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Qing KX, Lo ACY, Lu S, Zhou Y, Yang D, Yang D. Integrated bioinformatics analysis of retinal ischemia/reperfusion injury in rats with potential key genes. BMC Genomics 2024; 25:367. [PMID: 38622534 PMCID: PMC11017533 DOI: 10.1186/s12864-024-10288-0] [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: 12/29/2023] [Accepted: 04/07/2024] [Indexed: 04/17/2024] Open
Abstract
The tissue damage caused by transient ischemic injury is an essential component of the pathogenesis of retinal ischemia, which mainly hinges on the degree and duration of interruption of the blood supply and the subsequent damage caused by tissue reperfusion. Some research indicated that the retinal injury induced by ischemia-reperfusion (I/R) was related to reperfusion time.In this study, we screened the differentially expressed circRNAs, lncRNAs, and mRNAs between the control and model group and at different reperfusion time (24h, 72h, and 7d) with the aid of whole transcriptome sequencing technology, and the trend changes in time-varying mRNA, lncRNA, circRNA were obtained by chronological analysis. Then, candidate circRNAs, lncRNAs, and mRNAs were obtained as the intersection of differentially expression genes and trend change genes. Importance scores of the genes selected the key genes whose expression changed with the increase of reperfusion time. Also, the characteristic differentially expressed genes specific to the reperfusion time were analyzed, key genes specific to reperfusion time were selected to show the change in biological process with the increase of reperfusion time.As a result, 316 candidate mRNAs, 137 candidate lncRNAs, and 31 candidate circRNAs were obtained by the intersection of differentially expressed mRNAs, lncRNAs, and circRNAs with trend mRNAs, trend lncRNAs and trend circRNAs, 5 key genes (Cd74, RT1-Da, RT1-CE5, RT1-Bb, RT1-DOa) were selected by importance scores of the genes. The result of GSEA showed that key genes were found to play vital roles in antigen processing and presentation, regulation of the actin cytoskeleton, and the ribosome. A network included 4 key genes (Cd74, RT1-Da, RT1-Bb, RT1-DOa), 34 miRNAs and 48 lncRNAs, and 81 regulatory relationship axes, and a network included 4 key genes (Cd74, RT1-Da, RT1-Bb, RT1-DOa), 9 miRNAs and 3 circRNAs (circRNA_10572, circRNA_03219, circRNA_11359) and 12 regulatory relationship axes were constructed, the subcellular location, transcription factors, signaling network, targeted drugs and relationship to eye diseases of key genes were predicted. 1370 characteristic differentially expressed mRNAs (spec_24h mRNA), 558 characteristic differentially expressed mRNAs (spec_72h mRNA), and 92 characteristic differentially expressed mRNAs (spec_7d mRNA) were found, and their key genes and regulation networks were analyzed.In summary, we screened the differentially expressed circRNAs, lncRNAs, and mRNAs between the control and model groups and at different reperfusion time (24h, 72h, and 7d). 5 key genes, Cd74, RT1-Da, RT1-CE5, RT1-Bb, RT1-DOa, were selected. Key genes specific to reperfusion time were selected to show the change in biological process with the increased reperfusion time. These results provided theoretical support and a reference basis for the clinical treatment.
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Affiliation(s)
- Kai-Xiong Qing
- Department of Cardiac & Vascular Surgery, First Affiliated Hospital of Kunming Medical University, Kunming Medical University, Kunming, Yunnan Province, China
| | - Amy C Y Lo
- Department of Ophthalmology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China
| | - Siduo Lu
- Department of Ophthalmology, First Affiliated Hospital of Kunming Medical University, Kunming Medical University, Kunming, Yunnan Province, China
| | - You Zhou
- Department of Ophthalmology, First Affiliated Hospital of Kunming Medical University, Kunming Medical University, Kunming, Yunnan Province, China
| | - Dan Yang
- Department of Ophthalmology, First Affiliated Hospital of Kunming Medical University, Kunming Medical University, Kunming, Yunnan Province, China
| | - Di Yang
- Department of Ophthalmology, First Affiliated Hospital of Kunming Medical University, Kunming Medical University, Kunming, Yunnan Province, China.
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Deng S, Huang S, Yang A, Muir ER. Imaging ocular water inflow in the mouse with deuterium oxide MRI. Magn Reson Imaging 2023; 101:47-53. [PMID: 36965834 PMCID: PMC11104035 DOI: 10.1016/j.mri.2023.03.017] [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: 01/31/2023] [Accepted: 03/21/2023] [Indexed: 03/27/2023]
Abstract
Abnormal intraocular fluid flow or clearance is involved with a variety of eye diseases such as glaucoma and diabetic retinopathy, but measurement of water exchange dynamics in the vitreous and aqueous remain challenging. 2H MRI can be used to image deuterium oxide (D₂O) as a tracer, but the signal-to-noise ratio for deuterium is low due to its low concentration, which has hampered its application to imaging the eye. To overcome this challenge, we investigated the feasibility of direct D2O MRI to measure water dynamics in the mouse eye. The balanced steady-state free precession (bSSFP) sequence provided substantially higher signal-to-noise ratio for imaging D2O in fluid compared to standard gradient echo and spin echo sequences. bSSFP allowed dynamic imaging of intraocular water inflow in the mouse with 41 s temporal resolution. The inflow rate in the vitreous was found to be faster than in the aqueous. These studies demonstrate the feasibility of in vivo imaging of water inflow dynamics into the both the vitreous and aqueous in mice, which could be useful in studies of abnormal fluid exchange in rodent models of eye disease.
