1
|
Blair NP, Matei N, Leahy S, Rahimi M, Shahidi M. The accumulated oxygen deficit as an indicator of the ischemic retinal insult. Exp Eye Res 2023; 230:109439. [PMID: 36931487 PMCID: PMC10133208 DOI: 10.1016/j.exer.2023.109439] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2022] [Revised: 02/24/2023] [Accepted: 03/13/2023] [Indexed: 03/17/2023]
Abstract
We here attempt to improve quantification of the ischemic retinal insult, that is, what is imposed on the retinal tissue by ischemia, especially in experimental models of ischemia. The ischemic retinal insult initiates the ischemic retinal injury (or outcome). Accordingly, it is reasonable to assume that the better the quantification of the insult, the better the correlation with, and thereby estimation of, the injury. The insult seldom has been quantified in terms of the relevant physiological factors, especially in connection with the rate of oxygen delivery (DO2). We here propose the accumulated oxygen deficit (AO2D) as an indicator of the ischemic retinal insult. We hypothesized that AO2D is correlated with the rate of oxygen metabolism measured 1 h after reperfusion following an episode of ischemia (MO2_1_Hr). Previously, we showed that MO2_1_Hr is related to the electroretinogram amplitude and the retinal thickness when they are measured seven days after reperfusion. We studied 27 rats, as well as 26 rats from our published data on retinal ischemia in which we had measurements of DO2 and duration of ischemia (T) of various levels and durations. We also measured DO2 in 29 rats treated with sham surgery. Ischemia was induced by either ipsilateral or bilateral common carotid artery occlusion or by ophthalmic artery occlusion, which gave a wide range of DO2. DO2 and MO2_1_Hr were evaluated based on three types of images: 1) red-free images to measure vessel diameters, 2) fluorescence images to estimate blood velocities by the displacement of intravascular fluorescent microspheres over time, and 3) phosphorescence images to quantify vascular oxygen tension from the phosphorescence lifetime of an intravascular oxygen sensitive phosphor. Loss of oxygen delivery (DO2L) was calculated as the difference between DO2 under normal/sham condition and DO2 during ischemia. AO2D, a volume of oxygen, was calculated as the product DO2L and T. Including all data, the linear relationship between AO2D and MO2_1_Hr was significant (R2 = 0.261, P = 0.0003). Limiting data to that in which T or DO2L was maximal also yielded significant relationships, and revealed that DO2L at a long duration of ischemia contributed disproportionately more than T to MO2_1_Hr. We discuss the potential of AO2D for quantifying the ischemic retinal insult, predicting the ischemic retinal injury and evaluating the likelihood of infarction.
Collapse
Affiliation(s)
- Norman P Blair
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, 1855 West Taylor Street, Chicago, IL 60612, USA.
| | - Nathanael Matei
- Department of Ophthalmology, University of Southern California, 1450 San Pablo St, Suite 4700, Los Angeles, CA 9003, USA.
| | - Sophie Leahy
- Department of Ophthalmology, University of Southern California, 1450 San Pablo St, Suite 4700, Los Angeles, CA 9003, USA.
| | - Mansour Rahimi
- Department of Ophthalmology, University of Southern California, 1450 San Pablo St, Suite 4700, Los Angeles, CA 9003, USA.
| | - Mahnaz Shahidi
- Department of Ophthalmology, University of Southern California, 1450 San Pablo St, Suite 4700, Los Angeles, CA 9003, USA.
| |
Collapse
|
2
|
Balaratnasingam C, An D, Hein M, Yu P, Yu DY. Studies of the retinal microcirculation using human donor eyes and high-resolution clinical imaging: Insights gained to guide future research in diabetic retinopathy. Prog Retin Eye Res 2022; 94:101134. [PMID: 37154065 DOI: 10.1016/j.preteyeres.2022.101134] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2022] [Revised: 09/18/2022] [Accepted: 10/03/2022] [Indexed: 11/06/2022]
Abstract
The microcirculation plays a key role in delivering oxygen to and removing metabolic wastes from energy-intensive retinal neurons. Microvascular changes are a hallmark feature of diabetic retinopathy (DR), a major cause of irreversible vision loss globally. Early investigators have performed landmark studies characterising the pathologic manifestations of DR. Previous works have collectively informed us of the clinical stages of DR and the retinal manifestations associated with devastating vision loss. Since these reports, major advancements in histologic techniques coupled with three-dimensional image processing has facilitated a deeper understanding of the structural characteristics in the healthy and diseased retinal circulation. Furthermore, breakthroughs in high-resolution retinal imaging have facilitated clinical translation of histologic knowledge to detect and monitor progression of microcirculatory disturbances with greater precision. Isolated perfusion techniques have been applied to human donor eyes to further our understanding of the cytoarchitectural characteristics of the normal human retinal circulation as well as provide novel insights into the pathophysiology of DR. Histology has been used to validate emerging in vivo retinal imaging techniques such as optical coherence tomography angiography. This report provides an overview of our research on the human retinal microcirculation in the context of the current ophthalmic literature. We commence by proposing a standardised histologic lexicon for characterising the human retinal microcirculation and subsequently discuss the pathophysiologic mechanisms underlying key manifestations of DR, with a focus on microaneurysms and retinal ischaemia. The advantages and limitations of current retinal imaging modalities as determined using histologic validation are also presented. We conclude with an overview of the implications of our research and provide a perspective on future directions in DR research.
