Retinal changes in multiple sclerosis: An optical coherence tomography and angiography study

BACKGROUND

Multiple sclerosis (MS) is an autoimmune demyelinating disease of the central nervous system with neuroaxonal damage. It is the principal driver of non-traumatic disability in young adults. Visual symptoms are common and optic neuritis (ON) may be the revealing feature in up to 30% of cases. Structural optical coherence tomography (OCT) represents a biomarker of central nervous system neurodegeneration in MS. OCT-angiography (OCT-A) is a noninvasive tool allowing the study of retinal vasculature and the detection of microvascular damage in neuro-retinal diseases. In this study, we aimed to assess structural and microvascular retinal changes in patients with MS with and without ON and to correlate the findings with visual function and MS disability.

METHODS

We conducted a cross-sectional study including patients diagnosed with MS according to the 2017 McDonald criteria. All patients underwent complete neurological examination with evaluation of the Expanded Disability Status Scale (EDSS) and the Multiple Sclerosis Severity Score (MSSS) and an ophthalmological examination including OCT and OCT-A. Patients were compared with age- and sex-matched healthy subjects. The primary endpoints were assessment of retinal nerve fiber layer (RNFL) thickness, ganglion cell layer (GCL+), and ganglion cell complex (GCL++) thicknesses on OCT. Vascular densities in the superficial capillary plexus (SCP), deep capillary plexus (DCP), and choriocapillaris (CC) were assessed on OCT-A, as well as central avascular zone (CAZ) parameters, lacunarity and fractal dimension.

RESULTS

A total of 160 MS eyes with and without a previous history of ON and 64 age- and gender-matched healthy eyes were analyzed. Among 160 eyes with MS, 69 had a history of ON. We observed a decrease in RNFL and GCL++ thickness in all 12 quadrants in MS patients when compared to healthy controls. Multivariate analysis by linear regression noted a significant correlation for temporal GCL++ and inferonasal RNFL thickness that were decreased in the MS group. A greater decrease in retinal layers thickness was identified in MS patients with a history of ON. On OCT-A, vascular density in (SCP) was significantly reduced in the MS group (P<0.002). A significant correlation between RNFL thickness and retinal vascular density was found but only in less than half of the hourly quadrants. A significant correlation was noted between visual acuity and CC density (P<0.0001). We also noted an inverse correlation between EDSS scores and CC density (P=0.02 and r=-0.275) and between MSSS and RNFL/GCL++ thicknesses.

CONCLUSIONS

RNFL and GCL++ layers were thinner in MS patients with a history of ON and were reversely correlated with disease severity. Moreover, retinal vascular changes were observed in MS even in eyes without ON, and CC was reversely correlated with visual function and current disability. Thus, structural OCT coupled with OCT-A could represent a noninvasive and dynamic biomarker of MS severity and progression.

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.

Multiple Sclerosis: What Methods are Available for the Assessment of Subclinical Visual System Damage?

We aimed to assess the visual fields and optical coherence tomography (OCT) measurements in patients with multiple sclerosis (MS) to detect subclinical visual system disease. The study included 15 MS patients with previous optic neuritis (Group I), 17 MS patients without previous optic neuritis (Group II), and 14 healthy controls (Group III). Each subject underwent standard automated perimetry (SAP), frequency doubling technology perimetry (FDTP), and OCT. The mean deviation of SAP in Group I was lower than those in Groups II (p = .018) and III (p = .001). The pattern standard deviation of SAP in Group I was higher than those in Group III (p < .0001). The mean deviation of FDTP in Groups I and II was lower than those in Group III (p = .0001 and p = .016, respectively). The temporal quadrant of the retinal nerve fibre layer in Group I was thinner than those in Groups II and III (p = .005 and p = .003, respectively). The mean macular volume in Group I was thinner than those in Groups II and III (p = .004 and p = .002, respectively). A single method is inadequate for establishing early and/or mild visual impairment in MS. All conventional and non-conventional techniques are complementary in demonstrating subclinical visual damage in MS.

Progressive Functional and Neuroretinal Affectation in Patients With Multiple Sclerosis Treated With Fingolimod

BACKGROUND

To evaluate the effect of fingolimod in visual function and neuroretinal structures in patients with multiple sclerosis (MS) for a period of 1 year.

METHODS

This longitudinal and observational cohort study included 78 eyes of 78 patients with MS treated with fingolimod. All subjects were evaluated every 3 months during 12 months and compared with 32 patients treated with interferon beta. All patients were examined for high-contrast and low-contrast (2.5% and 1.25%) visual acuity (VA), contrast sensitivity vision (CSV) (using Pelli-Robson and CSV-1000E tests), color vision (Farnsworth D-15 and L'Anthony D-15 desaturated tests), and retinal structural measurements (retinal nerve fiber layer [RNFL] and ganglion cell layer [GCL] thickness) using optical coherence tomography (OCT) technology.

RESULTS

Patients with MS treated with fingolimod for a period of 1 year showed significant reduction in 100% and 1.25% contrast VA (P = 0.009 and 0.008, respectively), an alteration of contrast sensitivity and color perception (Pelli-Robson test, CSV-1000E test, Farnsworth D-15 desaturated test, and L'Anthony D-15 desaturated test; P < 0.001), GCL thickness reduction (P = 0.007), and an average macular central thickness increase of 2.6 μm (P = 0.006). Patients with MS treated with interferon beta did not show significant changes in visual function tests neither in macular thickness measurements, but they showed a significant reduction in GCL and RNFL thicknesses. The reduction in neuroretinal structures observed by OCT was significantly higher in the interferon-beta group, but patients treated with fingolimod showed a significant increase in macular central thickness and a reduction in low contrast vision (P < 0.001).

CONCLUSIONS

Patients with MS treated with fingolimod and with no clinically observable macular edema show a significant change in visual function parameters and average macular central thickness increase compared with those treated with interferon beta. These findings are probably due to subclinical macular edema produced by fingolimod, which might be considered as an indicator for pharmacovigilance of sphingosine-1-phosphate inhibitors to be improved.

Non-linear associations between retinal nerve fibre layer (RNFL) and positive and negative symptoms among men with acute and chronic schizophrenia spectrum disorder

BACKGROUND

Schizophrenia Spectrum Disorder (SSD) is a chronic psychiatric disorder with modest treatment outcomes. Changes in neuronal morphology may be associated with the symptomatology of SSD. In the present study, we compared the retinal nerve fibre layer thickness (RNFLT) of typically developed adults with that of individuals with SSD in both acute and chronic stages.

