Study of a retinal layer model to generate a spike waveform for a color deficient and strabismus individual

2019 ◽  
Vol 64 (3) ◽  
pp. 285-295
Author(s):  
T. Rajalakshmi ◽  
Shanthi Prince
Keyword(s):  
Ganglion Cell ◽  
Spike Train ◽  
Visual Information ◽  
Retinal Layer ◽  
Layer Model ◽  
Temporal Filtering ◽  
Photoreceptor Layer ◽  
Retinal Layers ◽  
Cell Layers ◽  
Insight Into

Abstract The physiological modeling of retinal layers to provide an insight into how the incoming image is converted into its equivalent spike train that can be decoded by the human brain is a key issue. Most of the retinal layer models concentrate mainly on image compression, edge detection and image reconstruction. A retinal layer model to generate spike waveform corresponding to the visual information is not covered much in the literature. The aim of this study was to develop a mathematical model of retinal layers that has complex neural structures, that can detect the incoming signal and transform the signal into the equivalent spike train. The proposed retinal layer model includes a photoreceptor, an outer plexiform (OPL), an inner plexiform (IPL) and ganglion cell layers exhibiting the properties of compression, luminance and spatial temporal filtering in the processing of visual information. The photoreceptor layer enhances the contrast visibility in the dark region and maintains the same in the bright regions. The OPL is modeled to enhance the contour of the image. The finer detail of the image is extracted by mathematically modeling the IPL. The ganglion cell layer is modeled using the Hodgkin-Huxley model to generate the spike train for the incoming information. The spike train was generated for color deficient individuals namely protanopia, deuteranopia, tritanopia and for individuals suffering from night blindness. Simulation results showed a spike train was generated only for a certain threshold stimulus value. The differences in spike pattern for a normal and visually impaired individual were studied. This may lead to a methodology for earlier diagnosis.

scholarly journals Evidence of subclinical quantitative retinal layer abnormalities in AQP4-IgG seropositive NMOSD

2020 ◽  
pp. 135245852097777
Author(s):  
Angeliki G Filippatou ◽  
Eleni S Vasileiou ◽  
Yufan He ◽  
Kathryn C Fitzgerald ◽  
Grigorios Kalaitzidis ◽  
...  
Keyword(s):  
Ganglion Cell ◽  
Outer Nuclear Layer ◽  
Sensitivity Analyses ◽  
Retinal Layer ◽  
Inner Plexiform Layer ◽  
Fiber Layer ◽  
Foveal Thickness ◽  
Cross Sectional ◽  
Photoreceptor Layer ◽  
History Of

Background: Prior studies have suggested that subclinical retinal abnormalities may be present in aquaporin-4 immunoglobulin G (AQP4-IgG) seropositive neuromyelitis optica spectrum disorder (NMOSD), in the absence of a clinical history of optic neuritis (ON). Objective: Our aim was to compare retinal layer thicknesses at the fovea and surrounding macula between AQP4-IgG+ NMOSD eyes without a history of ON (AQP4-nonON) and healthy controls (HC). Methods: In this single-center cross-sectional study, 83 AQP4-nonON and 154 HC eyes were studied with spectral-domain optical coherence tomography (OCT). Results: Total foveal thickness did not differ between AQP4-nonON and HC eyes. AQP4-nonON eyes exhibited lower outer nuclear layer (ONL) and inner photoreceptor segment (IS) thickness at the fovea (ONL: −4.01 ± 2.03 μm, p = 0.049; IS: −0.32 ± 0.14 μm, p = 0.029) and surrounding macula (ONL: −1.98 ± 0.95 μm, p = 0.037; IS: −0.16 ± 0.07 μm, p = 0.023), compared to HC. Macular retinal nerve fiber layer (RNFL: −1.34 ± 0.51 μm, p = 0.009) and ganglion cell + inner plexiform layer (GCIPL: −2.44 ± 0.93 μm, p = 0.009) thicknesses were also lower in AQP4-nonON compared to HC eyes. Results were similar in sensitivity analyses restricted to AQP4-IgG+ patients who had never experienced ON in either eye. Conclusions: AQP4-nonON eyes exhibit evidence of subclinical retinal ganglion cell neuronal and axonal loss, as well as structural evidence of photoreceptor layer involvement. These findings support that subclinical anterior visual pathway involvement may occur in AQP4-IgG+ NMOSD.

scholarly journals Macular Retinal Layer Thickness and Associated Factors. The Beijing Eye Study 2011

