Is the ganglion cell layer thickness to macular thickness ratio a new biomarker for multiple sclerosis?

PURPOSE

Ganglion cell layer thickness (GCLT)-to-total macular thickness (MT) is a new parameter that has not been studied in multiple sclerosis (MS) before. The current study aims to reveal the status of the GCLT-to-MT ratio in MS and its role in supporting the diagnosis of MS.

METHODS

In this retrospective and cross sectional study, the medical records of the MS patients between January 2016 and December 2021 were reviewed. Age-sex matched healthy control group was generated. Demographic and clinical data recorded. All participants were examined using a spectral-domain optic coherence tomography (OCT) device. Retinal layers, choroidal thickness (CT) was recorded. GCLT-to-MT ratio was calculated.

RESULTS

A total of 74 eyes of 37 MS (9 male,28 female) patients and 82 eyes of 41 control (13 male, 28 female) were included in the study. The mean age was 37 ± 9.0 (years) in MS group. The MS patients and the control group were compared in terms of OCT parameters, CT was thicker at all regions in MS patients (p < 0.001). Macular thickness, GCLT, and inner plexiform layer thickness (IPLT) were thinner than the control group (p < 0.05). For distinguishing MS patients from healthy subjects, AUROC values for central GCLT/MT, temporal GCLT/MT, superior GCLT/MT, nasal GCLT/MT, and inferior GCLT/MT were 0.717, 0.689, 0.694, 0.733, and 0.740, respectively.

CONCLUSIONS

In conclusion MT, GCLT, and IPLT thickness were thinner in MS patients, regardless of optic neuritis. The AUROC values of GCLT/MT were high and GCLT/MT ratio may be a helpful modality in demonstrating retinal neurodegeneration in MS patients.

Optical coherence tomography (OCT) in neuro-ophthalmology

Optical coherence tomography (OCT) is a non-invasive medical imaging technology that is playing an increasing role in the routine assessment and management of patients with neuro-ophthalmic conditions. Its ability to characterise the optic nerve head, peripapillary retinal nerve fibre layer and cellular layers of the macula including the ganglion cell layer enables qualitative and quantitative assessment of optic nerve disease. In this review, we discuss technical features of OCT and OCT-based imaging techniques in the neuro-ophthalmic context, potential pitfalls to be aware of, and specific applications in more common neuro-ophthalmic conditions including demyelinating, inflammatory, ischaemic and compressive optic neuropathies, optic disc drusen and raised intracranial pressure. We also review emerging applications of OCT angiography within neuro-ophthalmology.

Retinal Nerve Fiber Layer Thickness and Total Macular Volume in Multiple Sclerosis Subtypes and Their Relationship with Severity of Disease, a Cross-Sectional Study

Background

Optic neuritis (ON) is an inflammatory demyelinating lesion in the optic nerve, which is strongly associated with multiple sclerosis (MS). Optical coherence tomography (OCT) is a noninvasive technique for the evaluation of the retinal layers. Our aim was to examine OCT metrics including retinal nerve fiber layer thickness (RNFLT), and total macular volume (TMV), in MS subtypes and their relationship with duration, first manifestation, and severity of disease.

Material and Methods

In this cross-sectional study, patients with a definite diagnosis of MS underwent complete ophthalmic and neurologic examination. OCT parameters including TMV and RNFLT were compared between MS subtypes and different first manifestations of MS. Their relationships were also studied with the duration and severity of disease based on the Expanded Disability Status Scale (EDSS) score.

Results

A total of 240 eyes were examined in 120 enrolled MS patients. The differences in RNFLT were not analytically meaningful between the subtypes of MS, but the differences in TMV values were statistically significant between the subtypes of MS (P: 0.39 and P: 0.04, respectively). The differences between RNFLT and TMV of eyes with and without ON were statistically significant between these two groups (P<0.001 and P<0.001). There was also an inverse correlation between EDSS disability score and RNFLT and TMV values (P: 0.00, r: −0.33 and P: 0.034, r: −0.11, respectively) and a significant inverse correlation between the duration of MS and RNFLT (P: 0.00, r: −0.47). The differences in RNFLT and TMV values were analytically meaningful between the categories of first manifestations of MS (P: 0.000 and P: 0.027, respectively).

Conclusion

RNFLT and TMV represent noninvasive parameters for assessment of neuroaxonal degeneration in the anterior visual pathway that correlate with the severity and duration of multiple sclerosis. The lowest RNFLT and TMV values were also seen in the perceptual category between the first manifestations of MS. Therefore, they may be useful in the evaluation of MS patients.

Optical coherence tomography in acute optic neuritis: A population-based study

OBJECTIVES

To measure early structural damage caused by autoimmune inflammatory optic neuritis (ON) by optical coherence tomography (OCT) in a population-based cohort.

