University of Toronto

Pathophysiology of outer retinal corrugations: Imaging dataset and mechanical models

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This article presents high-resolution swept-source optical coherence tomography (SS-OCT) imaging data used to elaborate a mechanical model that elucidates the formation of outer retinal corrugations (ORCs) in rhegmatogenous retinal detachments (RRD). The imaging data shared in the repository and presented in this article is related to the research paper entitled “Outer Retinal Corrugations in Rhegmatogenous Retinal Detachment: The Retinal Pigment Epithelium-Photoreceptor Dysregulation Theory” (Muni et al., AJO, 2022). The dataset consists of 69 baseline cross-sectional SS-OCT scans from 66 patients that were assessed for the presence of ORCs and analyzed considering the clinical features of each case. From the 66 cases, we selected SS-OCT images of 4 RRD patients with visible ORCs and no cystoid macular edema (CME) to validate the mechanical model. We modelled the retina as a composite material consisting of the outer retinal layer (photoreceptor layer) and the inner retinal layer...

En Face Optical Coherence Tomography in Diagnosis of Persistent Subretinal Fluid & Outer Retinal Folds after Rhegmatogenous Retinal Detachment Repair

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Purpose To evaluate the role of en face optical coherence tomography (OCT) as a diagnostic tool for the detection of persistent subretinal fluid (PSRF) and outer retinal folds (ORF) following successful rhegmatogenous retinal detachment (RRD) repair. Design Observational post hoc analysis of two prospective surgical trials. Participants All patients with gradable (signal strength ≥ 5 and no segmentation error) 6x6 mm macular cube scans using spectral-domain OCT (SD-OCT) (Carl Zeiss Meditec, Jena, Germany) obtained between 1 and 2 months postoperatively were included in this study. Methods Scans were assessed for the presence or absence of PSRF or ORFs using en face OCT and cross-sectional B scans by two masked graders with any disagreements adjudicated by the third senior masked grader. Main Outcome Measure Sensitivity, specificity and predictive accuracy {using area under curve (AUC)} of en face OCT in comparison to cross-sectional OCT as the gold standard Results Two hu...

Morphologic Stages of Rhegmatogenous Retinal Detachment Assessed with Swept-Source Optical Coherence Tomography

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Purpose: To describe the sequential morphological changes following rhegmatogenous retinal detachment (RRD), utilizing a novel, objective, and clinically relevant staging system based on swept-source optical coherence tomography (SS-OCT) and determine its association with duration of fovea-off and postoperative visual acuity. Design: Prospective cohort study. Subjects: Consecutive patients with primary fovea-involving RRD referred to St. Michael's Hospital, Toronto, Canada, from January 2020-April 2022. Methods: All patients had SS-OCT and ultra-widefield SS-OCT at baseline. Primary RRDs with breaks above 8 and 4 o'clock were included. Patients with vision loss≥3 months, PVR≥grade B, demarcation line, previous vitrectomy or other retinal pathology were excluded. Staging was based on the assessment of outer retinal morphology on successive SS-OCT scans from the peripheral break to the most posterior aspect of the RRD, following its direction of progression. Main outcome measure...

Prognostic Features of Preoperative Optical Coherence Tomography in Retinal Detachments: A systematic review and meta-analysis

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Topic: To evaluate the prognostic association between preoperative features seen on optical coherence tomography (OCT) imaging and postoperative visual acuity (VA) outcomes in rhegmatogenous retinal detachments (RRD). Clinical relevance: Currently, there is limited literature on the prognostic value of preoperative RRD OCT features. Methods: A literature search was conducted on Ovid MEDLINE, EMBASE and Cochrane CENTRAL from inception through September 15, 2022. A meta-analysis was performed using a random-effects model. Quality of studies and evidence was assessed using the JBI tools and GRADE framework, respectively. Results: A total of 1,671 eyes of 1,670 patients from 29 observational studies were included. Eighty-nine percent of eyes had a macula-off RRD at presentation. The mean average duration of detachment was 15±10 days. The majority of eyes (62%) underwent pars plana vitrectomy. Six preoperative OCT features were analyzed: height of retinal detachment (HRD) at the f...

Optical Coherence Tomography Features In Idiopathic Noninfectious Intermediate, Posterior, Or Panuveitis

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Purpose: To characterize optical coherence tomography features in patients with idiopathic intermediate, posterior, or panuveitis. Methods: This is a retrospective case series of all consecutive cases of idiopathic intermediate, posterior, or panuveitis at four tertiary care centres between 2010 and 2021. Results: A total of 94 eyes (55 patients) were followed for an average duration of 29.8 (SD 21) months. The median central macular thickness was 284 µ m at baseline and 267 µ m at last follow-up. At baseline and last follow-up, respectively, 24% and 20% of uveitic eyes had intraretinal fluid, 12% and 1% subretinal fluid, and 43% and 54% epiretinal membrane. In addition, ellipsoid zone abnormalities on en-face were noted in 34% and 19% of cases at baseline and last follow-up, respectively. The baseline median visual acuity was significantly lower among cases with ellipsoid zone en-face slab abnormalities compared with those without (0.2 logarithm of minimum angle of reso...

