In vivo assessment of retinal neuronal layers in multiple sclerosis with manual and automated optical coherence tomography segmentation techniques

Functional optical coherence tomography at altitude: retinal microvascular perfusion and retinal thickness at 3,800 meters

Cerebral hypoxia is a serious consequence of several cardiorespiratory illnesses. Measuring the retinal microvasculature at high altitude provides a surrogate for cerebral microvasculature, offering potential insight into cerebral hypoxia in critical illness. Additionally, while sex-specific differences in cardiovascular diseases are strongly supported, few have focused on differences in ocular blood flow. We evaluated the retinal microvasculature in males (n=11) and females (n=7) using functional optical coherence tomography at baseline (1,130m) (Day 0), following rapid ascent (Day 2) and prolonged exposure (Day 9) to high altitude (3,800m). Retinal vascular perfusion density (rVPD; an index of total blood supply), retinal thickness (RT; reflecting vascular and neural tissue volume) and arterial blood were acquired. As a group, rVPD increased on Day 2 vs. Day 0 (p<0.001) and was inversely related to PaO₂ (R²=0.45; p=0.006). By Day 9, rVPD recovered to baseline, but was significantly lower in males vs. females (p=0.007). RT was not different on Day 2 vs. Day 0 (p>0.99) but was reduced by Day 9 relative to Day 0 and Day 2 (p<0.001). RT changes relative to Day 0 were inversely related to changes in PaO₂ on Day 2 (R²=0.6; p=0.001) and Day 9 (R²=0.4; p=0.02). RT did not differ between sexes. These data suggest differential time course and regulation of the retina during rapid ascent and prolonged exposure to high altitude and are the first to demonstrate sex-specific differences in rVPD at high altitude. The ability to assess intact microvasculature contiguous with the brain has widespread research and clinical applications.

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

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

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.

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.

The effect of hemodialysis on individual retinal layer thickness

PURPOSE

The aim of this study was to employ newly developed advanced image analysis software to evaluate changes in retinal layer thickness following hemodialysis.

METHODS

A non-randomized prospective study of patients with end-stage renal disease assessed on the same day before and after hemodialysis. Intraocular pressure and central corneal thickness were analyzed, and spectral domain optical coherence tomography results were automatically segmented using the Orion software and then compared. All patients had normal retinal optical coherence tomography findings before hemodialysis.

RESULTS

Of the 31 suitable end-stage renal disease patients treated with hemodialysis who provided consent to participate, seven were unable to complete all evaluations, leaving 24 patients for analysis in the final study group. Their mean age was 66.67±14.3 years (range: 35-88), and 62.5% were males. Mean central corneal thickness did not change following hemodialysis (563.4±30.2 µm to 553.1±47.2 µm, p=.247), while mean intraocular pressure decreased (14.48±2.5 mmHg to 13.16±2.28 mmHg, p=.028). Individual mean retinal layer thickness showed no significant change, including the retinal nerve fiber layer (40.9±6.8 µm to 40.1±5.2 µm, p=.412), the ganglion cell and the inner plexiform layer (68.66±8 µm to 69.03±7.6 µm, p=.639), and the photoreceptor layer (50.26±2.8 µm to 50.32±3.1 µm, p=.869). Total retinal thickness similarly remained constant, with a mean of 303.7±17.3 µm before and 304.33±18.4 µm after hemodialysis (p=.571).

CONCLUSIONS

Thickness of retinal layers, as assessed by individual segmentation, and central corneal thickness were not affected by hemodialysis treatment, while intraocular pressure was significantly reduced among patients with end-stage renal disease without pre-existing ocular pathology who were undergoing hemodialysis. These results support the view that hemodialysis does not have a negative impact on the retinal morphology of end-stage renal disease patients, who comprise a population with high rates of diabetic and/or hypertensive retinopathy as well as vision-threatening complications.

Inner retinal thickening affects microperimetry thresholds in the presence of photoreceptor thinning in patients with RPGR retinitis pigmentosa

BACKGROUND

Loss of photoreceptors cause degeneration in areas of the retina beyond the photoreceptors. The pattern of changes has implications for disease monitoring and measurement of functional changes. The aim of the study was to study the changes in inner retinal structure associated with photoreceptor disease, and the impact of these on microperimetry threshold.

METHODS

This retrospective cohort study was conducted on optical coherence tomography (OCT) images and microperimetry tests collected between 2013 and 2019. 22 eyes with RPGR retinitis pigmentosa completed both OCT imaging and microperimetry assessment. 18 control eyes underwent OCT imaging. Photoreceptor layer and inner retinal thickness calculated for different eccentric areas were obtained. The relationship between the photoreceptor layer and inner retinal thickness, and microperimetry threshold was explored.

RESULTS

Central 1° photoreceptor layer and inner retinal thickness were 96±34 and 139±75 μm in RPGR patients, and 139±15 and 62±14 μm in controls. Photoreceptor layer thickness differed between patient and control groups across increasing visual field areas (p<0.01, Kruskal-Wallis 1-way ANOVA), whereas the inner retinal thickness significantly differed between groups for the central 1° and 3° only. Microperimetry thresholds were explained by a combination of photoreceptor thickness (coefficient 0.15, 95% CI 0.13 to 0.18) and inner retinal thickness (coefficient 0.05, 95% CI 0.03 to 0.06).

CONCLUSION

OCT shows evidence of remodelling in the inner retinal layers secondary to photoreceptor disease. This appears to have an impact on microperimetry threshold measurements.

Differences in morphology and visual function of myelin oligodendrocyte glycoprotein antibody and multiple sclerosis associated optic neuritis

Background

Myelin oligodendrocyte glycoprotein immunoglobulin G associated optic neuritis (MOG-ON) is a recently described entity. Recent studies have shown that MOG-ON has a more severe clinical presentation than classic optic neuritis (ON).

Objective

This study aimed to define morphological characteristics of MOG-ON, correlate these with clinical characteristics and compare them with multiple sclerosis associated ON (MS-ON) and healthy controls (CTRL).

Methods

In a retrospective study, we included MOG-ON and MS-ON patients seen between 2011 and 2018 at the University Hospital Bern. Data from clinical examination, perimetry, and optical coherence tomography (OCT) were analyzed.

Results

A total of 66 eyes of 43 patients were included; 22 MS-ON and 33 CTRL eyes were sex- and age-matched to 11 MOG-ON eyes. We found significantly worse visual acuity at nadir, but better recovery and thinner global peripapillary retinal nerve fiber layer thickness in MOG-ON patients compared to MS-ON patients. Both groups exhibited irregular thinning of the macular ganglion cell layer. Furthermore, the visual acuity and visual field parameters correlated to retinal layer thickness only in MOG-ON eyes.

Conclusion

In comparison to MS-ON, MOG-ON is associated with more prominent acute vision loss and more pronounced global thinning of the pRNFL. Both entities result in similar final visual acuity and atrophy of the macular ganglion cell layer.

Promising recovery biomarkers after first event acute demyelinating optic neuritis

BACKGROUND

Acute demyelinating optic neuritis is often a first episode of subsequent CNS demyelinating disease, most frequently multiple sclerosis (MS). The majority of the patients have substantial recovery of the high contrast visual acuity (HCVA) and 30-2 perimetry, but reduced contrast sensitivity persists in 56% of eyes after an episode of optic neuritis. Cross sectional studies of MS patients show low contrast visual acuity (LCVA) correlates modestly with RNFL thickness and macula ganglion cell +IPL layer (GCL) thickness. Considering the potential severity of the vision deficits at onset, and GCL thinning at outcome, we hypothesized 10-2 perimetry and LCVA deficits would be frequent following an episode of optic neuritis.