METHODS

Fifteen healthy adult males (mean age: 36.40 years) and 30 individuals with SSD (mean age: 37.9 years) took part in the study. Among the latter, 15 had a chronic mean SSD for 15.33 years, while 15 were in an acute psychotic phase with a mean illness duration of 12.20 years. Experts rated positive and negative symptoms of SSD. Retinal nerve fibre layer thickness (RNFLT) of all participants was measured with optical coherence tomography (OCT).

RESULTS

Compared to healthy controls, individuals with acute SSD had the lowest macula thickness in the right eye. For nerve fiber layer atrophy, participants with acute SSD showed the largest atrophy (right eye, inferior quadrant). For retinal thickness and macular volume cube, compared to healthy controls, participants with acute SSD had the lowest thickness in the subfield of the right eye. Non-linear associations were observed between RNFL and positive and negative symptoms: e.g., for macula central and subfoveal thickness (left and right eye) and for participants with both acute and chronic SSD, exclusively positive and exclusively negative symptoms (as opposed to prevalently negative with some positive symptoms or prevalently positive with some negative symptoms) were associated with lower volumes. In participants with acute SSD, a longer disease duration was associated with thicker RNFL, while in participants with a chronic SSD a longer disease duration was associated with a thinner RNFL.

CONCLUSION

The present results confirm previous findings that specific neuronal morphological abnormalities can be observed among individuals with SSD. The non-linear associations between neuronal alterations and positive and negative symptomatology suggested that higher pronounced SSD severity appears to be particularly related to morphological changes. Disease duration and RNFL thickness were linearly associated, though, in opposite directions depending on the chronic or acute state.

Is retinal nerve fibre layer thickness correlated with visual function in individuals having optic neuritis?

CLINICAL RELEVANCE

The existence of a correlation between the results of paraclinical retinal imaging and clinical tests such as contrast sensitivity can reduce time and cost in diagnosing optic neuritis (ON).

BACKGROUND

To demonstrate whether changes of peripapillary retinal nerve fibre layer (RNFL) thickness are correlated with the results of visual acuity, contrast sensitivity and colour vision in eyes with acute ON.

METHODS

Thirty patients with acute ON, 23 females and seven males, who had no previous history of ON in neither eye, were examined. Inclusion criteria were: subjects had spherical refraction of less than ±5D, no prior ON or optic disc swelling, no history of amblyopia or colour blindness, and no history or ophthalmoscopic evidence of glaucoma, diabetic retinopathy, or maculopathies. Visual acuity, contrast sensitivity and colour vision were tested and optical coherence tomography was performed for all patients after complete ophthalmologic examinations including refraction, biomicroscopy, and funduscopy with a 90D lens by a neuro-ophthalmologist.

RESULTS

Thirty patients who were 18-45 years old entered the study. There was an inverse correlation between contrast sensitivity and nasal (r = -0.430, p = 0.018), inferior (r = -0.503, p = 0.005) and mean (r = -0.510, p = 0.004) RNFL thickness. The multiple linear regression model, after adjustment for age and sex, showed a significant association between visual acuity and nasal RNFL thickness (coefficient = 0.025, p = 0.032). There was also a significant inverse correlation between contrast sensitivity and nasal (coefficient = -0.003, p = 0.036), inferior (coefficient = -0.006, p = 0.010) and mean (coefficient = -0.007, p = 0.012) RNFL thickness. No significant correlation was found between colour vision and RNFL thickness.

CONCLUSION

Contrast sensitivity is more correlated with changes in RNFL thickness in comparison with visual acuity and colour vision. Contrast sensitivity measurement therefore can be used as one of the first assessments in patients with ON.

Optical Coherence Tomography and Visual Evoked Potentials as Prognostic and Monitoring Tools in Progressive Multiple Sclerosis

Understanding the mechanisms underlying progression and developing new treatments for progressive multiple sclerosis (PMS) are among the major challenges in the field of central nervous system (CNS) demyelinating diseases. Over the last 10 years, also because of some technological advances, the visual pathways have emerged as a useful platform to study the processes of demyelination/remyelination and their relationship with axonal degeneration/protection. The wider availability and technological advances in optical coherence tomography (OCT) have allowed to add information on structural neuroretinal changes, in addition to functional information provided by visual evoked potentials (VEPs). The present review will address the role of the visual pathway as a platform to assess functional and structural damage in MS, focusing in particular on the role of VEPs and OCT, alone or in combination, in the prognosis and monitoring of PMS.

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.

Focal Loss Analysis of Nerve Fiber Layer Reflectance for Glaucoma Diagnosis

Purpose

To evaluate nerve fiber layer (NFL) reflectance for glaucoma diagnosis.

Methods

Participants were imaged with 4.5 × 4.5 mm volumetric disc scans using spectral-domain optical coherence tomography. The normalized NFL reflectance map was processed by an azimuthal filter to reduce directional reflectance bias caused by variation of beam incidence angle. The peripapillary area of the map was divided into 160 superpixels. Average reflectance was the mean of superpixel reflectance. Low-reflectance superpixels were identified as those with NFL reflectance below the fifth percentile normative cutoff. Focal reflectance loss was measured by summing loss in low-reflectance superpixels.

Results

Thirty-five normal, 30 preperimetric, and 35 perimetric glaucoma participants were enrolled. Azimuthal filtering improved the repeatability of the normalized NFL reflectance, as measured by the pooled superpixel standard deviation (SD), from 0.73 to 0.57 dB (P < 0.001, paired t-test) and reduced the population SD from 2.14 to 1.78 dB (P < 0.001, t-test). Most glaucomatous reflectance maps showed characteristic patterns of contiguous wedge or diffuse defects. Focal NFL reflectance loss had significantly higher diagnostic sensitivity than the best NFL thickness parameter (from map or profile): 77% versus 55% (P < 0.001) in glaucoma eyes with the specificity fixed at 99%.

Conclusions

Azimuthal filtering reduces the variability of NFL reflectance measurements. Focal NFL reflectance loss has excellent glaucoma diagnostic accuracy compared to the standard NFL thickness parameters. The reflectance map may be useful for localizing NFL defects.

Translational Relevance

The high diagnostic accuracy of NFL reflectance may make population-based screening feasible.

