optical coherence tomography in early multiple sclerosis (MS) patients.

METHODS

A prospective cohort study was conducted at a tertiary care center. Patients of early MS (expanded disability status scale <3) with or without optic neuritis (ON) and idiopathic ON were included. Twenty age-matched individuals were taken as controls. Changes in RNFL and GCL thickness were evaluated along with the correlation with visual function parameters such as visual acuity, contrast sensitivity, and visual evoked response at first visit and again at six months.

RESULTS

Forty-four patients of MS with or without ON (24 and 20 patients respectively), 29 patients with idiopathic ON, and 20 healthy controls constituted the cohorts. Mean LogMAR best-corrected visual acuity was found to be significantly reduced in all groups except fellow eyes (FE) of ON group. Mean values of average RNFL thickness and values in superior, temporal, and inferior quadrant were significantly reduced. Similarly, overall mean values of average GCL-inner plexiform layer (IPL) thickness and values in superior, superonasal, superotemporal, inferonasal, and inferotemporal quadrant were significantly reduced in all groups except FE of ON group (P < 0.05). All the visual parameters significantly correlated with GCL + IPL thickness.

CONCLUSION

GCL + IPL thickness is a more sensitive clinical structural marker than RNFL in early MS with/without ON and ON patients and correlates with all the visual parameters better than RNFL thickness.

Predictors of vision impairment in Multiple Sclerosis

Visual impairment significantly alters the quality of life of people with Multiple Sclerosis (MS). The objective of this study was to identify predictors (independent variables) of visual outcomes, and to define their relationship with neurological disability and retinal atrophy when assessed by optical coherence tomography (OCT). We performed a cross-sectional analysis of 119 consecutive patients with MS, assessing vision using high contrast visual acuity (LogMar), 2.5% and 1.25% low contrast visual acuity (Sloan charts), and color vision (Hardy-Rand-Rittler plates). Quality of vision is a patient reported outcome based on an individual's unique perception of his or her vision and was assessed with the Visual Functioning Questionnaire-25 (VFQ-25) with the 10 neuro-ophthalmologic items. MS disability was assessed using the expanded disability status scale (EDSS), the MS functional composite (MSFC) and the brief repetitive battery-neuropsychology (BRB-N). Retinal atrophy was assessed using spectral domain OCT, measuring the thickness of the peripapillar retinal nerve fiber layer (pRNFL) and the volume of the ganglion cell plus inner plexiform layer (GCIPL). The vision of patients with MS was impaired, particularly in eyes with prior optic neuritis. Retinal atrophy (pRNFL and GCIPL) was closely associated with impaired low contrast vision and color vision, whereas the volume of the GCIPL showed a trend (p = 0.092) to be associated with quality of vision. Multiple regression analysis revealed that EDSS was an explanatory variable for high contrast vision after stepwise analysis, GCIPL volume for low contrast vision, and GCIPL volume and EDSS for color vision. The explanatory variables for quality of vision were high contrast vision and color vision. In summary, quality of vision in MS depends on the impairment of high contrast visual acuity and color vision due to the disease.

Retinal biomarkers provide "insight" into cortical pharmacology and disease

The retina is an easily accessible out-pouching of the central nervous system (CNS) and thus lends itself to being a biomarker of the brain. More specifically, the presence of neuronal, vascular and blood-neural barrier parallels in the eye and brain coupled with fast and inexpensive methods to quantify retinal changes make ocular biomarkers an attractive option. This includes its utility as a biomarker for a number of cerebrovascular diseases as well as a drug pharmacology and safety biomarker for the CNS. It is a rapidly emerging field, with some areas well established, such as stroke risk and multiple sclerosis, whereas others are still in development (Alzheimer's, Parkinson's, psychological disease and cortical diabetic dysfunction). The current applications and future potential of retinal biomarkers, including potential ways to improve their sensitivity and specificity are discussed. This review summarises the existing literature and provides a perspective on the strength of current retinal biomarkers and their future potential.

Optical coherence tomography: A quantitative tool to measure neurodegeneration and facilitate testing of novel treatments for tissue protection in multiple sclerosis

Optical coherence tomography (OCT) is a relatively new imaging technology that has been introduced as a powerful biomarker in neurological disease, including multiple sclerosis. In this review, OCT as an imaging technique, its reproducibility and validation in multiple sclerosis, application to other neurodegenerative diseases and future technological directions are discussed.

Quantitative visual tests after poorly recovered optic neuritis due to multiple sclerosis

BACKGROUND

Visual dysfunction in MS can be quantified using a variety of tests. Many vision tests have not been formally evaluated among MS patients with existing visual dysfunction.

OBJECTIVE

Evaluate several versions of visual acuity and contrast sensitivity tests, measures of central and peripheral vision, retina structure, electrophysiologic function, and quality of life among MS patients with moderate/severe visual dysfunction.

