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Hein M, Qambari H, An D, Balaratnasingam C. Current understanding of subclinical diabetic retinopathy informed by histology and high-resolution in vivo imaging. Clin Exp Ophthalmol 2024. [PMID: 38363022 DOI: 10.1111/ceo.14363] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2023] [Revised: 01/21/2024] [Accepted: 01/26/2024] [Indexed: 02/17/2024]
Abstract
The escalating incidence of diabetes mellitus has amplified the global impact of diabetic retinopathy. There are known structural and functional changes in the diabetic retina that precede the fundus photography abnormalities which currently are used to diagnose clinical diabetic retinopathy. Understanding these subclinical alterations is important for effective disease management. Histology and high-resolution clinical imaging reveal that the entire neurovascular unit, comprised of retinal vasculature, neurons and glial cells, is affected in subclinical disease. Early functional manifestations are seen in the form of blood flow and electroretinography disturbances. Structurally, there are alterations in the cellular components of vasculature, glia and the neuronal network. On clinical imaging, changes to vessel density and thickness of neuronal layers are observed. How these subclinical disturbances interact and ultimately manifest as clinical disease remains elusive. However, this knowledge reveals potential early therapeutic targets and the need for imaging modalities that can detect subclinical changes in a clinical setting.
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Affiliation(s)
- Martin Hein
- Physiology and Pharmacology Group, Lions Eye Institute, Perth, Western Australia, Australia
- Centre for Ophthalmology and Visual Science, University of Western Australia, Perth, Western Australia, Australia
| | - Hassanain Qambari
- Physiology and Pharmacology Group, Lions Eye Institute, Perth, Western Australia, Australia
- Centre for Ophthalmology and Visual Science, University of Western Australia, Perth, Western Australia, Australia
| | - Dong An
- Physiology and Pharmacology Group, Lions Eye Institute, Perth, Western Australia, Australia
- Centre for Ophthalmology and Visual Science, University of Western Australia, Perth, Western Australia, Australia
| | - Chandrakumar Balaratnasingam
- Physiology and Pharmacology Group, Lions Eye Institute, Perth, Western Australia, Australia
- Centre for Ophthalmology and Visual Science, University of Western Australia, Perth, Western Australia, Australia
- Department of Ophthalmology, Sir Charles Gairdner Hospital, Perth, Western Australia, Australia
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Yuan PHS, Athwal A, Shalaby M, Mehnert A, Yu DY, Preti RC, Sarunic M, Navajas EV. Retinal capillary perfusion heterogeneity in diabetic retinopathy detected by optical coherence tomography angiography. Int J Retina Vitreous 2024; 10:12. [PMID: 38273321 PMCID: PMC10809479 DOI: 10.1186/s40942-024-00528-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2023] [Accepted: 01/06/2024] [Indexed: 01/27/2024] Open
Abstract
BACKGROUND Diabetic retinopathy (DR) is a leading cause of blindness and involves retinal capillary damage, microaneurysms, and altered blood flow regulation. Optical coherence tomography angiography (OCTA) is a non-invasive way of visualizing retinal vasculature but has not been used extensively to study blood flow heterogeneity. The purpose of this study is to detect and quantify blood flow heterogeneity utilizing en-face swept source OCTA in patients with DR. METHODS This is a prospective clinical study which examined patients with either type 1 or 2 diabetes mellitus. Each included eye was graded clinically as no DR, mild DR, or moderate-severe DR. Ten consecutive en face 6 × 6 mm foveal SS-OCTA images were obtained from each eye using a PLEX Elite 9000 (Zeiss Meditec, Dublin, CA). Built-in fixation-tracking, follow-up functions were utilized to reduce motion artifacts and ensure same location imaging in sequential frames. Images of the superficial and deep vascular complexes (SVC and DVC) were arranged in temporal stacks of 10 and registered to a reference frame for segmentation using a deep neural network. The vessel segmentation was then masked onto each stack to calculate the pixel intensity coefficient of variance (PICoV) and map the spatiotemporal perfusion heterogeneity of each stack. RESULTS Twenty-nine eyes were included: 7 controls, 7 diabetics with no DR, 8 mild DR, and 7 moderate-severe DR. The PICoV correlated significantly and positively with DR severity. In patients with DR, the perfusion heterogeneity was higher in the temporal half of the macula, particularly in areas of capillary dropout. PICoV also correlates as expected with the established OCTA metrics of perfusion density and vessel density. CONCLUSION PICoV is a novel way to analyze OCTA imaging and quantify perfusion heterogeneity. Retinal capillary perfusion heterogeneity in both the SVC and DVC increased with DR severity. This may be related to the loss of retinal capillary perfusion autoregulation in diabetic retinopathy.