Tutorial on Biostatistics: Receiver-Operating Characteristic (ROC) Analysis for Correlated Eye Data

Purpose: To demonstrate methods for receiver-operating characteristic (ROC) analysis of correlated eye data.Methods: We applied the Obuchowski's nonparametric approach and cluster bootstrap for estimating and comparing the area under ROC curve (AUC) between different sets of predictors to three datasets with varying inter-eye correlation.Results: In an optic neuritis (ON) study of 152 eyes (80 patients), the AUC of optical coherence tomography retinal nerve fiber layer thickness for diagnosing ON (inter-eye kappa = 0.13) was 0.71 [95% confidence interval (95% CI): 0.622, 0.792] from the naïve approach without accounting for inter-eye correlation was narrower than from nonparametric (95% CI: 0.613, 0.801) or cluster bootstrap (95% CI: 0.614, 0.797) approaches. In an analysis of 198 eyes (135 patients), the baseline Age-related Eye disease Study scale predicted 5-year incidence of advanced age-related macular degeneration (inter-eye kappa = 0.23) with AUC of 0.72. The 95% CI from the naïve approach was slightly narrower (0.645, 0.794) than from the nonparametric (0.641, 0.797) or cluster bootstrap (0.641, 0.793) approaches. In an analysis of 1542 eyes (771 infants), birthweight and gestational age predicted treatment-requiring retinopathy of prematurity (inter-eye kappa = 0.98) with AUC of 0.80. Furthermore, the 95% CI from the naïve approach was narrower (0.769, 0.835) than from the nonparametric (0.755, 0.848) or cluster bootstrap (0.755, 0.845) approaches. 95% CIs for AUC differences between different models were narrower in the naïve approach than the nonparametric or cluster bootstrap approaches.Conclusion: In ROC analysis of correlated eye data, ignoring inter-eye correlation leads to narrower 95% CI with underestimation dependent on magnitude of inter-eye correlation. Nonparametric and cluster bootstrap approaches properly account for inter-eye correlation.

Retinal correlates of neurological disorders

Considering the retina as an extension of the brain provides a platform from which to study diseases of the nervous system. Taking advantage of the clear optical media of the eye and ever-increasing resolution of modern imaging techniques, retinal morphology can now be visualized at a cellular level in vivo. This has provided a multitude of possible biomarkers and investigative surrogates that may be used to identify, monitor and study diseases until now limited to the brain. In many neurodegenerative conditions, early diagnosis is often very challenging due to the lack of tests with high sensitivity and specificity, but, once made, opens the door to patients accessing the correct treatment that can potentially improve functional outcomes. Using retinal biomarkers in vivo as an additional diagnostic tool may help overcome the need for invasive tests and histological specimens, and offers the opportunity to longitudinally monitor individuals over time. This review aims to summarise retinal biomarkers associated with a range of neurological conditions including Alzheimer’s disease (AD), Parkinson’s disease (PD), multiple sclerosis (MS), amyotrophic lateral sclerosis (ALS) and prion diseases from a clinical perspective. By comparing their similarities and differences according to primary pathological processes, we hope to show how retinal correlates can aid clinical decisions, and accelerate the study of this rapidly developing area of research.

Identification of clusters in multifocal electrophysiology recordings to maximize discriminant capacity (patients vs. control subjects)

PURPOSE

To propose a new method of identifying clusters in multifocal electrophysiology (multifocal electroretinogram: mfERG; multifocal visual-evoked potential: mfVEP) that conserve the maximum capacity to discriminate between patients and control subjects.

METHODS

The theoretical framework proposed creates arbitrary N-size clusters of sectors. The capacity to discriminate between patients and control subjects is assessed by analysing the area under the receiver operator characteristic curve (AUC). As proof of concept, the method is validated using mfERG recordings taken from both eyes of control subjects (n = 6) and from patients with multiple sclerosis (n = 15).

RESULTS

Considering the amplitude of wave P1 as the analysis parameter, the maximum value of AUC = 0.7042 is obtained with N = 9 sectors. Taking into account the AUC of the amplitudes and latencies of waves N1 and P1, the maximum value of the AUC = 0.6917 with N = 8 clustered sectors. The greatest discriminant capacity is obtained by analysing the latency of wave P1: AUC = 0.8854 with a cluster of N = 12 sectors.

CONCLUSION

This paper demonstrates the effectiveness of a method able to determine the arbitrary clustering of multifocal responses that possesses the greatest capacity to discriminate between control subjects and patients when applied to the visual field of mfERG or mfVEP recordings. The method may prove helpful in diagnosing any disease that is identifiable in patients' mfERG or mfVEP recordings and is extensible to other clinical tests, such as optical coherence tomography.

Ability of Swept-Source Optical Coherence Tomography to Detect Retinal and Choroidal Changes in Patients with Multiple Sclerosis

Purpose

To evaluate the ability of new swept-source (SS) optical coherence tomography (OCT) technology to detect changes in retinal and choroidal thickness in patients with multiple sclerosis (MS).

Methods

A total of 101 healthy and 97 MS eyes underwent retinal and choroidal assessment using SS Triton OCT (Topcon). Macular thickness and peripapillary data (retinal, ganglion cell layer (GCL+, GCL++) and retinal nerve fiber layer (RNFL) thickness) were analyzed, including choroidal thickness evaluation.

Results

Significant macular thinning was observed in all ETDRS areas (p < 0.001) in MS patients. Peripapillary retinal, RNFL, and GCL ++ thickness showed a significant reduction in patients in all sectors (p < 0.001) except in the nasal quadrant/sector (p > 0.05). GCL+ measurements were found to be reduced in the nasal (p=0.003), inferonasal (p=0.045), and temporal (p=0.001) sectors and total thickness (p < 0.001). Choroidal thickness was reduced in the outer macular ring in MS patients compared with controls (p=0.038).

Conclusion

New swept-source technology for OCT devices detects retinal thinning in MS patients, providing increased depth analysis of the choroid in these patients. MS patients present reduced retinal and choroidal thickness in the macular area and reduced peripapillary retinal, RNFL, and GCL thickness.

