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Zhang X, Wang F, Su Y. TRPV: An emerging target in glaucoma and optic nerve damage. Exp Eye Res 2024; 239:109784. [PMID: 38199261 DOI: 10.1016/j.exer.2024.109784] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2023] [Revised: 11/30/2023] [Accepted: 01/06/2024] [Indexed: 01/12/2024]
Abstract
Transient receptor potential vanilloid (TRPV) channels are members of the TRP channel superfamily, which are ion channels that sense mechanical and osmotic stimuli and participate in Ca2+ signalling across the cell membrane. TRPV channels play important roles in maintaining the normal functions of an organism, and defects or abnormalities in TRPV channel function cause a range of diseases, including cardiovascular, neurological and urological disorders. Glaucoma is a group of chronic progressive optic nerve diseases with pathological changes that can occur in the tissues of the anterior and posterior segments of the eye, including the ciliary body, trabecular meshwork, Schlemm's canal, and retina. TRPV channels are expressed in these tissues and play various roles in glaucoma. In this article, we review various aspects of the pathogenesis of glaucoma, the structure and function of TRPV channels, the relationship between TRPV channels and systemic diseases, and the relationship between TRPV channels and ocular diseases, especially glaucoma, and we suggest future research directions. This information will help to further our understanding of TRPV channels and provide new ideas and targets for the treatment of glaucoma and optic nerve damage.
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Affiliation(s)
- Xiaotong Zhang
- Department of Ophthalmology, The Fourth Affiliated Hospital, Harbin Medical University, Harbin, China
| | - Feng Wang
- Department of Ophthalmology, The Fourth Affiliated Hospital, Harbin Medical University, Harbin, China.
| | - Ying Su
- Eye Hospital, The First Affiliated Hospital, Harbin Medical University, Harbin, China.
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Montesano G, Redmond T, Mulholland PJ, Garway-Heath DF, Ometto G, Romano D, Antonacci F, Tanga L, Carnevale C, Rossetti LM, Crabb DP, Oddone F. Spatial Summation in the Glaucomatous Macula: A Link With Retinal Ganglion Cell Damage. Invest Ophthalmol Vis Sci 2023; 64:36. [PMID: 38010697 PMCID: PMC10683773 DOI: 10.1167/iovs.64.14.36] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2023] [Accepted: 10/03/2023] [Indexed: 11/29/2023] Open
Abstract
Purpose The purpose of this study was to test whether functional loss in the glaucomatous macula is characterized by an enlargement of Ricco's area (RA) through the application of a computational model linking retinal ganglion cell (RGC) damage to perimetric sensitivity. Methods One eye from each of 29 visually healthy subjects <40 years old, 30 patients with glaucoma, and 20 age-similar controls was tested with a 10-2 grid with stimuli of 5 different area sizes. Structural estimates of point-wise RGC density were obtained from optical coherence tomography (OCT) scans. Structural and functional data from the young healthy cohort were used to estimate the parameters of a computational spatial summation model to generate a template. The template was fitted with a Bayesian hierarchical model to estimate the latent RGC density in patients with glaucoma and age-matched controls. We tested two alternative hypotheses: fitting the data by translating the template horizontally (H1: change in RA) or vertically (H2: loss of sensitivity without a change in RA). Root mean squared error (RMSE) of the model fits to perimetric sensitivity were compared. Ninety-five percent confidence intervals were bootstrapped. The dynamic range of the functional and structural RGC density estimates was denoted by their 1st and 99th percentiles. Results The RMSE was 2.09 (95% CI = 1.92-2.26) under H1 and 2.49 (95% CI = 2.24-2.72) under H2 (P < 0.001). The average dynamic range for the structural RGC density estimates was only 11% that of the functional estimates. Conclusions Macular sensitivity loss in glaucoma is better described by a model in which RA changes with RGC loss. Structural measurements have limited dynamic range.