Collapse
Affiliation(s)
- Chandrakumar Balaratnasingam
- Lions Eye Institute, Nedlands, Western Australia, Australia; Centre for Ophthalmology and Visual Science, University of Western Australia, Perth, Australia; Department of Ophthalmology, Sir Charles Gairdner Hospital, Western Australia, Australia.
| | - Dong An
- Lions Eye Institute, Nedlands, Western Australia, Australia; Centre for Ophthalmology and Visual Science, University of Western Australia, Perth, Australia
| | - Martin Hein
- Lions Eye Institute, Nedlands, Western Australia, Australia; Centre for Ophthalmology and Visual Science, University of Western Australia, Perth, Australia
| | - Paula Yu
- Lions Eye Institute, Nedlands, Western Australia, Australia; Centre for Ophthalmology and Visual Science, University of Western Australia, Perth, Australia
| | - Dao-Yi Yu
- Lions Eye Institute, Nedlands, Western Australia, Australia; Centre for Ophthalmology and Visual Science, University of Western Australia, Perth, Australia
| |
Collapse
|
3
|
Retinal Oxygen Delivery, Metabolism, and Extraction Fraction during Long-Term Bilateral Common Carotid Artery Occlusion in Rats. Sci Rep 2020; 10:10371. [PMID: 32587289 PMCID: PMC7316776 DOI: 10.1038/s41598-020-67255-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2019] [Accepted: 05/27/2020] [Indexed: 12/04/2022] Open
Abstract
Retinal functional, biochemical, and anatomical changes have been previously reported in long-term experimental permanent bilateral common carotid artery occlusion (BCCAO). The purpose of the current study was to investigate progressive reductions in retinal oxygen metabolism (MO2) due to inadequate compensation by oxygen delivery (DO2) and extraction fraction (OEF) after BCCAO. Twenty-nine rats were subjected to BCCAO and were imaged after 3 hours, 3 days, 7 days, or 14 days. Six rats underwent a sham procedure. Phosphorescence lifetime and blood flow imaging were performed in both eyes to measure retinal oxygen contents and total retinal blood flow, respectively. DO2, MO2, and OEF were calculated from these measurements. Compared to the sham group, DO2 and MO2 were reduced after all BCCAO durations. OEF was increased after 3 hours and 3 days of BCCAO, but was not different from the sham group after 7 and 14 days. Between 3 and 7 days of BCCAO, DO2 increased, OEF decreased, and there was no significant difference in MO2. These findings may be useful to understand the pathophysiology of retinal ischemia.
Collapse
|
4
|
Xu X, Yannuzzi NA, Fernández-Avellaneda P, Echegaray JJ, Tran KD, Russell JF, Patel NA, Hussain RM, Sarraf D, Freund KB. Differentiating Veins From Arteries on Optical Coherence Tomography Angiography by Identifying Deep Capillary Plexus Vortices. Am J Ophthalmol 2019; 207:363-372. [PMID: 31226248 DOI: 10.1016/j.ajo.2019.06.009] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2019] [Revised: 06/07/2019] [Accepted: 06/08/2019] [Indexed: 01/26/2023]
Abstract
PURPOSE To introduce a simple method for differentiating retinal veins from arteries on optical coherence tomography angiography (OCTA). DESIGN Cross-sectional pilot study. METHODS Four default en face slabs including color depth encoded, grayscale full-thickness retina, superficial plexus, and deep capillary plexus (DCP) from nine 3×3-mm and nine 6×6-mm OCTA scans were exported and aligned. Nine ophthalmologists with minimum OCTA experience from 2 eye institutions were instructed to classify labeled vessels as arteries or veins in 3 stages. Classification was performed based on graders' own assessment at stage 1. Graders were taught that a capillary-free zone was an anatomic feature of arteries at stage 2 and were trained to identify veins originating from vortices within the DCP at stage 3. Grading accuracy was analyzed and correlated with grading time and graders' years in practice. RESULTS Overall grading accuracy in stages 1, 2, and 3 was (50.4% ± 17.0%), (75.4% ± 6.0%), and (94.7% ± 2.6%), respectively. Grading accuracy for 3×3-mm scans in stages 1, 2, and 3 was (49.9% ± 16.3%), (79.2% ± 9.6%), and (96.9% ± 3.1%), respectively. Accuracy for 6×6-mm scans in stages 1, 2, and 3 was (51.4% ± 20.8%), (72.3% ± 7.9%), and (93.2% ± 3.3%), respectively. Grading performance improved significantly at each stage (all P < .001). No significant correlation was found between accuracy and time spent grading or between accuracy and years in practice (r = -0.164 to 0.617, all P ≥ .077). CONCLUSIONS We describe a simple method for accurately distinguishing retinal arteries from veins on OCTA, which incorporates the use of vortices in the DCP to identify venous origin.
