OCT and OCT-A biomarkers in multiple sclerosis - review.

Objective: Retinal neuronal and vascular changes have been observed in multiple sclerosis (MS) patients. The aim of this review was to highlight the most current optical coherence tomography (OCT) and optical coherence tomography angiography (OCT-A) data in MS and to provide information about the possibility of using OCT / OCT-A parameters as biomarkers for screening, diagnosis and monitoring of MS. Methods: To carry out this review, a meticulous literature search was undergone on PubMed between 2014 and the present day, using the following terms: "multiple", "sclerosis", "optical", "coherence", "tomography" and "angiography". Additional studies were found via references, being chosen according to relevance. Results: Retinal nerve fiber layer (RNFL) and ganglion cell layer (GCL) were significantly lower in MS patients compared to controls, and correlated with clinical and paraclinical variables, such as visual function, disability, and magnetic resonance imaging (MRI). Retinal capillary plexuses could be higher, lower or the same, and the best OCT-A microvasculature parameter for the detection of MS was the superficial capillary plexus (SCP). The reduced retinal vessel density (VD) was correlated with the disability in MS. Conclusions: OCT and OCT-A parameters could improve the development of retinal biomarkers for screening, early diagnosis and monitoring the disease progression of MS, and they could improve the development of potential future therapies that could slow or stop the course of this incurable disease. Abbreviations: DCP = deep capillary plexus; EDSS = Expanded Disability Status Scale; GCC = ganglion cell complex; GCL = ganglion cell layer; MRI = magnetic resonance imaging; MS = Multiple sclerosis; OCT = optical coherence tomography; OCT-A = optical coherence tomography angiography; ON = optic neuritis; RNFL = retinal nerve fiber layer; SCP = superficial capillary plexus; VD = vessel density.

Combining retinal structural and vascular measurements improves discriminative power for multiple sclerosis patients.

Data on how retinal structural and vascular parameters jointly influence the diagnostic performance of detection of multiple sclerosis (MS) patients without optic neuritis (MSNON) are lacking. To investigate the diagnostic performance of structural and vascular changes to detect MSNON from controls, we performed a cross-sectional study of 76 eyes from 51 MS participants and 117 eyes from 71 healthy controls. Retinal macular ganglion cell complex (GCC), retinal nerve fiber layer (RNFL) thicknesses, and capillary densities from the superficial (SCP) and deep capillary plexuses (DCP) were obtained from the Cirrus AngioPlex. The best structural parameter for detecting MS was compensated RNFL from the optic nerve head (AUC = 0.85), followed by GCC from the macula (AUC = 0.79), while the best vascular parameter was the SCP (AUC = 0.66). Combining structural and vascular parameters improved the diagnostic performance for MS detection (AUC = 0.90; p<0.001). Including both structure and vasculature in the joint model considerably improved the discrimination between MSNON and normal controls compared to each parameter separately (p = 0.027). Combining optical coherence tomography (OCT)-derived structural metrics and vascular measurements from optical coherence tomography angiography (OCTA) improved the detection of MSNON. Further studies may be warranted to evaluate the clinical utility of OCT and OCTA parameters in the prediction of disease progression.

Microvascular changes in the macular and parafoveal areas of multiple sclerosis patients without optic neuritis.

Retinal imaging has been proposed as a biomarker for neurological diseases such as multiple sclerosis (MS). Recently, a technique for non-invasive assessment of the retinal microvasculature called optical coherence tomography angiography (OCTA) was introduced. We investigated retinal microvasculature alterations in participants with relapsing-remitting MS (RRMS) without history of optic neuritis (ON) and compared them to a healthy control group. The study was performed in a prospective, case-control design, including 58 participants (n = 100 eyes) with RRMS without ON and 78 age- and sex-matched control participants (n = 136 eyes). OCTA images of the superficial capillary plexus (SCP), deep capillary plexus (DCP) and choriocapillaris (CC) were obtained using a commercial OCTA system (Zeiss Cirrus HD-5000 Spectral-Domain OCT with AngioPlex OCTA, Carl Zeiss Meditec, Dublin, CA). The outcome variables were perfusion density (PD) and foveal avascular zone (FAZ) features (area and circularity) in both the SCP and DCP, and flow deficit in the CC. MS group had on average higher intraocular pressure (IOP) than controls (P < 0.001). After adjusting for confounders, MS participants showed significantly increased PD in SCP (P = 0.003) and decreased PD in DCP (P < 0.001) as compared to controls. A significant difference was still noted when large vessels (LV) in the SCP were removed from the PD calculation (P = 0.004). Deep FAZ was significantly larger (P = 0.005) and less circular (P < 0.001) in the eyes of MS participants compared to the control ones. Neither LV, PD or FAZ features in the SCP, nor flow deficits in the CC showed any statistically significant differences between the MS group and control group (P > 0.186). Our study indicates that there are microvascular changes in the macular parafoveal retina of RRMS patients without ON, showing increased PD in SCP and decreased PD in DCP. Further studies with a larger cohort of MS patients and MRI correlations are necessary to validate retinal microvascular changes as imaging biomarkers for diagnosis and screening of MS.

A multi-regression approach to improve optical coherence tomography diagnostic accuracy in multiple sclerosis patients without previous optic neuritis.

BACKGROUND: Optical coherence tomography (OCT) is a retinal imaging system that may improve the diagnosis of multiple sclerosis (MS) persons, but the evidence is currently equivocal. To assess whether compensating the peripapillary retinal nerve fiber layer (pRNFL) thickness for ocular anatomical features as well as the combination with macular layers can improve the capability of OCT in differentiating non-optic neuritis eyes of relapsing-remitting MS patients from healthy controls. METHODS: 74 MS participants (n = 129 eyes) and 84 age- and sex-matched healthy controls (n = 149 eyes) were enrolled. Macular ganglion cell complex (mGCC) thickness was extracted and pRNFL measurement was compensated for ocular anatomical factors. Thickness measurements and their corresponding areas under the receiver operating characteristic curves (AUCs) were compared between groups. RESULTS: Participants with MS showed significantly thinner mGCC, measured and compensated pRNFL (p ≤ 0.026). Compensated pRNFL achieved better performance than measured pRNFL for MS differentiation (AUC, 0.75 vs 0.80; p = 0.020). Combining macular and compensated pRNFL parameters provided the best discrimination of MS (AUC = 0.85 vs 0.75; p < 0.001), translating to an average improvement in sensitivity of 24 percent for differentiation of MS individuals. CONCLUSION: The capability of OCT in MS differentiation is made more robust by accounting OCT scans for individual anatomical differences and incorporating information from both optic disc and macular regions, representing markers of axonal damage and neuronal injury, respectively.

Hydrodynamic limits for kinetic flocking models of Cucker-Smale type.

We analyse the asymptotic behavior for kinetic models describing the collective behavior of animal populations. We focus on models for self-propelled individuals, whose velocity relaxes toward the mean orientation of the neighbors. The self-propelling and friction forces together with the alignment and the noise are interpreted as a collision/interaction mechanism acting with equal strength. We show that the set of generalized collision invariants, introduced in [1], is equivalent in our setting to the more classical notion of collision invariants, i.e., the kernel of a suitably linearized collision operator. After identifying these collision invariants, we derive the fluid model, by appealing to the balances for the particle concentration and orientation. We investigate the main properties of the macroscopic model for a general potential with radial symmetry.