METHODS

Cross-sectional study of 46 patients with stable, incompletely recovered optic neuritis. Testing included Snellen eye charts, several Sloan low contrast charts, Pelli Robson (PR) contrast sensitivity charts, optical coherence tomography, visual fields, Farnsworth Munsell 100-hue test, visual evoked potentials (VEP), and visual function quality of life (VFQ-25) testing.

RESULTS

98% of eyes could read two lines of the PR chart, while only 43% read the 2.5% contrast chart. Low contrast tests correlated strongly with each other and with retinal nerve fiber layer (RNFL) thickness, visual fields, and color vision but not with VEPs. For patients with RNFL <75µm, VFQ-25 scores dropped by approximately 2 points for every 1µm decrease in RNFL.

CONCLUSION

Among MS patients with visual impairment due to optic neuritis, PR contrast sensitivity could be utilized as a single chart. Visual quality of life was associated with RNFL thinning below 75µm.

Relationship between Visual Dysfunction and Retinal Changes in Patients with Multiple Sclerosis

Aim

To evaluate structural changes in the retina and their correlation with visual dysfunction in patients with multiple sclerosis.

Methods

Patients with multiple sclerosis (n = 84) and healthy controls (n = 84) underwent structural evaluation of the retinal nerve fiber layer, and macular and ganglion cell layer thicknesses using Spectral domain optical coherence tomography (SD-OCT). All subjects underwent high and low contrast visual acuity, color vision (using the Farnsworth and L´Anthony desaturated D15 color tests), and contrast sensitivity vision using the Pelli Robson chart and CSV 1000E test.

Results

Macular, retinal nerve fiber layer, and ganglion cell layer thinning was observed in multiple sclerosis patients compared to healthy controls (p<0.05). High- and low-contrast visual acuity and contrast sensitivity vision at four different spatial frequencies were significantly reduced in comparison with healthy subjects (p<0.05). Macular, retinal nerve fiber layer and ganglion cell layer measurements correlated with high and low contrast visual acuity, and contrast sensitivity vision. Contrast sensitivity vision was the functional parameter that most strongly correlated with the structural measurements in multiple sclerosis and was associated with ganglion cell layer measurements. The L´Anthony color vision score (age-corrected color confusion index) was associated with macular measurements.

Conclusions

Patients with multiple sclerosis had visual dysfunction that correlated with structural changes evaluated by SD-OCT. Macular and ganglion cell layer measurements may be good indicators of visual impairment in multiple sclerosis patients.

Dyschromatopsia in Multiple Sclerosis Patients: A Marker of Subclinical Involvement?

BACKGROUND

In multiple sclerosis (MS), even in the absence of a clinical episode of optic neuritis (ON), the optic nerve and retinal nerve fiber layer (RNFL) may be damaged leading to dyschromatopsia. Subclinical dyschromatopsia has been described in MS associated with lower motor and cognitive performances.

OBJECTIVES

To set the prevalence of dyschromatopsia in eyes of MS patients without a history of ON, to compare its prevalence in patients with and without ON history, and to explore the association between dyschromatopsia and disease duration, average peripapillary RNFL thickness, macular volume, and cognitive and motor performances.

METHODS

An observational cross-sectional study was conducted at multiple medical centers. Data were collected after single neurological and ophthalmological evaluations. Dyschromatopsia was defined by the presence of at least 1 error using Hardy-Rand-Rittler plates.

RESULTS

In our population of 125 patients, 79 patients (63.2%) never had ON and 35 (28.8%) had unilateral ON. The prevalence of dyschromatopsia in eyes of patients without ON was 25.7%. Patients with dyschromatopsia had a statistically significant lower RNFL thickness (P = 0.004 and P = 0.040, right and left eyes, respectively) and worse performance in symbol digit modalities test (P = 0.012). No differences were found in macular volume or motor function tasks.

CONCLUSIONS

Dyschromatopsia occurs frequently in MS patients. It may be associated with a worse disease status and possibly serve as a marker for the detection of subclinical disease progression since it was detected even in the absence of ON. It correlated with thinner peripapillary RNFL thickness and inferior cognitive performance.

