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1.
Ann N Y Acad Sci ; 2022 Jan 14.
Artigo em Inglês | MEDLINE | ID: mdl-35029314

RESUMO

We compare the focal structure-function correlation of structural measurements of peripapillary retinal nerve fiber layer thickness (RNFL-T) using optical coherence tomography (OCT), capillary density (CD) measurements using OCT-angiography (OCT-A), or a combination of both, with visual field deviation (VFD) in early to advanced glaucoma. Primary open angle glaucoma patients (n = 46, mean ± SD age: 67 ± 10 years; VF mean deviation: -10.41 ± 6.76 dB) were included in this cross-sectional study. We performed 30-2 standard automated perimetry OCT (3.5-mm diameter ring scan) and 15°×15° OCT-A (superficial vascular complex slab). Based on a nerve fiber trajectory model, each VF test spot was assigned to an OCT-A wedge and an OCT ring-sector. Two univariate linear models (Mv and Mt ) using either CD-based vascular (Mv ) or RNFL-T-based thickness information (Mt ) and one multivariate model using both (Mv:t ) were compared in their associations with measured focal VFD, which were higher for the multivariate model Mv:t (mean ± SD correlation coefficient: 0.710 ± 0.086) than for either nested model (0.627 ± 0.078 for Mv and 0.578 ± 0.095 for Mt ). Using a focal visual field approach, the combination of RNFL-T and CD showed better structure-function correlations than thickness or vascular information only.

2.
Invest Ophthalmol Vis Sci ; 62(15): 8, 2021 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-34878500

RESUMO

Purpose: To investigate modeling of the focal visual field (VF) loss by combining structural measurements and vascular measurements in eyes with early primary open-angle glaucoma (POAG). Methods: In this cross-sectional study, subjects with early glaucoma (VF mean deviation, ≥-6 dB) underwent optical coherence tomography (OCT) imaging, optical coherence tomography angiography (OCTA) imaging, and Humphrey 24-2 VF tests. Capillary perfusion densities (CPDs) were calculated after the removal of large vessels in the OCTA images. Focal associations between VF losses at the individual VF test locations, circumpapillary retinal nerve fiber layer (RNFL) thickness measurements from OCT, and CPDs were determined using nerve fiber trajectory tracings. Linear mixed models were used to model focal VF losses at each VF test location. Results: Ninety-seven eyes with early POAG (VF mean deviation, -2.47 ± 1.64 dB) of 71 subjects were included. Focal VF modeling using a combined RNFL-CPD approach resulted in a median adjusted R2 value of 0.30 (interquartile range [IQR], 0.13-0.55), whereas the RNFL-only and CPD-only approaches resulted in median values of 0.22 (IQR, 0.10-0.51) and 0.26 (IQR, 0.10-0.52), respectively. Seventeen VF locations with the combined approach had an adjusted R2 value greater than 0.50. Likelihood testing at each VF test location showed that the combined approach performed significantly better at the superior nasal VF regions of the eyes compared with the univariate approaches. Conclusions: Modeling of focal VF losses showed improvements when structural thickness and vascular parameters were included in tandem. Evaluation of VF defects in early glaucoma may benefit from considering both RNFL and OCTA characteristics.

