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Nork TM, Kim CBY, Katz AW, Rasmussen CA, Banghart M, Ver Hoeve JN. Multifocal electroretinography increases following experimental glaucoma in nonhuman primates with retinal ganglion cell axotomy. Doc Ophthalmol 2023; 146:97-112. [PMID: 36763214 PMCID: PMC10284020 DOI: 10.1007/s10633-023-09922-1] [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: 11/18/2021] [Accepted: 01/20/2023] [Indexed: 02/11/2023]
Abstract
PURPOSE To determine whether short-latency changes in multifocal electroretinography (mfERG) observed in experimental glaucoma (EG) are secondary solely to retinal ganglion cell (RGC) loss or whether there is a separate contribution from elevated intraocular pressure (IOP). METHODS Prior to operative procedures, a series of baseline mfERGs were recorded from six rhesus macaques using a 241-element unstretched stimulus. Animals then underwent hemiretinal endodiathermy axotomy (HEA) by placing burns along the inferior 180° of the optic nerve margin in the right eye (OD). mfERG recordings were obtained in each animal at regular intervals following for 3-4 months to allow stabilization of the HEA effects. Laser trabecular meshwork destruction (LTD) to elevate IOP was then performed; first-order kernel (K1) waveform root-mean-square (RMS) amplitudes for the short-latency segment of the mfERG wave (9-35 ms) were computed for two 7-hexagon groupings-the first located within the superior (non-axotomized) macula and the second within the inferior (axotomized) macula. Immunohistochemistry for glial fibrillary acidic protein (GFAP) was done. RESULTS By 3 months post HEA, there was marked thinning of the inferior nerve fiber layer as measured by optical coherence tomography. Compared with baseline, no statistically significant changes in 9-35 ms K1 RMS amplitudes were evident in either the axotomized or non-axotomized portions of the macula. Following LTD, mean IOP in HEA eyes rose to 46 ± 9 compared with 20 ± 2 mmHg (SD) in the fellow control eyes. In the HEA + EG eyes, statistically significant increases in K1 RMS amplitude were present in both the axotomized inferior and non-axotomized superior portions of the OD retinas. No changes in K1 RMS amplitude were found in the fellow control eyes from baseline to HEA epoch, but there was a smaller increase from baseline to HEA + EG. Upregulation of GFAP in the Müller cells was evident in both non-axotomized and axotomized retina in eyes with elevated IOP. CONCLUSIONS The RMS amplitudes of the short-latency mfERG K1 waveforms are not altered following axotomy but undergo marked increases following elevated IOP. This suggests that the increase in mfERG amplitude was not solely a result of RGC loss and may reflect photoreceptor and bipolar cell dysfunction and/or changes in Müller cells.
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Affiliation(s)
- T Michael Nork
- Department of Ophthalmology and Visual Sciences, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI, USA.
| | - Charlene B Y Kim
- Department of Ophthalmology and Visual Sciences, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI, USA
| | - Alexander W Katz
- Department of Ophthalmology and Visual Sciences, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI, USA
| | - Carol A Rasmussen
- Department of Ophthalmology and Visual Sciences, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI, USA
| | - Mark Banghart
- Department of Ophthalmology and Visual Sciences, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI, USA
| | - James N Ver Hoeve
- Department of Ophthalmology and Visual Sciences, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI, USA
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Raghunathan V, Eaton JS, Christian BJ, Morgan JT, Ver Hoeve JN, Yang CYC, Gong H, Rasmussen CA, Miller PE, Russell P, Nork TM, Murphy CJ. Biomechanical, ultrastructural, and electrophysiological characterization of the non-human primate experimental glaucoma model. Sci Rep 2017; 7:14329. [PMID: 29085025 PMCID: PMC5662689 DOI: 10.1038/s41598-017-14720-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2017] [Accepted: 10/13/2017] [Indexed: 11/08/2022] Open
Abstract
Laser-induced experimental glaucoma (ExGl) in non-human primates (NHPs) is a common animal model for ocular drug development. While many features of human hypertensive glaucoma are replicated in this model, structural and functional changes in the unlasered portions of trabecular meshwork (TM) of laser-treated primate eyes are understudied. We studied NHPs with ExGl of several years duration. As expected, ExGl eyes exhibited selective reductions of the retinal nerve fiber layer that correlate with electrophysiologic measures documenting a link between morphologic and elctrophysiologic endpoints. Softening of unlasered TM in ExGl eyes compared to untreated controls was observed. The degree of TM softening was consistent, regardless of pre-mortem clinical findings including severity of IOP elevation, retinal nerve fiber layer thinning, or electrodiagnostic findings. Importantly, this softening is contrary to TM stiffening reported in glaucomatous human eyes. Furthermore, microscopic analysis of unlasered TM from eyes with ExGl demonstrated TM thinning with collapse of Schlemm's canal; and proteomic analysis confirmed downregulation of metabolic and structural proteins. These data demonstrate unexpected and compensatory changes involving the TM in the NHP model of ExGl. The data suggest that compensatory mechanisms exist in normal animals and respond to elevated IOP through softening of the meshwork to increase outflow.