Collapse
Affiliation(s)
- Xiaoyu Xu
- Vitreous Retina Macula Consultants of New York, New York, New York, USA; LuEsther T. Mertz Retinal Research Center, Manhattan Eye, Ear, and Throat Hospital, New York, New York, USA; State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China
| | - Nicolas A Yannuzzi
- Department of Ophthalmology, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, Florida, USA
| | - Pedro Fernández-Avellaneda
- Vitreous Retina Macula Consultants of New York, New York, New York, USA; LuEsther T. Mertz Retinal Research Center, Manhattan Eye, Ear, and Throat Hospital, New York, New York, USA; Department of Ophthalmology, Basurto University Hospital, Bilbao, Spain
| | - Jose J Echegaray
- Department of Ophthalmology, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, Florida, USA
| | - Kimberly D Tran
- Department of Ophthalmology, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, Florida, USA
| | - Jonathan F Russell
- Department of Ophthalmology, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, Florida, USA
| | - Nimesh A Patel
- Department of Ophthalmology, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, Florida, USA
| | - Rehan M Hussain
- Department of Ophthalmology, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, Florida, USA
| | - David Sarraf
- Stein Eye Institute, University of California, Los Angeles, Los Angeles, California, USA
| | - K Bailey Freund
- Vitreous Retina Macula Consultants of New York, New York, New York, USA; LuEsther T. Mertz Retinal Research Center, Manhattan Eye, Ear, and Throat Hospital, New York, New York, USA; Department of Ophthalmology, New York University of Medicine; Edward S. Harkness Eye Institute, Columbia University Medical Center, New York, New York, USA.
| |
Collapse
|
5
|
McLeod D. Nonperfused Inner Retina May Be Anoxic, Hypoxic, or Normoxic. JAMA Ophthalmol 2019; 137:1333. [DOI: 10.1001/jamaophthalmol.2019.3588] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Affiliation(s)
- David McLeod
- Academic Department of Ophthalmology, Manchester Royal Eye Hospital, Manchester University, National Health Service Foundation Trust, Manchester, United Kingdom
| |
Collapse
|
6
|
McLeod D. Misery Perfusion, Diffusive Oxygen Shunting and Interarterial Watershed Infarction Underlie Oxygenation-Based Hypoperfusion Maculopathy. Am J Ophthalmol 2019; 205:153-164. [PMID: 30905727 DOI: 10.1016/j.ajo.2019.03.015] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2018] [Revised: 03/06/2019] [Accepted: 03/09/2019] [Indexed: 11/16/2022]
Abstract
PURPOSE To describe and explain the entire range of acute ischemic macular damage that follows panretinal hypoperfusion from central retinal artery or vein occlusion. DESIGN Perspective article. METHODS To correlate the fundoscopic, fluorescein angiographic, oximetric, and optical coherence tomographic (OCT) features developing within the posterior inner retina following incremental reductions in arteriovenous perfusion pressure across the retinal circulation. RESULTS The spectrum of acute oxygenation-based hypoperfusion maculopathy (OHM) is consistent with that predictable from a modified Krogh cylinder model of tissue oxygenation. Diffusive oxygen shunting plays a significant role in the "artery-dominated" generation of ischemic signs during misery perfusion. Three major grades of OHM severity can be discerned according to the predominant oxygenation status of ganglion cells within the superficial inner retina, whether this is normoxic (OHM1), hypoxic (OHM2), or anoxic (OHM3). Densely opaque axoplasmic sentinels are arranged along normoxic/hypoxic interfaces in OHM2. In OHM1 and OHM2, relative hypermetabolism and interarterial watershed infarction of fundal interneurons (WIFI) underpin subtle middle-retinal opacification with periarterial sparing. The fundal signs are optimally displayed en face using autofluorescence imaging whereas cross-sectional OCT reveals Paques' plaque formation. CONCLUSIONS An exquisite and supremely accessible exhibition of classical oxygen physiopathology unfolds in eyes with panretinal hypoperfusion courtesy of the transparent ocular media and the pattern of macular neuroretinal opacification that evolves as upstream tissues extract oxygen to the detriment of tissues downstream. Recent attempts to overrule the simple conceptual framework embodied in WIFI have no plausible anatomical nor physiological basis. Overreliance on OCT can result in misdiagnosis.