Detection and differentiation of semi-transparent materials simulating biological structures using optical coherence tomography: a phantom study

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SignificanceLymphatic and peripheral nervous system imaging is of prime importance for monitoring various important pathologic processes including cancer development and metastasis, and response to therapy.AimOptical coherence tomography (OCT) is a promising approach for this imaging task but is challenged by the near-transparent nature of these structures. Our aim is to detect and differentiate semi-transparent materials using OCT texture analysis, toward label-free neurography and lymphography.ApproachWe have recently demonstrated an innovative OCT texture analysis-based approach that used speckle statistics to image lymphatics and nerves in-vivo that does not rely on negative contrast. However, these two near-transparent structures could not be easily differentiated from each other in the texture analysis parameter space. Here, we perform a rigorous follow-up study to improve upon this differentiation in controlled phantoms mimicking the optical properties of these tissues.Result...

The Use of Optical Coherence Tomography for Gross Examination and Sampling of Fixed Breast Specimens: A Pilot Study

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Abstract Thorough gross examination of breast cancer specimens is critical in order to sample relevant portions for subsequent microscopic examination. This task would benefit from an imaging tool which permits targeted and accurate block selection. Optical coherence tomography (OCT) is a non-destructive imaging technique that visualizes tissue architecture and has the potential to be an adjunct at the gross bench. Our objectives were: (1) to familiarize pathologists with the appearance of breast tissue entities on OCT; and (2) to evaluate the yield and quality of OCT images of unprocessed, formalin-fixed breast specimens for the purpose of learning and establishment of an OCT-histopathology library. Methods: Firstly, 175 samples from 40 formalin-fixed, unprocessed breast specimens with residual tissue after final diagnosis were imaged with OCT and then processed into histology slides. Histology findings were correlated with features on OCT. Results: Residual malignancy was seen in ...

Optical Coherence Tomography Features in Idiopathic Non-Infectious Intermediate, Posterior, or Panuveitis

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Purpose: To characterize optical coherence tomography (OCT) features in patients with idiopathic intermediate, posterior, or panuveitis. Methods: This is a retrospective case series of all consecutive cases of idiopathic intermediate, posterior, or panuveitis at four tertiary care centres between 2010 and 2021. Results: A total of 94 eyes (55 patients) were followed for an average duration of 29.8 (SD 21) months. The median central macular thickness (CMT) was 284μm at baseline and 267μm at last follow-up. At baseline and last follow-up, respectively, 24% and 20% of uveitic eyes had Intraretinal fluid (IRF), 12% and 1% subretinal fluid (SRF), and 43% and 54% epiretinal membrane (ERM). Additionally, ellipsoid zone (EZ) abnormalities on en-face were noted in 34% and 19% of cases at baseline and last follow-up, respectively. The baseline median visual acuity was significantly lower amongst cases with EZ en-face slab abnormalities compared to those without (0.2 logMAR [IQR: 0-0.6] ...

The use of optical coherence tomography in neurology: a review

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Optical coherence tomography (OCT) is a non-invasive, cost-efficient technique that provides high-resolution in vivo imaging of retinal tissue. The peripapillary retinal nerve fibre layer (pRNFL) and macular ganglion cell complex (mGCC) are surrogate markers of neuroaxonal integrity in not only the eye, but also the central nervous system. Retinal atrophy may occur in tandem with central nervous system pathologies as a result of injury to ganglion cells, direct degeneration of the pregeniculate pathway, or retrograde transsynaptic degeneration secondary to postgeniculate lesions. In this review, we outline the basic principles of OCT and discuss its application to managing patients with demyelinating disorders, idiopathic intracranial hypertension, stroke, neurodegenerative conditions, and mitochondrial disorders. We demonstrate that measurements of pRNFL and mGCC thickness are paramount in diagnosing and monitoring neurologic disorders, including those with subclinical disease prog...

Persistent subfoveal fluid in pneumatic retinopexy versus pars plana vitrectomy for rhegmatogenous retinal detachment: posthoc analysis of the PIVOT randomised trial

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Purpose To assess the incidence of persistent subfoveal fluid (PSFF) in pneumatic retinopexy (PnR) versus pars plana vitrectomy (PPV) following rhegmatogenous retinal detachment (RRD) repair and to determine its association with functional outcomes. Methods Posthoc analysis of the PIVOT randomised trial. Eyes with gradable en face and cross-sectional spectral-domain optical coherence tomography (SD-OCT) scans at 1–2 months postoperatively were included. Primary outcome was the proportion of patients with PSFF following PnR versus PPV at 1–2 months postoperatively. Secondary outcomes included association of PSFF with Early Treatment Diabetic Retinopathy Study (ETDRS) letter score at 3, 6 and 12 months and metamorphopsia score (MCHARTs) at 12 months. Results Of 176 participants enrolled in PIVOT, 158 (89.8%) had gradable SD-OCT scans. Intergrader agreement was 0.870 (Cohen’s kappa). The incidence of PSFF was 16% (13/81) following PnR and 10.4% (8/77) following PPV (p...