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Affiliation(s)
- VijayKrishna Raghunathan
- Department of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California - Davis, Davis, California, 95616, United States of America
- Ocular Services On Demand (OSOD), Madison, Wisconsin, 53719, United States of America
- The Ocular Surface Institute, Department of Basic Sciences, College of Optometry, University of Houston, Houston, Texas, 77204, United States of America
| | - J Seth Eaton
- Department of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California - Davis, Davis, California, 95616, United States of America
- Ocular Services On Demand (OSOD), Madison, Wisconsin, 53719, United States of America
| | - Brian J Christian
- Covance Laboratories, Inc., Madison, Wisconsin, 53704, United States of America
| | - Joshua T Morgan
- Department of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California - Davis, Davis, California, 95616, United States of America
| | - James N Ver Hoeve
- Ocular Services On Demand (OSOD), Madison, Wisconsin, 53719, United States of America
- Department of Ophthalmology and Visual Sciences, School of Medicine and Public Health, University of Wisconsin - Madison, Madison, Wisconsin, 53792, United States of America
| | - Chen-Yuan Charlie Yang
- Department of Anatomy and Neurobiology, School of Medicine, Boston University, Boston, Massachusetts, 02118, United States of America
- Department of Ophthalmology, School of Medicine, Boston University, Boston, Massachusetts, 02118, United States of America
| | - Haiyan Gong
- Department of Anatomy and Neurobiology, School of Medicine, Boston University, Boston, Massachusetts, 02118, United States of America
- Department of Ophthalmology, School of Medicine, Boston University, Boston, Massachusetts, 02118, United States of America
| | - Carol A Rasmussen
- Ocular Services On Demand (OSOD), Madison, Wisconsin, 53719, United States of America
- Department of Ophthalmology and Visual Sciences, School of Medicine and Public Health, University of Wisconsin - Madison, Madison, Wisconsin, 53792, United States of America
| | - Paul E Miller
- Ocular Services On Demand (OSOD), Madison, Wisconsin, 53719, United States of America
- Department of Surgical Sciences, School of Veterinary Medicine, University of Wisconsin - Madison, Madison, Wisconsin, 53706, United States of America
| | - Paul Russell
- Department of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California - Davis, Davis, California, 95616, United States of America
- Ocular Services On Demand (OSOD), Madison, Wisconsin, 53719, United States of America
| | - T Michael Nork
- Ocular Services On Demand (OSOD), Madison, Wisconsin, 53719, United States of America.
- Department of Ophthalmology and Visual Sciences, School of Medicine and Public Health, University of Wisconsin - Madison, Madison, Wisconsin, 53792, United States of America.
| | - Christopher J Murphy
- Department of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California - Davis, Davis, California, 95616, United States of America.
- Ocular Services On Demand (OSOD), Madison, Wisconsin, 53719, United States of America.
- Department of Ophthalmology & Vision Science, School of Medicine, University of California - Davis, Sacramento, California, 95817, United States of America.