Collapse
Affiliation(s)
- David McLeod
- Academic Department of Ophthalmology, Manchester Royal Eye Hospital, Manchester University National Health Service Foundation Trust, and Centre for Ophthalmology and Vision Research, Institute of Human Development, University of Manchester, Manchester, United Kingdom.
| |
Collapse
|
7
|
Li H, Ding X, Lu L, Yang J, Ma J. Morphometry of the normal retinal periarteral capillary-free zone and changes during severe nonproliferative diabetic retinopathy. Clin Hemorheol Microcirc 2019; 72:169-178. [PMID: 30829616 DOI: 10.3233/ch-180458] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
PURPOSE To explore the normal morphological features of the retinal periarteral capillary free zone (paCFZ) and the changes associated with severe non-proliferative diabetic retinopathy (NPDR) by optical coherence tomography angiography (OCTA). METHODS A total of 148 normal subjects and 115 patients with severe NPDR were enrolled. Spectral-domain OCTA was used to acquire the image with a Cirrus prototype. Diameter and area of each paCFZ quadrant and adjacent large artery diameter was estimated. RESULTS In healthy subjects, the maximum width of paCFZ in the temporal quadrant (169.38 ± 19.26 μm) was smaller than the other three quadrants (all P <0.001). The ratio of maximum paCFZ width to artery caliber was much larger in the nasal quadrants than the rest quadrants (Ps <0.05). In patients with severe NPDR, both maximum width and area of paCFZ were significant larger, and the retinal artery inner diameters significant smaller in each quadrant compared to normal subjects (Ps <0.05). The ratio of paCFZ maximum width to artery caliber maximum width was significant greater, and the ratio of paCFZ area to artery caliber was significantly higher in all quadrants compared to normal eyes (Ps <0.05). CONCLUSIONS OCTA provides noninvasive and quantitative measurement of paCFZ dimensions. The maximum width and area of paCFZ quadrants and the ratios of these parameters to adjacent inner artery width and area are elevated in severe NPDR, suggesting that changes in paCFZ dimension can be used as clinical indices for diseases associated with changes in retinal microcirculation and oxygen pressure.PRÉCIS:Optical coherence tomography angiography revealed differences in retinal periarteral capillary free zone (paCFZ) morphometry between health retina and severe non-proliferative diabetic retinopathy. Morphometric indices of paCFZ may be useful for monitoring disease occurrence and progression.
Collapse
Affiliation(s)
- H Li
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China
| | - X Ding
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China
| | - L Lu
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China
| | - J Yang
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China
| | - J Ma
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China
| |
Collapse
|
8
|
Balaratnasingam C, An D, Sakurada Y, Lee CS, Lee AY, McAllister IL, Freund KB, Sarunic M, Yu DY. Comparisons Between Histology and Optical Coherence Tomography Angiography of the Periarterial Capillary-Free Zone. Am J Ophthalmol 2018; 189:55-64. [PMID: 29470970 DOI: 10.1016/j.ajo.2018.02.007] [Citation(s) in RCA: 56] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2017] [Revised: 02/10/2018] [Accepted: 02/11/2018] [Indexed: 12/27/2022]
Abstract
PURPOSE To use the capillary-free zone along retinal arteries, a physiologic area of superficial avascularization, as an anatomic paradigm to investigate the reliability of optical coherence tomography angiography (OCTA) for visualizing the deep retinal circulation. DESIGN Validity analysis and laboratory investigation. METHODS Five normal human donor eyes (mean age 69.8 years) were perfusion-labeled with endothelial antibodies and the capillary networks of the perifovea were visualized using confocal scanning laser microscopy. Regions of the capillary-free zone along the retinal artery were imaged using OCTA in 16 normal subjects (age range 24-51 years). Then, 3 × 3-mm scans were acquired using the RTVue XR Avanti (ver. 2016.1.0.26; Optovue, Inc, Fremont, California, USA), PLEX Elite 9000 (ver. 1.5.0.15909; Zeiss Meditec, Inc, Dublin, California, USA), Heidelberg Spectralis OCT2 (Family acquisition module 6.7.21.0; Heidelberg Engineering, Heidelberg, Germany), and DRI-OCT Triton (Ver. 1.1.1; Topcon Corp, Tokyo, Japan). Images of the superficial plexus, deep vascular plexus, and a slab containing all vascular plexuses were generated using manufacturer-recommended default settings. Comparisons between histology and OCTA were performed. RESULTS Histologic analysis revealed that the capillary-free zone along the retinal artery was confined to the plane of the superficial capillary plexus and did not include the intermediate and deep capillary plexuses. Images derived from OCTA instruments demonstrated a prominent capillary-free zone along the retinal artery in slabs of the superficial plexus, deep plexus, and all capillary plexuses. The number of deep retinal capillaries seen in the capillary-free zone was significantly greater on histology than on OCTA (P < .001). CONCLUSION Using the capillary-free zone as an anatomic paradigm, we show that the deep vascular beds of the retina are not completely visualized using OCTA. This may be a limitation of current OCTA techniques.