METHODS

We prospectively studied 32 eyes of 32 patients (9 men, 23 women, age 34 years ± 10) with first time acute optic neuritis. We measured LCVA 2.5% (# letters seen), GCL thickness and loss, and 10-2 mean deviation (MD in decibels, dB) within 15 days from symptoms onset and at six months. The 10-2 threshold perimetry, a novel assessment in the MS research field, included to further characterize central vision function. We used correlation analysis to assess associations between GCL thickness and thinning and 10-2 perimetry as well as LCVA 2.5% at six months.

RESULTS

Compared to fellow eyes we found significant residual LCVA deficits in 28/32 study eyes at 6 months with 12.6 ± 15.8 letters seen, p=0.001). Similarly, 10-2 MD threshold perimetry in the study eyes at 6 months showed significant difference relative to the fellow eyes, p=0.01. In regards to GCL changes at 6 months, we found statistically significant reduction of the GCL thickness in the study eyes relative to the fellow eyes (study eyes 69.6 ± 9.6 µm, fellow eyes 82.7 ± 4.7 µm, p=0.001), with thinning present in 29/32 eyes. The mean GCL thinning at 6 months in the study eyes was 12.4 ± 8.4 µm. Correlation analysis of associations between primary outcome measures at 6 months showed significant relationship between GCL thickness and 10-2 MD threshold perimetry (0.43, p = 0.015) but not with LCVA. At six months, the mean GCL thinning strongly correlated with the 10-2 MD (-0.60, p=0.01) and moderately with LCVA (-0.46, p=0.008).

CONCLUSIONS

GCL thickness is the best structural and LCVA and 10-2 MD are sensitive functional measures for determining residual deficits due to optic neuritis.  The 10-2 MD correlates best with the outcome GCL thickness and loss. Our findings also suggest that 10-2 threshold perimetry and macular GCL can provide functional and structural promising biomarker signals to explore neuro-protective research.

The International Multiple Sclerosis Visual System Consortium: Advancing Visual System Research in Multiple Sclerosis

BACKGROUND

The International Multiple Sclerosis Visual System Consortium (IMSVISUAL) was formed in November 2014 with the primary goal of improving research, care, and education regarding the role of the visual system in multiple sclerosis (MS) and related disorders.

METHODS

In this review, we describe the formation, goals, activities, and structure of IMSVISUAL, as well as the relationship of IMSVISUAL with the Americas Committee for Treatment and Research in MS (ACTRIMS). Finally, we provide an overview of the work IMSVISUAL has completed to date, as well as an outline of research projects ongoing under the auspices of IMSVISUAL.

RESULTS

IMSVISUAL has 140 members worldwide and continues to grow. Through IMSVISUAL-related research, optical coherence tomography (OCT)-derived peripapillary retinal nerve fiber layer (pRNFL) thinning has been established as a predictor of future disability in MS. IMSVISUAL has also developed guidelines for reporting OCT studies in MS. Moreover, a systematic review performed by IMSVISUAL found that not only are pRNFL and ganglion cell + inner plexiform layer (GCIPL) thicknesses reduced in patients with MS (particularly in eyes with prior optic neuritis [ON]), but that inner nuclear layer measures may be higher among MS ON eyes, relative to healthy control eyes. Currently, there are several ongoing IMSVISUAL projects that will establish a role for visual outcomes in diagnosing MS and quantifying the effects of emerging therapies in clinical trials.

CONCLUSIONS

The development of IMSVISUAL represents a major collaborative commitment to defining the role of visual outcomes in high-quality, large-scale studies that generate definitive and instructive findings in the field of MS. As a consortium, IMSVISUAL has completed several international collaborative projects, is actively engaged in numerous ongoing research studies, and is committed to expanding the role of vision research in MS and related disorders.

Photoreceptor outer nuclear layer thickness changes in optic neuritis follow up

BACKGROUND

Ganglion cell inner plexiform (GCIP) layer thinning following acute optic neuritis (ON) is well-known. However, the onset of changes in the outer retinal layers needs further study. In this study, we determine longitudinal changes in retinal layer thickness in ON.

METHODS

Thirty ON patients underwent optical coherence tomography (OCT) and visual function testing at baseline, one month, and 6 months.

RESULTS

Mean GCIPL thickness decreased at one month relative to baseline from 63.6 ± 7.5 μm to 57.3 ± 6.8 µm in 3 mm ring (P < 0.001). There were no significant changes in GCIPL thickness between one and 6 months (P = 0.42). Outer nuclear layer (ONL) thickness in the 6 mm macular area increased from 58.9 ± 5.8 µm to 63.2 ± 6.8 μm at one month (P < 0.001) and then decreased at six month (58.8 ± 5.8 µm) relative to one month, reaching the baseline thickness. While GCIPL thinning at 1 month correlated with baseline visual acuity, change in the central ONL thickness from baseline to month 1 predicted visual outcome at month 6 (r = 0.6, P = 0.001).

CONCLUSIONS

Following ON, transient changes occur in the photoreceptor nuclei layer and then revert to baseline. This finding could predict 6 month visual acuity after ON.

Normative Data and Minimally Detectable Change for Inner Retinal Layer Thicknesses Using a Semi-automated OCT Image Segmentation Pipeline

Neurodegenerative and neuroinflammatory diseases regularly cause optic nerve and retinal damage. Evaluating retinal changes using optical coherence tomography (OCT) in diseases like multiple sclerosis has thus become increasingly relevant. However, intraretinal segmentation, a necessary step for interpreting retinal changes in the context of these diseases, is not standardized and often requires manual correction. Here we present a semi-automatic intraretinal layer segmentation pipeline and establish normative values for retinal layer thicknesses at the macula, including dependencies on age, sex, and refractive error. Spectral domain OCT macular 3D volume scans were obtained from healthy participants using a Heidelberg Engineering Spectralis OCT. A semi-automated segmentation tool (SAMIRIX) based on an interchangeable third-party segmentation algorithm was developed and employed for segmentation, correction, and thickness computation of intraretinal layers. Normative data is reported from a 6 mm Early Treatment Diabetic Retinopathy Study (ETDRS) circle around the fovea. An interactive toolbox for the normative database allows surveying for additional normative data. We cross-sectionally evaluated data from 218 healthy volunteers (144 females/74 males, age 36.5 ± 12.3 years, range 18-69 years). Average macular thickness (MT) was 313.70 ± 12.02 μm, macular retinal nerve fiber layer thickness (mRNFL) 39.53 ± 3.57 μm, ganglion cell and inner plexiform layer thickness (GCIPL) 70.81 ± 4.87 μm, and inner nuclear layer thickness (INL) 35.93 ± 2.34 μm. All retinal layer thicknesses decreased with age. MT and GCIPL were associated with sex, with males showing higher thicknesses. Layer thicknesses were also positively associated with each other. Repeated-measurement reliability for the manual correction of automatic intraretinal segmentation results was excellent, with an intra-class correlation coefficient >0.99 for all layers. The SAMIRIX toolbox can simplify intraretinal segmentation in research applications, and the normative data application may serve as an expandable reference for studies, in which normative data cannot be otherwise obtained.

Optical coherence tomography and multiple sclerosis: Update on clinical application and role in clinical trials

Optical coherence tomography (OCT) has emerged as a fast, non-invasive, inexpensive, high-resolution imaging technique in multiple sclerosis (MS). Retinal layer quantification by OCT facilitates a 'window' into not only local retinal pathology but also global neurodegenerative processes, recognised to be the principal substrates of disability accumulation in MS. While OCT measures in MS have been demonstrated to reflect visual function, inflammatory activity outside of the visual pathways, disability measures including the prediction of disability progression, whole brain atrophy, and the differential neuroprotective effects of disease-modifying therapies, debate continues regarding the clinical utility of OCT in everyday practice. This review presents an overview of the evidence supporting OCT, with particular focus on its application in the MS clinic. We will also discuss the role of OCT in MS clinical trials to develop novel neuroprotective and potential remyelinating therapies.