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Affiliation(s)
- Shengwen Deng
- Department of Radiology, University Hospitals Cleveland Medical Center and Case Western Reserve University, Cleveland, OH, United States; Research Imaging Institute, University of Texas Health Science Center, San Antonio, TX, United States
| | - Shiliang Huang
- Research Imaging Institute, University of Texas Health Science Center, San Antonio, TX, United States
| | - Alivia Yang
- Department of Radiology, School of Medicine, Stony Brook University, Stony Brook, NY, United States
| | - Eric R Muir
- Research Imaging Institute, University of Texas Health Science Center, San Antonio, TX, United States; Department of Radiology, School of Medicine, Stony Brook University, Stony Brook, NY, United States.
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3
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Diabetic mice have retinal and choroidal blood flow deficits and electroretinogram deficits with impaired responses to hypercapnia. PLoS One 2021; 16:e0259505. [PMID: 34882677 PMCID: PMC8659412 DOI: 10.1371/journal.pone.0259505] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2021] [Accepted: 10/20/2021] [Indexed: 11/19/2022] Open
Abstract
Purpose The purpose of this study was to investigate neuronal and vascular functional deficits in the retina and their association in a diabetic mouse model. We measured electroretinography (ERG) responses and choroidal and retinal blood flow (ChBF, RBF) with magnetic resonance imaging (MRI) in healthy and diabetic mice under basal conditions and under hypercapnic challenge. Methods Ins2Akita diabetic (Diab, n = 8) and age-matched, wild-type C57BL/6J mice (Ctrl, n = 8) were studied under room air and moderate hypercapnia (5% CO2). Dark-adapted ERG a-wave, b-wave, and oscillatory potentials (OPs) were measured for a series of flashes. Regional ChBF and RBF under air and hypercapnia were measured using MRI in the same mice. Results Under room air, Diab mice had compromised ERG b-wave and OPs (e.g., b-wave amplitude was 422.2±10.7 μV in Diab vs. 600.1±13.9 μV in Ctrl, p < 0.001). Under hypercapnia, OPs and b-wave amplitudes were significantly reduced in Diab (OPs by 30.3±3.0% in Diab vs. -3.0±3.6% in Ctrl, b-wave by 17.9±1.4% in Diab vs. 1.3±0.5% in Ctrl). Both ChBF and RBF had significant differences in regional blood flow, with Diab mice having substantially lower blood flow in the nasal region (ChBF was 5.4±1.0 ml/g/min in Diab vs. 8.6±1.0 ml/g/min in Ctrl, RBF was 0.91±0.10 ml/g/min in Diab vs. 1.52±0.24 ml/g/min in Ctrl). Under hypercapnia, ChBF increased in both Ctrl and Diab without significant group difference (31±7% in Diab vs. 17±7% in Ctrl, p > 0.05), but an increase in RBF was not detected for either group. Conclusions Inner retinal neuronal function and both retinal and choroidal blood flow were impaired in Diab mice. Hypercapnia further compromised inner retinal neuronal function in diabetes, while the blood flow response was not affected, suggesting that the diabetic retina has difficulty adapting to metabolic challenges due to factors other than impaired blood flow regulation.
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Tonade D, Kern TS. Photoreceptor cells and RPE contribute to the development of diabetic retinopathy. Prog Retin Eye Res 2021; 83:100919. [PMID: 33188897 PMCID: PMC8113320 DOI: 10.1016/j.preteyeres.2020.100919] [Citation(s) in RCA: 76] [Impact Index Per Article: 25.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2020] [Revised: 10/27/2020] [Accepted: 10/31/2020] [Indexed: 12/26/2022]
Abstract
Diabetic retinopathy (DR) is a leading cause of blindness. It has long been regarded as vascular disease, but work in the past years has shown abnormalities also in the neural retina. Unfortunately, research on the vascular and neural abnormalities have remained largely separate, instead of being integrated into a comprehensive view of DR that includes both the neural and vascular components. Recent evidence suggests that the most predominant neural cell in the retina (photoreceptors) and the adjacent retinal pigment epithelium (RPE) play an important role in the development of vascular lesions characteristic of DR. This review summarizes evidence that the outer retina is altered in diabetes, and that photoreceptors and RPE contribute to retinal vascular alterations in the early stages of the retinopathy. The possible molecular mechanisms by which cells of the outer retina might contribute to retinal vascular damage in diabetes also are discussed. Diabetes-induced alterations in the outer retina represent a novel therapeutic target to inhibit DR.
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Affiliation(s)
- Deoye Tonade
- Department of Pharmacology, Case Western Reserve University, Cleveland, OH, USA
| | - Timothy S Kern
- Department of Pharmacology, Case Western Reserve University, Cleveland, OH, USA; Veterans Administration Medical Center Research Service, Cleveland, OH, USA; Gavin Herbert Eye Institute, University of California Irvine, Irvine, CA, USA; Veterans Administration Medical Center Research Service, Long Beach, CA, USA.
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Franceschiello B, Di Sopra L, Minier A, Ionta S, Zeugin D, Notter MP, Bastiaansen JAM, Jorge J, Yerly J, Stuber M, Murray MM. 3-Dimensional magnetic resonance imaging of the freely moving human eye. Prog Neurobiol 2020; 194:101885. [PMID: 32653462 DOI: 10.1016/j.pneurobio.2020.101885] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2019] [Revised: 04/21/2020] [Accepted: 07/07/2020] [Indexed: 12/16/2022]
Abstract
Eye motion is a major confound for magnetic resonance imaging (MRI) in neuroscience or ophthalmology. Currently, solutions toward eye stabilisation include participants fixating or administration of paralytics/anaesthetics. We developed a novel MRI protocol for acquiring 3-dimensional images while the eye freely moves. Eye motion serves as the basis for image reconstruction, rather than an impediment. We fully reconstruct videos of the moving eye and head. We quantitatively validate data quality with millimetre resolution in two ways for individual participants. First, eye position based on reconstructed images correlated with simultaneous eye-tracking. Second, the reconstructed images preserve anatomical properties; the eye's axial length measured from MRI images matched that obtained with ocular biometry. The technique operates on a standard clinical setup, without necessitating specialized hardware, facilitating wide deployment. In clinical practice, we anticipate that this may help reduce burdens on both patients and infrastructure, by integrating multiple varieties of assessments into a single comprehensive session. More generally, our protocol is a harbinger for removing the necessity of fixation, thereby opening new opportunities for ethologically-valid, naturalistic paradigms, the inclusion of populations typically unable to stably fixate, and increased translational research such as in awake animals whose eye movements constitute an accessible behavioural readout.