2019 ◽  
Author(s):  
Qian Wang ◽  
Wen Bin Wei ◽  
Ya Xing Wang ◽  
Yan Ni Yan ◽  
Jing Yan Yang ◽  
...  
Keyword(s):  
Ganglion Cell ◽  
Ganglion Cell Layer ◽  
Cell Layer ◽  
Outer Nuclear Layer ◽  
Plexiform Layer ◽  
Population Based ◽  
Retinal Layer ◽  
Inner Plexiform Layer ◽  
Beijing Eye Study ◽  
Retinal Layers

Abstract Background Diagnosis and follow-up of retinal diseases may be improved if the thickness of the various retinal layers, in addition to the total retinal thickness, is taken into account. Here we measured the thickness of the macular retinal layers in a population-based study group to assess the normative values and their associations. Methods Using spectral-domain optical coherence tomographic images, we measured the thickness of the macular retinal layers in participants of the population-based Beijing Eye Study without ocular diseases and without arterial hypertension, hyperlipidemia and diabetes mellitus. Results The study included 384 subjects (mean age:60.0±8.0 years). In multivariable analysis, the thickness of the retinal layers in the foveal region, of all retinal layers except for the outer plexiform layer in the parafoveal area, and the thickness of the ganglion cell layer, inner plexiform layer and inner and outer nuclear layer in the perifoveal area decreased with older age (all P<0.05). Men as compared to women had higher thickness measurements of the photoreceptor layer and outer nuclear layer in all areas, and of all layers between the retinal nerve fiber layer and inner nuclear layer in the parafovea area. The associations between the macular retinal layers thickness and axial length were not consistent. The inner plexiform layer was thicker, and the ganglion cell layer and inner nuclear layer were thinner, in the temporal areas than in the nasal areas, Conclusions The associations between decreasing thickness of most retinal layers with older age and the correlation of a higher thickness of some retinal layer layers with male gender may clinically be taken into account.

scholarly journals Serum neurofilament levels reflect outer retinal layer changes in multiple sclerosis

2021 ◽  
Vol 14 ◽  
pp. 175628642110034
Author(s):  
Caspar B. Seitz ◽  
Falk Steffen ◽  
Muthuraman Muthuraman ◽  
Timo Uphaus ◽  
Julia Krämer ◽  
...  
Keyword(s):  
Multiple Sclerosis ◽  
Optic Neuritis ◽  
Previous History ◽  
Supervised Machine Learning ◽  
Support Vector ◽  
Retinal Layer ◽  
Neurofilament Light Chain ◽  
Neurofilament Light ◽  
Retinal Layers ◽  
History Of

Background: Serum neurofilament light chain (sNfL) and distinct intra-retinal layers are both promising biomarkers of neuro-axonal injury in multiple sclerosis (MS). We aimed to unravel the association of both markers in early MS, having identified that neurofilament has a distinct immunohistochemical expression pattern among intra-retinal layers. Methods: Three-dimensional (3D) spectral domain macular optical coherence tomography scans and sNfL levels were investigated in 156 early MS patients (female/male: 109/47, mean age: 33.3 ± 9.5 years, mean disease duration: 2.0 ± 3.3 years). Out of the whole cohort, 110 patients had no history of optic neuritis (NHON) and 46 patients had a previous history of optic neuritis (HON). In addition, a subgroup of patients ( n = 38) was studied longitudinally over 2 years. Support vector machine analysis was applied to test a regression model for significant changes. Results: In our cohort, HON patients had a thinner outer plexiform layer (OPL) volume compared to NHON patients ( B = −0.016, SE = 0.006, p = 0.013). Higher sNfL levels were significantly associated with thinner OPL volumes in HON patients ( B = −6.734, SE = 2.514, p = 0.011). This finding was corroborated in the longitudinal subanalysis by the association of higher sNfL levels with OPL atrophy ( B = 5.974, SE = 2.420, p = 0.019). sNfL levels were 75.7% accurate at predicting OPL volume in the supervised machine learning. Conclusions: In summary, sNfL levels were a good predictor of future outer retinal thinning in MS. Changes within the neurofilament-rich OPL could be considered as an additional retinal marker linked to MS neurodegeneration.

scholarly journals Inner and outer retinal layer thickness alterations in pediatric and juvenile craniopharyngioma