METHODS

In a prospective population-based study over 24 months in Southern Denmark, patients diagnosed with acute ON and without prior diagnosis of a chronic neuroinflammatory disorder were included and examined with OCT, visual evoked potentials (VEP), visual fields, high contrast visual acuity (HCVA), and low contrast letter acuity (LCLA). Structural and functional outcomes were determined at 6-month follow-up based on interocular differences.

RESULTS

The 50 included patients had on average 16.9 μm peripapillary retinal nerve fiber layer loss, 10.6 μm ganglion cell and inner plexiform layer (GCIP) loss, and an average HCVA decrease of 0.22 dec. Based on a linear regression model, average GCIP loss amounted to -0.2 μm per day and started 8 days after onset. OCT outcomes but not VEP correlated well with all visual function measurements at follow-up. Structural and functional damage in 20 patients (40%) diagnosed de novo with multiple sclerosis (MS) and in 2 patients (4%) with positive myelin oligodendrocyte glycoprotein antibodies (MOG-IgG) test did not differ from patients with idiopathic ON.

CONCLUSIONS

Optic neuritis causes substantial retinal damage and vision loss independent of the underlying disease. Our study supports that GCIP damage starts closely to clinical onset. Good structure-function correlations between OCT and vision support the importance of OCT in monitoring acute ON.

Achievements and obstacles of remyelinating therapies in multiple sclerosis

Remyelination in the CNS is the natural process of damage repair in demyelinating diseases such as multiple sclerosis (MS). However, remyelination becomes inadequate in many people with MS, which results in axonal degeneration and clinical disability. Enhancement of remyelination is a logical therapeutic goal; nevertheless, all currently licensed therapies for MS are immunomodulatory and do not support remyelination directly. Several molecular pathways have been identified as potential therapeutic targets to induce remyelination, and some of these have now been assessed in proof-of-concept clinical trials. However, trial design faces several obstacles: optimal clinical or paraclinical outcome measures to assess remyelination remain ill-defined, and identification of the ideal timing of therapy is also a crucial issue. In addition, realistic expectations are needed concerning the probable benefits of such therapies. Nevertheless, approaches that enhance remyelination are likely to be protective for axons and so could prevent long-term neurodegeneration. Future MS treatment paradigms, therefore, are likely to comprise a combinatorial approach that involves both immunomodulatory and regenerative treatments.

SWEPT-SOURCE OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY OF THE OPTIC DISK IN OPTIC NEUROPATHY

PURPOSE

To evaluate the optic nerve head microvasculature in eyes with acute and chronic optic neuropathies using swept-source optical coherence tomography angiography.

METHODS

In this cross-sectional, observational study, optical coherence tomography angiography images were obtained from the optic nerve heads of 21 eyes of 12 patients with optic disk edema, pseudoedema and atrophy, and 12 eyes of 6 healthy subjects using a 1,050-nm optical coherence tomography angiography (Topcon DRI OCT; Triton). Peripapillary vasculature was assessed within five horizontal slabs consisting of the nerve fiber layer (NFL), ganglion cell layer, inner nuclear layer, choroidal layer, and full-thickness retinal layer. In addition, prelaminar and laminar slabs were evaluated. Vessel density was measured within a 3.4-mm diameter circle centered on the optic disk.

RESULTS

The abnormalities of the peripapillary capillary network were most apparent in the NFL and total retinal slabs. In eyes with disk edema, an increase or decrease in the visibility of the peripapillary capillary network was observed. Eyes with optic atrophy had decreased visibility of peripapillary capillary network corresponding to the region or sector of NFL thinning. Prelaminar capillary network was dilated and tortuous in eyes with disk edema. The mean vessel density was statistically significantly lower and the mean NFL thickness was statistically significantly thinner in eyes with optic atrophy compared with normal eyes (both P < 0.001). Vessel density was significantly correlated with the peripapillary NFL thickness (P < 0.001).

CONCLUSION

Optical coherence tomography angiography provides high-resolution, noninvasive visualization of the microvasculature of the optic nerve head and peripapillary region. Changes in the microvasculature in this region may prove useful in better characterization of optic neuropathies.

Retinal nerve fiber layer thickness by Stratus and Cirrus OCT in retrobulbar optic neuritis and nonarteritic ischemic optic neuropathy

PURPOSE

To compare retinal nerve fiber layer thickness (RNFLT) measurements by Stratus and Cirrus optical coherence tomography (OCT) and to evaluate agreement between the 2 instruments in retrobulbar optic neuritis (RON), nonarteritic ischemic optic neuropathy (NAION), and healthy controls.

