Changes in retinal structures as markers of multiple sclerosis progression

The involvement of the visual pathway in multiple sclerosis (MS) pathology determines the importance of studying the structures of the retina for earlier diagnosis and monitoring the severity of the neurodegeneration. The introduction of the reference method of optical coherence tomography (OCT) allows high resolution in vivo visualization of the retinal structures.Objective: to identify changes in various retinal structures in remitting (RMS) and secondary-progressive (SPMS) MS phenotypes.Patients and methods. The study included 80 patients with RMS (n=48) and SPMS (n=32); the control group included 20 age- and sex-adjusted healthy individuals. Clinical assessment was carried out using the Expanded Disability Status Scale (EDSS) and the Multiple Sclerosis Severity Score (MSSS). All patients were examined by an ophthalmologist. To assess changes in the retina, OCT was performed using the RTVue XR Avanti apparatus (Optovue, USA).Results and discussion. We found a significant (p<0.001) decrease in the thickness of the retina of the foveal and parafoveal regions, the thickness of the ganglionic cell complex when comparing the parameters of the retina of the control group and patients with RMS. There was also a significant (p<0.01) decrease in the retinal thickness in the perifoveal region, the thickness of the layer of retinal nerve fibers, the magnitude of focal and global losses. During comparation of the retinal OCT data between patients with RMS and SPMS, we revealed significant differences (p<0.001) in the thickness of the retinal nerve fiber layer, the retinal thickness in the parafoveal and foveal regions, and a significant (p<0.01) decrease in the thickness of the peripheral region, the thickness of the ganglionic cell complex, the volume of focal and global losses. Assessment of the correlations of OCT parameters with the EDSS and MSSS scales in both phenotypes showed a single significant (p<0.05) strong negative correlation (r=-0.70) of the EDSS score and retinal thickness in the foveal region in patients with SPMS.Conclusion. As a domain of criteria for the MS course without signs of disease activity (No Evidence of Disease Activity, NEDA), it is advisable to use retinal OCT with analysis of the retinal thickness in the foveal region, the thickness of the retinal nerve fiber layer, the ganglion cell complex for dynamic monitoring of the inflammatory process activity in patients with RMS and assessment of its progression in patients with SPMS.

Vessel Density and Retinal Thickness from Optical Coherence Tomography Angiography as New Indexes in Adolescent Myopia

Purpose. To evaluate and quantify blood perfusion and retinal thickness (RT) from the perspective of quadrants by optical coherence tomography angiography (OCTA) in adolescents with myopia and explore the relationship between axial elongation and related indexes of OCTA. Methods. A total of 88 subjects (149 eyes) with different degrees of myopia were included in this cross-sectional study. Vessel density (VD) and RT of quadrants in macular and peripheral regions were measured through OCTA. Results. The superficial VD (SVD) of the parainferior region was significantly correlated with axial length (AL) between the emmetropia (EM) group and high myopia (HI) group ( P = 0.012 ). There were significant differences in deep VD (DVD) in all quadrants, except for the foveal, perifoveal, and peri-inferior regions ( P > 0.05 ). However, there were significant alterations in the whole, parainferior, and perinasal regions ( P = 0.030 , 0.023, and 0.035) in the low-to-moderate myopia (L–M) group compared with those in the HI group. There were significant differences in the RT in all quadrants, except for the foveal, paratemporal, and paranasal regions ( P > 0.05 ) between the EM and L–M groups and the foveal region ( P > 0.05 ) between the EM and HI groups. Nevertheless, only RT in the peri-inferior region of the L–M and HI groups showed significant differences. AL was negatively correlated with SVD in the perifoveal and parainferior regions (r = −0.179, P = 0.029 ; r = −0.227, P = 0.005 ) and inversely correlated with DVD and RT in almost all quadrants, except for the foveal region (r = −0.020, P = 0.811 ; r = 0.135, P = 1.000 ). Conclusion. DVD and RT were closely associated with the severity of myopia and might be new indexes in assessing and detecting myopia development via OCTA.