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Affiliation(s)
- Benedetta Franceschiello
- The Laboratory for Investigative Neurophysiology (The LINE), Department of Radiology, University Hospital Center and University of Lausanne, Lausanne, Switzerland; Department of Ophthalmology, University of Lausanne, Jules Gonin Eye Hospital, Fondation Asile des aveugles, Lausanne, Switzerland.
| | - Lorenzo Di Sopra
- Department of Radiology, University Hospital Center and University of Lausanne, Lausanne, Switzerland
| | - Astrid Minier
- The Laboratory for Investigative Neurophysiology (The LINE), Department of Radiology, University Hospital Center and University of Lausanne, Lausanne, Switzerland; Department of Ophthalmology, University of Lausanne, Jules Gonin Eye Hospital, Fondation Asile des aveugles, Lausanne, Switzerland
| | - Silvio Ionta
- Department of Ophthalmology, University of Lausanne, Jules Gonin Eye Hospital, Fondation Asile des aveugles, Lausanne, Switzerland
| | - David Zeugin
- The Laboratory for Investigative Neurophysiology (The LINE), Department of Radiology, University Hospital Center and University of Lausanne, Lausanne, Switzerland; Department of Ophthalmology, University of Lausanne, Jules Gonin Eye Hospital, Fondation Asile des aveugles, Lausanne, Switzerland
| | - Michael P Notter
- The Laboratory for Investigative Neurophysiology (The LINE), Department of Radiology, University Hospital Center and University of Lausanne, Lausanne, Switzerland
| | - Jessica A M Bastiaansen
- Department of Radiology, University Hospital Center and University of Lausanne, Lausanne, Switzerland
| | - João Jorge
- École Polytechnique Fédérale de Lausanne (EPFL) Lausanne, Switzerland
| | - Jérôme Yerly
- Department of Radiology, University Hospital Center and University of Lausanne, Lausanne, Switzerland; Center for Biomedical Imaging (CIBM), Lausanne, Switzerland
| | - Matthias Stuber
- Department of Radiology, University Hospital Center and University of Lausanne, Lausanne, Switzerland; Center for Biomedical Imaging (CIBM), Lausanne, Switzerland
| | - Micah M Murray
- The Laboratory for Investigative Neurophysiology (The LINE), Department of Radiology, University Hospital Center and University of Lausanne, Lausanne, Switzerland; Department of Ophthalmology, University of Lausanne, Jules Gonin Eye Hospital, Fondation Asile des aveugles, Lausanne, Switzerland; Center for Biomedical Imaging (CIBM), Lausanne, Switzerland; Department of Hearing and Speech Sciences, Vanderbilt University Nashville, TN, USA.
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Jendzjowsky NG, Steinback CD, Herman RJ, Tsai WH, Costello FE, Wilson RJA. Functional-Optical Coherence Tomography: A Non-invasive Approach to Assess the Sympathetic Nervous System and Intrinsic Vascular Regulation. Front Physiol 2019; 10:1146. [PMID: 31572206 PMCID: PMC6751282 DOI: 10.3389/fphys.2019.01146] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2019] [Accepted: 08/22/2019] [Indexed: 11/13/2022] Open
Abstract
Sympathetic nervous system dysregulation and vascular impairment in neuronal tissue beds are hallmarks of prominent cardiorespiratory diseases. However, an accurate and convenient method of assessing SNA and local vascular regulation is lacking, hindering routine clinical and research assessments. To address this, we investigated whether spectral domain optical coherence tomography (OCT), that allows investigation of retina and choroid vascular responsiveness, reflects sympathetic activity in order to develop a quick, easy and non-invasive sympathetic index. Here, we compare choroid and retina vascular perfusion density (VPD) acquired with OCT and heart rate variability (HRV) to microneurography. We recruited 6 healthy males (26 ± 3 years) and 5 healthy females (23 ± 1 year) and instrumented them for respiratory parameters, ECG, blood pressure and muscle sympathetic nerve microneurography. Choroid VPD decreases with the cold pressor test, inhaled hypoxia and breath-hold, and increases with hyperoxia and hyperpnea suggesting that sympathetic activity dominates choroid responses. In contrast, retina VPD was unaffected by the cold pressor test, increased with hypoxia and breath hold and decreases with hyperoxia and hyperpnea, suggesting metabolic vascular regulation dominates the retina. With regards to integrated muscle sympathetic nerve activity, HRV had low predictive power whereas choroid VPD was strongly (inversely) correlated with integrated muscle sympathetic nerve activity (R = -0.76; p < 0.0001). These data suggest that Functional-OCT may provide a novel approach to assess sympathetic activity and intrinsic vascular responsiveness (i.e., autoregulation). Given that sympathetic nervous system activity is the main determinant of autonomic function, sympathetic excitation is associated with severe cardiovascular/cardiorespiratory diseases and autoregulation is critical for brain health, we suggest that the use of our new Functional-OCT technique will be of broad interest to clinicians and researchers.