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Affiliation(s)
- Giovanni Montesano
- City, University of London, Optometry and Visual Sciences, London, United Kingdom
- NIHR Biomedical Research Centre, Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, London, United Kingdom
| | - Tony Redmond
- School of Optometry and Vision Sciences, Cardiff University, Cardiff, United Kingdom
| | - Pádraig J. Mulholland
- NIHR Biomedical Research Centre, Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, London, United Kingdom
- Centre for Optometry and Vision Science, Biomedical Sciences Research Institute, Ulster University, Coleraine, United Kingdom
| | - David F. Garway-Heath
- NIHR Biomedical Research Centre, Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, London, United Kingdom
| | - Giovanni Ometto
- City, University of London, Optometry and Visual Sciences, London, United Kingdom
| | - Dario Romano
- ASST Santi Paolo e Carlo, Eye Clinic – University of Milan, Milan, Italy
| | - Federica Antonacci
- ASST Santi Paolo e Carlo, Eye Clinic – University of Milan, Milan, Italy
| | | | | | - Luca M. Rossetti
- ASST Santi Paolo e Carlo, Eye Clinic – University of Milan, Milan, Italy
| | - David P. Crabb
- City, University of London, Optometry and Visual Sciences, London, United Kingdom
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Dunn M, Cull G, Reynaud J, Jennings D, Holthausen T, Di Polo A, Fortune B. Utility of Light-Adapted Full-Field Electroretinogram ON and OFF Responses for Detecting Glaucomatous Functional Damage. Transl Vis Sci Technol 2023; 12:16. [PMID: 37594448 PMCID: PMC10445177 DOI: 10.1167/tvst.12.8.16] [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: 12/19/2022] [Accepted: 07/13/2023] [Indexed: 08/19/2023] Open
Abstract
Purpose To compare parameters of electroretinogram (ERG) responses for their ability to detect functional loss in early stages of nonhuman primate (NHP) experimental glaucoma (EG), including photopic negative responses (PhNR) to a standard brief red flash on a blue background (R/B) and 200-ms-long R/B and white-on-white (W/W) flashes, to W/W flicker stimuli (5-50 Hz), and to a dark-adapted intensity series. Methods Light-adapted ERGs were recorded in 12 anesthetized monkeys with unilateral EG. Amplitudes and implicit times of the a-wave, b-wave, and d-wave were measured, as well as amplitudes of PhNRs and oscillatory potentials for flash onset and offset. Flicker ERGs were measured using peak-trough and fundamental frequency analyses. Dark-adapted ERG parameters were modeled by Naka-Rushton relationships. Results Only PhNR amplitudes were significantly reduced in EG eyes compared to fellow control (FC) eyes. The d-wave implicit time was delayed in EG versus FC eyes only for the W/W long flash, but in all eyes it was 10 to 20 ms slower for R/B versus the W/W condition. Flicker ERGs were <0.5 ms delayed in EG versus FC overall, but amplitudes were affected only at 5 Hz. The brief R/B PhNR amplitude had the highest sensitivity to detect EG and strongest correlation to parameters of structural damage. Conclusions The PhNR to the standard brief R/B stimulus was best for detecting and following early-stage functional loss in NHP EG. Translational Relevance These results suggest that there would be no benefit in using longer duration flashes to separate onset and offset responses for clinical management of glaucoma.
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Affiliation(s)
- Michaela Dunn
- Discoveries in Sight Research Laboratories, Devers Eye Institute, Legacy Health, Portland, OR, USA
| | - Grant Cull
- Discoveries in Sight Research Laboratories, Devers Eye Institute, Legacy Health, Portland, OR, USA
| | - Juan Reynaud
- Discoveries in Sight Research Laboratories, Devers Eye Institute, Legacy Health, Portland, OR, USA
| | - Dawn Jennings
- Discoveries in Sight Research Laboratories, Devers Eye Institute, Legacy Health, Portland, OR, USA
| | - Trinity Holthausen
- Discoveries in Sight Research Laboratories, Devers Eye Institute, Legacy Health, Portland, OR, USA
| | - Adriana Di Polo
- Department of Neuroscience, Université de Montréal, Montréal, QC, Canada