Collapse
Affiliation(s)
- Chandrakumar Balaratnasingam
- Centre for Ophthalmology and Visual Science, University of Western Australia, Perth, Australia; Lions Eye Institute, Nedlands, Australia; Department of Ophthalmology, Sir Charles Gairdner Hospital, Nedlands, Australia
| | - Dong An
- Centre for Ophthalmology and Visual Science, University of Western Australia, Perth, Australia; Lions Eye Institute, Nedlands, Australia
| | - Yoichi Sakurada
- LuEsther T. Mertz Retinal Research Center, Manhattan Eye, Ear and Throat Hospital, New York, New York; Department of Ophthalmology, University of Yamanashi, Yamanashi, Japan
| | - Cecilia S Lee
- Department of Ophthalmology, University of Washington, Seattle, Washington
| | - Aaron Y Lee
- Department of Ophthalmology, University of Washington, Seattle, Washington
| | - Ian L McAllister
- Centre for Ophthalmology and Visual Science, University of Western Australia, Perth, Australia; Lions Eye Institute, Nedlands, Australia; Department of Ophthalmology, Royal Perth Hospital, Perth, Australia
| | - K Bailey Freund
- LuEsther T. Mertz Retinal Research Center, Manhattan Eye, Ear and Throat Hospital, New York, New York; Vitreous, Retina, Macula Consultants of New York, New York; Department of Ophthalmology, New York University School of Medicine, New York, New York
| | - Marinko Sarunic
- School of Engineering Science, Simon Fraser University, Burnaby, Canada
| | - Dao-Yi Yu
- Centre for Ophthalmology and Visual Science, University of Western Australia, Perth, Australia; Lions Eye Institute, Nedlands, Australia.
| |
Collapse
|
9
|
Author's Reply. Eur J Ophthalmol 2018. [DOI: 10.5301/ejo.5000133] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
|
10
|
Topography of Patchy Retinal Whitening during Acute Perfused Retinal Vein Occlusion by Optical Coherence Tomography and Adaptive Optics Fundus Imaging. Eur J Ophthalmol 2018; 21:653-6. [DOI: 10.5301/ejo.2011.6374] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/31/2011] [Indexed: 11/20/2022]
|
11
|
McLeod D. En Face Optical Coherence Tomography Analysis to Assess the Spectrum of Perivenular Ischemia and Paracentral Acute Middle Maculopathy in Retinal Vein Occlusion. Am J Ophthalmol 2017; 182:203-204. [PMID: 28802731 DOI: 10.1016/j.ajo.2017.06.037] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2017] [Accepted: 06/23/2017] [Indexed: 11/17/2022]
|
12
|
|
13
|
Evidence for an enduring ischaemic penumbra following central retinal artery occlusion, with implications for fibrinolytic therapy. Prog Retin Eye Res 2015; 49:82-119. [PMID: 26113210 DOI: 10.1016/j.preteyeres.2015.06.001] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2015] [Revised: 06/13/2015] [Accepted: 06/18/2015] [Indexed: 12/15/2022]
Abstract
The rationale behind hyperacute fibrinolytic therapy for cerebral and retinal arterial occlusion is to rescue ischaemic cells from irreversible damage through timely restitution of tissue perfusion. In cerebral stroke, an anoxic tissue compartment (the "infarct core") is surrounded by a hypoxic compartment (the "ischaemic penumbra"). The latter comprises electrically-silent neurons that undergo delayed apoptotic cell death within 1-6 h unless salvaged by arterial recanalisation. Establishment of an equivalent hypoxic compartment within the inner retina following central retinal artery occlusion (CRAO) isn't widely acknowledged. During experimental CRAO, electroretinography reveals 3 oxygenation-based tissue compartments (anoxic, hypoxic and normoxic) that contribute 32%, 27% and 41% respectively to the pre-occlusion b-wave amplitude. Thus, once the anoxia survival time (≈2 h) expires, the contribution from the infarcted posterior retina is irreversibly extinguished, but electrical activity continues in the normoxic periphery. Inbetween these compartments, an annular hypoxic zone (the "penumbra obscura") endures in a structurally-intact but functionally-impaired state until retinal reperfusion allows rapid recovery from electrical silence. Clinically, residual circulation of sufficient volume flow rate generates the heterogeneous fundus picture of "partial" CRAO. Persistent retinal venous hypoxaemia signifies maximal extraction of oxygen by an enduring "polar penumbra" that permeates or largely replaces the infarct core. On retinal reperfusion some days later, the retinal venous oxygen saturation reverts to normal and vision improves. Thus, penumbral inner retina, marginally oxygenated by the choroid or by residual circulation, isn't at risk of delayed apoptotic infarction (unlike hypoxic cerebral cortex). Emergency fibrinolytic intervention is inappropriate, therefore, once the duration of CRAO exceeds 2 h.