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Affiliation(s)
- Nicholas G Jendzjowsky
- Department of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada
| | - Craig D Steinback
- Program for Pregnancy and Postpartum Health, Physical Activity and Diabetes Laboratory, Faculty of Kinesiology, Sport and Recreation, University of Alberta, Edmonton, AB, Canada
| | - Robert J Herman
- Department of Medicine, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada
| | - Willis H Tsai
- Department of Medicine, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada.,Department of Community Health Sciences, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada
| | - Fiona E Costello
- Department of Medicine, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada.,Department of Clinical Neuroscience, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada.,Department of Surgery, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada
| | - Richard J A Wilson
- Department of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada
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Hsiao CC, Hsu HM, Yang CM, Yang CH. Correlation of retinal vascular perfusion density with dark adaptation in diabetic retinopathy. Graefes Arch Clin Exp Ophthalmol 2019; 257:1401-1410. [PMID: 31001668 DOI: 10.1007/s00417-019-04321-2] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2018] [Revised: 03/20/2019] [Accepted: 04/06/2019] [Indexed: 11/30/2022] Open
Abstract
PURPOSE To evaluate the anatomic versus functional changes in diabetic retinopathy (DR) by studying the correlation of retinal vascular perfusion density and dark adaptation (DA). METHODS Optical coherence tomography angiography (OCTA) and DA tests were performed in diabetic patients and nondiabetic controls. DA was measured using AdaptDx dark adaptometer and the rod intercept was recorded. Macular OCTA images were acquired using the RTVue XR Avanti with AngioVue. RESULTS Eighty-six eyes from 57 patients with diabetes (19 with no DR, 19 with non-proliferative DR [NPDR], and 19 with proliferative DR [PDR] who had undergone photocoagulation) and 10 eyes from 10 patients without diabetes were recruited. A significant decrease in vascular density and a prolonged rod intercept were found as DR progressed (P < .01). A negative trend was found between vascular density and the rod intercept. The negative trend in the deep layer (R2 = 0.28) was more substantial than that in the superficial layer (R2 = 0.14). A prolonged rod intercept was associated with elevated HbA1c (R2 = 0.08). CONCLUSIONS The vascular density of the macula could be assessed by OCTA and the functional change in the outer retina could be measured non-invasively by DA. The severity of decreasing vascular density and prolongation of DA are proportional to progression of DR. Decreased deep retinal vascular perfusion density and impaired DA response are correlated and show a negative trend according to the severity of DR.
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Affiliation(s)
- Chia-Chieh Hsiao
- Department of Ophthalmology, National Taiwan University Hospital, No. 7, Chun-Shan S. Rd., Taipei City, 100, Taiwan
| | - Hsueh-Min Hsu
- Department of Ophthalmology, National Taiwan University College of Medicine, No. 7, Chun-Shan S. Rd., Taipei City, 100, Taiwan
| | - Chung-May Yang
- Department of Ophthalmology, National Taiwan University Hospital, No. 7, Chun-Shan S. Rd., Taipei City, 100, Taiwan.,Department of Ophthalmology, National Taiwan University College of Medicine, No. 7, Chun-Shan S. Rd., Taipei City, 100, Taiwan
| | - Chang-Hao Yang
- Department of Ophthalmology, National Taiwan University Hospital, No. 7, Chun-Shan S. Rd., Taipei City, 100, Taiwan. .,Department of Ophthalmology, National Taiwan University College of Medicine, No. 7, Chun-Shan S. Rd., Taipei City, 100, Taiwan.
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8
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LoBue SA, Yamada N, Choi MJ, Olsen TW. Creating a Full-thickness Choroidal Incision: An Ex Vivo Analysis of Human and Porcine Tissue Contraction Dynamics. Transl Vis Sci Technol 2017; 6:5. [PMID: 29134136 PMCID: PMC5678367 DOI: 10.1167/tvst.6.6.5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2017] [Accepted: 09/30/2017] [Indexed: 02/02/2023] Open
Abstract
Purpose We hypothesized that the elastic nature of the choroid leads to tissue contraction following a full-thickness, sharp incision. Furthermore, we sought to quantify, measure, and compare tissue contraction in ex vivo porcine globes and human globes of various ages using predetermined variables. Method A full-thickness, ex vivo choroidal incision was performed in either pig (n = 97) or human (n = 30) specimens. Variables included trephine diameter (1.5, 2.0, or 2.5 mm) versus a straight surgical blade, and temperature (1.7 °–4.4° vs. 36.6°F). Central centripetal and surround centrifugal tissue contractions were measured. Mean percentage tissue contraction was assessed as a ratio of trephine diameter to final tissue contraction measured immediately following each incision using a standardized device. Results For trephination in pig specimens, centripetal contraction ranged from 38% to 50% with a mean of 44%. Centrifugal contraction was approximately 15%. Human choroidal contraction was 39% and 15%, respectively, with a statistically significant inverse relationship to age (R2 = 0.35, P ≤ 0.01). Asymmetric contraction was noted when incisions were closer to choroidal attachment sites to the sclera, such as near vortex ampullae. Linear incisions resulted in contraction that correlated with incision length (R2 = 0.35, P ≤ 0.001). Conclusions A full-thickness choroidal incision results in significant tissue contraction. For circular incisions, the centripetal contraction approaches 50% of the original incision size. For linear incisions, the contraction corresponds directly with incision length. In human specimens, there is less contraction with advancing age. Translational Relevance Our findings have clinical relevance for choroidal biopsy, traumatic injury, and choroidal translocation surgery.
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Affiliation(s)
- Stephen A LoBue
- Emory University, Department of Ophthalmology, Atlanta GA, USA
| | - Norihiro Yamada
- Emory University, Department of Ophthalmology, Atlanta GA, USA.,Gunma University, Department of Ophthalmology, Maebashi, Gunma Prefecture, Japan
| | | | - Timothy W Olsen
- Emory University, Department of Ophthalmology, Atlanta GA, USA.,Mayo Clinic, Department of Ophthalmology, Rochester, MN, USA
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Abstract
In diabetes, retinal blood flow is compromised, and retinal hypoxia is likely to be further intensified during periods of darkness. During dark adaptation, rod photoreceptors in the outer retina are maximally depolarized and continuously release large amounts of the neurotransmitter glutamate-an energetically demanding process that requires the highest oxygen consumption per unit volume of any tissue of the body. In complete darkness, even more oxygen is consumed by the outer retina, producing a steep fall in the retinal oxygen tension curve which reaches a nadir at the depth of the mitochondrial-rich rod inner segments. In contrast to the normal retina, the diabetic retina cannot meet the added metabolic load imposed by the dark-adapted rod photoreceptors; this exacerbates retinal hypoxia and stimulates the overproduction of vascular endothelial growth factor (VEGF). The use of nocturnal illumination to prevent dark adaptation, specifically reducing the rod photoreceptor dark current, should ameliorate diabetic retinopathy.