- Neuroscience Division, Centre de Recherche du Centre Hospitalier, Université de Montréal, Montréal, QC, Canada
| | - Brad Fortune
- Discoveries in Sight Research Laboratories, Devers Eye Institute, Legacy Health, Portland, OR, USA
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Wagner S, Strasser T. Impact of text contrast polarity on the retinal activity in myopes and emmetropes using modified pattern ERG. Sci Rep 2023; 13:11101. [PMID: 37423936 DOI: 10.1038/s41598-023-38192-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2023] [Accepted: 07/05/2023] [Indexed: 07/11/2023] Open
Abstract
Environmental factors favoring myopia development are still being studied and there is accumulating evidence for a significant role of nearwork. Recently, reading standard black-on-white text was found to activate the retinal OFF pathway and induce choroidal thinning, which is associated with myopia onset. Contrarily, reading white-on-black text led to thicker choroids, being protective against myopia. Respective effects on retinal processing are yet unknown. Here, we exploratively assessed the impact of contrast polarity on the retinal activity and possible interactions with eccentricity and refractive error. We recorded pattern electroretinograms in myopic and emmetropic adults while presenting a dead leaves stimulus (DLS), overlaid by masks of different size in ring or circle shape, either filled with uniform gray or text of inverted or standard contrast. In myopes, retinal responses for DLS with standard and inverted contrast were larger when the perifovea was stimulated (6-12 deg), however, including the fovea resulted in smaller amplitudes for inverted contrast than in emmetropes. The retina of emmetropes was more sensitive to inverted contrast than to standard and gray within 12 deg, but most sensitive for gray in the perifovea. This demonstrates that the refractive error influences the sensitivity to text contrast polarity, with a special role of the peripheral retina, which is in line with previous studies about blur sensitivity. Defining whether the differences derive from retinal processing or anatomical features of a myopic eye requires further investigation. Our approach might be a first step to explain how nearwork promotes the eye's elongation.
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Affiliation(s)
- Sandra Wagner
- Institute for Ophthalmic Research, University of Tuebingen, Elfriede-Aulhorn-Str. 7, 72076, Tuebingen, Germany.
| | - Torsten Strasser
- Institute for Ophthalmic Research, University of Tuebingen, Elfriede-Aulhorn-Str. 7, 72076, Tuebingen, Germany
- University Eye Hospital Tuebingen, Elfriede-Aulhorn-Str. 7, 72076, Tuebingen, Germany
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Breher K, Neumann A, Kurth D, Schaeffel F, Wahl S. ON and OFF receptive field processing in the presence of optical scattering. BIOMEDICAL OPTICS EXPRESS 2023; 14:2618-2628. [PMID: 37342711 PMCID: PMC10278613 DOI: 10.1364/boe.489117] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/03/2023] [Revised: 04/14/2023] [Accepted: 04/14/2023] [Indexed: 06/23/2023]
Abstract
The balance of ON/OFF pathway activation in the retina plays a role in emmetropization. A new myopia control lens design uses contrast reduction to down-regulate a hypothesized enhanced ON contrast sensitivity in myopes. The study thus examined ON/OFF receptive field processing in myopes and non-myopes and the impact of contrast reduction. A psychophysical approach was used to measure the combined retinal-cortical output in the form of low-level ON and OFF contrast sensitivity with and without contrast reduction in 22 participants. ON responses were lower than OFF responses (ON 1.25 ± 0.03 vs. OFF 1.39 ± 0.03 log(CS); p < 0.0001) and myopes showed generally reduced sensitivities (myopes 1.25 ± 0.05 vs. non-myopes 1.39 ± 0.05 log(CS); p = 0.05). These findings remained unaffected by contrast reduction (p > 0.05). The study suggests that perceptual differences in ON and OFF signal processing between myopes and non-myopes exist but cannot explain how contrast reduction can inhibit myopia development.