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Ga-In Lee ◽  
Kyung-Ah Park ◽  
Sei Yeul Oh ◽  
Doo-Sik Kong ◽  
Sang Duk Hong
Keyword(s):  
Layer Thickness ◽  
Outer Nuclear Layer ◽  
Plexiform Layer ◽  
Visual Field Defects ◽  
Retinal Layer ◽  
Inner Plexiform Layer ◽  
Healthy Controls ◽  
Fiber Layer ◽  
Photoreceptor Layer ◽  
Chiasmal Compression

AbstractWe evaluated postoperative retinal thickness in pediatric and juvenile craniopharyngioma (CP) patients with chiasmal compression using optical coherence tomography (OCT) auto-segmentation. We included 18 eyes of 18 pediatric or juvenile patients with CP and 20 healthy controls. Each thickness of the macular retinal nerve fiber layer (RNFL), ganglion cell layer (GCL), inner plexiform layer (IPL), inner nuclear layer, outer plexiform layer, outer nuclear layer, and photoreceptor layer was compared between the CP patients and healthy controls. There was significant thinning in the macular RNFL (estimates [μm], superior, − 10.68; inferior, − 7.24; nasal, − 14.22), all quadrants of GCL (superior, − 16.53; inferior, − 14.37; nasal, − 24.34; temporal, − 9.91) and IPL (superior, − 11.45; inferior, − 9.76; nasal, − 15.25; temporal, − 4.97) in pediatric and juvenile CP patients postoperatively compared to healthy control eyes after adjusting for age and refractive errors. Thickness reduction in the average and nasal quadrant of RNFL, GCL, and IPL was associated with peripapillary RNFL thickness, and reduced nasal quadrant GCL and IPL thicknesses were associated with postoperative visual field defects. In pediatric and juvenile patients with CP, decreased inner retinal layer thickness following chiasmal compression was observed. The changes in retinal structures were closely related to peripapillary RNFL thinning and functional outcomes.

scholarly journals Reconstructing feedback representations in ventral visual pathway with a generative adversarial autoencoder

2020 ◽  
Author(s):  
Haider Al-Tahan ◽  
Yalda Mohsenzadeh
Keyword(s):  
Neural Network ◽  
Visual Information ◽  
Visual Pathway ◽  
Functional Magnetic Resonance ◽  
Low Level ◽  
Ventral Visual Pathway ◽  
High Level ◽  
Feedback Connections ◽  
The Brain ◽  
Insight Into

AbstractWhile vision evokes a dense network of feedforward and feedback neural processes in the brain, visual processes are primarily modeled with feedforward hierarchical neural networks, leaving the computational role of feedback processes poorly understood. Here, we developed a generative autoencoder neural network model and adversarially trained it on a categorically diverse data set of images. We hypothesized that the feedback processes in the ventral visual pathway can be represented by reconstruction of the visual information performed by the generative model. We compared representational similarity of the activity patterns in the proposed model with temporal (magnetoencephalography) and spatial (functional magnetic resonance imaging) visual brain responses. The proposed generative model identified two segregated neural dynamics in the visual brain. A temporal hierarchy of processes transforming low level visual information into high level semantics in the feedforward sweep, and a temporally later dynamics of inverse processes reconstructing low level visual information from a high level latent representation in the feedback sweep. Our results append to previous studies on neural feedback processes by presenting a new insight into the algorithmic function and the information carried by the feedback processes in the ventral visual pathway.Author summaryIt has been shown that the ventral visual cortex consists of a dense network of regions with feedforward and feedback connections. The feedforward path processes visual inputs along a hierarchy of cortical areas that starts in early visual cortex (an area tuned to low level features e.g. edges/corners) and ends in inferior temporal cortex (an area that responds to higher level categorical contents e.g. faces/objects). Alternatively, the feedback connections modulate neuronal responses in this hierarchy by broadcasting information from higher to lower areas. In recent years, deep neural network models which are trained on object recognition tasks achieved human-level performance and showed similar activation patterns to the visual brain. In this work, we developed a generative neural network model that consists of encoding and decoding sub-networks. By comparing this computational model with the human brain temporal (magnetoencephalography) and spatial (functional magnetic resonance imaging) response patterns, we found that the encoder processes resemble the brain feedforward processing dynamics and the decoder shares similarity with the brain feedback processing dynamics. These results provide an algorithmic insight into the spatiotemporal dynamics of feedforward and feedback processes in biological vision.