Statistical Models of Signal and Noise and Fundamental Limits of Segmentation Accuracy in Retinal Optical Coherence Tomography

Optical coherence tomography (OCT) has revolutionized diagnosis and prognosis of ophthalmic diseases by visualization and measurement of retinal layers. To speed up the quantitative analysis of disease biomarkers, an increasing number of automatic segmentation algorithms have been proposed to estimate the boundary locations of retinal layers. While the performance of these algorithms has significantly improved in recent years, a critical question to ask is how far we are from a theoretical limit to OCT segmentation performance. In this paper, we present the Cramèr-Rao lower bounds (CRLBs) for the problem of OCT layer segmentation. In deriving the CRLBs, we address the important problem of defining statistical models that best represent the intensity distribution in each layer of the retina. Additionally, we calculate the bounds under an optimal affine bias, reflecting the use of prior knowledge in many segmentation algorithms. Experiments using in vivo images of human retina from a commercial spectral domain OCT system are presented, showing potential for improvement of automated segmentation accuracy. Our general mathematical model can be easily adapted for virtually any OCT system. Furthermore, the statistical models of signal and noise developed in this paper can be utilized for the future improvements of OCT image denoising, reconstruction, and many other applications.

Altered birefringence of peripapillary retinal nerve fiber layer in multiple sclerosis measured by polarization sensitive optical coherence tomography

Background

The retina has been used to study the pathophysiology of multiple sclerosis (MS). Peripapillary retinal nerve fiber layer (pRNFL) thinning has been suggested as an ocular biomarker of neurodegeneration in MS. The goal of this project was to determine the birefringence of the pRNFL by measuring the fiber birefringence using polarization sensitive optical coherence tomography (PS-OCT).

Methods

Sixty-six MS patients without history of optic neuritis (age: 39.9 ± 11.0 yrs. old, 53 females and 13 males) and 66 age- and gender-matched normal controls (age: 40.7 ± 11.4 yrs. old) were recruited. Custom built PS-OCT was used to measure phase retardation per unit depth (PR/UD, proportional to the birefringence) and pRNFL thickness in each quadrant of the pRNFL. In addition, clinical manifestation was used to correlate with the pRNFL birefringence.

Results

The pRNFL was thinner in the temporal and inferior quadrants in MS patients compared with normal controls (P < 0.05). The PR/UD of the pRNFL was significantly decreased in MS patients (P < 0.05) in all quadrants except for the nasal quadrant. In both groups, the PR/UD from all four quadrants was not related to the averaged pRNFL thickness (P > 0.05). In MS patients, the PR/UD was not related to the expanded disability status scale (EDSS) nor disease duration (r ranged from − 0.17 to 0.02, P > 0.05).

Conclusion

This is the first study using PS-OCT to study the pRNFL birefringence in MS patients. Decreased birefringence of the pRNFL may indicate microtubule abnormality, and could be a potential biomarker for detecting early neurodegeneration in MS.

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.

Development of a Non-invasive Cerebrovascular Status Algorithm to Estimate Cerebral Perfusion Pressure and Intracranial Pressure in a Porcine Model of Focal Brain Injury

Background

New tools for diagnosis, monitoring, and treatment of elevated intracranial pressure (ICP) or compromised cerebral perfusion pressure (CPP) are urgently needed to improve outcomes after brain injury. Previous success in applying advanced data analytics to build precision monitors based on large, noisy sensor datasets suggested applying the same approach to monitor cerebrovascular status. In these experiments, a new algorithm was developed to estimate ICP and CPP using the arterial pressure waveform.

Methods

Sixty-five porcine subjects were subjected to a focal brain injury to simulate a mass lesion with elevated ICP. The arterial pressure waveform and the measured ICP from these subjects during injury and treatment were then utilized to develop and calibrate an ICP and CPP estimation algorithm. These estimation algorithms were then subsequently evaluated on 14 new subjects.

Results

The root mean square difference between actual ICP and estimated ICP was 2.0961 mmHg. The root mean square difference between the actual CPP and the estimated CPP was 2.6828 mmHg.

Conclusion

A novel ICP or CPP monitor based on the arterial pressure signal produced a very close approximation to actual measured ICP and CPP and warrants further evaluation.

Progressive Changes in the Retinal Nerve Fiber Layer in Patients with Multiple Sclerosis

Purpose

To quantify changes in the retinal nerve fiber layer (RNFL) of patients with multiple sclerosis (MS) over a 1-year time period and to compare the ability of noninvasive diagnostic imaging devices and visual evoked potentials (VEP) to detect axonal loss in these patients.

Methods

Eighty-one patients with MS underwent a complete ophthalmic examination that included assessment of visual acuity and color vision, refractive evaluation, visual field examination, optical coherence tomography (OCT), scanning laser polarimetry (GDx), and measurement of VEP. All the patients were re-evaluated after a period of 12 months in order to quantify any change in the RNFL. Only one randomly chosen eye from each patient was included in the study.

Results

Statistically significant differences between the 2 examinations were recorded for the overall mean and inferior RNFL thickness and the macular volume, as assessed by OCT, as well as for the temporal-superior-nasal-inferior-temporal average standard deviation provided by GDx. The greatest differences were obtained for the mean RNFL thickness (90.46 μm vs 85.96 μm). Changes in the optic nerve were detected by structural measurements but not by functional assessments.

Conclusions

Axonal loss in the optic nerve of patients with MS is greater than that expected in healthy subjects, regardless of the presence of a previous optic neuritis.

Retinal Architecture and Melanopsin-Mediated Pupillary Response Characteristics: A Putative Pathophysiologic Signature for the Retino-Hypothalamic Tract in Multiple Sclerosis

Importance

A neurophysiologic signature of the melanopsin-mediated persistent constriction phase of the pupillary light reflex may represent a surrogate biomarker for the integrity of the retinohypothalamic tract, with potential utility for investigating alterations in homeostatic mechanisms associated with brain disorders and implications for identifying new treatments.

Objective

To characterize abnormalities of retinal architecture in patients with multiple sclerosis (MS) and corresponding alterations in the melanopsin-mediated sustained pupillary constriction response.

Design, Setting, and Participants

The case-control study was an experimental assessment of various stimulus-induced pupillary response characteristics and was conducted at a university clinical center for MS from September 6, 2012, to February 2015. Twenty-four patients with MS (48 eyes) and 15 individuals serving as controls (30 eyes) participated. The melanopsin-mediated, sustained pupillary constriction phase response following cessation of a blue light stimulus was compared with the photoreceptor-mediated pupillary constriction phase response following cessation of a red light stimulus. Optical coherence tomography was used to characterize the association between pupillary response characteristics and alterations in retinal architecture, specifically, the thickness of the retinal ganglion cell layer and inner plexiform layer (GCL + IPL).

Main Outcomes and Measures

Association of pupillary response characteristics with alterations in retinal architecture.