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Affiliation(s)
- David J Ramsey
- Department of Ophthalmology, Lahey Hospital & Medical Center, Tufts University School of Medicine, 41 Mall Road, Burlington, MA, 01805, USA.
| | - G B Arden
- University College London, London, UK.
- Moorfields Eye Hospital NHS Foundation Trust, London, UK.
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Berkowitz BA, Bissig D, Roberts R. MRI of rod cell compartment-specific function in disease and treatment in vivo. Prog Retin Eye Res 2015; 51:90-106. [PMID: 26344734 DOI: 10.1016/j.preteyeres.2015.09.001] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2015] [Revised: 08/26/2015] [Accepted: 09/01/2015] [Indexed: 10/23/2022]
Abstract
Rod cell oxidative stress is a major pathogenic factor in retinal disease, such as diabetic retinopathy (DR) and retinitis pigmentosa (RP). Personalized, non-destructive, and targeted treatment for these diseases remains elusive since current imaging methods cannot analytically measure treatment efficacy against rod cell compartment-specific oxidative stress in vivo. Over the last decade, novel MRI-based approaches that address this technology gap have been developed. This review summarizes progress in the development of MRI since 2006 that enables earlier evaluation of the impact of disease on rod cell compartment-specific function and the efficacy of anti-oxidant treatment than is currently possible with other methods. Most of the new assays of rod cell compartment-specific function are based on endogenous contrast mechanisms, and this is expected to facilitate their translation into patients with DR and RP, and other oxidative stress-based retinal diseases.
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Affiliation(s)
- Bruce A Berkowitz
- Dept. of Anatomy and Cell Biology, Wayne State University School of Medicine, Detroit, MI, USA; Dept. Of Ophthalmology, Wayne State University School of Medicine, Detroit, MI, USA.
| | - David Bissig
- Dept. of Anatomy and Cell Biology, Wayne State University School of Medicine, Detroit, MI, USA
| | - Robin Roberts
- Dept. Of Ophthalmology, Wayne State University School of Medicine, Detroit, MI, USA
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11
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Duong TQ. Magnetic resonance imaging of the retina: from mice to men. Magn Reson Med 2014; 71:1526-30. [PMID: 23716429 PMCID: PMC3783549 DOI: 10.1002/mrm.24797] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2013] [Revised: 03/25/2013] [Accepted: 04/15/2013] [Indexed: 11/09/2022]
Abstract
This mini-review provides an overview of magnetic resonance imaging (MRI) applications to study rodent, cat, non-human primate, and human retinas. These techniques include T(1) - and T(2) -weighted anatomical, diffusion, blood flow, blood volume, blood-oxygenation level dependent, manganese-enhanced, physiological, and functional MRI. Applications to study the retinas in diabetic retinopathy, glaucoma, and retinal degeneration are also reviewed. MRI offers some unique advantages compared with existing imaging techniques and has the potential to further our understanding of physiology and function in healthy and diseased retinas.
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Affiliation(s)
- Timothy Q Duong
- South Texas Veterans Health Care System, Research Imaging Institute, Department of Ophthalmology, University of Texas Health Science Center, San Antonio, Texas, USA
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12
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Zhang Y, Harrison JM, Nateras OSE, Chalfin S, Duong TQ. Decreased retinal-choroidal blood flow in retinitis pigmentosa as measured by MRI. Doc Ophthalmol 2013; 126:187-97. [PMID: 23408312 DOI: 10.1007/s10633-013-9374-1] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2012] [Accepted: 01/28/2013] [Indexed: 11/25/2022]
Abstract
PURPOSE To evaluate retinal and choroidal blood flow (BF) using high-resolution magnetic resonance imaging (MRI) as well as visual function measured by the electroretinogram (ERG) in patients with retinitis pigmentosa (RP). METHODS MRI studies were performed in 6 RP patients (29-67 years) and 5 healthy volunteers (29-64 years) on a 3-Tesla scanner with a custom-made surface coil. Quantitative BF was measured using the pseudo-continuous arterial spin-labeling technique at 0.5 × 0.8 × 6.0 mm. Full-field ERGs of all patients were recorded. Amplitudes and implicit times of standard ERGs were analyzed. RESULTS Basal BF in the posterior retinal-choroid was 142 ± 16 ml/100ml/min (or 1.14 ± 0.13 μl/mm(2)/min) in the control group and was 70 ±19 ml/100ml/min (or 0.56 ± 0.15 μl/mm(2)/min) in the RP group. Retinal-choroidal BF was significantly reduced by 52 ± 8 % in RP patients compared to controls (P<0.05). ERG a- and b-wave amplitudes of RP patients were reduced, and b-wave implicit times were delayed. There were statistically significant correlations between a-wave amplitude and BF value (r=0.9, P<0.05) but not between b-wave amplitude and BF value (r =0.7, P=0.2). CONCLUSIONS This study demonstrates a novel non-invasive MRI approach to measure quantitative retinal and choroidal BF in RP patients. We found that retinal-choroidal BF was markedly reduced and significantly correlated with reduced amplitudes of the a-wave of the standard combined ERG.