Glial pathology and retinal neurotoxicity in the anterior visual pathway in experimental autoimmune encephalomyelitis

The animal model experimental autoimmune encephalomyelitis (EAE) has been used extensively in the past to test mechanisms that target peripheral immune cells for treatment of multiple sclerosis (MS). While there have been some notable successes in relapsing MS, the development of therapies for progressive multiple sclerosis (MS) has been hampered by lack of an appropriate animal model. Further, the mechanisms underlying CNS inflammation and neuronal injury remain incompletely elucidated. It is known that the MOG _35-55 EAE mouse model does not have insidious behavioral progression as occurs in people with MS, but there is significant neuronal and axonal injury in EAE, as a result of the inflammation. In the present study, we describe the time course of glial activation and retinal neurodegeneration in the EAE model, and highlight the utility of studying the anterior visual pathway for modeling mechanisms of neuronal injury that may recapitulate critical aspects of the pathology described in people with MS following optic neuritis and subclinical optic neuropathy. We show that A1 neurotoxic astrocytes are prevalent in optic nerve tissue and retina, and are associated with subsequent RGC loss in the most commonly used form of the EAE model induced by MOG _35-55 peptide in C57/B6 mice. We developed a semi-automatic method to quantify retinal ganglion cells (RGC) and show that RGCs remain intact at peak EAE (PID 16) but are significantly reduced in late EAE (PID 42). Postsynaptic proteins and neurites were also compromised in the retina of late EAE mice. The retinal pathology manifests weeks after the microglial and astrocyte activation, which were prominent in optic nerve tissues at PID 16. Microglia expressed iNOS and had increased gene expression of C1q, TNF-α, and IL-1α. Astrocytes expressed high levels of complement component 3 and other genes associated with A1 neurotoxic astrocytes. Our data suggest that EAE can be used to study the pathobiology of optic neuropathy and to examine the preclinical neuroprotective effects of drugs that target activation of neurotoxic A1 astrocytes.

Sequential phases of RGC axonal and somatic injury in EAE mice examined using DTI and OCT

BACKGROUND

Clinical imaging modalities including optical coherence tomography (OCT) and diffusion tensor imaging (DTI) are vital in Multiple Sclerosis (MS), but their relationships during the different phases of Retinal ganglion cell (RGC) degeneration are not clear. We hypothesize that initial injury in optic nerve causes axonal degeneration leading to RGC loss in retina, which can be characterized by a combination of DTI and OCT. Our objective was to examine the correlation between noninvasive and histological data to chronicle the degeneration profile of RGCs in the retina and optic nerve in a mouse model of MS.

MATERIALS AND METHODS

Experimental Autoimmune Encephalomyelitis (EAE) was induced in 11 C57Bl/6 mice, with 8 mice reserved as controls. OCT and DTI was conducted 2-8 weeks after induction of EAE. The thickness of the retinal ganglion cell complex (GCC) was measured using OCT and compared to DTI indices measured in optic nerves. End-stage histology was used to quantify axon/myelin loss in the optic nerve and retinal thinning/RGC loss in the retina.

RESULTS

Significant changes in DTI-derived Axial Diffusivity (AD, -17.2%) and Trace Diffusivity (TR, -18.3%) began after 2 weeks of EAE. Later significant reductions in Fractional Anisotropy (FA) and AD, with increases in Radial Diffusion (RD) were apparent after 4 and 8 weeks. OCT-derived measures of GCC thickness were reduced after 4 weeks, and reached significant reduction after 8 weeks. Among EAE mice, DTI (FA, AD and RD measures) and OCT measures were all significantly correlated after 4 and 8 weeks. Among histology measures, RGC density (-23%), RGC size (-27%), and the number of SMI31+ axons (-54%) were reduced significantly. DTI measures of FA and AD along with GCC thinning were the best independent predictors of axon loss.

CONCLUSIONS

DTI and OCT measures are tightly correlated during the chronic phase of axonal degeneration (4-8 weeks) in EAE mice. After 8 weeks of EAE, both OCT and DTI measures are strong predictors of axon loss in the Optic Nerve.

Multifocal visual evoked potentials and contrast sensitivity correlate with ganglion cell-inner plexiform layer thickness in multiple sclerosis

OBJECTIVE

To examine the relationship between optical coherence tomography (OCT) macular ganglion cell-inner plexiform layer thickness (GCIPLT), peripapillary retinal nerve fiber layer thickness (RNFLT) and visual function in relapsing-remitting multiple sclerosis (RRMS).

METHODS

Cirrus OCT, VERIS 60-sector multifocal visual evoked potential (mfVEP) and Pelli-Robson contrast sensitivity (CS) were obtained for 53 eyes with last optic neuritis (ON) > 6 months and 105 non-ON eyes in 90 patients. One eye (43 ON, 73 non-ON) was used for correlations when both had the same history. Global (G, 60 sectors) and central 5.6° (C, 24 sectors) mfVEP amplitude and latency were calculated as mean logSNR and median latency.

RESULTS

Eyes showing abnormal mfVEP (amplitude or latency) vs OCT (GCIPLT or RNFLT) was 77% vs 69% (p = 0.33) in ON, 45% vs 22% (p < 0.0005) in non-ON. In ON and non-ON, mfVEP measures and CS correlated with GCIPLT and RNFLT (r = -0.24 to 0.78, p = 0.03-0.0001). In ON, mfVEP amplitude (C,G) correlated better with GCIPLT (r = 0.78, 0.76) than RNFLT (r = 0.43, 0.58; p < 0.001, 0.01).

CONCLUSIONS

MfVEP measures and CS correlated well with GCIPLT and RNFLT in ON and non-ON. MfVEP amplitudes were more highly correlated with GCIPLT than RNFLT in ON. MfVEP detected significantly more defects than OCT in non-ON.

SIGNIFICANCE

GCIPLT, mfVEP and CS provide useful measures of optic nerve integrity in RRMS.

Using the Anterior Visual System to Assess Neuroprotection and Remyelination in Multiple Sclerosis Trials

PURPOSE OF REVIEW

Clinical trials using agents directed at neuroprotection and remyelination in multiple sclerosis (MS) are needed. As optic neuritis (ON) is common in people with MS and the pathology of ON is similar to other MS lesions in the brain, measurements of the anterior visual system are frequently utilized in neuroprotection and remyelination trials. Understanding the strengths and weaknesses of the measurements is vital when interpreting the results of this research.

RECENT FINDINGS

Techniques such as visual evoked potentials (VEP) and optical coherence tomography (OCT) are well established in MS and are thought to measure axonal integrity and myelination. Novel imaging techniques can also be used in conjunction with these measurements to provide better insight into optic nerve structure and function. Magnetization transfer imaging (MTR) together with optic nerve area and volume measures neurodegeneration; diffusion tensor imaging (DTI) measures myelination status and neurodegeneration. However, these techniques require various levels of experience to interpret, and all can be confounded by ocular motion and surrounding fat and bone. This article provides a review of established and novel techniques to measure the anterior visual system in multiple sclerosis with a focus on the evidence to support their use as outcome measures in clinical trials focused on neuroprotection and remyelination therapies.

Frequent retinal ganglion cell damage after acute optic neuritis

BACKGROUND

To identify the extent of ganglion cell damage after first-time optic neuritis (ON) using the inter-ocular difference between affected and fellow eyes, and whether this approach is able to detect more patients suffering from ganglion cell damage than using absolute values.

METHODS

Thirty-four patients with first-time unilateral ON were followed for a median 413 days. Patients underwent optical coherence tomography testing to determine ganglion cell plus inner plexiform layer thickness (GCIP). Ganglion cell loss was quantified as GCIP difference between ON-affected and fellow eyes (inter-GCIP) and was compared against measurements from 93 healthy controls (HC). Visual function was assessed with high contrast visual acuity; and standard automated perimetry-derived measures of mean deviation and foveal threshold.