3.
Acta Ophthalmol ; 2021 Dec 08.
Artigo em Inglês | MEDLINE | ID: mdl-34881512

RESUMO

PURPOSE: To investigate the response of the superficial and deep capillary plexuses to hyperoxia and hypoxia using optical coherence tomography angiography (OCT-A) and retinal vessel analyzer. METHODS: Twenty-four healthy volunteers participated in this randomized, double-masked, cross-over study. For each subject, two study days were scheduled: on one study day, hyperoxia was induced by breathing 100% oxygen whereas on the other study day, hypoxia was induced by breathing a mixture of 88% nitrogen and 12% oxygen. Perfusion density was calculated in the superficial vascular plexus (SVP) and the deep capillary plexus (DCP), using OCT-A before (normal breathing) and during breathing of the gas mixtures. Retinal vessel calibres in major retinal vessels were measured using a dynamic vessel analyzer. RESULTS: During 100% oxygen breathing, a significant decrease in DCP perfusion density from 41.7 ± 2.4 a.u to 35.6 ± 3.1 a.u. (p < 0.001) was observed, which was accompanied by a significant decrease in vessel diameters in major retinal arteries and veins (p < 0.001 each). No significant change in perfusion density in the SVP occurred (p = 0.33). In contrast, during hypoxia, perfusion density in the SVP significantly increased from 34.4 ± 3.0 a.u. to 37.1 ± 2.2 a.u. (p < 0.001), while it remained stable in the DCP (p = 0.25). A significant increase in retinal vessel diameters was found (p < 0.01). Systemic oxygen saturation correlated negatively with perfusion density in the SVP and the DCP and retinal vessel diameters (p < 0.005 each). CONCLUSION: Our results show that systemic hyperoxia induces a significant decrease in vessel density in the DCP, while hypoxia leads to increased vessel density limited to the SVP. These results indicate that the retinal circulation shows the ability to adapt its blood flow to metabolic changes with high local resolution dependent on the capillary plexus.

4.
Front Med (Lausanne) ; 8: 778330, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34859021

RESUMO

Objective: Multiple studies have compared various optical coherence tomography angiography (OCTA) parameters in participants with systemic hypertension vs. controls and have presented discordant findings. We conducted a meta-analysis to pool together data from different studies to generate an overall effect size and find out whether OCTA parameter(s) significantly differed in participants with systemic hypertension as compared to controls. Methods: We conducted a literature search through a search of electronic databases to identify studies before 19 June 2021, which compared OCTA parameters in non-diabetic participants with systemic hypertension vs. controls. If the OCTA parameter had a minimum number of 3 studies that analyzed it, the mean difference between participants with systemic hypertension and controls were analyzed using a random-effects model. Results: We identified 11 eligible studies. At the macula, 9 studies analyzed vessel density at the superficial capillary plexus (SVD), 7 analyzed vessel density at the deep capillary plexus (DVD), and 6 analyzed the area of the superficial foveal avascular zone (FAZ). Participants with systemic hypertension had significantly lower SVD (standardized mean difference [SMD], -0.50 [-0.70, -0.30], P < 0.00001, I 2 = 63%), lower DVD (SMD, -0.38 [-0.64, -0.13], P = 0.004, I 2 = 67%) and larger superficial FAZ (SMD, 0.32 [0.04, 0.61], P = 0.020, I 2 = 77%). Conclusion: The eyes of people with systemic hypertension have robustly lower superficial and deep vascular densities at the macula when compared to control eyes. Our results suggest that OCTA can provide information about pre-clinical microvascular changes from systemic hypertension.

5.
Ann N Y Acad Sci ; 2021 Dec 10.
Artigo em Inglês | MEDLINE | ID: mdl-34893981

RESUMO

Intrinsic optical signals constitute a noninvasive biomarker promising the objective assessment of retinal photoreceptor function. We employed a commercial optical coherence tomography (OCT) system and an OCT signal model for evaluation of optical path length (OPL) changes in the temporal outer retina of five healthy subjects during light adaptation. Data were acquired at 30 time points, in ambient light and during long duration stimulation with white light, and analyzed, employing a signal model based on the sum of seven Gaussian curves corresponding to all relevant anatomical structures of the outer retina. During light stimulation, mean OPL between rod outer segment tips (ROST) and the retinal pigment epithelium (RPE) decreased by 21.4 ± 3.5%. Further, OPL between the external-limiting membrane (ELM) and the RPE decreased by 5.2 ± 0.9% versus baseline, while OPL between ELM and ROST showed an initial decrease by 2.1 ± 1.6% versus baseline and, thereafter, increased by 2.8 ± 2.1% versus baseline. Thus, the presented approach allowed for assess to dynamic changes in the outer retina in response to light. The change in the subretinal space occurring in the context of light adaptation could be measured using a standard OCT platform and a dedicated signal model.