Baseline Microperimetry and OCT in the RUSH2A Study: Structure-Function Association and Correlation with Disease Severity

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Purpose: To investigate baseline mesopic microperimetry (MP) and spectral domain optical coherence tomography (OCT) in the Rate of Progression in USH2A-related Retinal Degeneration (RUSH2A) study. Design: Natural history study SETTING: 16 clinical sites in Europe and North America STUDY POPULATION: Participants with Usher syndrome type 2 (USH2) (N=80) or autosomal recessive nonsyndromic RP (ARRP) (N=47) associated with biallelic disease-causing sequence variants in USH2A. Observation procedures: General linear models were used to assess characteristics including disease duration, MP mean sensitivity and OCT intact ellipsoid zone (EZ) area. The associations between mean sensitivity and EZ area with other measures, including best corrected visual acuity (BCVA) and central subfield thickness (CST) within the central 1 mm, were assessed using Spearman correlation coefficients. Main outcome measures: Mean sensitivity on MP; EZ area and CST on OCT RESULTS: All participants (N=127) had OCT...

Binary dose level classification of tumour microvascular response to radiotherapy using artificial intelligence analysis of optical coherence tomography images

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The dominant consequence of irradiating biological systems is cellular damage, yet microvascular damage begins to assume an increasingly important role as the radiation dose levels increase. This is currently becoming more relevant in radiation medicine with its pivot towards higher-dose-per-fraction/fewer fractions treatment paradigm (e.g., stereotactic body radiotherapy (SBRT)). We have thus developed a 3D preclinical imaging platform based on speckle-variance optical coherence tomography (svOCT) for longitudinal monitoring of tumour microvascular radiation responses in vivo. Here we present an artificial intelligence (AI) approach to analyze the resultant microvascular data. In this initial study, we show that AI can successfully classify SBRT-relevant clinical radiation dose levels at multiple timepoints (t = 2–4 weeks) following irradiation (10 Gy and 30 Gy cohorts) based on induced changes in the detected microvascular networks. Practicality of the obtained...

Machine learning classification of multiple sclerosis in children using optical coherence tomography

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Background: In children, multiple sclerosis (MS) is the ultimate diagnosis in only 1/5 to 1/3 of cases after a first episode of central nervous system (CNS) demyelination. As the visual pathway is frequently affected in MS and other CNS demyelinating disorders (DDs), structural retinal imaging such as optical coherence tomography (OCT) can be used to differentiate MS. Objective: This study aimed to investigate the utility of machine learning (ML) based on OCT features to identify distinct structural retinal features in children with DDs. Methods: This study included 512 eyes from 187 ( n eyes = 374) children with demyelinating diseases and 69 ( n eyes = 138) controls. Input features of the analysis comprised of 24 auto-segmented OCT features. Results: Random Forest classifier with recursive feature elimination yielded the highest predictive values and identified DDs with 75% and MS with 80% accuracy, while multiclass distinction between MS and monophasic DD was performed with 64% ac...

2 Postdoctoral Positions Available at the Biomedical Optics Research Group at the University of Waterloo

Two postdoctoral positions in the field of biomedical optical imaging are available at the University of Waterloo, Canada in the Biomedical Optics Research Group of Prof. Kostadinka Bizheva. The positions are available starting in September 2022, though the search will continue until both positions are filled. The initial appointment will be for one year with the possibility of extension for up-to three years upon mutual agreement.  Project description: Both projects will focus on development of multi-modality, high speed, UHR-OCT technology and image processing algorithms for ophthalmic applications (imaging the healthy and pathological human retina and cornea). The OCT technology will be used to image simultaneously morphological, blood flow and physiological changes in the ocular tissue in-vivo, while image processing algorithms will be developed to assess and characterize theses changes.  Requirement: Candidates with a PhD in physics or optical engineering and laborato...

Single-capture ultra-widefield guided swept-source optical coherence tomography in the management of rhegmatogenous retinal detachment and associated peripheral vitreoretinal patholog

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Background/Aim To assess the utility of single-capture ultra-widefield confocal scanning laser ophthalmoscope with integrated swept-source optical coherence tomography (UWF-SS-OCT) in the management of rhegmatogenous retinal detachment (RRD) and associated peripheral pathology. Methods 138 eyes of 101 consecutive patients with RRD and/or associated peripheral pathology at a vitreoretinal practice in Toronto, Canada between December 2020 and February 2021 that had UWF-SS-OCT with interpretable scans were included. A 200 degree fundus photograph was used to navigate a built-in 100 kHz UWF-SS-OCT to image pathology with a high-density 23 mm line scan and/or volume scan. Main outcomes were the microstructural details of the RRD and/or associated peripheral pathology and longitudinal assessment of response to laser retinopexy and cryopexy with UWF-SS-OCT. Results 56.5% (78/138) of eyes had prior or current RRD (6 eyes had combined retinoschisis detachment), 31.1% (43/138) had retinal tea...

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