Corneal Subbasal Nerve Plexus Evaluation by in Vivo Confocal Microscopy in Multiple Sclerosis: A Potential New Biomarker

Ocular Changes and Tear Cytokines in Individuals with Low Serum Vitamin D Levels: A Cross-Sectional, Controlled Study

BACKGROUND

We investigated the effects of vitamin D on the ocular surface, tear functions, corneal imaging, and tear film cytokine levels.

METHODS

Fifty-two patients with vitamin D levels were examined in 3 groups according to serum vitamin D levels; 28 in group 1 (<12 ng/ml), 10 in group 2 (12-20 ng/ml), and 14 in group 3 (>20 ng/ml). Ocular surface disease index (OSDI), tear break up time (BUT), lissamine green (LG) staining, Schirmer test, in vivo confocal microscopy (IVCM), and tear collection for cytokine analysis were performed.

RESULTS

The mean OSDI score was 35.2 ± 23.3, 36.2 ± 17.7, 24.4 ± 18.2 (p = .253), TBUT was 6.7 ± 2.5 sec, 9.3 ± 1.8 sec, 11.1 ± 2.8 sec (p < .001), Schirmer test was 16.7 ± 8.5 mm, 18.7 ± 7.6 mm, and 20.2 ± 7 mm (p = .254), median LG staining grade was 1 (0-3), 1 (0-2), 0 (0-1) (p = .008) in group 1, group 2, and group 3, respectively. Basal epithelial cell density was 4 027 ± 512 cells/mm2, 4 673 ± 451 cells/mm2, 5 067 ± 817 cells/mm2 (p = < 0.001), sub-basal nerve density was 978 ± 204 μm/frame, 1 236 ± 172 μm/frame, 1 425 ± 290 μm/frame (p = <0.001), median number of long nerve fibers was 3 (2-4) nerve/frame, 4 (3-4) nerve/frame, 4 (3-6) nerve/frame (p = .001), and median grade of nerve fiber tortuosity was 2 (0-3), 2.5 (2-3), 3 (2-4) (p < .001) in group 1, group 2, and group 3, respectively. Mean IL-1 β (82.62 ± 15.26, 85.57 ± 17.41, and 66.44 ± 11 ng/ml in group 1, 2 and 3, respectively, p = .002), IL-17 (77.80 ± 24.91, 64.46 ± 25.47, 55.42 ± 12.05 ng/ml in group 1, 2 and 3, respectively, p = .012), and IL-2 (75.7 ± 18.4, 66.13 ± 26.78, and 59.65 ± 16.04 ng/ml in group 1, 2 and 3, respectively, p = .048) levels were significantly lower in group 3, whereas, IL-13 levels were significantly higher in group 3 (16.12 ± 5.24, 19.20 ± 4.90, and 21.6 ± 5.55 ng/ml in groups 1, 2, and 3, respectively, p = .010).

CONCLUSIONS

Vitamin D deficiency/insufficiency is associated with ocular surface changes shown with significant TBUT, LG staining, and tear film cytokine contents. Besides, significant corneal basal epithelial, sub-basal nerve density, and structural sub-basal nerve changes were associated with lower Vitamin D levels.

In Vivo Corneal Confocal Microscopy for Detecting Corneal Nerve Fiber Changes in Patients with Different Types of Optic Neuritis: A Cross-Sectional Study

PURPOSE

Optic neuritis (ON), a demyelinating disease of the central nervous system, is often a precursor manifestation of neuromyelitis optica spectrum disorders (NMOSD) or multiple sclerosis (MS). Reduced corneal nerve fiber counts have been found in patients with NMOSD or MS. This study aimed to observe and compare the corneal subbasal nerve plexus in patients with three types of ON and controls without ON using in vivo corneal confocal microscopy (IVCM).

METHODS

Data were analyzed for 77 eyes of 48 patients with ON, grouped according to seropositivity for anti-aquaporin-4 IgG, myelin oligodendrocyte glycoprotein antibody, or no seropositivity, and 35 healthy eyes in the control group. Corneal parameters were quantified based on IVCM images. Visual function indicators were recorded, following which their correlations with IVCM parameters were analyzed.