RESULTS

At clinical presentation after median 19 days from symptom onset, 47.1% of patients showed early GCIP thinning in the ON-affected eye based on inter-GCIP. At the last visit acute ON was associated with 16.1 ± 10.0 µm GCIP thinning compared to fellow eyes (p = 3.669e-06). Based on inter-GCIP, 84.9% of ON patients sustained GCIP thinning in their affected eye at the last visit, whereas using absolute values only 71.0% of patients suffered from GCIP thinning (p = 0.002076). Only 32.3% of these patients had abnormal visual function. The best predictor of GCIP thinning as a measure of ON severity at the last visit was worse visual field mean deviation at clinical presentation.

CONCLUSION

Inter-ocular GCIP identifies significantly more eyes suffering damage from ON than absolute GCIP, visual fields or visual acuity loss. Effective interventional options are needed to prevent ganglion cell loss.

Multicenter reliability of semiautomatic retinal layer segmentation using OCT

Objective

To evaluate the inter-rater reliability of semiautomated segmentation of spectral domain optical coherence tomography (OCT) macular volume scans.

Methods

Macular OCT volume scans of left eyes from 17 subjects (8 patients with MS and 9 healthy controls) were automatically segmented by Heidelberg Eye Explorer (v1.9.3.0) beta-software (Spectralis Viewing Module v6.0.0.7), followed by manual correction by 5 experienced operators from 5 different academic centers. The mean thicknesses within a 6-mm area around the fovea were computed for the retinal nerve fiber layer, ganglion cell layer (GCL), inner plexiform layer (IPL), inner nuclear layer, outer plexiform layer (OPL), and outer nuclear layer (ONL). Intraclass correlation coefficients (ICCs) were calculated for mean layer thickness values. Spatial distribution of ICC values for the segmented volume scans was investigated using heat maps.

Results

Agreement between raters was good (ICC > 0.84) for all retinal layers, particularly inner retinal layers showed excellent agreement across raters (ICC > 0.96). Spatial distribution of ICC showed highest values in the perimacular area, whereas the ICCs were poorer for the foveola and the more peripheral macular area. The automated segmentation of the OPL and ONL required the most correction and showed the least agreement, whereas differences were less prominent for the remaining layers.

Conclusions

Automated segmentation with manual correction of macular OCT scans is highly reliable when performed by experienced raters and can thus be applied in multicenter settings. Reliability can be improved by restricting analysis to the perimacular area and compound segmentation of GCL and IPL.

Correlations among multifocal electroretinography and optical coherence tomography findings in patients with Parkinson's disease

To assess the correlation between functional and anatomical evaluations with multifocal electroretinography (mfERG) and spectral-domain optical coherence tomography (SD-OCT) in patients with Parkinson's disease (PD). This cross-sectional study involved 116 eyes of 58 patients with PD and 30 age- and sex-matched control subjects. All study participants underwent a comprehensive neuro-ophthalmic examination, retinal single-layer thicknesses and volumes, and peripapillary retinal nerve fiber layer (pRNFL) measurements with SD-OCT, and the patients' mfERG recordings were evaluated. The macular retinal nerve fiber layer (mRNFL), ganglion cell layer (GCL), inner plexiform layer (IPL), outer nuclear layer (ONL), retinal pigment epithelium (RPE), and photoreceptor layer (PR) thicknesses, and mRNFL, RPE, and PR volumes were found lower in PD compared to those of controls, while outer plexiform layer (OPL) volumes were increased (p < 0.05). We found delayed implicit times and decreased amplitudes in the mfERG of PD patients versus those in control subjects (p < 0.05). We found significant correlations between outer macular volumes, PR thicknesses, and N1 amplitudes of rings 2 and 3and P1 amplitudes of rings 3, 4, and 5. Our study revealed thinning of both inner and outer retinal single layers, increased OPL volume, and delayed implicit times and decreased amplitudes in the mfERG of PD patients versus control subjects and correlation between structural and functional parameters. Our findings point out that SD-OCT and mfERG could both serve as non-invasive tools for evaluating ophthalmic manifestations of Parkinson's disease.

Analysis of Agreement of Retinal-Layer Thickness Measures Derived from the Segmentation of Horizontal and Vertical Spectralis OCT Macular Scans

PURPOSE

Optical coherence tomography (OCT) is a reliable method used to quantify discrete layers of the retina. Spectralis OCT is a device used for this purpose. Spectralis OCT macular scan imaging acquisition can be obtained on either the horizontal or vertical plane. The vertical protocol has been proposed as favorable, due to postulated reduction in confound of Henle's fibers on segmentation-derived metrics. Yet, agreement of the segmentation measures of horizontal and vertical macular scans remains unexplored. Our aim was to determine this agreement.

MATERIALS AND METHODS

Horizontal and vertical macular scans on Spectralis OCT were acquired in 20 healthy controls (HCs) and 20 multiple sclerosis (MS) patients. All scans were segmented using Heidelberg software and a Johns Hopkins University (JHU)-developed method. Agreement was analyzed using Bland-Altman analyses and intra-class correlation coefficients (ICCs).

RESULTS

Using both segmentation techniques, mean differences (agreement at the cohort level) in the thicknesses of all macular layers derived from both acquisition protocols in MS patients and HCs were narrow (<1 µm), while the limits of agreement (LOA) (agreement at the individual level) were wider. Using JHU segmentation mean differences (and LOA) for the macular retinal nerve fiber layer (RNFL) and ganglion cell layer + inner plexiform layer (GCIP) in MS were 0.21 µm (-1.57-1.99 µm) and -0.36 µm (-1.44-1.37 µm), respectively.

CONCLUSIONS

OCT segmentation measures of discrete retinal-layer thicknesses derived from both vertical and horizontal protocols on Spectralis OCT agree excellently at the cohort level (narrow mean differences), but only moderately at the individual level (wide LOA). This suggests patients scanned using either protocol should continue to be scanned with the same protocol. However, due to excellent agreement at the cohort level, measures derived from both acquisitions can be pooled for outcome purposes in clinical trials.

Association of Retinal Architecture, Intrathecal Immunity, and Clinical Course in Multiple Sclerosis

Importance

Biomarkers to estimate long-term outcomes in patients with multiple sclerosis (MS) and to assign patients to individual treatment regimens are urgently needed.

Objective

To assess whether retinal layer volumes are correlated with immune cell subsets and immunoglobulin indices in the cerebrospinal fluid and whether retinal layer volumes alone or in combination with intrathecal variables are associated with worsening of disease in patients with relapsing-remitting MS.

Design, Setting, and Participants

This observational cohort study included 312 patients with relapsing-remitting MS in 2 independent cohorts (72 patients with short disease duration [cohort 1] and 240 patients with longer disease duration [cohort 2]) treated at a single German university hospital from April 15, 2013, through November 11, 2015.

Main Outcomes and Measures

The common ganglion cell and inner plexiform layer (GCIPL) and inner nuclear layer (INL) volumes were tested for association with the immunoglobulin indices and the frequencies of immune cells in the cerebrospinal fluid (including B cells, T cells, and natural killer cells) (cohort 1). Volumes of GCIPL alone (cohorts 1 and 2) or GCIPL corrected for intrathecal B-cell frequencies (cohort 1) were tested for their association with worsening disability.

Results

A total of 312 patients (212 women [67.9%] and 100 men [32.1%]; median age, 34.0 years [interquartile range (IQR), 28.0-42.0 years]) were available for analysis. In cohort 1 (50 women [69.4%] and 22 men [30.6%]; median age, 31.0 years [IQR, 26.3-38.3 years]), with short disease durations (median, 1.0 months [IQR, 1.0-2.0 months]), low GCIPL volumes were associated with increased intrathecal B-cell frequencies (median, 1.96% [IQR, 1.45%-4.20%]) and intrathecal IgG synthesis (median cerebrospinal fluid/serum IgG index, 0.78 [IQR, 0.53-1.07]). The INL volumes correlated with the frequencies of intrathecal CD56bright natural killer cells (r = 0.28; P = .007). Individuals with low GCIPL volumes (<1.99 mm3) had a 6.4-fold risk for worsening disability during follow-up compared with patients with higher GCIPL values (95% CI, 1.7-24.2; P = .007). This finding was reproduced in cohort 2 (162 women [67.5%] and 78 men [32.5%]; median age, 34.0 years [IQR, 29.0-42.0 years]) consisting of patients with longer disease durations (median, 36.0 months [IQR, 21.0-60.0 months]) (hazard ratio, 2.4; 95% CI, 1.2-4.8; P = .02). In both cohorts, INL volumes correlated with the prospective increase in T2 lesion load and the number of gadolinium-enhancing lesions.