Collapse
|
14
|
McLeod D. Emergent fibrinolysis for central artery occlusion is inappropriate after 2 hours’ ischemia. Can J Ophthalmol 2015; 50:249. [DOI: 10.1016/j.jcjo.2014.12.018] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2014] [Accepted: 12/12/2014] [Indexed: 11/26/2022]
|
15
|
Abstract
PURPOSE To investigate the clinical features of central retinal vein occlusion (CRVO) in relation to the presence of a prominent middle limiting membrane (p-MLM) sign on presenting optical coherence tomography, which may suggest macular ischemia and poor visual outcome. METHODS Fifty consecutive eyes with acute CRVO of <1 month of symptom duration before presentation were retrospectively reviewed. A hyperreflective line located in the outer plexiform layer (p-MLM) in optical coherence tomography was used as a sign of acute ischemia. Cases with p-MLM were grouped and compared with the group of eyes with no p-MLM sign (non-MLM group) for clinical features including visual acuities, central fovea thickness, and CRVO types. RESULTS Among the 50 eyes, 14 (28%) eyes showed a p-MLM sign, 21 (42%) eyes did not, and others had equivocal findings. Eyes with p-MLM sign presented worse initial and final best-corrected visual acuity compared with the non-MLM group (1.10 ± 0.72 vs. 0.47 ± 0.49 logMAR in the initial best-corrected visual acuity, P = 0.007; and 1.08 ± 0.86 vs. 0.32 ± 0.41 logMAR in the final best-corrected visual acuity, P = 0.044) in patients with a follow-up duration of 6 months or longer. The p-MLM group eyes showed a higher tendency toward being classified as ischemic type CRVO (57.1 vs. 4.8%, P = 0.001). CONCLUSION Central retinal vein occlusion showing p-MLM on optical coherence tomography had worse visual outcome with higher incidence of being classified into ischemic type CRVO.
Collapse
|
16
|
MacCormick IJC, Beare NAV, Taylor TE, Barrera V, White VA, Hiscott P, Molyneux ME, Dhillon B, Harding SP. Cerebral malaria in children: using the retina to study the brain. ACTA ACUST UNITED AC 2014; 137:2119-42. [PMID: 24578549 PMCID: PMC4107732 DOI: 10.1093/brain/awu001] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Cerebral malaria is a dangerous complication of Plasmodium falciparum infection, which takes a devastating toll on children in sub-Saharan Africa. Although autopsy studies have improved understanding of cerebral malaria pathology in fatal cases, information about in vivo neurovascular pathogenesis is scarce because brain tissue is inaccessible in life. Surrogate markers may provide insight into pathogenesis and thereby facilitate clinical studies with the ultimate aim of improving the treatment and prognosis of cerebral malaria. The retina is an attractive source of potential surrogate markers for paediatric cerebral malaria because, in this condition, the retina seems to sustain microvascular damage similar to that of the brain. In paediatric cerebral malaria a combination of retinal signs correlates, in fatal cases, with the severity of brain pathology, and has diagnostic and prognostic significance. Unlike the brain, the retina is accessible to high-resolution, non-invasive imaging. We aimed to determine the extent to which paediatric malarial retinopathy reflects cerebrovascular damage by reviewing the literature to compare retinal and cerebral manifestations of retinopathy-positive paediatric cerebral malaria. We then compared retina and brain in terms of anatomical and physiological features that could help to account for similarities and differences in vascular pathology. These comparisons address the question of whether it is biologically plausible to draw conclusions about unseen cerebral vascular pathogenesis from the visible retinal vasculature in retinopathy-positive paediatric cerebral malaria. Our work addresses an important cause of death and neurodisability in sub-Saharan Africa. We critically appraise evidence for associations between retina and brain neurovasculature in health and disease, and in the process we develop new hypotheses about why these vascular beds are susceptible to sequestration of parasitized erythrocytes.