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Affiliation(s)
- Katharina Breher
- Carl Zeiss Vision International GmbH, Turnstr. 27, 73430 Aalen, Germany
- Institute for Ophthalmic Research, University of Tübingen, Elfriede-Aulhorn-Str. 7, 72076 Tübingen, Germany
| | - Antonia Neumann
- Institute for Ophthalmic Research, University of Tübingen, Elfriede-Aulhorn-Str. 7, 72076 Tübingen, Germany
| | - Dominik Kurth
- Institute for Ophthalmic Research, University of Tübingen, Elfriede-Aulhorn-Str. 7, 72076 Tübingen, Germany
| | - Frank Schaeffel
- Institute for Ophthalmic Research, University of Tübingen, Elfriede-Aulhorn-Str. 7, 72076 Tübingen, Germany
- Institute of Molecular and Clinical Ophthalmology Basel, Mittlere Str. 91, 4056 Basel, Switzerland
| | - Siegfried Wahl
- Carl Zeiss Vision International GmbH, Turnstr. 27, 73430 Aalen, Germany
- Institute for Ophthalmic Research, University of Tübingen, Elfriede-Aulhorn-Str. 7, 72076 Tübingen, Germany
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Lagali PS, Shanmugalingam U, Baker AN, Mezey N, Smith PD, Coupland SG, Tsilfidis C. Assessment of the uniform field electroretinogram for mouse retinal ganglion cell functional analysis. Doc Ophthalmol 2023:10.1007/s10633-023-09933-y. [PMID: 37106219 DOI: 10.1007/s10633-023-09933-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2022] [Accepted: 03/26/2023] [Indexed: 04/29/2023]
Abstract
PURPOSE The uniform field electroretinogram (UF-ERG) has been suggested as an alternative to the pattern electroretinogram (PERG) for non-invasive assessment of retinal ganglion cell (RGC) function in primates. We evaluated the validity of the UF-ERG to assess mouse RGC activity in vivo. METHODS Unilateral optic nerve crush (ONC) was performed on adult C57BL/6J mice. Contralateral eyes with uncrushed optic nerves and eyes from surgically naive mice served as experimental controls. Electrophysiological visual assessment was performed at 12 weeks post-ONC. Flash-mediated visual-evoked cortical potentials (VEPs) were measured to confirm the robustness of the ONC procedure. Full-field flash ERGs were used to interrogate photoreceptor and retinal bipolar cell function. RGC function was assessed with pattern ERGs. Summed onset and offset UF-ERG responses to alternating dark and light uniform field flash stimuli of different intensities and wavelengths were recorded from ONC and control eyes, and relative differences were compared to the PERG results. Following electrophysiological analysis, RGC loss was monitored by immunohistochemical staining of the RGC marker protein, RBPMS, in post-mortem retinal tissues. RESULTS ONC dramatically impacts RGC integrity and optic nerve function, demonstrated by reduced RGC counts and near complete elimination of VEPs. ONC did not affect scotopic ERG a-wave and b-wave amplitudes, while PERG amplitudes of eyes subjected to ONC were reduced by approximately 50% compared to controls. Summation of ON and OFF UF-ERG responses did not reveal statistically significant differences between ONC and control eyes, regardless of visual stimulus. CONCLUSIONS PERG responses are markedly impaired upon ONC, while UF-ERG responses are not significantly affected by surgical trauma to RGC axons in mice. The more closely related pattern and uniform field ERGs recorded in primates suggests species-specific differences in RGC features or subpopulations corresponding to PERG and UF-ERG response generators, limiting the utility of the UF-ERG for mouse RGC functional analysis.
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Affiliation(s)
- Pamela S Lagali
- Neuroscience Program, Ottawa Hospital Research Institute, Ottawa, ON, K1H 8L6, Canada
- University of Ottawa Eye Institute, The Ottawa Hospital, Ottawa, ON, K1H 8L6, Canada
| | | | - Adam N Baker
- Neuroscience Program, Ottawa Hospital Research Institute, Ottawa, ON, K1H 8L6, Canada
- University of Ottawa Eye Institute, The Ottawa Hospital, Ottawa, ON, K1H 8L6, Canada
| | - Natalie Mezey
- Department of Neuroscience, Carleton University, Ottawa, ON, Canada
| | - Patrice D Smith
- Department of Neuroscience, Carleton University, Ottawa, ON, Canada
| | - Stuart G Coupland
- University of Ottawa Eye Institute, The Ottawa Hospital, Ottawa, ON, K1H 8L6, Canada
- Department of Ophthalmology, University of Ottawa, Ottawa, ON, K1H 8M5, Canada
- Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, ON, K1H 8M5, Canada
| | - Catherine Tsilfidis
- Neuroscience Program, Ottawa Hospital Research Institute, Ottawa, ON, K1H 8L6, Canada.
- University of Ottawa Eye Institute, The Ottawa Hospital, Ottawa, ON, K1H 8L6, Canada.
- Department of Ophthalmology, University of Ottawa, Ottawa, ON, K1H 8M5, Canada.
- Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, ON, K1H 8M5, Canada.