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Affiliation(s)
- Yi Zhang
- Research Imaging Institute, University of Texas Health Science Center, 8403 Floyd Curl Dr, San Antonio, TX 78229, USA
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Bissig D, Berkowitz BA. Light-dependent changes in outer retinal water diffusion in rats in vivo. Mol Vis 2012; 18:2561-xxx. [PMID: 23129976 PMCID: PMC3482170] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2012] [Accepted: 10/18/2012] [Indexed: 11/25/2022] Open
Abstract
PURPOSE To test the hypothesis that in rats, intraretinal light-dependent changes on diffusion-weighted magnetic resonance imaging (MRI) in vivo are consistent with known retinal layer-specific physiology. METHODS In male Sprague-Dawley rats, retinal morphology (thickness, extent, surface area, volume) and intraretinal profiles of the apparent diffusion coefficient (ADC, i.e., water mobility) parallel and perpendicular to the optic nerve were measured in vivo using quantitative MRI methods during light and dark stimulation. RESULTS The parallel ADC in the posterior half of the avascular, photoreceptor-dominated outer retina was significantly higher in light than dark, and this pattern was reversed (dark>light) in the anterior outer retina. The perpendicular ADC in the posterior outer retina was similar in light and dark, but was significantly higher in dark than light in the anterior outer retina. No light-dark changes in the inner retina were noted. CONCLUSIONS We identified light-dependent intraretinal diffusion changes that reflected established stimulation-based changes in outer retinal hydration. These findings are expected to motivate future applications of functional diffusion-based MRI in blinding disorders of the outer retina.
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Affiliation(s)
- David Bissig
- Department of Anatomy and Cell Biology, Wayne State University, Detroit, MI
| | - Bruce A. Berkowitz
- Department of Anatomy and Cell Biology, Wayne State University, Detroit, MI,Department of Ophthalmology, Wayne State University, Detroit, MI
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14
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Fanea L, Fagan AJ. Review: magnetic resonance imaging techniques in ophthalmology. Mol Vis 2012; 18:2538-60. [PMID: 23112569 PMCID: PMC3482169] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2011] [Accepted: 10/10/2012] [Indexed: 11/19/2022] Open
Abstract
Imaging the eye with magnetic resonance imaging (MRI) has proved difficult due to the eye's propensity to move involuntarily over typical imaging timescales, obscuring the fine structure in the eye due to the resulting motion artifacts. However, advances in MRI technology help to mitigate such drawbacks, enabling the acquisition of high spatiotemporal resolution images with a variety of contrast mechanisms. This review aims to classify the MRI techniques used to date in clinical and preclinical ophthalmologic studies, describing the qualitative and quantitative information that may be extracted and how this may inform on ocular pathophysiology.
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Affiliation(s)
- Laura Fanea
- Department of Biomedical Physics, Physics Faculty, Babes-Bolyai University, Cluj-Napoca, Romania,Department of Radiology, Cluj County Emergency Hospital, Cluj-Napoca, Romania
| | - Andrew J. Fagan
- Centre for Advanced Medical Imaging, St. James’s Hospital Dublin / University of Dublin Trinity College, Ireland
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15
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De La Garza BH, Li G, Shih YYI, Duong TQ. Layer-specific manganese-enhanced MRI of the retina in light and dark adaptation. Invest Ophthalmol Vis Sci 2012; 53:4352-8. [PMID: 22669725 DOI: 10.1167/iovs.11-8826] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE To employ functional manganese-enhanced MRI (MEMRI) to image layer-specific changes in calcium-dependent activities in the rat retina during light versus dark adaptation. METHODS Functional MEMRI at 20 × 20 × 700 μm was used to study light and dark adaptation in the same animals (N = 10) in which one eye was covered and the fellow eye was not. The activity encoding of the light and dark adaptation was achieved in awake conditions and imaged under anesthesia. T(1)-weighted MRI at 11.7 tesla (T) was performed using two identical radiofrequency transceiver coils to allow interleaved MRI acquisitions of the two eyes. An intravascular contrast agent was also used to verify layer assignments. RESULTS MEMRI detected contrasts among the inner retina, outer retina, and choroid. Independent confirmation of the vascular layers and boundaries between layers was documented with an intravascular contrast agent. The retinal layer thicknesses agreed with published data. The outer retina had lower MEMRI activity in light compared with dark adaption (P < 0.001), consistent with the increased metabolic demand associated with the "dark current." The inner retina had higher MEMRI activity in light compared with dark adaption (P < 0.05). The choroid MEMRI activity was not statistically different between light and dark adaptation (P > 0.05). CONCLUSIONS This study demonstrated a high-resolution MEMRI protocol to image functional activities among different layers of the retinas in awake animals during light and dark adaptation. This approach could have potential applications in animal models of retinal dysfunction.
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Affiliation(s)
- Bryan H De La Garza
- Research Imaging Institute, University of Texas Health Science Center, San Antonio, TX 78229, USA
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16
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Layer-specific blood-flow MRI of retinitis pigmentosa in RCS rats. Exp Eye Res 2012; 101:90-6. [PMID: 22721720 DOI: 10.1016/j.exer.2012.06.006] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2012] [Revised: 05/23/2012] [Accepted: 06/11/2012] [Indexed: 02/04/2023]
Abstract
The Royal College of Surgeons (RCS) rat is an established animal model of retinitis pigmentosa, a family of inherited retinal diseases which starts with loss of peripheral vision and progresses to eventual blindness. Blood flow (BF), an important physiological parameter, is intricately coupled to metabolic function under normal physiological conditions and is perturbed in many neurological and retinal diseases. This study reports non-invasive high-resolution MRI (44 × 44 × 600 μm) to image quantitative retinal and choroidal BF and layer-specific retinal thicknesses in RCS rat retinas at different stages of retinal degeneration compared with age-matched controls. The unique ability to separate retinal and choroidal BF was made possible by the depth-resolved MRI technique. RBF decreased with progressive retinal degeneration, but ChBF did not change in RCS rats up to post-natal day 90. We concluded that choroidal and retinal circulations have different susceptibility to progressive retinal degeneration in RCS rats. Layer-specific retinal thickness became progressively thinner and was corroborated by histological analysis in the same animals. MRI can detect progressive anatomical and BF changes during retinal degeneration with laminar resolution.