OCT changes in peri-tumour normal retina following ruthenium-106 and proton beam radiotherapy for uveal melanoma

2020 ◽  
pp. bjophthalmol-2019-314802
Author(s):  
Rumana Hussain ◽  
Florian Moritz Heussen ◽  
Heinrich Heimann
Keyword(s):  
Proton Beam ◽  
Uveal Melanoma ◽  
Choroidal Melanoma ◽  
Retinal Layer ◽  
Proton Beam Radiotherapy ◽  
Retinal Layers ◽  
Spectral Domain Oct ◽  
Ruthenium 106 Brachytherapy ◽  
Safety Margins ◽  
Plaque Brachytherapy

IntroductionUveal melanoma is most commonly treated with radiotherapy, destroying the tumour cells with adequate safety margins and limiting collateral damage to surrounding structures to preserve maximal vision. We used optical coherence tomography (OCT) to study the effects of radiotherapy on the retina.MethodsPatients with posteriorly located choroidal melanoma treated with proton beam radiotherapy (PBR) and ruthenium-106 brachytherapy between January 2010 and June 2014 underwent spectral domain OCT.ResultsImages of 32 patients following ruthenium-106 brachytherapy and 44 patients following proton beam teletherapy were analysed. Following plaque brachytherapy, an early marked disruption of the outer retinal layers could be observed in 30 cases (94%) with retinal atrophy evident in 26 cases (81%). In contrast, the images from patients who underwent PBR showed subtle outer retinal layer change with 16 cases (36%) showing some inner-outer segment junction disruption by 6 months and 63%  by 24 months with minimal atrophy. In cases with tumours <2 mm from the fovea, the visual loss was significantly less at 6 and 12 months in the proton beam group.ConclusionIn comparison to ruthenium-106 plaque brachytherapy, PBR leads to more subtle and slower changes in the outer retinal layers enabling retention of visual function for longer. The difference in dosing regime and dose distribution across the tumour is likely to be causative for this structural differential.

scholarly journals Optical coherence tomography identifies outer retina thinning in frontotemporal degeneration

Neurology ◽  
2017 ◽  
Vol 89 (15) ◽  
pp. 1604-1611 ◽  
Author(s):  
Benjamin J. Kim ◽  
David J. Irwin ◽  
Delu Song ◽  
Ebenezer Daniel ◽  
Jennifer D. Leveque ◽  
...  
Keyword(s):  
Optical Coherence Tomography ◽  
Outer Nuclear Layer ◽  
Retinal Layer ◽  
Optical Coherence ◽  
Outer Retina ◽  
Frontotemporal Degeneration ◽  
Cross Sectional ◽  
Clinical Criteria ◽  
Retinal Layers ◽  
Sd Oct

Objective:Whereas Alzheimer disease (AD) is associated with inner retina thinning visualized by spectral-domain optical coherence tomography (SD-OCT), we sought to determine if the retina has a distinguishing biomarker for frontotemporal degeneration (FTD).Methods:Using a cross-sectional design, we examined retinal structure in 38 consecutively enrolled patients with FTD and 44 controls using a standard SD-OCT protocol. Retinal layers were segmented with the Iowa Reference Algorithm. Subgroups of highly predictive molecular pathology (tauopathy, TAR DNA–binding protein 43, unknown) were determined by clinical criteria, genetic markers, and a CSF biomarker (total tau: β-amyloid) to exclude presumed AD. We excluded eyes with poor image quality or confounding diseases. SD-OCT measures of patients (n = 46 eyes) and controls (n = 69 eyes) were compared using a generalized linear model accounting for intereye correlation, and correlations between retinal layer thicknesses and Mini-Mental State Examination (MMSE) were evaluated.Results:Adjusting for age, sex, and race, patients with FTD had a thinner outer retina than controls (132 vs 142 μm, p = 0.004). Patients with FTD also had a thinner outer nuclear layer (ONL) (88.5 vs 97.9 μm, p = 0.003) and ellipsoid zone (EZ) (14.5 vs 15.1 μm, p = 0.009) than controls, but had similar thicknesses for inner retinal layers. The outer retina thickness of patients correlated with MMSE (Spearman r = 0.44, p = 0.03). The highly predictive tauopathy subgroup (n = 31 eyes) also had a thinner ONL (88.7 vs 97.4 μm, p = 0.01) and EZ (14.4 vs 15.1 μm, p = 0.01) than controls.Conclusions:FTD is associated with outer retina thinning, and this thinning correlates with disease severity.

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