METHODS

A total of 89 eyes with RON, 92 with NAION (6 to 12 months after diagnosis of acute disease), and 159 control eyes were studied. Average RNFLT was measured by Stratus and Cirrus OCTs. Comparisons among groups were performed by analysis of variance. Agreement between the 2 instruments was assessed using intraclass correlation coefficient (ICC) with 95% confidence interval (CI) and Bland-Altman analysis. Statistical significance was set at p≤0.05.

RESULTS

Average RNFLT was lower in NAION eyes than in RON and control ones using both OCT devices (60.0 ± 1.2, 69.9 ± 1.2, and 97.4 ± 0.9 μm, p&lt;0.001 by Cirrus; 49.7 ± 1.5, 65.9 ± 1.9, and 99.2 ± 1.3 μm, p&lt;0.001 by Stratus). The RNFLT values were higher with Cirrus than with Stratus in NAION (+10.30 μm, confidence interval [CI] 7.82-12.79 μm) and RON (+4.01 μm, CI 1.32-6.70 μm) eyes, and slightly lower in control ones (-1.75 μm, CI -3.51 to 0.01 μm). A stronger agreement between the 2 instruments was found in control and RON eyes than in NAION ones (ICC 0.682, CI 0.566-0.771; 0.635, CI 0.467-0.758; 0.321, CI 0.132-0.472, respectively).

CONCLUSIONS

Both Stratus and Cirrus OCT can identify RNFLT reduction in previous RON and NAION. Absolute RNFLT values differ between the 2 instruments; hence they are not to be considered interchangeable.

Optic Nerve

Optic nerve diseases arise from many different etiologies including inflammatory, neoplastic, genetic, infectious, ischemic, and idiopathic. Understanding some of the characteristics of the most common optic neuropathies along with therapeutic approaches to these diseases is helpful in designing recommendations for individual patients. Although many optic neuropathies have no specific treatment, some do, and it is those potentially treatable or preventable conditions which need to be recognized in order to help patients regain their sight or develop a better understanding of their own prognosis. In this chapter several diseases are discussed including idiopathic intracranial hypertension, optic neuritis, ischemic optic neuropathies, hereditary optic neuropathies, trauma, and primary tumors of the optic nerve. For each condition there is a presentation of the signs and symptoms of the disease, in some conditions the evaluation and diagnostic criteria are highlighted, and where possible, current therapy or past trials are discussed.

Distinguishing ischaemic optic neuropathy from optic neuritis by ganglion cell analysis

PURPOSE

To determine whether a pattern of altitudinal ganglion cell loss, as detected and measured by optical coherence tomography (OCT), can be used to distinguish non-arteritic ischaemic optic neuropathy (NAION) from optic neuritis (ON) during the acute phase, and whether the rate or severity of ganglion cell loss differs between the two diseases.

METHODS

We performed a retrospective, case-control study of 44 patients (50 eyes) with ON or NAION and 44 age-matched controls. Non-arteritic ischaemic optic neuropathy and ON patients had OCT at presentation and four consecutive follow-up visits. Controls had OCT at one point in time. The ganglion cell complex (GCC) was evaluated in the macula, and the retinal nerve fibre layer (RNFL) was evaluated in the peripapillary region. Ganglion cell complex thickness, RNFL thickness and GCC mean superior and inferior hemispheric difference were compared between NAION and ON patients at each time-point using unpaired t-tests and between disease and control subjects at first measurement using paired t-tests.

RESULTS

Mean time from onset of symptoms to initial presentation was 10.7 ± 6.6 days in NAION and 11.7 ± 8.6 days in ON (p = 0.67). There was a significantly greater vertical hemispheric difference in GCC thickness in NAION patients than ON patients at all time-points (5.5-10.7 μm versus 3.1-3.6 μm, p = 0.01-0.049). Mean GCC thickness was significantly decreased at less than 2 weeks after onset in NAION compared to age-matched controls (72.1 μm versus 82.1 μm, p < 0.001), as well as in ON compared to age-matched controls (74.3 μm versus 84.5 μm, p < 0.001). Progression and severity of GCC and RNFL loss did not differ significantly between NAION and ON.

CONCLUSION

A quantitative comparison of mean superior and inferior hemispheric GCC thickness with OCT may be used to distinguish NAION from ON.

Evaluation of the Innermost Retinal Layers and Visual Evoked Potentials in Patients with Multiple Sclerosis

PURPOSE

The present study was conducted to investigate alterations in the innermost layers of the retina using optical coherence tomography (OCT) and to assess potential associations of structural measures with functional markers in patients with Multiple Sclerosis (MS).

MATERIALS AND METHODS

Ninety-four eyes of 47 MS patients and 60 eyes of 30 healthy individuals were included in the study. All patients underwent complete ophthalmological examination and OCT imaging to analyze peripapillary retinal nerve fiber layer (RNFL) and ganglion cell-inner plexiform layer (GCIPL) thickness. Visual evoked potentials (VEPs) and expanded disability status scale (EDSS) score were assessed for MS patients.