6.
Front Neurosci ; 15: 764898, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34819834

RESUMO

Glaucoma is a neurodegenerative disease, which results in characteristic visual field defects. Intraocular pressure (IOP) remains the main risk factor for this leading cause of blindness. Recent studies suggest that disturbances in neurovascular coupling (NVC) may be associated with glaucoma. The resultant imbalance between vascular perfusion and neuronal stimulation in the eye may precede retinal ganglion cell (RGC) loss and increase the susceptibility of the eye to raised IOP and glaucomatous degeneration. Caveolin-1 (Cav-1) is an integral scaffolding membrane protein found abundantly in retinal glial and vascular tissues, with possible involvement in regulating the neurovascular coupling response. Mutations in Cav-1 have been identified as a major genetic risk factor for glaucoma. Therefore, we aim to evaluate the effects of Cav-1 depletion on neurovascular coupling, retinal vessel characteristics, RGC density and the positive scotopic threshold response (pSTR) in Cav-1 knockout (KO) versus wild type C57/Bl6 mice (WT). Following light flicker stimulation of the retina, Cav-1 KO mice showed a smaller increase in perfusion at the optic nerve head and peripapillary arteries, suggesting defective neurovascular coupling. Evaluation of the superficial capillary plexus in Cav-1 KO mice also revealed significant differences in vascular morphology with higher vessel density, junction density and decreased average vessel length. Cav-1 KO mice exhibited higher IOP and lower pSTR amplitude. However, there was no significant difference in RGC density between Cav-1 KO and wild type mice. These findings highlight the role of Cav-1 in regulating neurovascular coupling and IOP and suggest that the loss of Cav-1 may predispose to vascular dysfunction and decreased RGC signaling in the absence of structural loss. Current treatment for glaucoma relies heavily on IOP-lowering drugs, however, there is an immense potential for new therapeutic strategies that increase Cav-1 expression or augment its downstream signaling in order to avert vascular dysfunction and glaucomatous change.

7.
Neurobiol Aging ; 109: 239-246, 2021 Oct 22.
Artigo em Inglês | MEDLINE | ID: mdl-34814099

RESUMO

Comorbid neuropsychiatric symptoms are commonly found in individuals with dementia and is likely influenced by a combination of neurodegenerative and cerebrovascular pathophysiology. We evaluated the associations of a validated composite MRI-based quantitative measure of both neurodegeneration (hippocampus volume and cortical thickness of AD-specific regions) and cerebrovascular disease (CeVD; white matter hyperintensities and infarcts) with neuropsychiatric subsyndromes, and their interactions on cognition in a community-based sample across the disease spectrum (N = 773). Lower composite MRI scores corresponding to greater comorbid neurodegeneration and CeVD burden were associated with hyperactivity (OR = 1.48) and apathy (OR = 1.90) subsyndromes. Lower MRI scores with concomitant hyperactivity was associated with greater cognitive impairment, especially in patients who were at least moderately impaired, while the interaction with apathy was not dependent on disease stage. These MRI scores interaction models resulted in a better fit than models consisting of neurodegeneration or CeVD alone. Integrating multiple biomarkers with specific, disease stage-dependent neuropsychiatric subsyndromes may provide a more holistic risk profile to facilitate the identification of individuals at the highest risk of disease progression.