Collapse
Affiliation(s)
- Ian J C MacCormick
- 1 Malawi-Liverpool-Wellcome Trust Clinical Research Programme, PO Box 30096, Chichiri, Blantyre 3, Malawi2 University of Liverpool, Department of Eye and Vision Science, Faculty of Health & Life Sciences, University of Liverpool Room 356, 4th Floor, UCD Building, Daulby Street, Liverpool L69 3GA, UK
| | - Nicholas A V Beare
- 2 University of Liverpool, Department of Eye and Vision Science, Faculty of Health & Life Sciences, University of Liverpool Room 356, 4th Floor, UCD Building, Daulby Street, Liverpool L69 3GA, UK3 Royal Liverpool University Hospital, St. Paul's Eye Unit, Prescot St, Liverpool, Merseyside L7 8XP, UK
| | - Terrie E Taylor
- 5 Blantyre Malaria Project, Blantyre, Malawi6 Michigan State University, Department of Osteopathic Medical Specialities, West Fee Hall, 909 Fee Road, Room B305, East Lansing, MI 48824, USA
| | - Valentina Barrera
- 2 University of Liverpool, Department of Eye and Vision Science, Faculty of Health & Life Sciences, University of Liverpool Room 356, 4th Floor, UCD Building, Daulby Street, Liverpool L69 3GA, UK
| | - Valerie A White
- 7 Vancouver General Hospital, Department of Pathology and Laboratory Medicine, Vancouver, B.C. V5Z1M9, Canada
| | - Paul Hiscott
- 2 University of Liverpool, Department of Eye and Vision Science, Faculty of Health & Life Sciences, University of Liverpool Room 356, 4th Floor, UCD Building, Daulby Street, Liverpool L69 3GA, UK
| | - Malcolm E Molyneux
- 1 Malawi-Liverpool-Wellcome Trust Clinical Research Programme, PO Box 30096, Chichiri, Blantyre 3, Malawi4 University of Malawi College of Medicine, College of Medicine, P/Bag 360 Chichiri, Blantyre 3 Malawi8 Liverpool School of Tropical Medicine, Liverpool School of Tropical Medicine, Pembroke Place , Liverpool, L3 5QA , UK
| | - Baljean Dhillon
- 9 University of Edinburgh, Department of Ophthalmology, Edinburgh, UK10 Princess Alexandra Eye Pavilion, Edinburgh, UK
| | - Simon P Harding
- 2 University of Liverpool, Department of Eye and Vision Science, Faculty of Health & Life Sciences, University of Liverpool Room 356, 4th Floor, UCD Building, Daulby Street, Liverpool L69 3GA, UK3 Royal Liverpool University Hospital, St. Paul's Eye Unit, Prescot St, Liverpool, Merseyside L7 8XP, UK
| |
Collapse
|
17
|
Muqit MMK, Marcellino GR, Henson DB, Young LB, Patton N, Charles SJ, Turner GS, Stanga PE. Optos-guided pattern scan laser (Pascal)-targeted retinal photocoagulation in proliferative diabetic retinopathy. Acta Ophthalmol 2013; 91:251-8. [PMID: 22176513 DOI: 10.1111/j.1755-3768.2011.02307.x] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
PURPOSE To investigate the clinical effects and safety of targeted pattern scan laser (Pascal) retinal photocoagulation (TRP) in proliferative diabetic retinopathy (PDR). METHODS Prospective and non-randomized study of 28 eyes with treatment-naive proliferative diabetic retinopathy (PDR). Single-session 20-ms-Pascal TRP strategy applied 1500 burns to zones of retinal capillary non-perfusion and intermediate retinal ischaemia guided by wide-field fluorescein angiography (Optos). Main outcome measures at 12 and 24 weeks included; PDR grade (assessed by two masked retina specialists); central retinal thickness (CRT); mean deviation (MD) using 24-2 Swedish interactive threshold algorithm (SITA)-standard visual fields (VF); and ETDRS visual acuity (VA). RESULTS Following primary TRP, there was PDR regression in 76% of patients at 12 weeks (κ = 0.70; p < 0.001). No laser re-treatment was required at 4 weeks, and 10 eyes underwent repeat TRP at 12 weeks. Wide-field Optos angiography at 24 weeks showed complete disease regression in 37% and partial regression in 33%. Additional panretinal laser photocoagulation (PRP) was planned for active PDR in 30%. There were significant reductions in CRT over time (10.4 μm at 12-weeks, p = 0.007; 12.1 μm at 24-weeks, p = 0.0003). The MD on VFs improved after 12 weeks (+1.25 dB; p = 0.015) and 24 weeks (+1.26 dB, p = 0.01). The VA increased by +3 letters at 24 weeks (95% CI, 1.74-5.01; p < 0.0001). CONCLUSIONS This pilot study reports that Optos-guided Pascal 20-ms TRP using 1500 burns for treatment-naive PDR is a promising procedure with favourable safety profile.