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Choh V, Gurdita A, Tan B, Feng Y, Bizheva K, McCulloch DL, Joos KM. Isoflurane and ketamine:xylazine differentially affect intraocular pressure-associated scotopic threshold responses in Sprague-Dawley rats. Doc Ophthalmol 2017. [PMID: 28638951 DOI: 10.1007/s10633-017-9597-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
PURPOSE Amplitudes of electroretinograms (ERG) are enhanced during acute, moderate elevation of intraocular pressure (IOP) in rats anaesthetised with isoflurane. As anaesthetics alone are known to affect ERG amplitudes, the present study compares the effects of inhalant isoflurane and injected ketamine:xylazine on the scotopic threshold response (STR) in rats with moderate IOP elevation. METHODS Isoflurane-anaesthetised (n = 9) and ketamine:xylazine-anaesthetised (n = 6) rats underwent acute unilateral IOP elevation using a vascular loop anterior to the equator of the right eye. STRs to a luminance series (subthreshold to -3.04 log scotopic cd s/m2) were recorded from each eye of Sprague-Dawley rats before, during, and after IOP elevation. RESULTS Positive STR (pSTR) amplitudes for all conditions were significantly smaller (p = 0.0001) for isoflurane- than for ketamine:xylazine-anaesthetised rats. In addition, ketamine:xylazine was associated with a progressive increase in pSTR amplitudes over time (p = 0.0028). IOP elevation was associated with an increase in pSTR amplitude (both anaesthetics p < 0.0001). The absolute interocular differences in IOP-associated enhancement of pSTR amplitudes for ketamine:xylazine and isoflurane were similar (66.3 ± 35.5 vs. 54.2 ± 24.1 µV, respectively). However, the fold increase in amplitude during IOP elevation was significantly higher in the isoflurane- than in the ketamine:xylazine-anaesthetised rats (16.8 ± 29.7x vs. 2.1 ± 2.7x, respectively, p = 0.0004). CONCLUSIONS The anaesthetics differentially affect the STRs in the rat model with markedly reduced amplitudes with isoflurane compared to ketamine:xylazine. However, the IOP-associated enhancement is of similar absolute magnitude for the two anaesthetics, suggesting that IOP stress and anaesthetic effects operate on separate retinal mechanisms.
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Affiliation(s)
- Vivian Choh
- School of Optometry and Vision Science, University of Waterloo, Waterloo, ON, N2L 3G1, Canada.
| | - Akshay Gurdita
- School of Optometry and Vision Science, University of Waterloo, Waterloo, ON, N2L 3G1, Canada
| | - Bingyao Tan
- Department of Physics and Astronomy, University of Waterloo, Waterloo, ON, N2L 3G1, Canada
| | - Yunwei Feng
- School of Optometry and Vision Science, University of Waterloo, Waterloo, ON, N2L 3G1, Canada
| | - Kostadinka Bizheva
- School of Optometry and Vision Science, University of Waterloo, Waterloo, ON, N2L 3G1, Canada.,Department of Physics and Astronomy, University of Waterloo, Waterloo, ON, N2L 3G1, Canada
| | - Daphne L McCulloch
- School of Optometry and Vision Science, University of Waterloo, Waterloo, ON, N2L 3G1, Canada
| | - Karen M Joos
- Vanderbilt Eye Institute, Vanderbilt University Medical Center, Nashville, TN, USA
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Comparing three different modes of electroretinography in experimental glaucoma: diagnostic performance and correlation to structure. Doc Ophthalmol 2017; 134:111-128. [PMID: 28243926 DOI: 10.1007/s10633-017-9578-x] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2016] [Accepted: 02/13/2017] [Indexed: 10/20/2022]
Abstract
PURPOSE To compare diagnostic performance and structure-function correlations of multifocal electroretinogram (mfERG), full-field flash ERG (ff-ERG) photopic negative response (PhNR) and transient pattern-reversal ERG (PERG) in a non-human primate (NHP) model of experimental glaucoma (EG). METHODS At baseline and after induction of chronic unilateral IOP elevation, 43 NHP had alternating weekly recordings of retinal nerve fiber layer thickness (RNFLT) by spectral domain OCT (Spectralis) and retinal function by mfERG (7F slow-sequence stimulus, VERIS), ff-ERG (red 0.42 log cd-s/m2 flashes on blue 30 scotopic cd/m2 background, LKC UTAS-E3000), and PERG (0.8° checks, 99% contrast, 100 cd/m2 mean, 5 reversals/s, VERIS). All NHP were followed at least until HRT-confirmed