8.
Ophthalmol Glaucoma ; 2021 Oct 27.
Artigo em Inglês | MEDLINE | ID: mdl-34718222

RESUMO

PURPOSE: Detection of early glaucoma remains limited with the conventional analysis of the retinal nerve fiber layer (RNFL). This study assessed whether compensating the RNFL thickness for multiple demographic and anatomic factors improves the detection of glaucoma. DESIGN: Cross-sectional study. PARTICIPANTS: Three hundred eighty-seven patients with glaucoma and 2699 healthy participants. METHODS: Two thousand six hundred ninety-nine healthy participants were enrolled to construct and test a multivariate compensation model, which then was applied in 387 healthy participants and 387 patients with glaucoma (early glaucoma, n = 219; moderate glaucoma, n = 97; and advanced glaucoma, n = 71). Participants underwent Cirrus spectral-domain OCT (Carl Zeiss Meditec) imaging of the optic disc and macular cubes. Compensated RNFL thickness was generated based on ethnicity, age, refractive error, optic disc (ratio, orientation, and area), fovea (distance and angle), and retinal vessel density. The RNFL thickness measurements and their corresponding areas under the receiver operating characteristic curve (AUCs) were obtained. MAIN OUTCOME AND MEASURES: Measured and compensated RNFL thickness measurements. RESULTS: After applying the Asian-specific compensation model, the standard deviation of RNFL thickness reduced, where the effect was greatest for Chinese participants (16.9%), followed by Malay participants (13.9%), and Indian participants (12.1%). Multivariate normative comparison outperformed measured RNFL for discrimination of early glaucoma (AUC, 0.90 vs. 0.85; P < 0.001), moderate glaucoma (AUC, 0.94 vs. 0.91; P < 0.001), and advanced glaucoma (AUC, 0.98 vs. 0.96; P < 0.001). CONCLUSIONS: The multivariate normative database of RNFL showed better glaucoma discrimination capability than conventional age-matched comparisons, suggesting that accounting for demographic and anatomic variance in RNFL thickness may have usefulness in improving glaucoma detection.

9.
Front Neurosci ; 15: 761654, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34712117

RESUMO

Vascular changes and alterations of oxygen metabolism are suggested to be implicated in multiple sclerosis (MS) pathogenesis and progression. Recently developed in vivo retinal fundus imaging technologies provide now an opportunity to non-invasively assess metabolic changes in the neural retina. This study was performed to assess retinal oxygen metabolism, peripapillary capillary density (CD), large vessel density (LVD), retinal nerve fiber layer thickness (RNFLT) and ganglion cell inner plexiform layer thickness (GCIPLT) in patients with diagnosed relapsing multiple sclerosis (RMS) and history of unilateral optic neuritis (ON). 16 RMS patients and 18 healthy controls (HC) were included in this study. Retinal oxygen extraction was modeled using O2 saturations and Doppler optical coherence tomography (DOCT) derived retinal blood flow (RBF) data. CD and LVD were assessed using optical coherence tomography (OCT) angiography. RNFLT and GCIPLT were measured using structural OCT. Measurements were performed in eyes with (MS+ON) and without (MS-ON) history for ON in RMS patients and in one eye in HC. Total oxygen extraction was lowest in MS+ON (1.8 ± 0.2 µl O2/min), higher in MS-ON (2.1 ± 0.5 µl O2/min, p = 0.019 vs. MS+ON) and highest in HC eyes (2.3 ± 0.6 µl O2/min, p = 0.002 vs. MS, ANOVA p = 0.031). RBF was lower in MS+ON (33.2 ± 6.0 µl/min) compared to MS-ON (38.3 ± 4.6 µl/min, p = 0.005 vs. MS+ON) and HC eyes (37.2 ± 4.7 µl/min, p = 0.014 vs. MS+ON, ANOVA p = 0.010). CD, LVD, RNFLT and GCIPL were significantly lower in MS+ON eyes. The present data suggest that structural alterations in the retina of RMS patients are accompanied by changes in oxygen metabolism, which are more pronounced in MS+ON than in MS-ON eyes. Whether these alterations promote MS onset and progression or occur as consequence of disease warrants further investigation. Clinical Trial Registration: ClinicalTrials.gov registry, NCT03401879.