Spectrally Resolved Fundus Autofluorescence in Healthy Eyes: Repeatability and Topographical Analysis of the Green-Emitting Fluorophores

The aim of this study was to report normal measurements of green-emitting fluorophores in the macula of healthy young individuals and to assess the repeatability of these quantitative metrics. To do so, healthy young volunteers were imaged twice (7 ± 3 days apart) using a confocal blue-light fundus autofluorescence (FAF) device with a shorter excitation wavelength (peak at 450 nm) and the capability for separately detecting the red and green components of the emission spectrum. The main outcome measure was the percentage of area occupied by green-emitting fluorophores in the macula. In addition, this measure was performed in separate regions providing a topographical assessment in the foveal, parafoveal and perifoveal regions. Furthermore, the level of agreement between repeated measurements was evaluated. Thirty eyes from 30 healthy volunteers were included in this analysis. Mean age was 26.2 ± 2.8 years (median: 25.0 years; range: 23.0–32.0 years). Median (interquartile range—IQR) area occupied by green-emitting fluorophores was 3.6% (1.9–4.7%) in the macular region. In the topographical analysis, this percentage was higher in the foveal area (median = 33.3%, IQR = 21.9–41.2%), as compared with both the parafoveal (median = 5.3%; IQR = 2.4–8.1%; p < 0.0001) and perifoveal (median = 0.5%, IQR = 0.2–0.8%; p < 0.0001) regions. The coefficient of variation (CV; ranging from 1.1% to 1.7% in the analyzed regions) and the intraclass correlation coefficient (ICC; ranging from 0.93 to 0.97) indicated high levels of repeatability. In conclusion, the assessment of green-emitting fluorophores is repeatable. The distribution of these fluorophores is highest in the foveal region. Assuming that flavin adenine dinucleotide (FAD) emits in the green autofluorescence spectrum, this variability could be secondary to an increased quantity of mitochondria in the foveal region.

Comparative micromechanics of bushcricket ears with and without a specialized auditory fovea region in the crista acustica

In some insects and vertebrate species, the specific enlargement of sensory cell epithelium facilitates the perception of particular behaviourally relevant signals. The insect auditory fovea in the ear of the bushcricket Ancylecha fenestrata (Tettigoniidae: Phaneropterinae) is an example of such an expansion of sensory epithelium. Bushcricket ears developed in convergent evolution anatomical and functional similarities to mammal ears, such as travelling waves and auditory foveae, to process information by sound. As in vertebrate ears, sound induces a motion of this insect hearing organ (crista acustica), which can be characterized by its amplitude and phase response. However, detailed micromechanics in this bushcricket ear with an auditory fovea are yet unknown. Here, we fill this gap in knowledge for bushcricket, by analysing and comparing the ear micromechanics in Ancylecha fenestrata and a bushcricket species without auditory fovea ( Mecopoda elongata , Tettigoniidae: Mecopodinae) using laser-Doppler vibrometry. We found that the increased size of the crista acustica, expanded by a foveal region in A. fenestrata , leads to higher mechanical amplitudes and longer phase delays in A. fenestrata male ears. Furthermore, area under curve analyses of the organ oscillations reveal that more sensory units are activated by the same stimuli in the males of the auditory fovea-possessing species A. fenestrata . The measured increase of phase delay in the region of the auditory fovea supports the conclusion that tilting of the transduction site is important for the effective opening of the involved transduction channels. Our detailed analysis of sound-induced micromechanics in this bushcricket ear demonstrates that an increase of sensory epithelium with foveal characteristics can enhance signal detection and may also improve the neuronal encoding.

Foveation Pipeline for 360° Video-Based Telemedicine

Pan-tilt-zoom (PTZ) and omnidirectional cameras serve as a video-mediated communication interface for telemedicine. Most cases use either PTZ or omnidirectional cameras exclusively; even when used together, images from the two are shown separately on 2D displays. Conventional foveated imaging techniques may offer a solution for exploiting the benefits of both cameras, i.e., the high resolution of the PTZ camera and the wide field-of-view of the omnidirectional camera, but displaying the unified image on a 2D display would reduce the benefit of “omni-” directionality. In this paper, we introduce a foveated imaging pipeline designed to support virtual reality head-mounted displays (HMDs). The pipeline consists of two parallel processes: one for estimating parameters for the integration of the two images and another for rendering images in real time. A control mechanism for placing the foveal region (i.e., high-resolution area) in the scene and zooming is also proposed. Our evaluations showed that the proposed pipeline achieved, on average, 17 frames per second when rendering the foveated view on an HMD, and showed angular resolution improvement on the foveal region compared with the omnidirectional camera view. However, the improvement was less significant when the zoom level was 8× and more. We discuss possible improvement points and future research directions.