optic nerve head posterior deformation, most to later stages. mfERG responses were filtered into low- and high-frequency components (LFC, HFC, >75 Hz). Peak-to-trough amplitudes of LFC features (N1, P1, N2) and HFC RMS amplitudes were measured and ratios calculated for HFC:P1 and N2:P1. ff-ERG parameters included A-wave (at 10 ms), B-wave (trough-to-peak) and PhNR (baseline-to-trough) amplitudes as well as PhNR:B-wave ratio. PERG parameters included P50 and N95 amplitudes as well as N95:P50 ratio and N95 slope. Diagnostic performance of retinal function parameters was compared using the area under the receiver operating characteristic curve (A-ROC) to discriminate between EG and control eyes. Correlations to RNFLT were compared using Steiger's test. RESULTS Study duration was 15 ± 8 months. At final follow-up, structural damage in EG eyes measured by RNFLT ranged from 9% above baseline (BL) to 58% below BL; 29/43 EG eyes (67%) and 0/43 of the fellow control eyes exhibited significant (>7%) loss of RNFLT from BL. Using raw parameter values, the largest A-ROC findings for mfERG were: HFC (0.82) and HFC:P1 (0.90); for ff-ERG: PhNR (0.90) and PhNR:B-wave (0.88) and for PERG: P50 (0.64) and N95 (0.61). A-ROC increased when data were expressed as % change from BL, but the pattern of results persisted. At 95% specificity, the diagnostic sensitivity of mfERG HFC:P1 ratio was best, followed by PhNR and PERG. The correlation to RNFLT was stronger for mfERG HFC (R = 0.65) than for PhNR (R = 0.59) or PERG N95 (R = 0.36), (p = 0.20, p = 0.0006, respectively). The PhNR flagged a few EG eyes at the final time point that had not been flagged by mfERG HFC or PERG. CONCLUSIONS Diagnostic performance and structure-function correlation were strongest for mfERG HFC as compared with ff-ERG PhNR or PERG in NHP EG.
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Ortiz G, Odom JV, Passaglia CL, Tzekov RT. Efferent influences on the bioelectrical activity of the retina in primates. Doc Ophthalmol 2016; 134:57-73. [PMID: 28032236 DOI: 10.1007/s10633-016-9567-5] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2016] [Accepted: 12/13/2016] [Indexed: 11/28/2022]
Abstract
PURPOSE The existence of retinopetal (sometimes referred to as "efferent" or "centrifugal") axons in the mammalian optic nerve is a topic of long-standing debate. Opposition is fading as efferent innervation of the retina has now been widely documented in rodents and other animals. The existence and function of an efferent system in humans and non-human primates has not, though, been definitively established. Such a feedback pathway could have important functional, clinical, and experimental significance to the field of vision science and ophthalmology. METHODS Following a comprehensive literature review (PubMed and Google Scholar, until July 2016), we present evidence regarding a system that can influence the bioelectrical activity of the retina in primates. RESULTS Anatomical and physiological evidences are presented separately. Improvements in histological staining and the advent of retrograde nerve fiber tracers have allowed for more confidence in the identification of efferent optic nerve fibers, including back to their point of origin. CONCLUSION Even with the accumulation of more modern anatomical and physiological evidence, some limitations and uncertainties about crucial details regarding the origins and role of a top-down, efferent system still exist. However, the summary of the evidence from earlier and more modern studies makes a compelling case in support of such a system in humans and non-human primates.
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Affiliation(s)
- Gonzalo Ortiz
- Department of Ophthalmology, University of South Florida, 12901 Bruce B. Downs Blvd., MDC 21, Tampa, FL, 33612, USA
| | - J Vernon Odom
- Department of Ophthalmology, West Virginia University, Morgantown, WV, USA
| | - Christopher L Passaglia
- Department of Ophthalmology, University of South Florida, 12901 Bruce B. Downs Blvd., MDC 21, Tampa, FL, 33612, USA.,Department of Chemical and Biomedical Engineering, University of South Florida, Tampa, FL, USA
| | - Radouil T Tzekov
- Department of Ophthalmology, University of South Florida, 12901 Bruce B. Downs Blvd., MDC 21, Tampa, FL, 33612, USA. .,The Roskamp Institute, Sarasota, FL, USA.