10.
Surv Ophthalmol ; 2021 Oct 14.
Artigo em Inglês | MEDLINE | ID: mdl-34656556

RESUMO

The human eye has a unique immune architecture and behavior. While the conjunctiva is known to have a well-defined lymphatic drainage system, the cornea, sclera, and uveal tissues were historically considered "alymphatic" and thought to be immune privileged. The very fact that the aqueous outflow channels carry a clear fluid (aqueous humor) along the outflow pathway makes it hard to ignore its lymphatic-like characteristics. The development of novel lymphatic lineage markers and expression of these markers in aqueous outflow channels and improved imaging capabilities has sparked a renewed interest in the study of ocular lymphatics. Ophthalmic lymphatic research has had a directional shift over the last decade, offering an exciting new physiological platform that needs further in-depth understanding. The evidence of a presence of distinct lymphatic channels in the human ciliary body is gaining significant traction. The uveolymphatic pathway is an alternative new route for aqueous outflow and adds a new dimension to pathophysiology and management of glaucoma. Developing novel animal models, markers, and non-invasive imaging tools to delineate the core anatomical structure and physiological functions may help pave some crucial pathways to understand disease pathophysiology and help develop novel targeted therapeutic approaches for glaucoma.

11.
Clin Sci (Lond) ; 135(20): 2357-2376, 2021 10 29.
Artigo em Inglês | MEDLINE | ID: mdl-34661658

RESUMO

Ophthalmology has been one of the early adopters of artificial intelligence (AI) within the medical field. Deep learning (DL), in particular, has garnered significant attention due to the availability of large amounts of data and digitized ocular images. Currently, AI in Ophthalmology is mainly focused on improving disease classification and supporting decision-making when treating ophthalmic diseases such as diabetic retinopathy, age-related macular degeneration (AMD), glaucoma and retinopathy of prematurity (ROP). However, most of the DL systems (DLSs) developed thus far remain in the research stage and only a handful are able to achieve clinical translation. This phenomenon is due to a combination of factors including concerns over security and privacy, poor generalizability, trust and explainability issues, unfavorable end-user perceptions and uncertain economic value. Overcoming this challenge would require a combination approach. Firstly, emerging techniques such as federated learning (FL), generative adversarial networks (GANs), autonomous AI and blockchain will be playing an increasingly critical role to enhance privacy, collaboration and DLS performance. Next, compliance to reporting and regulatory guidelines, such as CONSORT-AI and STARD-AI, will be required to in order to improve transparency, minimize abuse and ensure reproducibility. Thirdly, frameworks will be required to obtain patient consent, perform ethical assessment and evaluate end-user perception. Lastly, proper health economic assessment (HEA) must be performed to provide financial visibility during the early phases of DLS development. This is necessary to manage resources prudently and guide the development of DLS.

12.
Biomed Opt Express ; 12(9): 5770-5781, 2021 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-34692214

RESUMO

Ocular deformation may be associated with biomechanical alterations in the structures of the eye, especially the cornea and sclera in conditions such as keratoconus, congenital glaucoma, and pathological myopia. Here, we propose a method to estimate ocular shape using an ultra-wide field MHz swept-source optical coherence tomography (SS-OCT) with a Fourier Domain Mode-Locked (FDML) laser and distortion correction of the images. The ocular biometrics for distortion correction was collected by an IOLMaster 700, and localized Gaussian curvature was proposed to quantify the ocular curvature covering a field-of-view up to 65°×62°. We achieved repeatable curvature shape measurements (intraclass coefficient = 0.88 ± 0.06) and demonstrated its applicability in a pilot study with individuals (N = 11) with various degrees of myopia.

13.
Biomed Opt Express ; 12(8): 4982-4996, 2021 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-34513237

RESUMO

Choroidal vasculature plays an important role in the pathogenesis of retinal diseases, such as myopic maculopathy, age-related macular degeneration, diabetic retinopathy, central serous chorioretinopathy, and ocular inflammatory diseases. Current optical coherence tomography (OCT) technology provides three-dimensional visualization of the choroidal angioarchitecture; however, quantitative measures remain challenging. Here, we propose and validate a framework to segment and quantify the choroidal vasculature from a prototype swept-source OCT (PLEX Elite 9000, Carl Zeiss Meditec, USA) using a 3×3 mm scan protocol centered on the macula. Enface images referenced from the retinal pigment epithelium were reconstructed from the volumetric data. The boundaries of the choroidal volume were automatically identified by tracking the choroidal vessel feature structure over the depth, and a selective sliding window was applied for segmenting the vessels adaptively from attenuation-corrected enface images. We achieved a segmentation accuracy of 96% ± 1% as compared with manual annotation, and a dice coefficient of 0.83 ± 0.04 for repeatability. Using this framework on both control (0.00 D to -2.00 D) and highly myopic (-8.00 D to -11.00 D) eyes, we report a decrease in choroidal vessel volume (p<0.001) in eyes with high myopia.