Collapse
|
18
|
Abstract
UNLABELLED ABSTRACT.: PURPOSE Malfunction of retinal blood flow or oxygenation is believed to be involved in various diseases. Among them are retinal vessel occlusions, diabetic retinopathy and glaucoma. Reliable, non-invasive technology for retinal oxygen measurements has been scarce and most of the knowledge on retinal oxygenation comes from animal studies. This thesis describes human retinal oximetry, performed with novel retinal oximetry technology. The thesis describes studies on retinal vessel oxygen saturation in (1) light and dark in healthy volunteers, (2) central retinal vein occlusion, (3) branch retinal vein occlusion, (4) central retinal artery occlusion, (5) diabetic retinopathy, (6) patients undergoing glaucoma surgery and (7) patients taking glaucoma medication. METHODS The retinal oximeter (Oxymap ehf., Reykjavik, Iceland) is based on a fundus camera. An attached image splitter allows the simultaneous capture of four images of the same area of the fundus. Two images are used for further analysis, one acquired with 586 nm light and one with 605 nm light. Light absorbance of retinal vessels is sensitive to oxygen saturation at 605 nm but not at 586 nm. Measurement of reflected light at these wavelengths allows estimation of oxygen saturation in the main retinal vessels. This is performed with custom-made analysis software. RESULTS LIGHT AND DARK: After 30 min in the dark, oxygen saturation in retinal arterioles of healthy volunteers was 92 ± 4% (mean ± SD, n = 15). After 5 min in 80 cd/m(2) light, the arteriolar saturation was 89 ± 5%. The decrease was statistically significant (p = 0.008). The corresponding values for retinal venules were 60 ± 5% in the dark and 55 ± 10% in the light (p = 0.020). Similar results were found after alternating 5 min periods of darkness and light. In a second experiment (n = 19), a significant decrease in retinal vessel oxygen saturation was found in 100 cd/m(2) light compared with darkness but 1 and 10 cd/m(2) light had no significant effect. CENTRAL RETINAL VEIN OCCLUSION: In patients with central retinal vein occlusion, the mean saturation in affected retinal venules was 49 ± 12%, while the mean value for venules in the fellow eye was 65 ± 6% (mean ± SD, p = 0.003, n = 8). The retinal arteriolar saturation was the same in affected (99 ± 3%) and the unaffected (99 ± 6%) eyes. The venous oxygen saturation showed much variation between affected eyes. BRANCH RETINAL VEIN OCCLUSION: Median oxygen saturation in venules affected by branch retinal vein occlusion was 59% (range, 12-93%, n = 22), while it was 63% (23-80%) in unaffected venules in the affected eye and 55% (39-80%) in venules in the fellow eye. The difference was not statistically significant (p > 0.05). There was a significant difference between affected arterioles (median 101%; range, 89-115%) and unaffected arterioles (95%, 85-104%) in the affected eye (p < 0.05, n = 18). CENTRAL RETINAL ARTERY OCCLUSION: In a patient with a day's history of central retinal artery occlusion due to temporal arteritis, the mean arteriolar saturation was 71 ± 9% and 63 ± 9% in the venules. One month later, after treatment with prednisolone, the mean arteriolar saturation was 100 ± 4% and the venous saturation 54 ± 5%. DIABETIC RETINOPATHY: When compared with healthy volunteers (n = 31), patients with all categories of diabetic retinopathy had on average 7-10 percentage points higher saturation in retinal arterioles (p < 0.05 for all categories, n = 6-8 in each category). In venules, the saturation was 8-12 percentage points higher (p < 0.05 for all categories). GLAUCOMA SURGERY: Oxygen saturation in retinal arterioles increased by 2 percentage points on average (p = 0.046, n = 19) with surgery, which lowered intraocular pressure from 23 ± 7 mmHg (mean ± SD) to 10 ± 4 mmHg (p < 0.0001). No other significant changes were found (p ≥ 0.35). DORZOLAMIDE: A significant reduction of 3 percentage points was found in arterioles (p < 0.01) and venules (p < 0.05) when patients with glaucoma or ocular hypertension changed from dorzolamide-timolol combination eye drops to timolol alone (n = 6). No change was found in patients, who started on timolol and switched to the combination therapy (p > 0.05, n = 7). CONCLUSIONS Dual wavelength oximetry can be used to non-invasively measure retinal vessel oxygen saturation in health and disease. The results indicate that retinal vessel oxygen saturation is (1) increased in the dark, (2) lower in venules affected by central retinal vein occlusions, (3) variable in branch retinal vein occlusion, (4) lower in retinal arterioles in central retinal artery occlusion, (5) increased in diabetic retinopathy, (6-7) mildly affected by glaucoma surgery or dorzolamide.
Collapse
|
19
|
Furukawa H, Arimoto H, Shirai T, Ooto S, Hangai M, Yoshimura N. Oximetry of retinal capillaries by multicomponent analysis. APPLIED SPECTROSCOPY 2012; 66:962-969. [PMID: 22800727 DOI: 10.1366/11-06525] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Retinal oximetry of capillaries was performed for early detection of retinal vascular abnormalities, which are caused predominantly by complications of systemic circulatory diseases. As the conventional method for determining absorbance is not applicable to capillaries, multicomponent analysis was used to estimate the absorbance spectra of the retinal blood vessels. In this analysis, the capillary spectrum was classified as intermediate between those of the retinal arteries and veins, enabling relative estimation of oxygen saturation in the capillaries. This method could be useful for early recognition of disturbances in the peripheral circulation. Furthermore, a spectroscopic ophthalmoscope system based on the proposed method was developed to examine the human retina. A clinical trial of this system demonstrated that oximetry of the retinal capillaries may be an improvement over the present diagnosis for patients of malignant hypertension.
Collapse
Affiliation(s)
- Hiromitsu Furukawa
- Electronics and Photonics Research Institute of AIST, Umezono 1-1-1, Tsukuba 305-8568, Japan.
| | | | | | | | | | | |
Collapse
|