Neuroaxonal Degeneration in Patients With Multiple Sclerosis: An Optical Coherence Tomography and in Vivo Corneal Confocal Microscopy Study

Corneal immune cells as a biomarker of inflammation in multiple sclerosis: a longitudinal study

Background

Corneal immune cells (ICs) are antigen-presenting cells that are known to increase ocular and systemic inflammatory conditions.

Objective

We aimed to assess longitudinal changes in corneal IC in patients with multiple sclerosis (MS) and relation to disability and ongoing treatment.

Design

Prospective observational study conducted between September 2016 and February 2020.

Methods

Patients with relapsing-remitting MS (RRMS) (n = 45) or secondary progressive MS (SPMS) (n = 15) underwent corneal confocal microscopy (CCM) at baseline and 2-year follow-up for estimation of corneal IC density [dendritic cells with (DCF) (cells/mm2) or without nerve fiber contact (DCP); and non-dendritic cells with (NCF) or without nerve fiber contact (NCP)]. Optical coherence tomography, neuroimaging, and disability assessments were additionally performed. Healthy controls (n = 20) were assessed at baseline.

Results

In both RRMS and SPMS compared to controls, DCP (p < 0.001 and p < 0.001, respectively) and DCF (p < 0.001 and p = 0.005) were higher and NCF (p = 0.007 and p = 0.02) was lower at baseline. DCP showed excellent performance in identifying patients with MS (sensitivity/specificity = 0.88/0.90) followed by DCF (0.80/0.75) and NCF (0.80/0.85). At follow-up compared to baseline, DCP (p = 0.01) was significantly reduced, and NCP (p = 0.004) and NCF (p = 0.04) were increased. Subgroup analysis showed that baseline NCP and NCF were significantly higher (p = 0.04-0.05) in patients who switched disease-modifying treatment, and baseline NCP (p = 0.05) was higher in patients on interferon.

Conclusion

Baseline and change in corneal IC were related to axonal degeneration and treatment status. Evaluation of corneal IC using CCM may allow an assessment of ongoing inflammation, disease progression, and the effect of treatment in MS.

Corneal axonal loss as an imaging biomarker of neurodegeneration in multiple sclerosis: a longitudinal study

Background

Resourceful endpoints of axonal loss are needed to predict the course of multiple sclerosis (MS). Corneal confocal microscopy (CCM) can detect axonal loss in patients with clinically isolated syndrome and established MS, which relates to neurological disability.

Objective

To assess corneal axonal loss over time in relation to retinal atrophy, and neurological and radiological abnormalities in MS.

Methods

Patients with relapsing-remitting (RRMS) (n = 68) or secondary progressive MS (SPMS) (n = 15) underwent CCM and optical coherence tomography. Corneal nerve fibre density (CNFD-fibres/mm²), corneal nerve branch density (CNBD-branches/mm²), corneal nerve fibre length (CNFL-mm/mm²) and retinal nerve fibre layer (RNFL-μm) thickness were quantified along with neurological and radiological assessments at baseline and after 2 years of follow-up. Age-matched, healthy controls (n = 20) were also assessed.

Results

In patients with RRMS compared with controls at baseline, CNFD (p = 0.004) and RNFL thickness (p < 0.001) were lower, and CNBD (p = 0.003) was higher. In patients with SPMS compared with controls, CNFD (p < 0.001), CNFL (p = 0.04) and RNFL thickness (p < 0.001) were lower. For identifying RRMS, CNBD had the highest area under the receiver operating characteristic (AUROC) curve (0.99); and for SPMS, CNFD had the highest AUROC (0.95). At follow-up, there was a further significant decrease in CNFD (p = 0.04), CNBD (p = 0.001), CNFL (p = 0.008) and RNFL (p = 0.002) in RRMS; in CNFD (p = 0.04) and CNBD (p = 0.002) in SPMS; and in CNBD (p = 0.01) in SPMS compared with RRMS. Follow-up corneal nerve loss was greater in patients with new enhancing lesions and optic neuritis history.

Conclusion

Progressive corneal and retinal axonal loss was identified in patients with MS, especially those with more active disease. CCM may serve as an imaging biomarker of axonal loss in MS.

In vivo confocal microscopy of corneal nerve fiber damage in early course of multiple sclerosis

PURPOSE

To evaluate the corneal nerve fiber morphology in patients with multiple sclerosis (MS) by in vivo corneal confocal microscopy (CCM).

METHODS

Retinal nerve fiber layer thickness (RNFLT), central macular thickness (CMT), corneal nerve fiber length (CNFL), corneal nerve fiber density (CNFD), corneal nerve branch density (CNBD) and corneal nerve fiber tortuosity (CNFT) were measured. Correlation of corneal nerve findings with duration and clinical severity of MS was calculated.