14.
Transl Vis Sci Technol ; 10(11): 16, 2021 09 01.
Artigo em Inglês | MEDLINE | ID: mdl-34524409

RESUMO

Purpose: Artificial intelligence (AI) deep learning (DL) has been shown to have significant potential for eye disease detection and screening on retinal photographs in different clinical settings, particular in primary care. However, an automated pre-diagnosis image assessment is essential to streamline the application of the developed AI-DL algorithms. In this study, we developed and validated a DL-based pre-diagnosis assessment module for retinal photographs, targeting image quality (gradable vs. ungradable), field of view (macula-centered vs. optic-disc-centered), and laterality of the eye (right vs. left). Methods: A total of 21,348 retinal photographs from 1914 subjects from various clinical settings in Hong Kong, Singapore, and the United Kingdom were used for training, internal validation, and external testing for the DL module, developed by two DL-based algorithms (EfficientNet-B0 and MobileNet-V2). Results: For image-quality assessment, the pre-diagnosis module achieved area under the receiver operating characteristic curve (AUROC) values of 0.975, 0.999, and 0.987 in the internal validation dataset and the two external testing datasets, respectively. For field-of-view assessment, the module had an AUROC value of 1.000 in all of the datasets. For laterality-of-the-eye assessment, the module had AUROC values of 1.000, 0.999, and 0.985 in the internal validation dataset and the two external testing datasets, respectively. Conclusions: Our study showed that this three-in-one DL module for assessing image quality, field of view, and laterality of the eye of retinal photographs achieved excellent performance and generalizability across different centers and ethnicities. Translational Relevance: The proposed DL-based pre-diagnosis module realized accurate and automated assessments of image quality, field of view, and laterality of the eye of retinal photographs, which could be further integrated into AI-based models to improve operational flow for enhancing disease screening and diagnosis.


Assuntos
Aprendizado Profundo , Algoritmos , Área Sob a Curva , Inteligência Artificial , Humanos , Fotografação
15.
Sci Rep ; 11(1): 16625, 2021 08 17.
Artigo em Inglês | MEDLINE | ID: mdl-34404833

RESUMO

To examine the use of anterior segment-optical coherence tomography angiography (AS-OCTA) in the assessment of limbal ischemia in an animal model chemical ocular injury. We conducted a prospective study using an established chemical ocular injury model in 6 rabbits (12 eyes), dividing the cornea limbus into 4 quadrants. Chemical injury grade was induced based on extent of limbal injury (0 to 360 degrees) and all eyes underwent serial slit-lamp with AS-OCTA imaging up to one month. Main outcome measure was changes in AS-OCTA vessel density (VD) comparing injured and control cornea limbal quadrants within 24 h and at one month. AS-OCTA was able to detect differences in limbal VD reduction comparing injured (3.3 ± 2.4%) and control quadrants (7.6 ± 2.3%; p < 0.001) within 24 h of ocular chemical injury. We also observed that AS-OCTA VD reduction was highly correlated with the number of quadrants injured (r = - 0.89; p < 0.001; 95% CI - 5.65 to - 1.87). Corneal vascularization was detected by AS-OCTA in injured compared to control quadrants (10.1 ± 4.3% vs 7.0 ± 1.2%; p = 0.025) at 1 month. Our animal pilot study suggests that AS-OCTA was able to detect limbal vessel disruption from various severities of acute chemical insult, and in the future, could potentially serve as an adjunct in providing objective grading of acute ocular chemical injury once validated in a clinical trial.