Results

Of 24 patients with MS included in the analysis, 17 were women (71%); mean (SD) age was 47 (11) years. Compared with eyes from individuals with MS who had normal optical coherence tomography-derived measures of retinal GCL + IPL thickness, eyes of patients who had GCL + IPL thickness reductions to less than the first percentile exhibited a correspondingly significant attenuation of the melanopsin-mediated sustained pupillary response (mean [SD] pupillary diameter ratios at a point in time, 0.18 [0.1] vs 0.33 [0.09]; P < .001, generalized estimating equation models accounting for age and within-patient intereye correlations).

Conclusions and Relevance

In this case-control study, attenuation of the melanopsin-mediated sustained pupillary constriction response was significantly associated with thinning of the GCL + IPL sector of the retina in the eyes of patients with MS, particularly those with a history of acute optic neuritis. Melanopsin-containing ganglion cells in the retina represent, at least in part, the composition of the retinohypothalamic tract. As such, our findings may signify the ability to elucidate a putative surrogate neurophysiologic signature that correlates with a constellation of homeostatic mechanisms in both health and illness.

Validity of low-contrast letter acuity as a visual performance outcome measure for multiple sclerosis

Low-contrast letter acuity (LCLA) has emerged as the leading outcome measure to assess visual disability in multiple sclerosis (MS) research. As visual dysfunction is one of the most common manifestations of MS, sensitive visual outcome measures are important in examining the effect of treatment. Low-contrast acuity captures visual loss not seen in high-contrast visual acuity (HCVA) measurements. These issues are addressed by the MS Outcome Assessments Consortium (MSOAC), including representatives from advocacy organizations, Food and Drug Administration (FDA), European Medicines Agency (EMA), National Institute of Neurological Disorders and Stroke (NINDS), academic institutions, and industry partners along with persons living with MS. MSOAC goals are acceptance and qualification by regulators of performance outcomes that are highly reliable and valid, practical, cost-effective, and meaningful to persons with MS. A critical step is elucidation of clinically relevant benchmarks, well-defined degrees of disability, and gradients of change that are clinically meaningful. This review shows that MS and disease-free controls have similar median HCVA, while MS patients have significantly lower LCLA. Deficits in LCLA and vision-specific quality of life are found many years after an episode of acute optic neuritis, even when HCVA has recovered. Studies reveal correlations between LCLA and the Expanded Disability Status Score (EDSS), Multiple Sclerosis Functional Composite (MSFC), retinal nerve fiber layer (RNFL) and ganglion cell layer plus inner plexiform layer (GCL + IPL) thickness on optical coherence tomography (OCT), brain magnetic resonance imaging (MRI), visual evoked potential (VEP), electroretinogram (ERG), pupillary function, and King-Devick testing. This review also concludes that a 7-point change in LCLA is clinically meaningful. The overall goal of this review is to describe and characterize the LCLA metric for research and clinical use among persons with MS.

How strong is the relationship between glaucoma, the retinal nerve fibre layer, and neurodegenerative diseases such as Alzheimer's disease and multiple sclerosis?

Glaucoma is a neurodegenerative disorder with established relationships with ocular structures such as the retinal nerve fibre layer (RNFL) and the ganglion cell layer (GCL). Ocular imaging techniques such as optical coherence tomography (OCT) allow for quantitative measurement of these structures. OCT has been used in the monitoring of glaucoma, as well as investigating other neurodegenerative conditions such as Alzheimer's disease (AD) and multiple sclerosis (MS). In this review, we highlight the association between these disorders and ocular structures (RNFL and GCL), examining their usefulness as biomarkers of neurodegeneration. The average RNFL thickness loss in patients with AD is 11 μm, and 7 μm in MS patients. Most of the studies investigating these changes are cross-sectional. Further longitudinal studies are required to assess sensitivity and specificity of these potential ocular biomarkers to neurodegenerative disease progression.

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.

Clinical trials to clinical use: using vision as a model for multiple sclerosis and beyond

Optical coherence tomography (OCT) has made possible the structure-function correlations that uniquely characterize the afferent visual pathway as a model for understanding multiple sclerosis (MS) and for developing new treatments. During the past decade, OCT measures of retinal nerve fiber layer (RNFL) and ganglion cell/inner plexiform layer (GCL + IPL) thickness have evolved from being a means to validate visual function tests, such as low-contrast letter acuity, to provide a window on the axonal and neuronal loss that are now widely recognized as contributors to permanent visual dysfunction in MS. Although acute optic neuritis (ON) leads to thinning of the RNFL by 20%-40% within 3 months after a single episode, thinning of the RNFL and GCL + IPL occur over time in MS eyes even in the absence of an acute ON history. As such, OCT and its functional and patient-reported correlates of low-contrast acuity and vision-specific quality of life (QOL) have now been incorporated into MS clinical trials. Results of an ongoing, phase 2 trial of a remyelinating agent that uses acute ON as a model for assessing therapeutic efficacy will define even further the important role for OCT in documenting structural changes as we move forward from clinical trials to clinical use.

Neuromyelitis optica and multiple sclerosis: Seeing differences through optical coherence tomography

Neuromyelitis optica (NMO) is an inflammatory autoimmune disease of the central nervous system that preferentially targets the optic nerves and spinal cord. The clinical presentation may suggest multiple sclerosis (MS), but a highly specific serum autoantibody against the astrocytic water channel aquaporin-4 present in up to 80% of NMO patients enables distinction from MS. Optic neuritis may occur in either condition resulting in neuro-anatomical retinal changes. Optical coherence tomography (OCT) has become a useful tool for analyzing retinal damage both in MS and NMO. Numerous studies showed that optic neuritis in NMO typically results in more severe retinal nerve fiber layer (RNFL) and ganglion cell layer thinning and more frequent development of microcystic macular edema than in MS. Furthermore, while patients’ RNFL thinning also occurs in the absence of optic neuritis in MS, subclinical damage seems to be rare in NMO. Thus, OCT might be useful in differentiating NMO from MS and serve as an outcome parameter in clinical studies.

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.

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.