RESULTS

CNFL (9.50 ± 0.60 vs. 11.20 ± 0.57 mm/mm², P = 0.046) and CNBD (57.46 ± 5.04 vs. 77.65 ± 3.41 no/mm², P = 0.001) were significantly lower with no significant difference in CNFD (21.24 ± 1.20 vs. 23.62 ± 0.95 no/mm², P = 0.125), CNFT (2.00 ± 0.15 vs. 1.73 ± 0.12, P = 0.180), CMT (269.57 ± 12.53 vs. 271.10 ± 18.84 μm, P = 0.716) or RNFLT (102.82 ± 6.98 vs. 105.33 ± 12.70 μm, P = 0.351) between patients with RRMS compared to controls. There was no significant correlation between CCM parameters with EDSS and duration of disease in MS patients.

CONCLUSION

The current study demonstrated that a decrease in CNFL, CNFD and CNBD in CCM analysis in the early course of MS.

Corneal confocal microscopy demonstrates axonal loss in different courses of multiple sclerosis

Axonal loss is the main determinant of disease progression in multiple sclerosis (MS). This study aimed to assess the utility of corneal confocal microscopy (CCM) in detecting corneal axonal loss in different courses of MS. The results were confirmed by two independent segmentation methods. 72 subjects (144 eyes) [(clinically isolated syndrome (n = 9); relapsing–remitting MS (n = 20); secondary-progressive MS (n = 22); and age-matched, healthy controls (n = 21)] underwent CCM and assessment of their disability status. Two independent algorithms (ACCMetrics; and Voxeleron deepNerve) were used to quantify corneal nerve fiber density (CNFD) (ACCMetrics only), corneal nerve fiber length (CNFL) and corneal nerve fractal dimension (CNFrD). Data are expressed as mean ± standard deviation with 95% confidence interval (CI). Compared to controls, patients with MS had significantly lower CNFD (34.76 ± 5.57 vs. 19.85 ± 6.75 fibers/mm², 95% CI − 18.24 to − 11.59, P < .0001), CNFL [for ACCMetrics: 19.75 ± 2.39 vs. 12.40 ± 3.30 mm/mm², 95% CI − 8.94 to − 5.77, P < .0001; for deepNerve: 21.98 ± 2.76 vs. 14.40 ± 4.17 mm/mm², 95% CI − 9.55 to − 5.6, P < .0001] and CNFrD [for ACCMetrics: 1.52 ± 0.02 vs. 1.45 ± 0.04, 95% CI − 0.09 to − 0.05, P < .0001; for deepNerve: 1.29 ± 0.03 vs. 1.19 ± 0.07, 95% − 0.13 to − 0.07, P < .0001]. Corneal nerve parameters were comparably reduced in different courses of MS. There was excellent reproducibility between the algorithms. Significant corneal axonal loss is detected in different courses of MS including patients with clinically isolated syndrome.

Visual Dysfunction in Multiple Sclerosis and its Animal Model, Experimental Autoimmune Encephalomyelitis: a Review

Visual disabilities in central nervous system autoimmune diseases such as multiple sclerosis (MS) and its animal model, experimental autoimmune encephalomyelitis (EAE), are important symptoms. Past studies have focused on neuro-inflammatory changes and demyelination in the white matter of the brain and spinal cord. In MS, neuro-inflammatory lesions have been diagnosed in the visual pathway; the lesions may perturb visual function. Similarly, neuropathological changes in the retina and optic nerves have been found in animals with chronic EAE. Although the retina and optic nerves are immunologically privileged sites via the blood-retina barrier and blood-brain barrier, respectively, inflammation can occur via other routes, such as the uvea (e.g., iris and choroid) and cerebrospinal fluid in the meninges. This review primarily addresses the direct involvement of the blood-retina barrier and the blood-brain barrier in the development of retinitis and optic neuritis in EAE models. Additional routes, including pro-inflammatory mediator-filled choroidal and subarachnoid spaces, are also discussed with respect to their roles in EAE-induced visual disability and as analogues of MS in humans.

Generative Adversarial Network Based Automatic Segmentation of Corneal Subbasal Nerves on In Vivo Confocal Microscopy Images

Purpose

In vivo confocal microscopy (IVCM) is a noninvasive, reproducible, and inexpensive diagnostic tool for corneal diseases. However, widespread and effortless image acquisition in IVCM creates serious image analysis workloads on ophthalmologists, and neural networks could solve this problem quickly. We have produced a novel deep learning algorithm based on generative adversarial networks (GANs), and we compare its accuracy for automatic segmentation of subbasal nerves in IVCM images with a fully convolutional neural network (U-Net) based method.

Methods

We have collected IVCM images from 85 subjects. U-Net and GAN-based image segmentation methods were trained and tested under the supervision of three clinicians for the segmentation of corneal subbasal nerves. Nerve segmentation results for GAN and U-Net-based methods were compared with the clinicians by using Pearson's R correlation, Bland-Altman analysis, and receiver operating characteristics (ROC) statistics. Additionally, different noises were applied on IVCM images to evaluate the performances of the algorithms with noises of biomedical imaging.

Results

The GAN-based algorithm demonstrated similar correlation and Bland-Altman analysis results with U-Net. The GAN-based method showed significantly higher accuracy compared to U-Net in ROC curves. Additionally, the performance of the U-Net deteriorated significantly with different noises, especially in speckle noise, compared to GAN.