Longitudinal time-domain optic coherence study of retinal nerve fiber layer in IFNβ-treated and untreated multiple sclerosis patients

Quantification of the retinal nerve fiber layer (RNFL) by optical coherence tomography (OCT) has been proposed to provide an indirect measure for retinal axonal loss. The aim of the present study was to determine whether interferon beta (IFNβ) treatment impedes retinal axonal loss in multiple sclerosis (MS) patients. A total of 48 patients with MS (24 IFNβ-1b-treated and 24 untreated subjects) and 12 healthy controls were enrolled in a prospective longitudinal OCT study. OCT measurements were performed for both eyes of each subject at baseline, and at 3-, 6-, and 12-month follow-up examinations using a time-domain OCT. At each visit, we additionally recorded full-field visual evoked potential (VEP) responses and performed the paced auditory serial addition test (PASAT), in addition to expanded disability status scale (EDSS) scoring. Generalized estimation equation (GEE) was used to account for repeated measurements and paired-data. The model-based approach predicted a monthly reduction in the RNFL thickness by 0.19 µm in the eyes of the MS subjects. The reduction was estimated to be 0.17 µm in case of IFNβ-treatment and 0.16 µm in case of no treatment. Treatment duration and group allocation were not significantly associated with the RNFL thickness. Inclusion of further longitudinal data (EDSS, two and three second PASAT) in each of our models did not result in any significant association. In summary, over a period of one year no significant association between IFNβ-1b treatment and RNFL thinning was identified in patients with MS.

Color vision impairment in multiple sclerosis points to retinal ganglion cell damage

Multiple Sclerosis (MS) results in color vision impairment regardless of optic neuritis (ON). The exact location of injury remains undefined. The objective of this study is to identify the region leading to dyschromatopsia in MS patients' NON-eyes. We evaluated Spearman correlations between color vision and measures of different regions in the afferent visual pathway in 106 MS patients. Regions with significant correlations were included in logistic regression models to assess their independent role in dyschromatopsia. We evaluated color vision with Hardy-Rand-Rittler plates and retinal damage using Optical Coherence Tomography. We ran SIENAX to measure Normalized Brain Parenchymal Volume (NBPV), FIRST for thalamus volume and Freesurfer for visual cortex areas. We found moderate, significant correlations between color vision and macular retinal nerve fiber layer (rho = 0.289, p = 0.003), ganglion cell complex (GCC = GCIP) (rho = 0.353, p < 0.001), thalamus (rho = 0.361, p < 0.001), and lesion volume within the optic radiations (rho = -0.230, p = 0.030). Only GCC thickness remained significant (p = 0.023) in the logistic regression model. In the final model including lesion load and NBPV as markers of diffuse neuroaxonal damage, GCC remained associated with dyschromatopsia [OR = 0.88 95 % CI (0.80-0.97) p = 0.016]. This association remained significant when we also added sex, age, and disease duration as covariates in the regression model. Dyschromatopsia in NON-eyes is due to damage of retinal ganglion cells (RGC) in MS. Color vision can serve as a marker of RGC damage in MS.

[Investigation of color vision in acute unilateral optic neuritis using a web-based color vision test]

BACKGROUND

In acute unilateral optic neuritis (ON) color vision defects combined with a decrease in visual acuity and contrast sensitivity frequently occur. This study investigated whether a web-based color vision test is a reliable detector of acquired color vision defects in ON and, if so, which charts are particularly suitable.

METHODS

In 12 patients with acute unilateral ON, a web-based color vision test ( www.farbsehtest.de ) with 25 color plates (16 Velhagen/Broschmann and 9 Ishihara color plates) was performed. For each patient the affected eye was tested first and then the unaffected eye.

RESULTS

The mean best-corrected distance visual acuity (BCDVA) in the ON eye was 0.36 ± 0.20 and 1.0 ± 0.1 in the contralateral eye. The number of incorrectly read plates correlated with the visual acuity. For the ON eye a total of 134 plates were correctly identified and 166 plates were incorrectly identified, while for the disease-free fellow eye, 276 plates were correctly identified and 24 plates were incorrectly identified. Both of the blue/yellow plates were identified correctly 14 times and incorrectly 10 times using the ON eye and exclusively correctly (24 times) using the fellow eye. The Velhagen/Broschmann plates were incorrectly identified significantly more frequently in comparison with the Ishihara plates. In 4 out of 16 Velhagen/Broschmann plates and 5 out of 9 Ishihara plates, no statistically significant differences between the ON eye and the fellow eye could be detected.

CONCLUSION

The number of incorrectly identified plates correlated with a decrease in visual acuity. Red/green and blue/yellow plates were incorrectly identified significantly more frequently with the ON eye, while the Velhagen/Broschmann color plates were incorrectly identified significantly more frequently than the Ishihara color plates. Thus, under defined test conditions the web-based color vision test can also be used to detect acquired color vision defects, such as those caused by ON. Optimization of the test by altering the combination of plates may be a useful next step.