Relationship between Structural and Functional Assessment of the Visual System in Mildly Disabled Relapsing-Remitting Multiple Sclerosis Patients

Studies that explored the anterior visual pathway in the patients with multiple sclerosis (MS) have demonstrated contradictory results about the correlation between structural and functional status of optic nerve and retina. We aimed to investigate the functional and structural findings in our cohort of mildly disabled relapsing-remitting MS patients. A total of 134 eyes (80 eyes of the patients with MS and 54 eyes of the control group) were investigated. Eyes of MS patients were divided into two groups-as eyes with history of optic neuritis (ON group) and without history of optic neuritis (NON group). Ophthalmological investigation including visual evoked potentials, standard automated perimetry, and optical coherence tomography were performed for all participants. Retinal and macular thicknesses were significantly decreased in ON and NON groups compared with controls. Also, visual evoked potential latencies and visual field loss were worse in the both MS groups compared with control group. We did not find any correlation between visual evoked potentials and retinal or macular thickness values but visual field parameters were correlated between retinal and macular layer loss in the NON group. According to our results and some previous studies, although both functional and structural changes were detected in patients with MS, functional status markers do not always show parallelism (or synchrony) with structural changes, especially in eyes with history of optic neuritis.

Visual issues in multiple sclerosis

Multiple sclerosis has several ophthalmic manifestations, including optic neuritis, internuclear ophthalmoplegia, and nystagmus. The presentation, treatment, and prognosis of visual complaints secondary to multiple sclerosis are discussed. Additionally, the use of optical coherence tomography and complications related to the use of fingolimod are considered.

Retinal nerve fiber layer thickness and cognitive ability in older people: the Lothian Birth Cohort 1936 study

Background

This study aims to examine the relationship between the retinal nerve fiber layer (RNFL) thickness as measured by optical coherence tomography (OCT) and lifetime cognitive change in healthy older people.

Methods

In a narrow-age sample population from the Lothian Birth Cohort 1936 who were all aged approximately 72 years when tested, participants underwent RNFL measurements using OCT. General linear modeling was used to calculate the effect of RNFL thickness on three domains; general cognitive ability (g-factor), general processing speed (g-speed) and general memory ability (g-memory) using age at time of assessment and gender as co-variates.

Results

Of 105 participants, 96 completed OCT scans that were of suitable quality for assessment were analyzed. Using age and gender as covariates, we found only one significant association, between the inferior area RNFL thickness and g-speed (p = 0.049, η² = 0.045). Interestingly, when we included age 11 IQ as a covariate in addition to age and gender, there were several statistically significant associations (p = 0.029 to 0.048, η² = 0.00 to 0.059) in a negative direction; decreasing scores on measures of g-factor and g-speed were associated with increasing RNFL thickness (r = −0.229 to −0.243, p < 0.05). No significant associations were found between RNFL thickness and g-memory ability. When we considered the number of years of education as a covariate, we found no significant associations between the RNFL thickness and cognitive scores.

Conclusions

In a community dwelling cohort of healthy older people, increased RNFL thickness appeared to be associated with lower general processing speed and lower general cognitive ability when age 11 IQ scores were included as a covariate.

Measures of visual pathway structure and function in MS: Clinical usefulness and role for MS trials

Over the past decade, the visual pathway in multiple sclerosis (MS) has become an important system for assessing both patient function and disease burden. Abnormalities of low-contrast acuity, long recognized as important correlates of driving, facial recognition, and other activities of daily living, are now noted to be common among patients with MS, even among those with no history of acute optic neuritis (ON). Low-contrast letter acuity scores correlate well with brain MRI lesion burden, visual-evoked potential (VEP) amplitudes, health-related quality of life (QOL), and retinal nerve fiber layer (RNFL) axonal and neuronal loss as measured by optical coherence tomography (OCT). Axonal and neuronal degeneration in MS is likely to be an important cause of visual impairment and disability, particularly among patients with progressive MS subtypes. With the advent of OCT and the use of low-contrast letter acuity charts in MS research and clinical trials, the structure-function correlations afforded by the anterior visual pathway can be assessed and potentially harnessed as a model for testing new therapies. Recent advances in OCT, such as high resolution spectral-domain techniques and computerized algorithms for image analysis, have allowed for measurement of specific retinal layers, including the ganglion cell (GCL) neuronal layer and its intimately associated, thin layer of interneurons, the inner plexiform layer (IPL). Longitudinal collaborative studies of GCL+IPL thinning and RNFL axonal loss are providing an in vivo view into neuroretinal pathology, and are providing new insights into how the visual pathway may reflect overall mechanisms of disease in MS.

Retinal damage in multiple sclerosis disease subtypes measured by high-resolution optical coherence tomography

Background. Optical coherence tomography (OCT) has facilitated characterisation of retinal alterations in MS patients. Only scarce and in part conflicting data exists on different MS subtypes. Objective. To analyse patterns of retinal changes in different subtypes of MS with latest spectral-domain technology. Methods. In a three-centre cross-sectional study 414 MS patients and 94 healthy controls underwent spectral-domain OCT examination. Results. Eyes of MS patients without a previous optic neuritis showed a significant reduction of both retinal nerve fibre layer (RNFL) thickness and total macular volume (TMV) compared to healthy controls independent of the MS subtype (P < 0.001 for all subtypes). RNFL thickness was lower in secondary progressive MS (SPMS) eyes compared to relapsing-remitting MS (RRMS) eyes (P = 0.007), and TMV was reduced in SPMS and primary progressive MS (PPMS) eyes compared to RRMS eyes (SPMS: P = 0.039, PPMS: P = 0.005). Independent of the subtype a more pronounced RNFL thinning and TMV reduction were found in eyes with a previous optic neuritis compared to unaffected eyes. Conclusion. Analysis of this large-scale cross-sectional dataset of MS patients studied with spectral-domain OCT confirmed and allows to generalize previous findings. Furthermore it carves out distinct patterns in different MS subtypes.

Comparative study of the retinal nerve fibre layer thickness performed with optical coherence tomography and GDx scanning laser polarimetry in patients with primary open-angle glaucoma

Background

We compared the parameters of retinal nerve fibre layer in patients with advanced glaucoma with the use of different OCT (Optical Coherence Tomograph) devices in relation to analogical measurements performed with GDx VCC (Nerve Fiber Analyzer with Variable Corneal Compensation) scanning laser polarimetry.

Material/Methods

Study subjects had advanced primary open-angle glaucoma, previously treated conservatively, diagnosed and confirmed by additional examinations (visual field, ophthalmoscopy of optic nerve, gonioscopy), A total of 10 patients were enrolled (9 women and 1 man), aged 18–70 years of age. Nineteen eyes with advanced glaucomatous neuropathy were examined. 1) Performing a threshold perimetry Octopus, G2 strategy and ophthalmoscopy of optic nerve to confirm the presence of advanced primary open-angle glaucoma; 2) performing a GDx VCC scanning laser polarimetry of retinal nerve fibre layer; 3) measuring the retinal nerve fibre layer thickness with 3 different optical coherence tomographs.