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17
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Zhang Y, Nateras OSE, Peng Q, Kuranov RV, Harrison JM, Milner TE, Duong TQ. Lamina-specific anatomic magnetic resonance imaging of the human retina. Invest Ophthalmol Vis Sci 2011; 52:7232-7. [PMID: 21828153 DOI: 10.1167/iovs.11-7623] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE Magnetic resonance imaging (MRI) of the human retina faces two major challenges: eye movement and hardware limitation that could preclude human retinal MRI with adequate spatiotemporal resolution. This study investigated eye-fixation stability and high-resolution anatomic MRI of the human retina on a 3-Tesla (T) MRI scanner. Comparison was made with optical coherence tomography (OCT) on the same subjects. METHODS Eye-fixation stability of protocols used in MRI was evaluated on four normal volunteers using an eye tracker. High-resolution MRI (100 × 200 × 2000 μm) protocol was developed on a 3-T scanner. Subjects were instructed to maintain stable eye fixation on a target with cued blinks every 8 seconds during MRI. OCT imaging of the retina was performed. Retinal layer thicknesses measured with MRI and OCT were analyzed for matching regions of the same eyes close to the optic nerve head. RESULTS The temporal SDs of the horizontal and vertical displacements were 78 ± 51 and 130 ± 51 μm (±SD, n = 4), respectively. MRI detected three layers within the human retina, consistent with MRI findings in rodent, feline, and baboon retinas. The hyperintense layer 1 closest to the vitreous likely consisted of nerve fiber, ganglion cell, and inner nuclear layer; the hypointense layer 2, the outer nuclear layer and the inner and outer segments; and the hyperintense layer 3, the choroid. The MRI retina/choroid thickness was 711 ± 37 μm, 19% (P < 0.05) thicker than OCT thickness (579 ± 34 μm). CONCLUSIONS This study reports high-resolution MRI of lamina-specific structures in the human retina. These initial results are encouraging. Further improvement in spatiotemporal resolution is warranted.
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Affiliation(s)
- Yi Zhang
- Research Imaging Institute, University of Texas Health Science Center, San Antonio, Texas 78229, USA
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18
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Shih YYI, De la Garza BH, Muir ER, Rogers WE, Harrison JM, Kiel JW, Duong TQ. Lamina-specific functional MRI of retinal and choroidal responses to visual stimuli. Invest Ophthalmol Vis Sci 2011; 52:5303-10. [PMID: 21447679 DOI: 10.1167/iovs.10-6438] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE To demonstrate lamina-specific functional magnetic resonance imaging (MRI) of retinal and choroidal responses to visual stimulation of graded luminance, wavelength, and frequency. MATERIALS AND METHODS High-resolution (60 × 60 μm) MRI was achieved using the blood-pool contrast agent, monocrystalline iron oxide nanoparticles (MION) and a high-magnetic-field (11.7 T) scanner to image functional changes in the normal rat retina associated with various visual stimulations. MION functional MRI measured stimulus-evoked blood-volume (BV) changes. Graded luminance, wavelength, and frequency were investigated. Stimulus-evoked fMRI signal changes from the retinal and choroidal vascular layers were analyzed. RESULTS MRI revealed two distinct laminar signals that corresponded to the retinal and choroidal vascular layers bounding the retina and were separated by the avascular layer in between. The baseline outer layer BV index was 2-4 times greater than the inner layer BV, consistent with higher choroidal vascular density. During visual stimulation, BV responses to flickering light of different luminance, frequency, and wavelength in the inner layer were greater than those in the outer layer. The inner layer responses were dependent on luminance, frequency, and wavelength, whereas the outer layer responses were not, suggesting differential neurovascular coupling between the two vasculatures. CONCLUSIONS This is the first report of simultaneous resolution of layer-specific functional responses of the retinal and choroid vascular layers to visual stimulation in the retina. This imaging approach could have applications in early detection and longitudinal monitoring of retinal diseases where retinal and choroidal hemodynamics may be differentially perturbed at various stages of the diseases.
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Affiliation(s)
- Yen-Yu I Shih
- Research Imaging Institute, University of Texas Health Science Center, San Antonio, Texas, USA
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19
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Muir ER, Duong TQ. Layer-specific functional and anatomical MRI of the retina with passband balanced SSFP. Magn Reson Med 2011; 66:1416-21. [PMID: 21604296 DOI: 10.1002/mrm.22935] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2010] [Revised: 02/23/2011] [Accepted: 03/07/2011] [Indexed: 11/09/2022]
Abstract
The retina consists of multiple cellular and synaptic layers and is nourished by two distinct (retinal and choroidal) circulations bounding the retina, separated by an avascular layer. High spatiotemporal resolution, layer-specific MRI of the retina remains challenging due to magnetic inhomogeneity-induced artifacts. This study reports passband balanced steady-state free-precession (bSSFP) MRI at 45×45×500 μm and 1.6 s temporal resolution to image the mouse retina, overcoming geometric distortion and signal dropout while maintaining rapid acquisition and high signal-to-noise ratio. bSSFP images revealed multiple alternating dark-bright-dark-bright retinal layers. Hypoxic (10% O(2) ) inhalation decreased bSSFP signals in the two layers bounding the retina, corresponding to the retinal and choroidal vasculatures. The layer in between showed no substantial response and was assigned the avascular photoreceptor layers. Choroidal responses (-25.9 ± 6.4%, mean ± SD, n=6) were significantly (P<0.05) larger than retinal vascular responses (-11.6±2.4%). bSSFP offers very high spatiotemporal resolution and could have important applications in imaging layer-specific changes in retinal diseases.