Re-evaluating the treatment of acute optic neuritis

Clinical case reports and prospective trials have demonstrated a reproducible benefit of hypothalamic-pituitary-adrenal (HPA) axis modulation on the rate of recovery from acute inflammatory central nervous system (CNS) demyelination. As a result, corticosteroid preparations and adrenocorticotrophic hormones are the current mainstays of therapy for the treatment of acute optic neuritis (AON) and acute demyelination in multiple sclerosis.Despite facilitating the pace of recovery, HPA axis modulation and corticosteroids have failed to demonstrate long-term benefit on functional recovery. After AON, patients frequently report visual problems, motion perception difficulties and abnormal depth perception despite 'normal' (20/20) vision. In light of this disparity, the efficacy of these and other therapies for acute demyelination require re-evaluation using modern, high-precision paraclinical tools capable of monitoring tissue injury.In no arena is this more amenable than AON, where a new array of tools in retinal imaging and electrophysiology has advanced our ability to measure the anatomic and functional consequences of optic nerve injury. As a result, AON provides a unique clinical model for evaluating the treatment response of the derivative elements of acute inflammatory CNS injury: demyelination, axonal injury and neuronal degeneration.In this article, we examine current thinking on the mechanisms of immune injury in AON, discuss novel technologies for the assessment of optic nerve structure and function, and assess current and future treatment modalities. The primary aim is to develop a framework for rigorously evaluating interventions in AON and to assess their ability to preserve tissue architecture, re-establish normal physiology and restore optimal neurological function.

Retinal axonal loss in very early stages of multiple sclerosis

BACKGROUND AND PURPOSE

The lack of surrogates of clinical progression has limited the design of neuroprotection trials in multiple sclerosis (MS). Our aim was to study the association between time-domain optical coherence tomography measures and clinical and magnetic resonance imaging outcomes in early MS.

METHODS

Forty-three relapsing-remitting MS patients within 1 year of onset were followed for up to 3 years.

RESULTS

The peripapillary retinal nerve fiber layer (RNFL) decreased annually by 2 μm (95% confidence interval -3.89, -0.11; P = 0.038). The RNFL tended to be associated with normalized normal appearing white matter volume in cross-sectional (P = 0.08) and longitudinal analyses (P = 0.06).

CONCLUSIONS

There is substantial RNFL loss even in very early MS. Our data suggest that retinal axonal atrophy is associated with atrophy in global white matter volume in early MS.

Structural and functional changes in glaucoma: comparing the two-flash multifocal electroretinogram to optical coherence tomography and visual fields

PURPOSE

To correlate multifocal electroretinogram (mfERG) findings in the macular area of glaucoma patients with automated perimetry (visual fields) and with optical coherence tomography (OCT).

METHODS

A two-global flash mfERG (VERIS™) was recorded in 20 eyes with primary open-angle glaucoma. The root mean square was calculated, and three response epochs were analysed: the direct component (15-45 ms) and two induced components (IC-1 at 45-75 ms and IC-2 at 75-105 ms). The central 10° of the mfERG was compared to the central 10° of the OCT and of the visual field. Responses grouped in a superior and in an inferior semicircle, extending between 10° and 20°, were also compared to the corresponding areas of the OCT and of the visual fields. In addition, the area of the papillomacular bundle was also analysed separately.

RESULTS

In glaucoma patients, mfERG responses showed a significant positive association with retinal thickness in the central 10° for IC2 (p = 0.001) and a trend for IC1 (p = 0.066). A significant association was found between the central IC1 and IC2 of the mfERG and corresponding perimetric sensitivities expressed in linear units (p < 0.01). The OCT showed a positive association with visual field sensitivities (p < 0.05) in all areas examined (p < 0.05). Separation of the papillomacular bundle area did not improve structure-function association further.

CONCLUSIONS

In our study, mfERG showed a statistically significant correlation with perimetric sensitivity measured in linear units and with structural macular changes detected with time-domain OCT.

Vision and vision-related outcome measures in multiple sclerosis

Visual impairment is a key manifestation of multiple sclerosis. Acute optic neuritis is a common, often presenting manifestation, but visual deficits and structural loss of retinal axonal and neuronal integrity can occur even without a history of optic neuritis. Interest in vision in multiple sclerosis is growing, partially in response to the development of sensitive visual function tests, structural markers such as optical coherence tomography and magnetic resonance imaging, and quality of life measures that give clinical meaning to the structure-function correlations that are unique to the afferent visual pathway. Abnormal eye movements also are common in multiple sclerosis, but quantitative assessment methods that can be applied in practice and clinical trials are not readily available. We summarize here a comprehensive literature search and the discussion at a recent international meeting of investigators involved in the development and study of visual outcomes in multiple sclerosis, which had, as its overriding goals, to review the state of the field and identify areas for future research. We review data and principles to help us understand the importance of vision as a model for outcomes assessment in clinical practice and therapeutic trials in multiple sclerosis.

The multiple sclerosis visual pathway cohort: understanding neurodegeneration in MS

Background

Multiple Sclerosis (MS) is an immune-mediated disease of the Central Nervous System with two major underlying etiopathogenic processes: inflammation and neurodegeneration. The latter determines the prognosis of this disease. MS is the main cause of non-traumatic disability in middle-aged populations.