Results

The parameters of the retinal nerve fibre layer thickness are highly correlated between the GDx and OCT Stratus and 3D OCT-1000 devices in mean retinal nerve fibre layer thickness, retinal nerve fibre layer thickness in the upper sector, and correlation of NFI (GDx) with mean retinal nerve fibre layer thickness in OCT examinations. Absolute values of the retinal nerve fibre layer thickness (measured in μm) differ significantly between GDx and all OCT devices.

Conclusions

Examination with OCT devices is a sensitive diagnostic method of glaucoma, with good correlation with the results of GDx scanning laser polarimetry of the patients.

Time-Domain and Spectral-Domain Optical Coherence Tomography of Retinal Nerve Fiber Layer in MS Patients and Healthy Controls

Objective. The aim of this study was to compare retinal nerve fiber layer thickness (RNFLT) between spectral-domain (SD-) and time-domain optical coherence tomography (TD-OCT) in MS patients and healthy controls (HC). Furthermore, RNFLT between MS eyes with and without optic neuritis (ON) and HC should be explored. Finally, the relationship between RNFLT, disease duration, EDSS, and disease modifying therapy (DMT) should be established. Design. Prospective, cross-sectional study. Participants. 28 MS patients and 35 HC. Methods. Both groups underwent TD- and SD-OCT measurements. RFNLT was correlated between the two machines and between MS eyes with and without ON and HC. Furthermore, RNFLT was correlated to disease duration, EDSS and DMT. Results. A strong correlation (Pearson's r = 0.921, P < 0.001), but a statistically significant difference of 2 μm (P < 0.001), was found between the two devices. RNFLT was significantly different between MS eyes with history of ON (mean RFNLT (SD) 72.21 μm (15.83 μm)), MS eyes without history of ON 93.03 μm (14.25 μm), and HC 99.07 μm (7.23 μm) (P < 0.001). Conclusions. The measurements between different generation of OCT machines are not interchangeable, which should be taken into account if comparing results between different machines and switching OCT machine in longitudinal studies.

Nerve fiber layer and macular thinning measured with different imaging methods during the course of acute optic neuritis

PURPOSE

To compare retinal nerve fiber layer thickness (RNFLT) and inner macula thickness changes measured with Fourier-domain optical coherence tomography (FD-OCT) and scanning laser polarimetry during the course of acute optic neuritis (ON).

METHODS

Nine eyes of 7 consecutive patients with multiple sclerosis (MS) were prospectively imaged from the onset of ON for 6 to 12 months. Nine healthy eyes were imaged for 12 to 19 months.

RESULTS

Retinal nerve fiber layer thickness measured with FD-OCT initially increased in all eyes with diffuse optic disc edema. Inner macula thickness and polarimetric RNFLT decreased already in the acute phase, in all eyes. All parameters stabilized at 2 to 5 months. The relative structural loss was different with the different methods. Poor image quality with polarimetry occurred in 2 eyes in the acute phase of ON. In the control eyes all parameters were stable.

CONCLUSIONS

Change of RNFLT and macular thickness during the course of acute ON in MS strongly depends on the method used for the measurement. Inner macula thickness, measured with FD-OCT, was especially useful for the follow-up, since it was not influenced by initial disc edema and had consistently high image quality.

Degeneration of retinal layers in multiple sclerosis subtypes quantified by optical coherence tomography

BACKGROUND

Optical coherence tomography can be used to assess retinal degeneration in multiple sclerosis (MS). Thinning of the retinal nerve fibre layer and macular thickness have been well characterized, but newer devices allow quantification of all retinal layers.

OBJECTIVES

The objective of this study was to evaluate the thickness of the paramacular retina, peripapillary retinal nerve fibre layer, and deeper paramacular layers in MS patient subgroups, using state-of-the-art optical coherence tomography.

METHODS

Using a Heidelberg Engineering Spectralis device, we performed paramacular volumetric retinal scans and circular peripapillary fibre-layer scans, manually segmenting different retinal layers into single horizontal foveal scans in 95 patients with definite MS (42 relapsing-remitting, 41 secondary progressive, 12 primary progressive), plus 91 age- and sex-matched controls.

RESULTS

Even without a history of optic neuritis, all MS subgroups had significant thinning of the peripapillary retinal nerve fibre layer, the paramacular retinal thickness and the retinal ganglion cell- and inner plexiform layer. Only in primary progressive MS was the inner nuclear layer significantly reduced.

CONCLUSIONS

Our findings indicate a primary retinal pathology involving the inner nuclear layer in primary progressive MS. Results in eyes without history of optic neuritis suggest possible subclinical episodes of optic neuritis or retrograde trans-synaptic degeneration of retinal ganglion cells and their axons.

Vision in multiple sclerosis: the story, structure-function correlations, and models for neuroprotection

Visual dysfunction is one of the most common clinical manifestations of multiple sclerosis (MS). Just over a decade ago, MS clinical trials did not include visual outcomes, but experts recognized the need for more sensitive measures of visual function. Low-contrast letter acuity emerged as the leading candidate to measure visual disability in MS, and subsequent studies found low-contrast acuity testing to correlate well with brain MRI lesion burden, visual-evoked potentials, quality of life (QOL), and retinal nerve fiber layer (RNFL) loss, as measured by optical coherence tomography (OCT). OCT in MS has allowed for assessment of structure-function correlations that make the anterior visual pathway and acute optic neuritis (ON) ideal models for testing novel agents for neuroprotection and repair. New therapies that reduce axonal loss by neuroprotective or myelin repair mechanisms can now be assessed noninvasively by OCT and coupled with visual function data. Based on OCT studies in MS, RNFL thickness is reduced significantly among patients (92 μm) vs controls (105 μm) and is particularly reduced in MS eyes with a history of ON (85 μm). Worsening of visual function by a clinically significant ≥ 7 letters or approximately 1.5 lines for low-contrast acuity is associated with approximately 4.5 μm reductions in RNFL thickness in MS eyes. Longitudinal studies of OCT have also shown RNFL axonal loss over time that occurs even in the absence of acute ON and that correlates with clinically meaningful worsening of vision and QOL, even in patients with benign MS. The latest OCT investigations involve high-resolution spectral-domain (SD) OCT with segmentation and measurement of specific retinal layers using computerized algorithms. These methods allow quantitation of ganglion cell (neuronal) layer loss and axonal degeneration in MS in vivo. In this review, we examine the data from these studies and ongoing trials that highlight the entity of ON as a model to investigate neuroprotection and neurorepair. In doing so, we also present representative group data from studies that have examined visual function, OCT measures, and QOL scales in patients with MS and ON and disease-free controls. These data, and those from recent meta-analyses, may be used to provide reference values for the development of clinical trial protocols.