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Naguib S, DeJulius CR, Backstrom JR, Haider AA, Ang JM, Boal AM, Calkins DJ, Duvall CL, Rex TS. Intraocular Sustained Release of EPO-R76E Mitigates Glaucoma Pathogenesis by Activating the NRF2/ARE Pathway. Antioxidants (Basel) 2023; 12:556. [PMID: 36978804 PMCID: PMC10045745 DOI: 10.3390/antiox12030556] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2023] [Revised: 02/03/2023] [Accepted: 02/15/2023] [Indexed: 02/25/2023] Open
Abstract
Erythropoietin (EPO) is neuroprotective in multiple models of neurodegenerative diseases, including glaucoma. EPO-R76E retains the neuroprotective effects of EPO but diminishes the effects on hematocrit. Treatment with EPO-R76E in a glaucoma model increases expression of antioxidant proteins and is neuroprotective. A major pathway that controls the expression of antioxidant proteins is the NRF2/ARE pathway. This pathway is activated endogenously after elevation of intraocular pressure (IOP) and contributes to the slow onset of pathology in glaucoma. In this study, we explored if sustained release of EPO-R76E in the eye would activate the NRF2/ARE pathway and if this pathway was key to its neuroprotective activity. Treatment with PLGA.EPO-E76E prevented increases in retinal superoxide levels in vivo, and caused phosphorylation of NRF2 and upregulation of antioxidants. Further, EPO-R76E activates NRF2 via phosphorylation by the MAPK pathway rather than the PI3K/Akt pathway, used by the endogenous antioxidant response to elevated IOP.
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Affiliation(s)
- Sarah Naguib
- Neuroscience Program, Vanderbilt University, Nashville, TN 37232, USA
| | - Carlisle R. DeJulius
- Department of Biomedical Engineering, Vanderbilt University, Nashville, TN 37232, USA
| | - Jon R. Backstrom
- Vanderbilt Eye Institute, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Ameer A. Haider
- Neuroscience Program, Vanderbilt University, Nashville, TN 37232, USA
| | - John M. Ang
- Neuroscience Program, Vanderbilt University, Nashville, TN 37232, USA
| | - Andrew M. Boal
- Neuroscience Program, Vanderbilt University, Nashville, TN 37232, USA
| | - David J. Calkins
- Neuroscience Program, Vanderbilt University, Nashville, TN 37232, USA
- Vanderbilt Eye Institute, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Craig L. Duvall
- Department of Biomedical Engineering, Vanderbilt University, Nashville, TN 37232, USA
| | - Tonia S. Rex
- Neuroscience Program, Vanderbilt University, Nashville, TN 37232, USA
- Vanderbilt Eye Institute, Vanderbilt University Medical Center, Nashville, TN 37232, USA
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Predicting Visual Field Progression by Optical Coherence Tomography Angiography and Pattern Electroretinography in Glaucoma. J Glaucoma 2022; 31:881-890. [PMID: 35882039 DOI: 10.1097/ijg.0000000000002088] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2022] [Accepted: 06/12/2022] [Indexed: 02/04/2023]
Abstract
PRCIS Reduced P50-N95 amplitude on pattern electroretinography (PERG) and the presence of microvasculature dropout (MvD) on optical coherence tomography angiography (OCT-A) at baseline were significant factors associated with visual field (VF) progression in predominantly normal tension glaucoma (NTG) patients. OBJECTIVE We investigated the baseline demographics and ocular characteristics that predict future progression in glaucoma patients, including PERG and OCT-A parameters. METHODS One Hundred forty eyes with open angle glaucoma that were prospectively enrolled and followed up for at least 3 years, and underwent at least 5 serial VF tests were included. Baseline PERG was performed, and N35, P50, and N95 latencies and amplitudes were obtained. Superficial vessel density at the macula and complete loss of microvasculature within the deep retinal layer of the parapapillary region (MvD) were evaluated from baseline OCT-A images. Eyes with a glaucomatous VF defect in either both hemifields within 24 points of a central 10 degrees of fixation, and with no VF abnormality in the nasal periphery outside 10 degrees of fixation, were considered to have isolated central scotoma. During follow-up, detected disc hemorrhage (DH) was recorded. Parameters associated with VF progression were determined using linear regression analysis of the mean deviation (MD) values, in combination with an event-based analysis using the Glaucoma Progression Analysis (GPA) software from the Humphrey Field Analyzer. "Likely progression" using GPA was considered to have glaucoma progression. RESULTS Of the 140 eyes, 107 (76.4%) were NTG and 57 (40.7%) exhibited glaucoma progression as defined by Humphrey VF GPA. The MD slopes were -0.43±1.11 dB/y in the progressors and 0.59±1.27 dB/y in the nonprogressors ( P <0.001). Glaucoma patients with progression showed frequent MvD on OCT-A, isolated central scotoma, frequent DH, and reduced baseline P50-N95 amplitude compared with patients without progression. Age at diagnosis ( P =0.038) and baseline P50-N95 amplitude ( P =0.019) showed significant associations with the MD slope. The presence of MvD on OCT-A ( P <0.001) and baseline P50-N95 amplitude ( P =0.037) were significantly associated with VF progression on GPA. CONCLUSIONS The presence of MvD and retinal ganglion cell dysfunction by PERG at baseline, DH or central scotoma were significant factors associated with VF progression in predominantly NTG patients. These patients should be monitored more closely.