Findings

The MS-VisualPath Cohort was set up to study the neurodegenerative component of MS using advanced imaging techniques by focusing on analysis of the visual pathway in a middle-aged MS population in Barcelona, Spain. We started the recruitment of patients in the early phase of MS in 2010 and it remains permanently open. All patients undergo a complete neurological and ophthalmological examination including measurements of physical and disability (Expanded Disability Status Scale; Multiple Sclerosis Functional Composite and neuropsychological tests), disease activity (relapses) and visual function testing (visual acuity, color vision and visual field). The MS-VisualPath protocol also assesses the presence of anxiety and depressive symptoms (Hospital Anxiety and Depression Scale), general quality of life (SF-36) and visual quality of life (25-Item National Eye Institute Visual Function Questionnaire with the 10-Item Neuro-Ophthalmic Supplement). In addition, the imaging protocol includes both retinal (Optical Coherence Tomography and Wide-Field Fundus Imaging) and brain imaging (Magnetic Resonance Imaging). Finally, multifocal Visual Evoked Potentials are used to perform neurophysiological assessment of the visual pathway.

Discussion

The analysis of the visual pathway with advance imaging and electrophysilogical tools in parallel with clinical information will provide significant and new knowledge regarding neurodegeneration in MS and provide new clinical and imaging biomarkers to help monitor disease progression in these patients.

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.

Perspectives of an innovative ophthalmological technology: optical coherence tomography (OCT)--what should be of interest to the neurologist?

Ocular coherence tomography has revolutionised the prospects of measuring the loss of retinal ganglion cells secondary to degenerative diseases and monitoring time-dependent changes of optic disc morphology, since the resolution has been improved considerably and the time required has been reduced. Although the non-invasive technique promises a high inter-session reproducibility, the limitations of retinal imaging and the problems of segmenting of the retinal layers have to be taken into account. While the first studies were limited to single sessions in small groups, further trials will elucidate how the retinal nerve fibre layer (RNFL) is altered in the course of different episodic forms of multiple sclerosis. This review points out that the examination technique already provides comprehensive information, valuable in the daily care of neurological patients.

Optical coherence tomography in patients with a history of juvenile multiple sclerosis reveals early retinal damage

BACKGROUND AND PURPOSE

Some 3%-10% of patients with multiple sclerosis (MS) experience disease onset before the age of 18 years ('early' onset MS, EOMS). Optical coherence tomography is a non-invasive method to measure retinal nerve fibre layer thickness (RNFLT) and total macular volume (TMV) and may be useful to differentiate axonal and neuronal damage in the retina of patients with a history of EOMS. Here RNFLT and TMV in EOMS patients after a mean disease duration of 11.6 years were compared with patients with age- or disease-duration-matched later onset MS (LOMS) and healthy controls (HCs).

METHODS

In this observational cross-sectional study at two German academic MS centres, RNFLT and TMV were measured by spectral-domain optical coherence tomography in 32 HCs, 36 EOMS (mean age at onset 15.5 ± 2.0 years) and 58 LOMS patients.

RESULTS

In comparison with HCs, EOMS patients displayed a significant reduction of RNFLT and TMV independently of a history of optic neuritis. In particular, RNFLT loss in EOMS was similar to that in LOMS and TMV loss was slightly higher compared with disease-duration-matched LOMS. In a generalized estimating model, the EOMS group also displayed a similar correlation between disease duration and RNFLT or TMV loss to LOMS patients.

CONCLUSIONS

These data argue for a significant amount of axonal and neuronal damage in the retina of EOMS patients and may provide a structural basis for the observation that EOMS patients reach states of irreversible disability at a younger age than patients with LOMS.

The visual pathway as a model to understand brain damage in multiple sclerosis

Patients with multiple sclerosis (MS) almost always experience effects in the visual pathway; and thus, visual dysfunction is not only common but also highly relevant. The visual pathway represents a model of acute focal central nervous system (CNS) damage, through acute optic neuritis and retinal periphlebitis, as well as a model of chronic, diffuse CNS damage through chronic retinopathy and optic neuropathy. The optic pathway can be accurately evaluated in detail, due to the availability of highly sensitive imaging techniques (e.g. magnetic resonance imaging or optical coherent tomography) or electrophysiological tests (multifocal visual evoked potentials or electroretinography). These techniques allow the interactions between the different processes at play to be evaluated, such as inflammation, demyelination, axonal damage and neurodegeneration. Moreover, these features mean that the visual pathway can be used as a model to test new neuroprotective or regenerative therapies.

A randomized controlled phase II trial of riluzole in early multiple sclerosis

Objectives

We evaluated the effect of riluzole versus placebo added to weekly IM interferon beta-1a in early multiple sclerosis (MS).