Challenges to clinical trials in multiple sclerosis: outcome measures in the era of disease-modifying drugs

PURPOSE OF REVIEW

This review summarizes standard and evolving outcome measures in multiple sclerosis (MS) clinical trials.

RECENT FINDINGS

Progress in the development of MS treatments has led to an increasing number of clinical trials and a need for sensitive, timely, and clinically relevant outcome measures. Relapse rate and the Expanded Disability Status Scale remain the standard clinical outcome measures, but the MS Functional Composite continues to gain additional validation as a meaningful outcome measure. The uncertain relationship between MRI outcome measures and clinical disability has been a persistent challenge in MS clinical trials, but there is increasing evidence supporting a correlation between MRI changes and disability in relapsing-remitting MS patients. Additionally, new imaging techniques are being developed to further increase the sensitivity of MRI as a tool in MS clinical trials. Optical coherence tomography is another outcome measure gaining influence in clinical trials. Some of the greatest challenges remain in the subset of primary progressive MS clinical trials in which brain atrophy appears to be the most promising imaging outcome measure, but the optimal clinical measures and study durations are still uncertain.

SUMMARY

Progress in MS clinical trials requires critical evaluation of existing and future outcome measures and their relationships to one another.

RNFL thickness in MS-associated acute optic neuritis using SD-OCT: critical interpretation and limitations

PURPOSE

Axonal loss is considered a key prognostic factor in diagnosing and monitoring the progress of multiple sclerosis (MS). The purpose of our research was to determine whether the measurement of retinal nerve fibre layer thickness (RNFLT) as measured with high-resolution spectral-domain optical coherence tomography (SD-OCT) differs between optic nerve injury following acute optic neuritis (ON) or following unregistered subclinical axonal damage in patients with MS.

METHODS

High-resolution SD-OCT measurements of RNFLT were initially carried out in the acute phase of ON and again after 3 months, in 25 patients with clinical definite MS and 25 sex- and age-matched healthy controls, all at the University Eye Hospital, Vienna.

RESULTS

Conventional OCT-based RNFLT analysis correctly identified all three patients with initial RNFL swelling. However, only two of three acute ON eyes with a history of ON were registered with RNFLT decrease in seven peripapillary sectors (PPs). The remaining have only been revealed using RNFLT symmetry comparison. Two of 22 (9%) first-episode ON eyes were labelled as pathologic. The number and metric RNFL values of pathologically labelled PPs remained unchanged after 3 months. Our age- and sex-match-based measurement model, with patients with MS being plotted individually and towards the fellow eye, identified all acute ON eyes (with a history of prior ON) with RNFLT reduction in 11 PPs. A global RNFL loss was registered in 36.4% (eight of 22 eyes). However, in 72%, or 16 of 22 ON eyes presenting with first episode of acute ON, a segmental RNFL loss was initially registered in 39 PPs upon baseline examination. The number of PPs with identified axonal decrease increased to a total of 48 PPs within the observational period.

CONCLUSIONS

Spectral-domain optical coherence tomography imaging of identical scanning locations, combined with an optimized scan centring around the optic disc, offers the technological potential of detecting prior, subtle, clinically unregistered optic nerve injury within MS individuals. Significant discrepancy in RNFLT to the potential ON eye may be achieved by comparing OCT metrics with the fellow eye and a sufficient number of age and sex-matched controls.

Retinal Nerve Fibre Layer and Macular Thinning in Spinocerebellar Ataxia and Cerebellar Multisystem Atrophy

The spinocerebellar ataxias, like all neurodegenerative diseases, lack objective disease- and stage-specific biomarkers. Based on reports of clinically evident optic disc atrophy or retinal disease in some ataxia patients, and the discovery that pre-symptomatic retinal thinning occurs in other neurologic diseases such as multiple sclerosis, we tested the hypothesis that subclinical neuronal or axonal loss in the retina could occur in the degenerative ataxias. Spectral domain optical coherence tomography was performed on 29 ataxia patients with genetically proven spinocerebellar ataxia (SCA) 1, 2, 3, or 6, or multisystem atrophy type C (MSA-C) and 27 age-matched normal subjects. Ataxia patients were assessed using the scale for assessment and rating of ataxia. Compared with normal control subjects, retinal nerve fibre layer (RNFL) thickness was reduced for patients with SCA2 and SCA3, and thickness in the macular region was reduced for all SCAs but SCA2.

Comparison of retinal nerve fibre layer thickness with visual evoked potential and visual field in patients with multiple sclerosis

BACKGROUND

To evaluate retinal nerve fibre layer thickness and to compare results with visual evoked potentials and visual field in patients with multiple sclerosis.

DESIGN

A prospective, case-control study, university hospital setting.

PARTICIPANTS

Seventy-three eyes of 37 multiple sclerosis patients and 74 eyes of 37 healthy subjects.

METHODS

All patients underwent a complete neurological and ophthalmological examination and peri-papillary retinal nerve fibre layer thickness was evaluated using scanning laser polarimetry (GDx). Furthermore, visual evoked potential and visual field testing were performed.

MAIN OUTCOME MEASURES

The χ(2) test, Student's t-test, Mann-Whitney U-test and Pearson's correlation coefficient analysis of the GDx, visual evoked potential and visual field testing parameters.

RESULTS

GDx measurements showed significantly more retinal nerve fibre layer damage in the patients than in the control groups. Comparison of the GDx parameters between patients with optic neuritis and non-optic neuritis demonstrated a statistically significant difference in symmetry (P = 0.046) and superior/nasal parameters (P = 0.009). A correlation was found between the number, superior and inferior ratio parameters, and P100 amplitude obtained with visual evoked potential in patients with non-optic neuritis. Additionally, there was a correlation between the number, inferior ratio and superior/nasal parameters, and the mean deviation of visual field in the non-optic neuritis group.

CONCLUSIONS

For retinal nerve fibre layer thickness measurements in multiple sclerosis patients, the GDx, along with other techniques, such as visual evoked potential, can be used as a diagnostic and follow-up criterion, particularly in patients without optic neuritis.