Assuntos
Angiografia/métodos , Segmento Anterior do Olho/diagnóstico por imagem , Tomografia de Coerência Óptica/métodos , Animais , Segmento Anterior do Olho/irrigação sanguínea , Queimaduras Químicas/diagnóstico por imagem , Traumatismos Oculares/diagnóstico por imagem , Masculino , Modelos Animais , Projetos Piloto , Estudos Prospectivos , Coelhos
16.
Biomed Opt Express ; 12(7): 3865-3877, 2021 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-34457385

RESUMO

We performed full circumferential imaging of the Schlemm's canal (SC) of two human eyes using a Fourier domain mode-lock laser (FDML) based 1.66-MHz SS-OCT prototype at 1060 nm. Eight volumes with overlapping margins were acquired around the limbal area with customized raster scanning patterns designed to fully cover the SC while minimizing motion artifacts. The SC was segmented from the volumes using a semi-automated active contour segmentation algorithm, whose mean dice similarity coefficient was 0.76 compared to the manual segmentation results. We also reconstructed three-dimensional (3D) renderings of the 360° SC by stitching the segmented SCs from the volumetric datasets. Quantitative metrics of the full circumferential SC were provided, including the mean and standard deviation (SD) of the cross-sectional area (CSA), the maximum CSA, the minimum and maximum SC opening width, and the number of collector channels (CC) stemming from the SC.

17.
Biomed Opt Express ; 12(7): 4032-4045, 2021 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-34457397

RESUMO

Visualizing and characterizing microvascular abnormalities with optical coherence tomography angiography (OCTA) has deepened our understanding of ocular diseases, such as glaucoma, diabetic retinopathy, and age-related macular degeneration. Two types of microvascular defects can be detected by OCTA: focal decrease because of localized absence and collapse of retinal capillaries, which is referred to as the non-perfusion area in OCTA, and diffuse perfusion decrease usually detected by comparing with healthy case-control groups. Wider OCTA allows for insights into peripheral retinal vascularity, but the heterogeneous perfusion distribution from the macula, parapapillary area to periphery hurdles the quantitative assessment. A normative database for OCTA could estimate how much individual's data deviate from the normal range, and where the deviations locate. Here, we acquired OCTA images using a swept-source OCT system and a 12×12 mm protocol in healthy subjects. We automatically segmented the large blood vessels with U-Net, corrected for anatomical factors such as the relative position of fovea and disc, and segmented the capillaries by a moving window scheme. A total of 195 eyes were included and divided into 4 age groups: < 30 (n=24) years old, 30-49 (n=28) years old, 50-69 (n=109) years old and >69 (n=34) years old. This provides an age-dependent normative database for characterizing retinal perfusion abnormalities in 12×12 mm OCTA images. The usefulness of the normative database was tested on two pathological groups: one with diabetic retinopathy; the other with glaucoma.

18.
Biomed Opt Express ; 12(6): 3228-3240, 2021 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-34221656

RESUMO

Assessment of the circumpapillary retinal nerve fiber layer (RNFL) provides crucial knowledge on the status of the optic nerve. Current circumpapillary RNFL measurements consider only thickness, but an accurate evaluation should also consider blood vessel contribution. Previous studies considered the presence of major vessels in RNFL thickness measurements from optical coherence tomography (OCT). However, such quantitative measurements do not account for smaller vessels, which could also affect circumpapillary RNFL measurements. We present an approach to automatically segregate the neuronal and vascular components in circumpapillary RNFL by combining vascular information from OCT angiography (OCTA) and structural data from OCT. Automated segmentation of the circumpapillary RNFL using a state-of-the-art deep learning network is first performed and followed by the lateral and depth-resolved localization of the vascular component by vertically projecting the vessels along the circular scan from OCTA vessels map onto the segmented RNFL. Using this proposed approach, we compare the correlations of circumpapillary RNFL thicknesses with age at different levels of vessel exclusion (exclusion of major vessels only vs both major- and micro-vessels) and also evaluate the thickness variability in 75 healthy eyes. Our results show that the ratio of major- and micro-vessels to circumpapillary RNFL achieved a stronger correlation with aging (r = 0.478, P < .001) than the ratio with only major vessels to circumpapillary RNFL (r = 0.027, P = .820). Exclusion of blood vessels from circumpapillary RNFL thickness using OCTA imaging provides a better measure of the neuronal components and could potentially improve the diagnostic performance for disease detection.