Methods

This is a randomized (1:1), double-blind, placebo-controlled trial of riluzole 50 mg twice daily in subjects with MS onset less than 1 year prior. Trial participation was up to 3 years. The primary endpoint was change in percent brain volume change. Secondary endpoints included changes in normalized gray and normal-appearing white matter volumes, retinal nerve fiber layer thickness (RNFL), MS Functional Composite and Symbol Digit Modalities Test scores. Mixed model regression analysis was used to compare the changes over time between groups.

Results

Forty-three subjects were randomized to study drug (22 riluzole, 21 placebo). Baseline characteristics were overall similar between groups except for older age (P = 0.042), higher normalized cerebrospinal fluid volume (P = 0.050), lower normalized gray matter volume (P = 0.14), and thinner RNFL (P = 0.043) in the riluzole group. In the primary analysis, percent brain volume change in the placebo group decreased at a rate of 0.49% per year whereas the riluzole group decreased by 0.86% per year (0.37% more per year; 95% CI −0.78, 0.024; P = 0.065). Although age did not influence the rate of brain volume decline, the difference between groups was attenuated after adjustment for baseline normalized gray matter and lesion volume (0.26% more per year in riluzole group; 95% CI −0.057, 0.014; P = 0.22). Analyses of secondary outcomes showed no differences between groups.

Interpretation

This trial provides class 1 evidence that riluzole treatment does not meaningfully reduce brain atrophy progression in early MS.

Chromatic visual evoked potentials in young patients with demyelinating disease

The purpose of this study was to evaluate color vision in young patients with demyelinating disease both clinically and electrophysiologically. Thirty young patients (8-28 years, mean age 19 years) with demyelinating disease with or without a history of optic neuritis (ON) were investigated. Color vision was evaluated clinically with the Ishihara test and the Farnsworth-Munsell 100 hue (FM 100 hue) test and electrophysiologically with chromatic visual evoked potentials (cVEPs). Color deficiency axis and error score (ES) obtained with the FM 100 hue test were analyzed. cVEPs to isoluminant red-green (R-G) and blue-yellow (B-Y) stimuli were recorded. The stimulus was a 7 deg circle composed of horizontal sinusoidal gratings with a spatial frequency of 2 cycles/deg and 90% chromatic contrast. Onset-offset mode of stimulation (ON:OFF=300∶700  ms) was used. Since the majority of the patients were adults (>18  years), the negative wave (N wave) of the cVEP respones is the prominent part and therefore was analyzed. Sixty eyes were studied-22 with at least one episode of ON (ON group) and 38 without any clinically evident episode of ON (nON group). The average ES in the ON group was 179.18±171.8, whereas in the nON group it was 87.60±65.34. The average N-wave latency in the ON group was 144±44  ms for the R-G stimulus and 146±56  ms for the B-Y stimulus, whereas in the nON group, it was 117±13  ms for the R-G stimulus and 121±22  ms for the B-Y one. The average N-wave amplitude in the ON group was 9.3±7.1  μV for the R-G stimulus and 5.1±3.9  μV for the B-Y one, whereas in the nON group, it was 10.8±8.3  μV for the R-G stimulus and 6.4±4.3  μV for the B-Y one. A significant difference between the ON and the nON group was found: in the ON group, ES was higher (p=0.01) and N-wave latency was longer (p=0.01) compared with those in the nON group. The study showed that color vision is expectedly more affected in the ON group, but also often in the nON group, which may indicate increased parvocellular visual pathway vulnerability in demyelinating diseases.

Optic neuritis

Acute optic neuritis is the most common optic neuropathy affecting young adults. Exciting developments have occurred over the past decade in understanding of optic neuritis pathophysiology, and these developments have been translated into treatment trials. In its typical form, optic neuritis presents as an inflammatory demyelinating disorder of the optic nerve, which can be associated with multiple sclerosis. Atypical forms of optic neuritis can occur, either in association with other inflammatory disorders or in isolation. Differential diagnosis includes various optic nerve and retinal disorders. Diagnostic investigations include MRI, visual evoked potentials, and CSF examination. Optical coherence tomography can show retinal axonal loss, which correlates with measures of persistent visual dysfunction. Treatment of typical forms with high-dose corticosteroids shortens the period of acute visual dysfunction but does not affect the final visual outcome. Atypical forms can necessitate prolonged immunosuppressive regimens. Optical coherence tomography and visual evoked potential measures are suitable for detection of neuroaxonal loss and myelin repair after optic neuritis. Clinical trials are underway to identify potential neuroprotective or remyelinating treatments for acutely symptomatic inflammatory demyelinating CNS lesions.