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The non-human primate experimental glaucoma model. Exp Eye Res 2015; 141:57-73. [PMID: 26070984 DOI: 10.1016/j.exer.2015.06.005] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2015] [Revised: 06/03/2015] [Accepted: 06/06/2015] [Indexed: 01/05/2023]
Abstract
The purpose of this report is to summarize the current strengths and weaknesses of the non-human primate (NHP) experimental glaucoma (EG) model through sections devoted to its history, methods, important findings, alternative optic neuropathy models and future directions. NHP EG has become well established for studying human glaucoma in part because the NHP optic nerve head (ONH) shares a close anatomic association with the human ONH and because it provides the only means of systematically studying the very earliest visual system responses to chronic intraocular pressure (IOP) elevation, i.e. the conversion from ocular hypertension to glaucomatous damage. However, NHPs are impractical for studies that require large animal numbers, demonstrate spontaneous glaucoma only rarely, do not currently provide a model of the neuropathy at normal levels of IOP, and cannot easily be genetically manipulated, except through tissue-specific, viral vectors. The goal of this summary is to direct NHP EG and non-NHP EG investigators to the previous, current and future accomplishment of clinically relevant knowledge in this model.
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Porciatti V. Electrophysiological assessment of retinal ganglion cell function. Exp Eye Res 2015; 141:164-70. [PMID: 25998495 DOI: 10.1016/j.exer.2015.05.008] [Citation(s) in RCA: 143] [Impact Index Per Article: 15.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2014] [Revised: 04/17/2015] [Accepted: 05/17/2015] [Indexed: 01/22/2023]
Abstract
The function of retinal ganglion cells (RGCs) can be non-invasively assessed in experimental and genetic models of glaucoma by means of variants of the ERG technique that emphasize the activity of inner retina neurons. The best understood technique is the Pattern Electroretinogram (PERG) in response to contrast-reversing gratings or checkerboards, which selectively depends on the presence of functional RGCs. In glaucoma models, the PERG can be altered before histological loss of RGCs; PERG alterations may be either reversed with moderate IOP lowering or exacerbated with moderate IOP elevation. Under particular luminance-stimulus conditions, the Flash-ERG displays components that may reflect electrical activity originating in the proximal retina and be altered in some experimental glaucoma models (positive Scotopic Threshold response, pSTR; negative Scotopic Threshold Response, nSTR; Photopic Negative Response, PhNR; Oscillatory Potentials, OPs; multifocal ERG, mfERG). It is not yet known which of these components is most sensitive to glaucomatous damage. Electrophysiological assessment of RGC function appears to be a necessary outcome measure in experimental glaucoma models, which complements structural assessment and may even predict it. Neuroprotective strategies could be tested based on enhancement of baseline electrophysiological function that results in improved RGC survival. The use of electrophysiology in glaucoma models may be facilitated by specifically designed instruments that allow high throughput, robust assessment of electrophysiological function.
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Affiliation(s)
- Vittorio Porciatti
- Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, McKnight Vision Research Center, 1638 NW 10th Ave., Miami, FL 33136, United States.