Conclusions and Relevance

Retinal layers reflect different aspects of disease activity during MS. Loss of GCIPL is associated with intrathecal B-cell immunity and constitutes an independent risk factor for worsening disability, whereas high INL volumes are associated with activity on magnetic resonance imaging in the brain parenchyma. Thus, retinal optical coherence tomography might be a means to support stratification of patients with MS for different therapeutic regimens.

Long-term Characterization of Retinal Degeneration in Royal College of Surgeons Rats Using Spectral-Domain Optical Coherence Tomography

Purpose

Prospective treatments for age-related macular degeneration and inherited retinal degenerations are commonly evaluated in the Royal College of Surgeons (RCS) rat before translation into clinical application. Historically, retinal thickness obtained through postmortem anatomic assessments has been a key outcome measure; however, utility of this measurement is limited because it precludes the ability to perform longitudinal studies. To overcome this limitation, the present study was designed to provide a baseline longitudinal quantification of retinal thickness in the RCS rat by using spectral-domain optical coherence tomography (SD-OCT).

Methods

Horizontal and vertical linear SD-OCT scans centered on the optic nerve were captured from Long-Evans control rats at P30, P60, P90 and from RCS rats between P17 and P90. Total retina (TR), outer nuclear layer+ (ONL+), inner nuclear layer (INL), and retinal pigment epithelium (RPE) thicknesses were quantified. Histologic sections of RCS retina obtained from P21 to P60 were compared to SD-OCT images.

Results

In RCS rats, TR and ONL+ thickness decreased significantly as compared to Long-Evans controls. Changes in INL and RPE thickness were not significantly different between control and RCS retinas. From P30 to P90 a subretinal hyperreflective layer (HRL) was observed and quantified in RCS rats. After correlation with histology, the HRL was identified as disorganized outer segments and the location of accumulated debris.

Conclusions

Retinal layer thickness can be quantified longitudinally throughout the course of retinal degeneration in the RCS rat by using SD-OCT. Thickness measurements obtained with SD-OCT were consistent with previous anatomic thickness assessments. This study provides baseline data for future longitudinal assessment of therapeutic agents in the RCS rat.

Retinal ganglion cell analysis in multiple sclerosis and optic neuritis: a systematic review and meta-analysis

The aim of this study was to summarise existing findings regarding optical coherence tomography (OCT) measurements of ganglion cell layer (GCL) alterations in optic neuritis (ON) and multiple sclerosis (MS). Peer-reviewed studies published prior to April 2016 were searched using PubMed, EMBASE, Web of Science and Scopus. Studies were included if they measured GCL thickness using OCT in patients with either ON, MS or clinically isolated syndrome. For the meta-analysis, we compared GCL thickness in MS patients with and without prior ON, to healthy controls. 42/252 studies were reviewed. In acute ON, studies showed significant thinning of the GCL within the first 5 weeks (n = 5), earlier than retinal nerve fibre layer (RNFL) thinning. GCL thinning at 1-2 months after acute ON predicted visual function at 6 months (n = 3). The meta-analysis showed that the thickness of the GCL was significantly reduced in MS patients both with and without previous ON compared to healthy controls. GCL thinning was associated with visual function in most studies (n = 10) and expanded disability status scale (EDSS) scores (n = 6). In acute ON, thinning of the GCL is measurable prior to RNFL thinning, and GCL thickness after 1-2 months may predict visual function after 6 months. Furthermore, GCL thinning occurs in MS both with and without prior ON, and may be associated with visual function and EDSS score. This suggests that the GCL is a promising biomarker, which may be used to examine in vivo neurodegeneration in ON and MS.

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.

Retinal ganglion cell and axonal loss in optic neuritis: risk factors and visual functions

PurposeThe peripapillary retinal nerve fiber layer (pRNFL) and the macular ganglion cell-inner plexiform layer (GCIPL) are important predictive factors for the prognosis of optic neuritis (ON). We investigated the risk factors for pRNFL and GCIPL thinning in ON and its relationship with visual function.Patients and methodsWe analyzed 33 eyes of 33 patients with a first attack of unilateral ON. Patients were divided into two groups according to pRNFL and GCIPL thinning, using spectral-domain optical coherence tomography. We evaluated patients' age, sex, color vision, visual acuity (VA), optic nerve findings on MRI, elapsed period from onset of visual symptoms to steroid treatment, visual field (VF) mean deviation (MD), average pRNFL thickness, and GCIPL thickness.ResultsThere was no patient with residual VF defect in the groups without pRNFL or GCIPL thinning. Significant correlations were found between pRNFL (some sectors) and GCIPL (all sectors) thickness and BCVA and VF MD (P<0.03 for all). Multivariate logistic regression analysis revealed that only worse initial VF MD was a significant risk factor of pRFNL and GCIPL thinning after ON (OR, 0.841; 95% CI, 0.730-0.970; P=0.017 and OR, 0.871; 95% CI, 0.761-0.998; P=0.046, respectively).ConclusionRetinal ganglion cell and axonal losses occurred in ON cases showing severe initial VF loss. Therefore, it is necessary to pay more attention to the degree of initial VF loss in ON while considering the possibility of residual VF loss accompanying pRNFL and GCIPL thinning.

Volume Averaging of Spectral-Domain Optical Coherence Tomography Impacts Retinal Segmentation in Children

PURPOSE

To determine the influence of volume averaging on retinal layer thickness measures acquired with spectral-domain optical coherence tomography (SD-OCT) in children.

METHODS

Macular SD-OCT images were acquired using three different volume settings (i.e., 1, 3, and 9 volumes) in children enrolled in a prospective OCT study. Total retinal thickness and five inner layers were measured around an Early Treatment Diabetic Retinopathy Scale (ETDRS) grid using beta version automated segmentation software for the Spectralis. The magnitude of manual segmentation required to correct the automated segmentation was classified as either minor (<12 lines adjusted), moderate (>12 and <25 lines adjusted), severe (>26 and <48 lines adjusted), or fail (>48 lines adjusted or could not adjust due to poor image quality). The frequency of each edit classification was assessed for each volume setting. Thickness, paired difference, and 95% limits of agreement of each anatomic quadrant were compared across volume density.

RESULTS

Seventy-five subjects (median age 11.8 years, range 4.3-18.5 years) contributed 75 eyes. Less than 5% of the 9- and 3-volume scans required more than minor manual segmentation corrections, compared with 71% of 1-volume scans. The inner (3 mm) region demonstrated similar measures across all layers, regardless of volume number. The 1-volume scans demonstrated greater variability of the retinal nerve fiber layer (RNLF) thickness, compared with the other volumes in the outer (6 mm) region.

CONCLUSIONS

In children, volume averaging of SD-OCT acquisitions reduce retinal layer segmentation errors.

TRANSLATIONAL RELEVANCE

This study highlights the importance of volume averaging when acquiring macula volumes intended for multilayer segmentation.

Adding Papillomacular Bundle Measurements to Standard Optical Coherence Tomography Does Not Increase Sensitivity to Detect Prior Optic Neuritis in Patients with Multiple Sclerosis

Purpose

To improve the detection of retinal nerve fiber layer (RNFL) thinning in multiple sclerosis (MS), a special peripapillary ring scanning algorithm (N-site RNFL, N-RNFL) was developed for spectral domain optical coherence tomography (SD-OCT). In contrast to the standard protocol (ST-RNFL) scanning starts nasally, not temporally, and provides an additional sector of analysis, the papillomacular bundle (PMB). We aimed to ascertain whether the temporal RNFL differs between the two techniques, whether N-RNFL is more sensitive than ST-RNFL to detect previous optic neuritis (ON), and whether analyzing the PMB adds additional sensitivity. Furthermore, we investigated whether RNFL is associated with disease severity and/or disease duration.