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Differential susceptibility of retinal ganglion cell subtypes against neurodegenerative diseases. Graefes Arch Clin Exp Ophthalmol 2022; 260:1807-1821. [PMID: 35038014 DOI: 10.1007/s00417-022-05556-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2021] [Revised: 11/27/2021] [Accepted: 01/06/2022] [Indexed: 12/15/2022] Open
Abstract
Retinal ganglion cells (RGCs) are essential to propagate external visual information from the retina to the brain. Death of RGCs is speculated to be closely correlated with blinding retinal diseases, such as glaucoma and traumatic optic neuropathy (TON). Emerging innovative technologies have helped refine and standardize the classification of RGCs; at present, they are classified into more than 40 subpopulations in mammals. These RGC subtypes are identified by a combination of anatomical morphologies, electrophysiological functions, and genetic profiles. Increasing evidence suggests that neurodegenerative diseases do not collectively affect the RGCs. In fact, which RGC subtype exhibits the strongest or weakest susceptibility is hotly debated. Although a consensus has not yet been reached, it is certain that assorted RGCs display differential susceptibility against irreversible degeneration. Interestingly, a single RGC subtype can exhibit various vulnerabilities to optic nerve damage in diverse injury models. Thus, elucidating how susceptible RGC subtypes are to various injuries can protect vulnerable RGCs from damage and improve the possibility of preventing and treating visual impairment caused by neurodegenerative diseases. In this review, we summarize in detail the progress and status quo of research on the type-specific susceptibility of RGCs and point out current limitations and the possible directions for future research in this field.
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7,8-Dihydroxiflavone Maintains Retinal Functionality and Protects Various Types of RGCs in Adult Rats with Optic Nerve Transection. Int J Mol Sci 2021; 22:ijms222111815. [PMID: 34769247 PMCID: PMC8584116 DOI: 10.3390/ijms222111815] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2021] [Revised: 10/26/2021] [Accepted: 10/27/2021] [Indexed: 12/13/2022] Open
Abstract
To analyze the neuroprotective effects of 7,8-Dihydroxyflavone (DHF) in vivo and ex vivo, adult albino Sprague-Dawley rats were given a left intraorbital optic nerve transection (IONT) and were divided in two groups: One was treated daily with intraperitoneal (ip) DHF (5 mg/kg) (n = 24) and the other (n = 18) received ip vehicle (1% DMSO in 0.9% NaCl) from one day before IONT until processing. At 5, 7, 10, 12, 14, and 21 days (d) after IONT, full field electroretinograms (ERG) were recorded from both experimental and one additional naïve-control group (n = 6). Treated rats were analyzed 7 (n = 14), 14 (n = 14) or 21 d (n = 14) after IONT, and the retinas immune stained against Brn3a, Osteopontin (OPN) and the T-box transcription factor T-brain 2 (Tbr2) to identify surviving retinal ganglion cells (RGCs) (Brn3a+), α-like (OPN+), α-OFF like (OPN+Brn3a+) or M4-like/α-ON sustained RGCs (OPN+Tbr+). Naïve and right treated retinas showed normal ERG recordings. Left vehicle-treated retinas showed decreased amplitudes of the scotopic threshold response (pSTR) (as early as 5 d), the rod b-wave, the mixed response and the cone response (as early as 10 d), which did not recover with time. In these retinas, by day 7 the total numbers of Brn3a+RGCs, OPN+RGCs and OPN+Tbr2+RGCs decreased to less than one half and OPN+Brn3a+RGCs decreased to approximately 0.5%, and Brn3a+RGCs showed a progressive loss with time, while OPN+RGCs and OPN+Tbr2+RGCs did not diminish after seven days. Compared to vehicle-treated, the left DHF-treated retinas showed significantly greater amplitudes of the pSTR, normal b-wave values and significantly greater numbers of OPN+RGCs and OPN+Tbr2+RGCs for up to 14 d and of Brn3a+RGCs for up to 21 days. DHF affords significant rescue of Brn3a+RGCs, OPN+RGCs and OPN+Tbr2+RGCs, but not OPN+Brn3a+RGCs, and preserves functional ERG responses after IONT.