MRI texture heterogeneity in the optic nerve predicts visual recovery after acute optic neuritis

PURPOSE

To test the feasibility of using multi-scale MRI texture analysis to assess optic nerve pathology and to investigate how visual recovery relates to the severity of acute tissue damage in the optic nerve in patients after optic neuritis (ON).

MATERIALS AND METHODS

We recruited 25 patients with acute ON. Retinal nerve fiber layer (RNFL) thickness; MRI lesion length and enhancement; optic nerve area ratio; and multi-scale MRI texture analysis, a measure of structural integrity, were used to assess tissue damage at baseline, and at 6 and 12 months. The recovery in vision was defined as the functional outcome. Eight healthy subjects were imaged for control.

RESULTS

We identified 25 lesions in the affected eyes (9 enhanced) and 5 in the clinically non-affected eyes (none enhanced). At baseline, we found that RNFL values were 20% thicker and lesion texture 14% more heterogeneous in the affected eyes than in the non-affected eyes, and lesion texture ratio of affected to non-affected eyes was greater in patients than in controls. In the affected eyes, visual acuity recovered significantly over 6 (18/23 patients) and 12 months (18/21 patients) when RNFL thickness and optic nerve area ratio decreased over time. Texture heterogeneity in the standard MRI of acute optic nerve lesions was the only measure that predicted functional recovery after ON.

CONCLUSIONS

Tissue heterogeneity may be a potential measure of functional outcome in ON patients and advanced analysis of the texture in standard MRI could provide insights into mechanisms of injury and recovery in patients with similar disorders.

Colour vision impairment is associated with disease severity in multiple sclerosis

Background:

Colour vision assessment correlates with damage of the visual pathway and might be informative of overall brain damage in multiple sclerosis (MS).

Objective:

The objective of this paper is to investigate the association between impaired colour vision and disease severity.

Methods:

We performed neurological and ophthalmic examinations, as well as magnetic resonance imaging (MRI) and optical coherence tomography (OCT) analyses, on 108 MS patients, both at baseline and after a follow-up of one year. Colour vision was evaluated by Hardy, Rand and Rittler plates. Dyschromatopsia was defined if colour vision was impaired in either eye, except for participants with optic neuritis (ON), for whom only the unaffected eye was considered. We used general linear models adjusted for sex, age, disease duration and MS treatment for comparing presence of dyschromatopsia and disease severity.

Results:

Impaired colour vision in non-ON eyes was detected in 21 out of 108 patients at baseline. At baseline, patients with dyschromatopsia had lower Multiple Sclerosis Functional Composite (MSFC) scores and Brief Repeatable Battery-Neuropsychology executive function scores than those participants with normal colour vision. In addition, these patients had thinner retinal nerve fiber layer (RNFL), and smaller macular volume, normalized brain volume and normalized gray matter volume (NGMV) at baseline. Moreover, participants with incident dyschromatopsia after one-year follow-up had a greater disability measured by the Expanded Disability Status Scale and MSFC-20 and a greater decrease in NGMV than participants with normal colour vision.

Conclusions:

Colour vision impairment is associated with greater MS severity.

Trans-synaptic axonal degeneration in the visual pathway in multiple sclerosis

OBJECTIVE

To evaluate the association between the damage to the anterior and posterior visual pathway as evidence of the presence of retrograde and anterograde trans-synaptic degeneration in multiple sclerosis (MS).

METHODS

We performed a longitudinal evaluation on a cohort of 100 patients with MS, acquiring retinal optical coherence tomography to measure anterior visual pathway damage (peripapillary retinal nerve fiber layer [RNFL] thickness and macular volume) and 3T brain magnetic resonance imaging (MRI) for posterior visual pathway damage (volumetry and spectroscopy of visual cortex, lesion volume within optic radiations) at inclusion and after 1 year. Freesurfer and SPM8 software was used for MRI analysis. We evaluated the relationships between the damage in the anterior and posterior visual pathway by voxel-based morphometry (VBM), multiple linear regressions, and general linear models.

RESULTS

VBM analysis showed that RNFL thinning was specifically associated with atrophy of the visual cortex and with lesions in optic radiations at study inclusion (p < 0.05). Visual cortex volume (β = +0.601, 95% confidence interval [CI] = +0.04 to +1.16), N-acetyl aspartate in visual cortex (β = +1.075, 95% CI = +0.190 to +1.961), and lesion volume within optic radiations (β = -2.551, 95% CI = -3.910 to -1.192) significantly influenced average RNFL thinning at study inclusion independently of other confounders, especially optic neuritis (ON). The model indicates that a decrease of 1cm(3) in visual cortex volume predicts a reduction of 0.6μm in RNFL thickness. This association was also observed after 1 year of follow-up. Patients with severe prior ON (adjusted difference = -3.01, 95% CI = -5.08 to -0.95) and mild prior ON (adjusted difference = -1.03, 95% CI = -3.02 to +0.95) had a lower adjusted mean visual cortex volume than patients without ON.