Methods

We conducted a cross-sectional case-control study of 38 patients with MS, of whom 24 had a history of ON, and 40 healthy controls (HC). Subjects with ON within the previous 6 months were excluded. Records included clinical characteristics, visual evoked potentials (VEP), and SD-OCT in both techniques.

Results

In a total of 73 evaluable MS eyes, temporal N-RNFL was abnormal in 17.8%, temporal ST-RNFL in 19.2%, and the PMB-RNFL in 21.9%. In ON eyes, the sensitivity of temporal N-RNFL and ST-RNFL did not differ significantly (37.0%/33.3%, p = 0.556). The sensitivity of VEP was 85.2%. RNFL thickness was associated with disease severity in all eyes, with and without a history of ON, and with disease duration.

Conclusion

The two OCT techniques detected previous ON with similar sensitivity, but the sensitivity of VEPs was superior to that of both N-RNFL and ST-RNFL. Our results indicate that the widely used ST-RNFL technique is appropriate for peripapillary RNFL measurements in MS patients.

Investigating Tissue Optical Properties and Texture Descriptors of the Retina in Patients with Multiple Sclerosis

Purpose

To assess the differences in texture descriptors and optical properties of retinal tissue layers in patients with multiple sclerosis (MS) and to evaluate their usefulness in the detection of neurodegenerative changes using optical coherence tomography (OCT) image segmentation.

Patients and Methods

38 patients with MS were examined using Stratus OCT. The raw macular OCT data were exported and processed using OCTRIMA software. The enrolled eyes were divided into two groups, based on the presence of optic neuritis (ON) in the history (MSON+ group, n = 36 and MSON- group, n = 31). Data of 29 eyes of 24 healthy subjects (H) were used as controls. A total of seven intraretinal layers were segmented and thickness as well as optical parameters such as contrast, fractal dimension, layer index and total reflectance were measured. Mixed-model ANOVA analysis was used for statistical comparisons.

Results

Significant thinning of the retinal nerve fiber layer (RNFL), ganglion cell/inner plexiform layer complex (GCL+IPL) and ganglion cell complex (GCC, RNFL+GCL+IPL) was observed between study groups in all comparisons. Significant difference was found in contrast in the RNFL, GCL+IPL, GCC, inner nuclear layer (INL) and outer plexiform layer when comparing MSON+ to the other groups. Higher fractal dimension values were observed in GCL+IPL and INL layers when comparing H vs. MSON+ groups. A significant difference was found in layer index in the RNFL, GCL+IPL and GCC layers in all comparisons. A significant difference was observed in total reflectance in the RNFL, GCL+IPL and GCC layers between the three examination groups.

Conclusion

Texture and optical properties of the retinal tissue undergo pronounced changes in MS even without optic neuritis. Our results may help to further improve the diagnostic efficacy of OCT in MS and neurodegeneration.

Reliability of Intra-Retinal Layer Thickness Estimates

PURPOSE

Measurement of intra-retinal layer thickness using optical coherence tomography (OCT) has become increasingly prominent in multiple sclerosis (MS) research. Nevertheless, the approaches used for determining the mean layer thicknesses vary greatly. Insufficient data exist on the reliability of different thickness estimates, which is crucial for their application in clinical studies. This study addresses this lack by evaluating the repeatability of different thickness estimates.

METHODS

Studies that used intra-retinal layer segmentation of macular OCT scans in patients with MS were retrieved from PubMed. To investigate the repeatability of previously applied layer estimation approaches, we generated datasets of repeating measurements of 15 healthy subjects and 13 multiple sclerosis patients using two OCT devices (Cirrus HD-OCT and Spectralis SD-OCT). We calculated each thickness estimate in each repeated session and analyzed repeatability using intra-class correlation coefficients and coefficients of repeatability.

RESULTS

We identified 27 articles, eleven of them used the Spectralis SD-OCT, nine Cirrus HD-OCT, two studies used both devices and two studies applied RTVue-100. Topcon OCT-1000, Stratus OCT and a research device were used in one study each. In the studies that used the Spectralis, ten different thickness estimates were identified, while thickness estimates of the Cirrus OCT were based on two different scan settings. In the simulation dataset, thickness estimates averaging larger areas showed an excellent repeatability for all retinal layers except the outer plexiform layer (OPL).

CONCLUSIONS

Given the good reliability, the thickness estimate of the 6mm-diameter area around the fovea should be favored when OCT is used in clinical research. Assessment of the OPL was weak in general and needs further investigation before OPL thickness can be used as a reliable parameter.

Repeatability of Foveal Measurements Using Spectralis Optical Coherence Tomography Segmentation Software

Purpose

To investigate repeatability and reproducibility of thickness of eight individual retinal layers at axial and lateral foveal locations, as well as foveal width, measured from Spectralis spectral domain optical coherence tomography (SD-OCT) scans using newly available retinal layer segmentation software.

Methods

High-resolution SD-OCT scans were acquired for 40 eyes of 40 young healthy volunteers. Two scans were obtained in a single visit for each participant. Using new Spectralis segmentation software, two investigators independently obtained thickness of each of eight individual retinal layers at 0°, 2° and 5° eccentricities nasal and temporal to foveal centre, as well as foveal width measurements. Bland-Altman Coefficient of Repeatability (CoR) was calculated for inter-investigator and inter-scan agreement of all retinal measurements. Spearman's ρ indicated correlation of manually located central retinal thickness (RT₀) with automated minimum foveal thickness (MFT) measurements. In addition, we investigated nasal-temporal symmetry of individual retinal layer thickness within the foveal pit.

Results

Inter-scan CoR values ranged from 3.1μm for axial retinal nerve fibre layer thickness to 15.0μm for the ganglion cell layer at 5° eccentricity. Mean foveal width was 2550μm ± 322μm with a CoR of 13μm for inter-investigator and 40μm for inter-scan agreement. Correlation of RT₀ and MFT was very good (ρ = 0.97, P < 0.0005). There were no significant differences in thickness of any individual retinal layers at 2° nasal compared to temporal to fovea (P > 0.05); however this symmetry could not be found at 5° eccentricity.

Conclusions

We demonstrate excellent repeatability and reproducibility of each of eight individual retinal layer thickness measurements within the fovea as well as foveal width using Spectralis SD-OCT segmentation software in a young, healthy cohort. Thickness of all individual retinal layers were symmetrical at 2°, but not at 5° eccentricity away from the fovea.

Applying an Open-Source Segmentation Algorithm to Different OCT Devices in Multiple Sclerosis Patients and Healthy Controls: Implications for Clinical Trials

Background. The lack of segmentation algorithms operative across optical coherence tomography (OCT) platforms hinders utility of retinal layer measures in MS trials. Objective. To determine cross-sectional and longitudinal agreement of retinal layer thicknesses derived from an open-source, fully-automated, segmentation algorithm, applied to two spectral-domain OCT devices. Methods. Cirrus HD-OCT and Spectralis OCT macular scans from 68 MS patients and 22 healthy controls were segmented. A longitudinal cohort comprising 51 subjects (mean follow-up: 1.4 ± 0.9 years) was also examined. Bland-Altman analyses and interscanner agreement indices were utilized to assess agreement between scanners. Results. Low mean differences (-2.16 to 0.26 μm) and narrow limits of agreement (LOA) were noted for ganglion cell and inner and outer nuclear layer thicknesses cross-sectionally. Longitudinally we found low mean differences (-0.195 to 0.21 μm) for changes in all layers, with wider LOA. Comparisons of rate of change in layer thicknesses over time revealed consistent results between the platforms. Conclusions. Retinal thickness measures for the majority of the retinal layers agree well cross-sectionally and longitudinally between the two scanners at the cohort level, with greater variability at the individual level. This open-source segmentation algorithm enables combining data from different OCT platforms, broadening utilization of OCT as an outcome measure in MS trials.