19.
Adv Ther ; 38(8): 4333-4343, 2021 08.
Artigo em Inglês | MEDLINE | ID: mdl-34241779

RESUMO

INTRODUCTION: To describe anterior segment optical coherence tomography angiography (AS-OCTA) imaging to monitor corneal vascularisation (CoNV) and scar reduction after combined fine-needle diathermy (FND) with subconjunctival ranibizumab. METHODS: Prospective clinical study of six eyes from six subjects with corneal scar and CoNV which underwent combined FND with subconjunctival ranibizumab. All eyes were imaged using slit-lamp photography (SLP) and AS-OCTA (Optovue, Inc., Fremont, CA, wavelength: 840 nm) before and after the operation, with two independent masked assessors analysing all images. Main outcome measures were changes in median corneal scar area and vessel density (AS-OCTA) comparing pre- and postoperative imaging up to month 3 and 6. RESULTS: The mean age of the subjects was 60 ± 23 years, with three males and three females. CoNV and corneal scarring involving the visual axis were present in all eyes, secondary to previous infective keratitis (n = 3), severe blepharokeratoconjunctivitis (n = 2), or chemical injury (n = 1). Follow-up time frame ranged from 2 to 6 months postoperation. There was a reduction in median corneal scar area from 30.2 mm2 (IQR 18.7-38.5) before surgery to 14.8 mm2 (IQR 7.1-19.6) after surgery, with a median reduction of 37.1% (IQR = - 3.1-86.9, p = 0.046). There was also a reduction in median cornea vessel density (AS-OCTA) from 20.8% (IQR 16.1-20.8) before surgery to 17.6% (IQR 14.0-17.6) after surgery, with a median reduction of 15.1% (IQR 13.2-15.1, p < 0.001). CONCLUSIONS: Combined imaging of SLP and AS-OCTA is useful for monitoring treatment response of corneal scarring and CoNV after combined FND with subconjunctival Ranibizumab.


Assuntos
Diatermia , Ranibizumab , Adulto , Idoso , Idoso de 80 Anos ou mais , Feminino , Angiofluoresceinografia , Humanos , Masculino , Pessoa de Meia-Idade , Projetos Piloto , Estudos Prospectivos , Ranibizumab/uso terapêutico , Tomografia de Coerência Óptica
20.
Curr Opin Ophthalmol ; 32(5): 459-467, 2021 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-34324454

RESUMO

PURPOSE OF REVIEW: The development of deep learning (DL) systems requires a large amount of data, which may be limited by costs, protection of patient information and low prevalence of some conditions. Recent developments in artificial intelligence techniques have provided an innovative alternative to this challenge via the synthesis of biomedical images within a DL framework known as generative adversarial networks (GANs). This paper aims to introduce how GANs can be deployed for image synthesis in ophthalmology and to discuss the potential applications of GANs-produced images. RECENT FINDINGS: Image synthesis is the most relevant function of GANs to the medical field, and it has been widely used for generating 'new' medical images of various modalities. In ophthalmology, GANs have mainly been utilized for augmenting classification and predictive tasks, by synthesizing fundus images and optical coherence tomography images with and without pathologies such as age-related macular degeneration and diabetic retinopathy. Despite their ability to generate high-resolution images, the development of GANs remains data intensive, and there is a lack of consensus on how best to evaluate the outputs produced by GANs. SUMMARY: Although the problem of artificial biomedical data generation is of great interest, image synthesis by GANs represents an innovation with yet unclear relevance for ophthalmology.


Assuntos
Aprendizado Profundo , Processamento de Imagem Assistida por Computador , Redes Neurais de Computação , Oftalmologia , Inteligência Artificial , Humanos , Processamento de Imagem Assistida por Computador/métodos
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