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Analysis of a method for establishing a model with more stable chronic glaucoma in rhesus monkeys. Exp Eye Res 2015; 131:56-62. [DOI: 10.1016/j.exer.2014.12.012] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2014] [Revised: 11/03/2014] [Accepted: 12/19/2014] [Indexed: 11/30/2022]
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Nork TM, Kim CBY, Munsey KM, Dashek RJ, Hoeve JNV. Regional choroidal blood flow and multifocal electroretinography in experimental glaucoma in rhesus macaques. Invest Ophthalmol Vis Sci 2014; 55:7786-98. [PMID: 25370515 DOI: 10.1167/iovs.14-14527] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE To test a hypothesis of regional variation in the effect of experimental glaucoma on choroidal blood flow (ChBF) and retinal function. METHODS Five rhesus macaques underwent laser trabecular destruction (LTD) to induce elevated intraocular pressure (IOP). Intraocular pressures were elevated for 56 to 57 weeks. Multifocal electroretinographic (mfERG) and multifocal visual evoked cortical potential (mfVEP) testing were performed at regular intervals before and during the period of IOP elevation. At euthanasia, the IOP was manometrically controlled at 35 (experimentally glaucomatous eye) and 15 (fellow control eye) mm Hg. Fluorescent microspheres were injected into the left ventricle. Regional ChBF was determined. RESULTS All of the experimentally glaucomatous eyes exhibited supranormal first-order kernel (K1) root mean square (RMS) early portions of the mfERG waveforms and decreased amplitudes of the late waveforms. The supranormality was somewhat greater in the central macula. Second-order kernel, first slice (K2.1) RMS mfVEP response was inversely correlated (R(2) = 0.97) with axonal loss. Total ChBF was reduced in the experimentally glaucomatous eyes. The mean blood flow was 893 ± 123 and 481 ± 37 μL/min in the control and glaucomatous eyes, respectively. The ChBF showed regional variability with the greatest proportional decrement most often found in the central macula. CONCLUSIONS This is the first demonstration of globally reduced ChBF in chronic experimental glaucoma in the nonhuman primate. Both the alteration of mfERG waveform components associated with outer retinal function and the reduction in ChBF were greatest in the macula, suggesting that there may be a spatial colocalization between ChBF and some outer retinal effects in glaucoma.
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Affiliation(s)
- T Michael Nork
- Department of Ophthalmology and Visual Sciences, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, United States
| | - Charlene B Y Kim
- Department of Ophthalmology and Visual Sciences, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, United States
| | - Kaitlyn M Munsey
- Department of Ophthalmology and Visual Sciences, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, United States
| | - Ryan J Dashek
- Department of Ophthalmology and Visual Sciences, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, United States
| | - James N Ver Hoeve
- Department of Ophthalmology and Visual Sciences, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, United States
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Dashek RJ, Kim CBY, Rasmussen CA, Hennes-Beean EA, Ver Hoeve JN, Nork TM. Structural and functional effects of hemiretinal endodiathermy axotomy in cynomolgus macaques. Invest Ophthalmol Vis Sci 2013; 54:3479-92. [PMID: 23620427 DOI: 10.1167/iovs.12-11265] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE Outer retinal injury has been well described in glaucoma. To better understand the source of this injury, we wanted to develop a reliable model of partial retinal ganglion cell (RGC) axotomy. METHODS Endodiathermy spots were placed along the inferior 180° adjacent to the optic nerve margin in the right eyes of four cynomolgus monkeys. Fluorescein angiography, spectral domain optical coherence tomography (SD-OCT), and multifocal electroretinography (mfERG) were performed at various intervals. Two animals were sacrificed at 3 months. Two animals were sacrificed at 4 months, at which time they underwent an injection of fluorescent microspheres to measure regional choroidal blood flow. Retinal immunohistochemistry for glial fibrillary acidic protein (GFAP), rhodopsin, S-cone opsin, and M/L-cone opsin were performed, as were axon counts of the optic nerves. RESULTS At 3 months, there was marked thinning of the inferior nerve fiber layer on SD-OCT. The mfERG waveforms were consistent with inner but not outer retinal injury. Greater than 95% reduction in axons was seen in the inferior optic nerves but no secondary degeneration superiorly. There was marked thinning of the nerve fiber and ganglion cell layers in the inferior retinas. However, the photoreceptor histology was similar in the axotomized and nonaxotomized areas. Regional choroidal blood flow was not affected by the axotomy. CONCLUSIONS Unlike experimental glaucoma, hemiretinal endodiathermy axotomy (HEA) of the RGCs produces no apparent anatomic, functional, or blood flow effects on the outer retina and choroid.