Temporal retinal nerve fibre layer thinning in cluster headache patients detected by optical coherence tomography

BACKGROUND

The exact pathophysiology of cluster headache (CH) is still not fully clarified. Various studies confirmed changes in ocular blood flow during CH attacks. Furthermore, vasoconstricting medication influences blood supply to the eye. We investigated the retina of CH patients for structural retinal alterations with optical coherence tomography (OCT), and how these changes correlate to headache characteristics, oxygen use and impaired visual function.

METHODS

Spectral domain OCT of 107 CH patients - 67 episodic, 35 chronic, five former chronic sufferers - were compared to OCT from 65 healthy individuals. Visual function tests with Sloan charts and a substantial ophthalmologic examination were engaged.

RESULTS

Reduction of temporal and temporal-inferior retinal nerve fibre layer (RNFL) thickness was found in both eyes for CH patients with a predominant thinning on the headache side in the temporal-inferior area. Chronic CH patients revealed thinning of the macula compared to episodic suffers and healthy individuals. Bilateral thinning of temporal RNFL was also found in users of 100% oxygen compared to non-users and healthy controls. Visual function did not differ between patients and controls.

DISCUSSION

Our OCT findings show a systemic effect causing temporal retinal thinning in both eyes of CH patients possibly due to attack-inherent or medication-induced frequent bilateral vessel diameter changes. The temporal retina with its thinly myelinated parvo-cellular axons and its more susceptible vessels for the vasoconstricting influence of oxygen inhalation seems to be predisposed for tissue damage-causing processes related to CH.

Retina measurements for diagnosis of Parkinson disease

PURPOSE

To test the diagnostic ability of spectral domain optical coherence tomography for the detection of Parkinson disease using retinal nerve fiber layer and retinal thickness parameters. Retinal pigment epithelium produces levodopa.

METHODS

Patients with Parkinson disease (n = 111) and healthy subjects (n = 200) were enrolled. The Spectralis optical coherence tomography was used to obtain retinal nerve fiber layer thickness and retinal measurements. Two linear discriminant functions (LDFs) were developed, one using retinal nerve fiber layer parameters and another using retinal thickness. A validating set was used to test the performance of both LDFs. Receiver operating characteristic curves were plotted and compared with the standard parameters provided by optical coherence tomography for both LDFs. Sensitivity and specificity were used to evaluate diagnostic performance.

RESULTS

The Retinal LDF combines only retinal thickness parameters and provided the best performance: 31.173 + 0.026 × temporal outer - 0.267 × superior outer + 0.159 × nasal outer - 0.197 × inferior outer - 0.060 × superior inner + 0.049 × foveal thickness. The largest areas under the receiver operating characteristic curve were 0.902 for Retinal LDF. The Retinal LDF yielded the highest sensitivity values.

CONCLUSION

Measurements of retinal thickness differentiate between subjects who are healthy and those with advanced Parkinson disease.

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.

Reproducibility and repeatability of ganglion cell-inner plexiform layer thickness measurements in healthy subjects

PURPOSE

To assess the reproducibility and repeatability of macular ganglion cell-inner plexiform layer (GC-IPL) thickness measurements in healthy subjects.

PROCEDURES

In this observational study, 60 healthy eyes were subjected to macular GC-IPL thickness measurements by means of Cirrus™ high-definition optical coherence tomography (Cirrus version 6.0; Carl Zeiss Meditec, Dublin, Calif., USA) by two examiners in two sessions. Average, minimum and 6 sectoral GC-IPL thicknesses were measured. Inter- and intraobserver reproducibility was tested and analyzed by means of the concordance correlation coefficient (CCC). The repeatability of measurements was assessed by the coefficient of repeatability (CR).

RESULTS

Mean age (±SD) was 29.63 (±5.1) years. The CRs for average GC-IPL thickness were 2.1 and 2.2 µm for the first and the second operator, respectively. Inter- and intraobserver CCCs ranged from 0.91 (95% CI: 0.89-0.93) to 0.98 (95% CI: 0.96-0.99) and from 0.92 (95% CI: 0.88-0.94) to 0.98 (95% CI: 0.97-0.99), respectively.

CONCLUSIONS

GC-IPL thickness measurements in young healthy subjects showed excellent reproducibility and repeatability, especially for average and sectoral GC-IPL thickness measurements.

Baseline retinal nerve fiber layer thickness and macular volume quantified by OCT in the North American phase 3 fingolimod trial for relapsing-remitting multiple sclerosis

BACKGROUND

Patients with multiple sclerosis (MS) demonstrate thinning of peripapillary retinal nerve fiber layer (RNFL) and decreased macular volume as measured by optical coherence tomography (OCT). To our knowledge, there are no previous reports from a large MS OCT database with strict quality control measures that quantitate RNFL and macula in patients with relapsing-remitting multiple sclerosis.

METHODS

The University of California Davis OCT Reading Center gathered OCT data at baseline as part of the North American phase 3 trial of fingolimod (Gilenya). Average RNFL thickness (RNFLT) and macular volume (TMV) were measured using time domain OCT (TD-OCT). RNFL quadrants, clock hours, and macular subfields were included. With strict quality control and accounting for signal strength differences, scans were categorized as "reduced" or "not reduced" for each field, based on being less than 5th percentile for age-matched controls derived from the normative database in the scanner software. Patients were deemed "abnormal" if at least 1 eye had reduced values for a given parameter. Patients with abnormalities in corresponding RNFL and macular subfields were compared by cross-tabulation.

RESULTS

The TD-OCT data were prospectively collected from 939 of the 1,083 trial patients, 712 of whom met all final quality and data inclusion criteria. Of the final cohort, 242 (34.0%) demonstrated reduced (less than 5th percentile) average RNFLT in at least 1 eye. One hundred seventy-eight (25.0%) patients had reduced TMV. One hundred twenty-eight (18.0%) demonstrated both reduced TMV and RNFLT in the same eye, whereas 42 (5.8%) had reduced TMV and RNFLT in both eyes. Of the 242 patients with reduced average RNFL thickness, 128 (52.9%) also had reduced TMV. Fifty patients had reduced TMV in the absence of reduced RNFLT in at least 1 eye, a cohort prevalence of 7.0%. Quadrant and subfield analysis showed a predominance of temporal and inferior RNFL thinning, with inferior macular thinning corresponding best to RNFL thinning.

CONCLUSION

RNFL and macular thinning/volume loss is common at baseline in relapsing-remitting multiple sclerosis, as measured by TD-OCT. When the RNFL is thin, the macular volume is reduced in more than half of the patients. There is a population of reduced TMV without any reduction in RNFLT. Documenting the prevalence and distribution of these structural abnormalities supports recent reports and suggests new retinal areas to probe for functional vision changes in MS.

Quality control for retinal OCT in multiple sclerosis: validation of the OSCAR-IB criteria

BACKGROUND

Retinal optical coherence tomography (OCT) permits quantification of retinal layer atrophy relevant to assessment of neurodegeneration in multiple sclerosis (MS). Measurement artefacts may limit the use of OCT to MS research.

OBJECTIVE

An expert task force convened with the aim to provide guidance on the use of validated quality control (QC) criteria for the use of OCT in MS research and clinical trials.

METHODS

A prospective multi-centre (n = 13) study. Peripapillary ring scan QC rating of an OCT training set (n = 50) was followed by a test set (n = 50). Inter-rater agreement was calculated using kappa statistics. Results were discussed at a round table after the assessment had taken place.

RESULTS

The inter-rater QC agreement was substantial (kappa = 0.7). Disagreement was found highest for judging signal strength (kappa = 0.40). Future steps to resolve these issues were discussed.