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Affiliation(s)
- Po Hsiang Shawn Yuan
- Department of Ophthalmology and Visual Sciences, Faculty of Medicine, University of British Columbia, Vancouver, BC, Canada
| | - Arman Athwal
- School of Engineering Science, Simon Fraser University, Burnaby, BC, Canada
| | - Mena Shalaby
- School of Engineering Science, Simon Fraser University, Burnaby, BC, Canada
| | - Andrew Mehnert
- Centre for Ophthalmology and Visual Science, University of Western Australia, Perth, Australia
- Lions Eye Institute, Nedlands, WA, Australia
| | - Dao-Yi Yu
- Centre for Ophthalmology and Visual Science, University of Western Australia, Perth, Australia
- Lions Eye Institute, Nedlands, WA, Australia
| | - Rony C Preti
- Department of Ophthalmology, University of Sao Paulo, Sau Paulo, Brazil
| | - Marinko Sarunic
- School of Engineering Science, Simon Fraser University, Burnaby, BC, Canada
- Institute of Ophthalmology, University College London, London, UK
- Department of Medical Physics and Biomedical Engineering, University College London, London, UK
| | - Eduardo V Navajas
- Department of Ophthalmology and Visual Sciences, Faculty of Medicine, University of British Columbia, Vancouver, BC, Canada.
- Eye Care Centre at Vancouver General Hospital, 2550 Willow Street, Vancouver, BC, V5Z 0A6, Canada.
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Javed A, Khanna A, Palmer E, Wilde C, Zaman A, Orr G, Kumudhan D, Lakshmanan A, Panos GD. Optical coherence tomography angiography: a review of the current literature. J Int Med Res 2023; 51:3000605231187933. [PMID: 37498178 PMCID: PMC10387790 DOI: 10.1177/03000605231187933] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/28/2023] Open
Abstract
This narrative review presents a comprehensive examination of optical coherence tomography angiography (OCTA), a non-invasive retinal vascular imaging technology, as reported in the existing literature. Building on the coherence tomography principles of standard OCT, OCTA further delineates the retinal vascular system, thus offering an advanced alternative to conventional dye-based imaging. OCTA provides high-resolution visualisation of both the superficial and deep capillary networks, an achievement previously unattainable. However, image quality may be compromised by factors such as motion artefacts or media opacities, potentially limiting the utility of OCTA in certain patient cohorts. Despite these limitations, OCTA has various potential clinical applications in managing retinal and choroidal vascular diseases. Still, given its considerable cost implications relative to current modalities, further research is warranted to justify its broader application in clinical practice.
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Affiliation(s)
- Ahmed Javed
- Department of Ophthalmology, Queen's Medical Centre, Nottingham University Hospitals, Nottingham, United Kingdom
| | - Aishwarya Khanna
- Department of Ophthalmology, Royal Derby Hospital, Derby, United Kingdom
| | - Eleanor Palmer
- Department of Ophthalmology, Queen's Medical Centre, Nottingham University Hospitals, Nottingham, United Kingdom
| | - Craig Wilde
- Department of Ophthalmology, Queen's Medical Centre, Nottingham University Hospitals, Nottingham, United Kingdom
| | - Anwar Zaman
- Department of Ophthalmology, Queen's Medical Centre, Nottingham University Hospitals, Nottingham, United Kingdom
| | - Gavin Orr
- Department of Ophthalmology, Queen's Medical Centre, Nottingham University Hospitals, Nottingham, United Kingdom
| | - Dharmalingam Kumudhan
- Department of Ophthalmology, Queen's Medical Centre, Nottingham University Hospitals, Nottingham, United Kingdom
| | - Arun Lakshmanan
- Department of Ophthalmology, Queen's Medical Centre, Nottingham University Hospitals, Nottingham, United Kingdom
| | - Georgios D Panos
- Department of Ophthalmology, Queen's Medical Centre, Nottingham University Hospitals, Nottingham, United Kingdom
- Division of Ophthalmology and Visual Sciences, School of Medicine, University of Nottingham, Nottingham, United Kingdom
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Hein M, Vukmirovic A, Constable IJ, Raja V, Athwal A, Freund KB, Balaratnasingam C. Angiographic biomarkers are significant predictors of treatment response to intravitreal aflibercept in diabetic macular edema. Sci Rep 2023; 13:8128. [PMID: 37208427 DOI: 10.1038/s41598-023-35286-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2023] [Accepted: 05/16/2023] [Indexed: 05/21/2023] Open
Abstract
This prospective single-center study aims to identify biomarkers that predict improvement in best-corrected visual acuity (BCVA) and central retinal thickness (CRT) at 6 months, in 76 eyes with diabetic macular edema (DME) treated monthly with intravitreal aflibercept. At baseline, all patients underwent standardized imaging with color photography, optical coherence tomography (OCT), fluorescein angiography (FA) and OCT angiography (OCTA). Glycosylated hemoglobin, renal function, dyslipidemia, hypertension, cardiovascular disease and smoking were recorded. Retinal images were graded in a masked fashion. Baseline imaging, systemic and demographic variables were investigated to detect associations to BCVA and CRT change post aflibercept. Predictors of BCVA improvement included greater macular vessel density quantified using OCTA (p = 0.001) and low-density lipoprotein (LDL) ≥ 2.6 mmol/L (p = 0.017). Lower macular vessel density eyes showed a significant reduction in CRT but no BCVA improvement. Predictors of CRT reduction included peripheral non-perfusion seen on ultrawide-field FA (p = 0.005) and LDL ≥ 2.6 mmol/L (p < 0.001). Retinal angiographic biomarkers derived from OCTA and ultrawide-field FA may help predict functional and anatomic response to anti-vascular endothelial growth factor (VEGF) therapy in patients with DME. Elevated LDL is associated with treatment response in DME. These results may be used to better-select patients who will benefit from intravitreal aflibercept for treatment of DME.