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Kong AW, Turner ML, Chan H, Stamper RL, Arnold BF, Della Santina L, Ou Y. Asymmetric Functional Impairment of ON and OFF Retinal Pathways in Glaucoma. OPHTHALMOLOGY SCIENCE 2021; 1:100026. [PMID: 35756578 PMCID: PMC9232180 DOI: 10.1016/j.xops.2021.100026] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/03/2021] [Revised: 04/29/2021] [Accepted: 05/03/2021] [Indexed: 11/17/2022]
Abstract
Purpose To investigate ON-pathway versus OFF-pathway dysfunction in glaucoma using handheld electroretinography (ERG) with a temporally modulated sinusoidal flicker stimulus. Design Cross-sectional study. Participants Fifty-nine participants accounting for 104 eyes, comprised of 19 control eyes, 26 glaucoma suspect eyes, and 59 glaucoma eyes. Methods Participants underwent portable ERG testing, which included the photopic flash, photopic flicker, photopic negative response stimulus, ON-OFF stimulus, and a custom-written sinusoidal flicker stimulus that was modulated from 50 to 0.3 Hz. Main Outcome and Measures The ERG response amplitudes were measured by the handheld ERG. For the custom-written sinusoidal flicker stimulus, we derived and compared the log10 first harmonic frequency response amplitudes. Patient discomfort and fatigue after ERG testing were rated on a scale from 1 to 5. Results Baseline demographics were not significantly different between groups, except for ocular characteristics. Analysis was performed adjusting for participant age, sex, race, and dilation status, and the sinusoidal frequency responses were stratified at 10 Hz because higher frequencies are associated with the OFF-pathway, whereas lower frequencies are associated with the ON-pathway. After stratification, glaucoma eyes showed an adjusted decrease of 32.1% at frequencies of more than 10 Hz (95% confidence interval [CI], -51.8% to -4.1%; P = 0.03). For 10 Hz stimulus frequencies or less, an adjusted 11.5% reduction was found (95% CI, -39.5% to 29.1%; P = 0.50). Glaucoma suspect eyes did show a decreased response, but this was not significant at either frequency range. When comparing handheld ERG with traditional visual field assessments, participants found the handheld ERG to result in much less discomfort and fatigue. Conclusions Our finding that glaucoma participants showed greater decreases in ERG response at higher frequencies supports the hypothesis that the OFF-pathway may be more vulnerable in human glaucoma. Using a handheld ERG device with a sinusoidal flicker stimulus may provide an objective assessment of visual function in glaucoma.
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Affiliation(s)
- Alan W. Kong
- Department of Ophthalmology, University of California, San Francisco, San Francisco, California
| | - Marcus L. Turner
- Department of Ophthalmology, University of California, San Francisco, San Francisco, California
| | - Hoover Chan
- Department of Ophthalmology, University of California, San Francisco, San Francisco, California
| | - Robert L. Stamper
- Department of Ophthalmology, University of California, San Francisco, San Francisco, California
| | - Benjamin F. Arnold
- Department of Ophthalmology, University of California, San Francisco, San Francisco, California
- Francis I. Proctor Foundation, University of California, San Francisco, San Francisco, California
| | - Luca Della Santina
- Department of Ophthalmology, University of California, San Francisco, San Francisco, California
- Bakar Computational Health Sciences Institute, University of California, San Francisco, San Francisco, California
| | - Yvonne Ou
- Department of Ophthalmology, University of California, San Francisco, San Francisco, California
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