Conclusions

This study is the first application of GAN-based algorithms on IVCM images. The GAN-based algorithms demonstrated higher accuracy than U-Net for automatic corneal nerve segmentation in IVCM images, in patient-acquired images and noise applied images. This GAN-based segmentation method can be used as a facilitating diagnostic tool in ophthalmology clinics.

Translational Relevance

Generative adversarial networks are emerging deep learning models for medical image processing, which could be important clinical tools for rapid segmentation and analysis of corneal subbasal nerves in IVCM images.

Could contact lens dryness discomfort symptoms sometimes have a neuropathic basis?

Symptoms of dryness discomfort in soft contact lens wearers frequently lead to discontinuation from wear. The negative influence of pre-fitting tear dysfunctions appears likely to be exacerbated by the challenges to tear homeostasis caused by contact lenses. The corneal mechanisms for symptoms in contact lens wearers are different to those for dry eye disease because the cornea is insulated by the lens from ambient conditions as well as from lid wiper friction during blinking. Symptoms of dryness discomfort might be the consequence of increased lid wiper friction during blinking when the lens front surface becomes soiled and dry and exhibits very rapid tear break up. It is possible that some cases of contact lens intolerance and discontinuation could be a function of lid wiper neuropathy. In relation to the possibility of corneal neuropathy, a stagnant post-lens tear pool with the possibility of increased concentrations of metabolic by-products, cellular debris, and bacterial exotoxins, might have the potential to disturb the corneal epithelial and sub-basal nerves. Contributions by contact lens-induced inflammation to any neuropathic changes may partly depend on the degree to which inflammatory mediators are concentrated in a stagnant post-lens tear pool. It does not appear to be known if corneal neuropathic changes could develop under these conditions. The chances of neuropathic involvement may be greater if discomfort develops after a significant period of successful wear and there is a history of comorbid pain conditions. Esthesiometry and in vivo confocal microscopy in discontinued contact lens wearers may support a diagnosis of contact lens-related corneal neuralgia.

A novel investigation method for axonal damage in neuromyelitis optica spectrum disorder: In vivo corneal confocal microscopy

Background

Neuromyelitis optica spectrum disorder (NMOSD) is an inflammatory autoimmune disorder that damages optic nerves, brainstem, and spinal cord. In vivo corneal confocal microscopy (IVCM) is a noninvasive technique that provides corneal images with dendritic cells (DCs) and corneal subbasal nerve plexus (SBP), which arises from the trigeminal nerve.

Objective

We investigated corneal SBP changes in NMOSD and proposed IVCM as a potential new disease severity biomarker for NMOSD.

Methods

Seventeen age-sex matched NMOSD patients and 19 healthy participants underwent complete neurologic and ophthalmologic examinations. The duration of disease, first symptom, presence of optic neuritis attack, antibody status, Expanded Disability Status Scale(EDSS) score and disease severity score(DSS) were recorded. Retinal nerve fibre layer (RNFL) thickness was measured with optical coherence tomography, and corneal SBP images were taken with IVCM.

Results

NMOSD patients had significantly reduced corneal nerve fibre lenght-density and corneal nerve branch lenght-density compared with controls, while DC density was increased. NMOSD patients also showed significantly reduced RNFL thickness compared with controls. EDSS,DSS levels were inversely correlated with IVCM parameters.

Conclusion

We observed significant corneal nerve fibre loss in NMOSD patients in relation to disease severity. IVCM can be a candidate noninvasive imaging method for axonal damage assessment in NMOSD that warrants further investigation.

Corneal epithelial dendritic cells in patients with multiple sclerosis: An in vivo confocal microscopy study

PURPOSE

To evaluate density and morphology of corneal epithelial dendritic cells (DCs) in patients with multiple sclerosis (MS) using in vivo confocal microscopy (IVCM).

METHODS

This was a single-center cross-sectional comparative study. All MS patients were clinically scored using the Expanded Disability Status Scale (EDSS) score. Patients underwent ophthalmological examination and then cornea was analyzed by IVCM Heidelberg Retina Tomograph (HRT 3) in combination with Rostock Cornea Module and CCD camera. Five sectors (central, nasal, temporal, inferior, superior and central area) were analyzed in both patient eyes, then for each sector one image was selected and analyzed by using the manual cell counting system offered with the software and ImageJ program. DCs density (cell/mm²) and DCs size (µm²) were considered for the analyses. Difference between the two groups and correlation between DCs, MS type, EDSS score, optic neuritis and ongoing therapy were analyzed.

RESULTS

We enrolled 46 consecutive patients: 23 with MS (age 47.87 ± 7.22 years (mean ± standard deviation) and 21 healthy subjects (age 46.0 ± 12.6 years) from July 2017 to July 2018. MS patients showed a lower DCs density when compared with healthy subjects (p < 0.05). Moreover, we found a direct correlation (r:0.48, p < 0.05) between DCs density and ongoing disease-modifying therapy.

CONCLUSION

IVCM was able to show a difference in corneal DCs density between MS patients and healthy subjects, providing an insight to the underlying changes of the clinical manifestations of MS. Further studies are needed to provide evidence of possible clinical implications.