RESULTS

The average RNFL and GCIPL thicknesses were thinner in MS patients (86.2 ± 11.9 µm and 73.6 ± 9.7 µm, respectively) when compared with those of healthy controls (96.7 ± 8.2 µm and 85.9 ± 4.6 µm, respectively, p < 0.001 for both). Within MS patients, the average RNFL and GCIPL thicknesses were lower in eyes with a prior history of optic neuritis (MS ON) than in eyes with no optic neuritis history (MS non-ON) (p = 0.012 and p < 0.001, respectively). RNFL and GCIPL thicknesses were inversely correlated with VEP latency (r = -0.40, p < 0.001 and r = -0.36, p < 0.001, respectively) in MS patient eyes. There was a correlation between GCIPL thickness and VEP amplitude in eyes with previous ON history (r = 0.34, p = 0.035). No significant correlations were found between OCT measurements and EDSS score.

CONCLUSIONS

Innermost layers of the retina are highly affected by the pathophysiologic process in MS disease, manifesting as a reduction in RNFL and GCIPL thickness. The structural retinal changes show correlation with alterations in potentials showing the optic pathway function.

Visual pathway neurodegeneration winged by mitochondrial dysfunction

Objectives

To test for structural and functional contribution of mitochondrial dysfunction to neurodegeneration in multiple sclerosis (MS). A visual pathway model void of MS lesions was chosen in order to exclude neurodegeneration secondary to lesion related axonotmesis.

Methods

A single-centre cohort study (230 MS patients, 63 controls). Spectral domain optical coherence tomography of the retina, 3T magnetic resonance imaging of the brain, spectrophotometric assessment of serum lactate levels. Postmortem immunohistochemistry.

Results

The visual pathway was void of MS lesions in 31 patients and 31 age-matched controls. Serum lactate was higher in MS compared to controls (P = 0.029). High serum lactate was structurally related to atrophy of the retinal nerve fiber layer at the optic disc (P = 0.041), macula (P = 0.025), and the macular ganglion cell complex (P = 0.041). High serum lactate was functionally related to poor color vision (P < 0.01), Expanded Disability Status Scale score (R = 0.37, P = 0.041), Guy's Neurological disability score (R = 0.38, P = 0.037), MS walking scale (R = 0.50, P = 0.009), upper limb motor function (R = 0.53, P = 0.002). Immunohistochemistry demonstrated increased astrocytic expression of a key lactate generating enzyme in MS lesions as well as profound vascular expression of monocarboxylate transporter-1, which is involved in lactate transport.

Interpretation

This study provides structural, functional, and translational evidence for visual pathway neurodegeneration in MS related to mitochondrial dysfunction.

Relationship Between Optic Nerve Appearance and Retinal Nerve Fiber Layer Thickness as Explored with Spectral Domain Optical Coherence Tomography

PURPOSE

To study the relationship between the appearance of the optic nerve and the retinal nerve fiber layer (RNFL) thickness determined by spectral domain optical coherence tomography (OCT).

METHODS

Records from patients with spectral domain-OCT imaging in a neuro-ophthalmology practice were reviewed. Eyes with glaucoma/glaucoma suspicion, macular/optic nerve edema, pseudophakia, and with refractive errors > 6D were excluded. Optic nerve appearance by slit lamp biomicroscopy was related to the RNFL thickness by spectral domain-OCT and to visual field results.

RESULTS

Ninety-one patients (176 eyes; mean age: 49 ± 15 years) were included. Eighty-three eyes (47%) showed optic nerve pallor; 89 eyes (50.6%) showed RNFL thinning (sectoral or average peripapillary). Average peripapillary RNFL thickness in eyes with pallor (mean ± SD = 76 ± 17 μm) was thinner compared to eyes without pallor (91 ± 14 μm, P < 0.001). Optic nerve pallor predicted RNFL thinning with a sensitivity of 69% and a specificity of 75%. Optic nerve appearance predicted RNFL thinning (with a sensitivity and specificity of 81%) when RNFL had thinned by ∼ 40%. Most patients with pallor had RNFL thinning with (66%) or without (25%) visual field loss; the remainder had normal RNFL and fields (5%) or with visual field abnormalities (4%).

CONCLUSIONS

Optic nerve pallor as a predictor of RNFL thinning showed fair sensitivity and specificity, although it is optimally sensitive/specific only when substantial RNFL loss has occurred.

TRANSLATIONAL RELEVANCE

Finding an acceptable relationship between the optic nerve appearance by ophthalmoscopy and spectral domain-OCT RNFL measures will help the clinician's interpretation of the information provided by this technology, which is gaining momentum in neuro-ophthalmic research.

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

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

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

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