RESULTS

Significant differences in IVCM parameters were detected among the different groups. Reductions in corneal nerve fiber counts were negatively correlated with visual acuity. Corneal nerve fibers were significantly more damaged in the affected eye than in the unaffected eye in patients with ON.

CONCLUSION

IVCM revealed corneal nerve fiber loss of varying degrees, depending on the type of ON. This indicates that, although ON primarily affects the central nervous system, peripheral nerves, such as the trigeminal nerve, which innervates the corneal subbasal nerve plexus may also be damaged in affected patients.

Clinical associations of corneal neuromas with ocular surface diseases

Corneal neuromas, also termed microneuromas, refer to microscopic, irregularly-shaped enlargements of terminal subbasal nerve endings at sites of nerve damage or injury. The formation of corneal neuromas results from damage to corneal nerves, such as following corneal pathology or corneal or intraocular surgeries. Initially, denervated areas of sensory nerve fibers become invaded by sprouts of intact sensory nerve fibers, and later injured axons regenerate and new sprouts called neuromas develop. In recent years, analysis of corneal nerve abnormalities including corneal neuromas which can be identified using in vivo confocal microscopy, a non-invasive imaging technique with microscopic resolution, has been used to evaluate corneal neuropathy and ocular surface dysfunction. Corneal neuromas have been shown to be associated with clinical symptoms of discomfort and dryness of eyes, and are a promising surrogate biomarker for ocular surface diseases, such as neuropathic corneal pain, dry eye disease, diabetic corneal neuropathy, neurotrophic keratopathy, Sjögren's syndrome, bullous keratopathy, post-refractive surgery, and others. In this review, we have summarized the current literature on the association between these ocular surface diseases and the presentation of corneal microneuromas, as well as elaborated on their pathogenesis, visualization via in vivo confocal microscopy, and utility in monitoring treatment efficacy. As current quantitative analysis on neuromas mainly relies on manual annotation and quantification, which is user-dependent and labor-intensive, future direction includes the development of artificial intelligence software to identify and quantify these potential imaging biomarkers in a more automated and sensitive manner, allowing it to be applied in clinical settings more efficiently. Combining imaging and molecular biomarkers may also help elucidate the associations between corneal neuromas and ocular surface diseases.

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.

Quantitative assessment of the effect of SARS-CoV-2 on the corneal sub-basal nerve plexus of post-COVID-19 patients using in vivo confocal microscopy

OBJECTIVES

To investigate whether SARS-CoV-2 causes morphological changes in the corneal sub-basal nerve plexus (CSNP) of post-COVID-19 patients using in vivo confocal microscopy (IVCM).

METHODS

A total of 70 participants were included in the study and were divided into three groups. Post-COVID-19 patients with neurological manifestations were considered Group 1 (n = 24), and post-COVID-19 patients without neurological manifestations were considered Group 2 (n = 24). Healthy control participants were considered Group 3 (n = 22). The parameters of the CSNP, including nerve fibre density (NFD), nerve branch density (NBD), and nerve fibre length (NFL), were investigated in all participants using IVCM. Additionally, corneal sensitivity was tested by corneal esthesiometry.

RESULTS

The mean NFD, NBD, and NFL values of Group 1 (16.12 ± 4.84 fibre/mm², 27.97 ± 9.62 branch/mm², and 11.60 ± 2.89 mm/mm²) were significantly lower than those of Group 2 (19.55 ± 3.01 fibre/mm², 40.44 ± 7.16 branch/mm², and 15.92 ± 2.08 mm/mm²) and Group 3 (25.24 ± 3.75 fibre/mm², 44.61 ± 11.80 branch/mm², and 17.76 ± 3.32 mm/mm²) (p < 0.05 for all). Except the mean NFD value (p < 0.001), there were no significant differences in terms of the mean NBD and NFL values between Group 2 and Group 3 (p = 0.445, p = 0.085). The value of the mean corneal sensitivity was significantly higher in Group 3 (59.09 ± 1.97 mm) compared to Group 1 (55.21 ± 1.02 mm) and Group 2 (55.28 ± 1.18 mm) (p < 0.001, p < 0.001) but there was no significant difference between Group 1 and Group 2 (p = 1.000).

CONCLUSION

In post-COVID-19 patients, the mean parameters of CSNP were lower than in the control group. These differences were more pronounced in patients who had neurological manifestations of COVID-19.

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.