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Affiliation(s)
- Eric R Muir
- Department of Ophthalmology, Research Imaging Institute, University of Texas Health Science Center, San Antonio, Texas, USA
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20
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Effects of common anesthetics on eye movement and electroretinogram. Doc Ophthalmol 2011; 122:163-76. [PMID: 21519880 DOI: 10.1007/s10633-011-9271-4] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2010] [Accepted: 04/04/2011] [Indexed: 10/18/2022]
Abstract
High-resolution magnetic resonance imaging (MRI) provides non-invasive images of retinal anatomy, physiology, and function with depth-resolved laminar resolution. Eye movement and drift, however, could limit high spatial resolution imaging, and anesthetics that minimize eye movement could significantly attenuate retinal function. The aim of this study was to determine the optimal anesthetic preparations to minimize eye movement and maximize visual-evoked retinal response in rats. Eye movements were examined by imaging of the cornea with a charge-coupled device (CCD) camera under isoflurane, urethane, ketamine/xylazine, and propofol anesthesia at typical dosages in rats. Combination of the paralytic pancuronium bromide with isoflurane or ketamine/xylazine anesthesia was also examined for the eye movement studies. Visual-evoked retinal responses were evaluated using full-field electroretinography (ERG) under isoflurane, ketamine/xylazine, urethane, and ketamine/xylazine + pancuronium anesthesia in rats. The degree of eye movement, measured as displacement per unit time, was the smallest under 1% isoflurane + pancuronium anesthesia. The ketamine/xylazine groups showed larger dark-adapted ERG a- and b-waves than other anesthetics tested. The isoflurane group showed the shortest b-wave implicit times. Photopic ERGs in the ketamine/xylazine groups showed the largest b-waves with the isoflurane group showing slightly shorter implicit times at the higher flash intensities. Oscillatory potentials revealed an early peak in the isoflurane group compared with ketamine/xylazine and urethane groups. Pancuronium did not affect the a- and b-wave, but did increase oscillatory potential amplitudes. Compared with the other anesthetics tested here, ketamine/xylazine + pancuronium was the best combination to minimize eye movement and maximize retinal function. These findings should set the stage for further development and application of high-resolution functional imaging techniques, such as MRI, to study retinal anatomy, physiology, and function in anesthetized rats.
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Duong TQ. Magnetic resonance imaging of the retina: A brief historical and future perspective. Saudi J Ophthalmol 2011; 25:137-43. [PMID: 23960915 PMCID: PMC3729810 DOI: 10.1016/j.sjopt.2011.01.004] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2011] [Accepted: 01/21/2011] [Indexed: 11/30/2022] Open
Abstract
This invited review starts with a brief introduction of retinal anatomy and magnetic resonance imaging techniques with contrast to optics, followed by a history and future perspective on MRI applications to investigate the retinas of rodents, non-human primates and humans.
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Affiliation(s)
- Timothy Q. Duong
- Address: University of Texas Health Science Center at San Antonio, Research Imaging Institute, 8403 Floyd Curl Dr, San Antonio, TX 78229, USA. Tel.: +1 567 8100; fax: +1 210 567 8152.
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22
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Zhang Y, Peng Q, Kiel JW, Rosende CA, Duong TQ. Magnetic resonance imaging of vascular oxygenation changes during hyperoxia and carbogen challenges in the human retina. Invest Ophthalmol Vis Sci 2011; 52:286-91. [PMID: 20847121 PMCID: PMC3053278 DOI: 10.1167/iovs.10-6108] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2010] [Revised: 08/11/2010] [Accepted: 08/11/2010] [Indexed: 11/24/2022] Open
Abstract
PURPOSE To demonstrate blood oxygenation level-dependent (BOLD) magnetic resonance imaging (MRI) of vascular oxygenation changes in normal, unanesthetized human retinas associated with oxygen and carbogen challenge. METHODS MRI was performed with a 3-T human scanner and a custom-made surface-coil detector on normal volunteers. BOLD MRI with inversion recovery was used to suppress the vitreous signal. During MRI measurements, volunteers underwent three episodes of air and 100% oxygen or carbogen (5% CO(2) and 95% O(2)) breathing. Eye movement was effectively managed with eye fixation, synchronized blinks, and postprocessing image coregistration. BOLD time-series images were analyzed using the cross-correlation method. Percent changes due to oxygen or carbogen inhalation versus air were tabulated for whole-retina and different regions of the retina. RESULTS Robust BOLD responses were detected. BOLD MRI percent change from a large region of interest at the posterior pole of the retina was 5.2 ± 1.5% (N = 9 trials from five subjects) for oxygen inhalation and 5.2 ± 1.3% (N = 11 trials from five subjects) for carbogen inhalation. Group-averaged BOLD percent changes were not significantly different between oxygen and carbogen challenges (P > 0.05). The foveal region had greater BOLD response compared with the optic nerve head region for both challenges. CONCLUSIONS BOLD retinal responses to oxygen and carbogen breathing in unanesthetized humans can be reliably imaged at high spatiotemporal resolution. BOLD MRI has the potential to provide a valuable tool to study retinal physiology and pathophysiology, such as how vascular oxygenation at the tissue level is regulated in the normal retina, and how retinal diseases may affect oxygen response.
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Affiliation(s)
- Yi Zhang
- From the Research Imaging Institute and
- the Departments of Radiology
| | - Qi Peng
- From the Research Imaging Institute and
- the Departments of Radiology
| | | | | | - Timothy Q. Duong
- From the Research Imaging Institute and
- the Departments of Radiology
- Ophthalmology, and
- Physiology, University of Texas Health Science Center, San Antonio, Texas; and
- South Texas Veterans Health Care System, San Antonio, Texas
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