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Affiliation(s)
- Ryan J Dashek
- Department of Ophthalmology and Visual Sciences, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin 53792-3220, USA
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The effect of pentobarbital sodium and propofol anesthesia on multifocal electroretinograms in rhesus macaques. Doc Ophthalmol 2011; 124:59-72. [PMID: 22200766 DOI: 10.1007/s10633-011-9306-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2011] [Accepted: 12/15/2011] [Indexed: 10/14/2022]
Abstract
We compared the suitability of pentobarbital sodium (PB) and propofol (PF) anesthetics for multifocal electroretinograms (mfERGs) in rhesus macaques. mfERGs were collected from 4 ocularly normal rhesus macaques. All animals were pre-anesthetized with intramuscular ketamine (10-15 mg/kg). Intravenous PB induction/maintenance levels were 15 mg/kg/2-10 mg/kg and for PF, 2-5 mg/kg/6-24 mg/kg/h. There were 3 testing sessions with PB anesthesia and 5-7 testing sessions with PF anesthesia. All PB sessions were carried out before PF. First-order (K1) and second-order (first slice) kernels (K2.1) response density amplitude (RDA), implicit time (IT), and root mean square signal-to-noise ratios (RMS SNR) of the low-frequency (LFC) and high-frequency (HFC) components were evaluated. The use of PF or PB anesthesia resulted in robust, replicable mfERGs in rhesus macaques; however, RMS SNR of K1 LFC in ring and quadrant analyses was significantly larger for PF than for PB. Additionally, K1 RDA under PF was significantly larger than under PB for N1, P1, and P2 components (ring and quadrant) and for N2 (quadrant). PF IT was significantly prolonged (<1 ms) relative to PB IT for N1, P1 (ring), and N1 (quadrant), while PB IT was significantly prolonged (0.8-4.2 ms) relative to PF IT for N2 and P2 (ring and quadrant). K1 HFC and K2.1 LFC did not differ significantly between PB and PF in the ring or quadrant analyses. The response differences found with PB and PF anesthesia likely arise from variable relative effects of the anesthetics on retinal γ-aminobutyric acid (GABA(A)) receptors, and in part, on glycine and on glutamate receptors. Given the advantages of a stable anesthetic plane with continuous intravenous infusion and a smoother, more rapid recovery, PF is an appealing alternative for mfERG testing in rhesus macaques.
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Nork TM, Murphy CJ, Kim CBY, Ver Hoeve JN, Rasmussen CA, Miller PE, Wabers HD, Neider MW, Dubielzig RR, McCulloh RJ, Christian BJ. Functional and anatomic consequences of subretinal dosing in the cynomolgus macaque. ACTA ACUST UNITED AC 2011; 130:65-75. [PMID: 21911651 DOI: 10.1001/archophthalmol.2011.295] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
OBJECTIVE To characterize functional and anatomic sequelae of a bleb induced by subretinal injection. METHODS Subretinal injections (100 μL) of balanced salt solution were placed in the superotemporal macula of 1 eye in 3 cynomolgus macaques. Fellow eyes received intravitreal injections (100 μL) of balanced salt solution. Fundus photography, ocular coherence tomography, and multifocal electroretinography were performed before and immediately after injection and again at intervals up to 3 months postinjection. Histopathologic analyses included transmission electron microscopy and immunohistochemistry for glial fibrillary acidic protein, rhodopsin, M/L-cone opsin, and S-cone opsin. RESULTS Retinas were reattached by 2 days postinjection (seen by ocular coherence tomography). Multifocal electroretinography waveforms were suppressed post-subretinal injection within the subretinal injection bleb and, surprisingly, also in regions far peripheral to this area. Multifocal electroretinography amplitudes were nearly completely recovered by 90 days. The spectral-domain ocular coherence tomography inner segment-outer segment line had decreased reflectivity at 92 days. Glial fibrillary acidic protein and S-cone opsin staining were unaffected. Rhodopsin and M/L-cone opsins were partially displaced into the inner segments. Transmission electron microscopy revealed disorganization of the outer segment rod (but not cone) discs. At all postinjection intervals, eyes with intravitreal injection were similar to baseline. CONCLUSIONS Subretinal injection is a promising route for drug delivery to the eye. Three months post-subretinal injection, retinal function was nearly recovered, although reorganization of the outer segment rod disc remained disrupted. Understanding the functional and anatomic effects of subretinal injection is important for interpretation of the effects of compounds delivered to the subretinal space. CLINICAL RELEVANCE Subretinal injection is a new potential route for drug delivery to the eye. Separating drug effects from the procedural effects is critical.
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Affiliation(s)
- T Michael Nork
- Comparative Ophthalmic Research Laboratories, University of Wisconsin, USA.
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