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Affiliation(s)
- Martin Hein
- Lions Eye Institute, Perth, Australia
- Centre for Ophthalmology and Visual Science, University of Western Australia, Perth, Australia
| | - Aleksandar Vukmirovic
- Lions Eye Institute, Perth, Australia
- Centre for Ophthalmology and Visual Science, University of Western Australia, Perth, Australia
| | - Ian J Constable
- Lions Eye Institute, Perth, Australia
- Centre for Ophthalmology and Visual Science, University of Western Australia, Perth, Australia
- Department of Ophthalmology, Sir Charles Gairdner Hospital, Perth, Australia
| | - Vignesh Raja
- Department of Ophthalmology, Sir Charles Gairdner Hospital, Perth, Australia
- Joondalup Eye Clinic, Perth, Australia
| | - Arman Athwal
- School of Engineering Science, Simon Fraser University, Burnaby, BC, Canada
- Department of Medical Physics and Biomedical Engineering, University College London, London, England
| | - K Bailey Freund
- Vitreous Retina Macula Consultants of New York, New York, USA
- Department of Ophthalmology, NYU Grossman School of Medicine, New York, NY, USA
| | - Chandrakumar Balaratnasingam
- Lions Eye Institute, Perth, Australia.
- Centre for Ophthalmology and Visual Science, University of Western Australia, Perth, Australia.
- Department of Ophthalmology, Sir Charles Gairdner Hospital, Perth, Australia.
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Miao Y, Song J, Hsu D, Ng R, Jian Y, Sarunic MV, Ju MJ. Numerical calibration method for a multiple spectrometer-based OCT system. BIOMEDICAL OPTICS EXPRESS 2022; 13:1685-1701. [PMID: 35414988 PMCID: PMC8973183 DOI: 10.1364/boe.450942] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/10/2021] [Revised: 02/14/2022] [Accepted: 02/17/2022] [Indexed: 06/14/2023]
Abstract
The present paper introduces a numerical calibration method for the easy and practical implementation of multiple spectrometer-based spectral-domain optical coherence tomography (SD-OCT) systems. To address the limitations of the traditional hardware-based spectrometer alignment across more than one spectrometer, we applied a numerical spectral calibration algorithm where the pixels corresponding to the same wavelength in each unit are identified through spatial- and frequency-domain interferometric signatures of a mirror sample. The utility of dual spectrometer-based SD-OCT imaging is demonstrated through in vivo retinal imaging at two different operation modes with high-speed and dual balanced acquisitions, respectively, in which the spectral alignment is critical to achieve improved retinal image data without any artifacts caused by misalignment of the spectrometers.
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Affiliation(s)
- Yusi Miao
- Department of Ophthalmology and Visual Sciences, University of British Columbia, Vancouver, BC, Canada
| | - Jun Song
- School of Biomedical Engineering, University of British Columbia, Vancouver, BC, Canada
| | - Destiny Hsu
- School of Engineering Science, Simon Fraser University, Burnaby, BC, Canada
| | - Ringo Ng
- School of Engineering Science, Simon Fraser University, Burnaby, BC, Canada
| | - Yifan Jian
- Casey Eye Institute, Oregon Health and Science University, Portland, Oregon 97239, USA
| | - Marinko V. Sarunic
- School of Engineering Science, Simon Fraser University, Burnaby, BC, Canada
- Institute of Ophthalmology, University College London, London, UK
- Department of Medical Physics and Biomedical Engineering, University College London, London, UK
| | - Myeong Jin Ju
- Department of Ophthalmology and Visual Sciences, University of British Columbia, Vancouver, BC, Canada
- School of Biomedical Engineering, University of British Columbia, Vancouver, BC, Canada
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Miao Y, Siadati M, Song J, Ma D, Jian Y, Beg MF, Sarunic MV, Ju MJ. Phase-corrected buffer averaging for enhanced OCT angiography using FDML laser. OPTICS LETTERS 2021; 46:3833-3836. [PMID: 34388753 DOI: 10.1364/ol.430915] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/13/2021] [Accepted: 07/07/2021] [Indexed: 05/18/2023]
Abstract
Megahertz-rate optical coherence tomography angiography (OCTA) is highly anticipated as an ultrafast imaging tool in clinical settings. However, shot-noise-limited sensitivity is inevitably reduced in high-speed imaging systems. In this Letter, we present a coherent buffer averaging technique for use with a Fourier-domain mode-locked (FDML) laser to improve OCTA contrast at 1060 nm MHz-rate retinal imaging. Full characterization of spectral variations among the FDML buffers and a numerical correction method are also presented, with the results demonstrating a 10-fold increase in the phase alignment among buffers. Coherent buffer averaging provided better OCTA contrast than the conventional multi-frame averaging approach with a faster acquisition time.
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