Intra- and interobserver reliability for predicting hip preservation versus hip arthroplasty utilizing plain radiographs with comparison of surgeon specialization

Surgeon subspecialty training and practice landscape are formative in diagnostic evaluation and treatment recommendations. Varying recommendations can have substantial impact on patients’ care pathways and outcomes. We investigated intra- and interobserver reliability of treatment predictions for total hip arthroplasty (THA) between surgeons performing arthroplasty and/or arthroscopic hip preservation surgery. Anterior–posterior (AP) hip radiographs cropped to include the lateral sourcil, medial sourcil and foveal region of 53 patients with Tönnis Grade 0–3 were evaluated by five surgeons (two performing arthroplasty, two performing arthroscopic hip preservation and one performing both interventions). Surgeons predicted THA versus no THA as the treatment for each image. Predictions were repeated three times with image order randomized, and intra- and interobserver reliability were calculated. Surgeons were blinded to patient characteristics and clinical information. Interobserver reliability was 0.452 whereas intraobserver reliability ranged from 0.270 to 0.690. Arthroscopic hip preservation surgeons were more likely to predict THA (36.9%) than arthroplasty surgeons (32.7%), P = 0.041. Intra- and interobserver reliabilities of surgeons predicting THA versus no THA based on an AP hip radiograph were average at best. Arthroscopic hip preservation surgeons were more likely to predict THA than arthroplasty surgeons. Subjective surgeon interpretation can lead to variability in recommendations to patients; potentially complicating care pathways.

Automatic Visual Acuity Estimation by Means of Computational Vascularity Biomarkers Using Oct Angiographies

Optical Coherence Tomography Angiography (OCTA) constitutes a new non-invasive ophthalmic image modality that allows the precise visualization of the micro-retinal vascularity that is commonly used to analyze the foveal region. Given that there are many systemic and eye diseases that affect the eye fundus and its vascularity, the analysis of that region is crucial to diagnose and estimate the vision loss. The Visual Acuity (VA) is typically measured manually, implying an exhaustive and time-consuming procedure. In this work, we propose a method that exploits the information of the OCTA images to automatically estimate the VA with an accurate error of 0.1713.

A new framework for understanding vision from the perspective of the primary visual cortex

Visual attention selects only a tiny fraction of visual input informationfor further processing. Selection starts in the primary visual cortex (V1), which creates abottom-up saliency map to guide the fovea to selected visual locations via gaze shifts.This motivates a new framework that views visionas consisting of encoding, selection, and decoding stages, placingselection on center stage. It suggests a massive loss of non-selectedinformation from V1 downstream along the visual pathway.Hence, feedback from downstream visual cortical areas to V1 for better decoding (recognition),through analysis-by-synthesis, should query for additional information and be mainly directed atthe foveal region. Accordingly, non-foveal vision is not only poorer in spatial resolution,but also more susceptible to many illusions.

Quantitative changes in the ageing choriocapillaris as measured by swept source optical coherence tomography angiography

AimTo analyse quantitative optical coherence tomography angiography (OCTA) parameters of choriocapillaris (CC) at the foveal, perifoveal and parafoveal regions in healthy subjects of different age.MethodsIn this observational cross-sectional study, consecutive healthy subjects underwent swept source OCTA (PLEX Elite 9000, Carl Zeiss Meditec, USA). 3×3 mm and 6×6 mm scans centred on the fovea were acquired analysed and postprocessed with thresholding and binarisation processes. The main outcome measures included CC quantitative OCTA features (perfusion density (PD), vessel length density (VLD) and vessel diameter index (VDI)) at the foveal, perifoveal and parafoveal regions, and their relationship with age.ResultsSeventy-two eyes (72 patients, mean age 47.4±19.2 years, mean axial length 24.0±0.7 mm) were included. The mean PD was statistically lower in the foveal region compared with the parafoveal region in 3×3 mm scans (p=0.009). In subjects aged 70–80, PD of the foveal region was significantly reduced compared with the perifoveal region in 6×6 mm scans (p=0.008). A strong negative correlation was found between PD and ageing in the foveal, parafoveal and perifoveal regions (p<0.001 in all analyses). Furthermore, PD in the nasal-perifoveal region was significantly lower than the temporal-perifoveal region (p=0.005). No significant correlation was found between VLD and age in all regions, whereas VDI was strictly correlated with age (p<0.001).ConclusionsWe reported in vivo a strong negative correlation between PD and ageing in the CC of healthy subjects. This reduction seems related to a reduced diameter, and not to a reduced number, of capillaries. The age-related changes were higher in the central area compared with the perifoveal area.