CONCLUSION

Substantial agreement for QC assessment was achieved with aid of the OSCAR-IB criteria. The task force has developed a website for free online training and QC certification. The criteria may prove useful for future research and trials in MS using OCT as a secondary outcome measure in a multi-centre setting.

Subtle retinal pathology in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is characterized by neuro-ophthalmological abnormalities beyond disturbed oculomotor control such as decreased visual acuity and disturbed visual evoked potentials. Here we report retinal alterations in a cohort of 24 patients with clinically definite (n = 20) or probable (n = 4) ALS as compared to matched controls. High-resolution spectral domain optical coherence tomography with retinal segmentation revealed a subtle reduction in the macular thickness and the retinal nerve fiber layer (RNFL) as well as a marked thinning of the inner nuclear layer (INL). Our data indicate an unprecedented retinal damage pattern and suggest neurodegeneration beyond the motor system in this disease.

Ganglion cell layer-inner plexiform layer thickness and vision loss in young children with optic pathway gliomas

PURPOSE

To determine if measures of macular ganglion cell layer-inner plexiform layer (GCL-IPL) thickness can discriminate between children with and without vision loss (visual acuity or field) from their optic pathway glioma (OPG) using spectral-domain optical coherence tomography (SD-OCT).

METHODS

Children with OPGs (sporadic or secondary to neurofibromatosis type 1) enrolled in a prospective study of SD-OCT were included if they were cooperative for vision testing and macular SD-OCT images were acquired. Manual segmentation of the macular GCL-IPL and macular retinal nerve fiber layer (RNFL) was performed using elliptical annuli with diameters of 1.5, 3.0, and 4.5 mm. Logistic regression assessed the ability of GCL-IPL and RNFL thickness measures (micrometers) to differentiate between the normal and abnormal vision groups.

RESULTS

Forty-seven study eyes (normal vision = 31, abnormal vision = 16) from 26 children with OPGs were included. Median age was 5.3 years (range, 2.5-12.8). Thickness of all GCL-IPL and RNFL quadrants differed between the normal and abnormal vision groups (P < 0.01). All GCL-IPL measures demonstrated excellent discrimination between groups (area under the curve [AUC] > 0.90 for all diameters). Using the lower fifth percentile threshold, the number of abnormal GCL-IPL inner macula (3.0 mm) quadrants achieved the highest AUC (0.989) and was greater than the macula RNFL AUCs (P < 0.05).

CONCLUSIONS

Decreased GCL-IPL thickness (<fifth percentile) can discriminate between children with and without vision loss from their OPG. Ganglion cell layer-inner plexiform layer thickness could be used as a surrogate marker of vision in children with OPGs.

Distribution of retinal layer atrophy in patients with Parkinson disease and association with disease severity and duration

PURPOSE

To evaluate the thickness of the 10 retinal layers in the paramacular area of Parkinson disease patients using a new segmentation technology of optical coherence tomography (OCT) to examine whether the thickness of specific layers predicts neurodegeneration or Parkinson disease severity.

DESIGN

Observational prospective study.

METHODS

Parkinson disease patients (n = 129) and age-matched healthy subjects (n = 129) were enrolled. The Spectralis OCT system was used to automatically segment all retinal layers in a parafoveal scan using the new segmentation application prototype. Mean thickness of each layer was calculated and compared between Parkinson disease patients and healthy subjects, and between Parkinson disease patients with disease durations of less than or at least 10 years. A correlation analysis was performed to evaluate the association between retinal layer thickness, duration of disease, and Parkinson disease severity. Logistic regression analysis was performed to determine the most sensitive layer for predicting axonal atrophy.

RESULTS

Parkinson disease patients showed statistically significant reduced thickness in the retinal nerve fiber, ganglion cell, inner plexiform, and outer plexiform layers and increased thickness in the inner nuclear layer compared with healthy subjects (P < .05). The inner retinal layers were more affected in Parkinson disease patients with long disease duration. The ganglion cell layer thickness was inversely correlated with disease duration and Parkinson disease severity, and was predictive of axonal damage in Parkinson disease patients.

CONCLUSIONS

The segmentation application of the Spectralis OCT revealed retinal layer atrophy in Parkinson disease patients, especially in the inner layers of patients with long disease duration. Ganglion cell layer reduction was associated with increased axonal damage.

Development of a semi-automatic segmentation method for retinal OCT images tested in patients with diabetic macular edema

PURPOSE

To develop EdgeSelect, a semi-automatic method for the segmentation of retinal layers in spectral domain optical coherence tomography images, and to compare the segmentation results with a manual method.

METHODS

SD-OCT (Heidelberg Spectralis) scans of 28 eyes (24 patients with diabetic macular edema and 4 normal subjects) were imported into a customized MATLAB application, and were manually segmented by three graders at the layers corresponding to the inner limiting membrane (ILM), the inner segment/ellipsoid interface (ISe), the retinal/retinal pigment epithelium interface (RPE), and the Bruch's membrane (BM). The scans were then segmented independently by the same graders using EdgeSelect, a semi-automated method allowing the graders to guide/correct the layer segmentation interactively. The inter-grader reproducibility and agreement in locating the layer positions between the manual and EdgeSelect methods were assessed and compared using the Wilcoxon signed rank test.

RESULTS

The inter-grader reproducibility using the EdgeSelect method for retinal layers varied from 0.15 to 1.21 µm, smaller than those using the manual method (3.36-6.43 µm). The Wilcoxon test indicated the EdgeSelect method had significantly better reproducibility than the manual method. The agreement between the manual and EdgeSelect methods in locating retinal layers ranged from 0.08 to 1.32 µm. There were small differences between the two methods in locating the ILM (p = 0.012) and BM layers (p<0.001), but these were statistically indistinguishable in locating the ISe (p = 0.896) and RPE layers (p = 0.771).

CONCLUSIONS

The EdgeSelect method resulted in better reproducibility and good agreement with a manual method in a set of eyes of normal subjects and with retinal disease, suggesting that this approach is feasible for OCT image analysis in clinical trials.

Inner nuclear layer thickening is inversley proportional to retinal ganglion cell loss in optic neuritis

Aim

To examine the relationship between retinal ganglion cell loss and changes in the inner nuclear layer (INL) in optic neuritis (ON).

Methods

36 multiple sclerosis (MS) patients with a history of ON and 36 age and sex-matched controls underwent Optical Coherence Tomography. The paramacular retinal nerve fiber layer (RNFL), combined ganglion cell and inner plexiform layers (GCL/IPL) and inner nuclear layer (INL) thickness were measured at 36 points around the fovea. To remove inter-subject variability, the difference in thickness of each layer between the ON and fellow eye of each patient was calculated. A topographic analysis was conducted.

Results

The INL of the ON patients was thicker than the controls (42.9µm versus 39.6µm, p=0.002). ON patients also had a thinner RNFL (27.8µm versus 32.2µm, p<0.001) and GCL/IPL (69.3µm versus 98.1µm, p<0.001). Among the controls, there was no correlation between RNFL and GCL/IPL as well as RNFL and INL, but a positive correlation was seen between GCL/IPL and INL (r=0.65, p<0.001). In the ON group, there was a positive correlation between RNFL and GCL/IPL (r=0.80, p<0.001) but a negative correlation between RNFL and INL (r=-0.61, p<0.001) as well as GCL/IPL and INL (r=-0.44, p=0.007). The negative correlation between GCL/IPL and INL strengthened in the ON group when inter-subject variability was removed (r=-0.75, p<0.001). Microcysts within the INL were present in 5 ON patients, mainly in the superior and infero-nasal paramacular regions. While patients with microcysts lay at the far end of the correlation curve between GCL/IPL and INL (i.e. larger INL and smaller GCL/IPL compared to other patients), their exclusion did not affect the correlation (r= -0.76, p<0.001).

Conclusions

INL enlargement in MS-related ON is associated with the severity of GCL loss. This is a continuous relationship and patients with INL microcysts may represent the extreme end of the scale.