INTERPRETATION

Our results suggest the presence of trans-synaptic degeneration as a contributor to chronic axon damage in MS.

A review of the anterior visual pathway model and the study of vitamin D in demyelinating disease

In recent years, theories about the anti-inflammatory properties of vitamin D in demyelinating disease have been well substantiated by human studies examining relapse reduction, MRI lesion activity and risk of MS conversion. However, the evidence that vitamin D may protect against neurodegeneration has not been established as of yet, and comes with the challenges of a manageable target over a manageable time period. Such challenges might be overcome by the anterior visual pathway (AVP) model of the central nervous system, which allows the non-invasive study (e.g. imaging, electrophysiology and clinical) of form and function within a much shorter time frame than pure clinical activity. This review outlines the state of current knowledge about vitamin D in demyelinating disease, and highlights the potential utility of using the AVP to study its neuroprotective effects.

The afferent visual pathway: designing a structural-functional paradigm of multiple sclerosis

Multiple sclerosis (MS) is a disease of the central nervous system (CNS) believed to arise from a dysfunctional immune-mediated response in a genetically susceptible host. The actual cause of MS is not known, and there is ongoing debate about whether this CNS disorder is predominantly an inflammatory versus a degenerative condition. The afferent visual pathway (AVP) is frequently involved in MS, such that one in every five individuals affected presents with acute optic neuritis (ON). As a functionally eloquent system, the AVP is amenable to interrogation with highly reliable and reproducible tests that can be used to define a structural-functional paradigm of CNS injury. The AVP has numerous unique advantages as a clinical model of MS. In this review, the parameters and merits of the AVP model are highlighted. Moreover, the roles the AVP model may play in elucidating mechanisms of brain injury and repair in MS are described.

Retinal periphlebitis is associated with multiple sclerosis severity

OBJECTIVES

To assess the association of primary retinal inflammation, namely retinal periphlebitis (RP) and microcystic macular edema, with clinical, brain, and retinal imaging biomarkers of multiple sclerosis (MS) severity.

METHODS

One hundred patients with MS underwent a neurologic and ophthalmic examination, MRI, and optical coherence tomography. Disability was assessed using the Expanded Disability Status Scale at baseline and after a 1-year follow-up. The normalized brain volume, the normal-appearing gray matter volume, and T1 lesion volume were assessed at baseline as radiologic biomarkers of disease severity. Retinal nerve fiber layer thickness and macular volume at baseline were used as surrogate markers of axonal damage. We used general linear models adjusted for sex, age, disease duration, and MS treatment to compared adjusted means of these parameters among patients with RP and patients without primary retinal inflammation.

RESULTS

Five patients showed RP, 2 showed microcystic macular edema, and the retina was normal in the remaining 93. Patients with RP had a tendency toward a higher adjusted-mean Expanded Disability Status Scale score at baseline and disability progression after a 1-year follow-up compared with patients without primary retinal inflammation. These patients also had a higher adjusted-mean T1 lesion volume (adjusted differences: 10.4, 95% confidence interval [CI]: 0.6 to 20.2; p = 0.038) and lower T1 brain volume (adjusted differences: -68, 95% CI: -139 to 2; p = 0.059). Patients with RP had a lower adjusted-mean retinal nerve fiber layer thickness (adjusted differences: -13.4, 95% CI: -24.4 to -2.3; p = 0.018) and a trend toward lower macular volume.

CONCLUSIONS

These results support the role of RP as a biomarker of MS severity.

Optical coherence tomography does not support optic nerve involvement in amyotrophic lateral sclerosis

BACKGROUND AND PURPOSE

In recent years a possible non-motor involvement of the nervous system in amyotrophic lateral sclerosis (ALS) has come into the focus of research and has been investigated by numerous techniques. Optical coherence tomography (OCT) - with its potential to reveal neuroaxonal retinal damage - may be an appropriate tool to investigate whether the anterior visual pathway is involved. Our aim was to determine whether OCT-based measures of retinal nerve fiber layer, ganglion cell layer, inner nuclear layer and outer nuclear layer thickness are abnormal in ALS, or correlated with disease severity.

METHODS

Seventy-six ALS patients (144 eyes) and 54 healthy controls (108 eyes; HCs) were examined with OCT, including automated intraretinal macular segmentation. ALS disease severity was determined with the Amyotrophic Lateral Sclerosis Functional Rating Scale - Revised.

RESULTS

There was no significant difference between ALS patients and HCs in any of the examined OCT measures. Moreover, OCT parameters showed no correlation with clinical measures of disease severity.

CONCLUSIONS

These findings indicate that involvement of the anterior visual pathway is not one of the non-motor manifestations of ALS.