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Kalloniatis M, Wang H, Katalinic P, Ly A, Apel W, Nivison-Smith L, Kalloniatis KF. Ocular ischaemia: signs, symptoms, and clinical considerations for primary eye care practitioners. Clin Exp Optom 2022; 105:117-134. [PMID: 34982952 DOI: 10.1080/08164622.2021.1999771] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022] Open
Abstract
Ischaemic stroke is a major disease burden as well as a leading cause of death. Early signs of ischaemic stroke can manifest in the eye, placing primary eyecare practitioners in an important position to identify patients at risk of ischaemic stroke and initiate suitable referral pathways. The vascular supply to the brain is reviewed with reference to vision including the various retinal signs and ocular symptoms associated with transient ischaemic attacks and ischaemic stroke. Using a range of clinical cases, the diverse clinical presentations of retinal embolic events, as well as other forms of vascular occlusion, are highlighted and the underlying pathophysiology is discussed. A succinct scheme for the assessment and management of ischaemic events for primary eye care practitioners is provided.
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Affiliation(s)
- Michael Kalloniatis
- Centre for Eye Health, the University of New South Wales, Sydney, Australia.,School of Optometry and Vision Science, The University of New South Wales, Sydney, Australia
| | - Henrietta Wang
- Centre for Eye Health, the University of New South Wales, Sydney, Australia.,School of Optometry and Vision Science, The University of New South Wales, Sydney, Australia
| | - Paula Katalinic
- Centre for Eye Health, the University of New South Wales, Sydney, Australia.,School of Optometry and Vision Science, The University of New South Wales, Sydney, Australia
| | - Angelica Ly
- Centre for Eye Health, the University of New South Wales, Sydney, Australia.,School of Optometry and Vision Science, The University of New South Wales, Sydney, Australia
| | - Warren Apel
- Centre for Eye Health, the University of New South Wales, Sydney, Australia.,The Eye Health Centre, Aspley, Australia
| | - Lisa Nivison-Smith
- Centre for Eye Health, the University of New South Wales, Sydney, Australia.,School of Optometry and Vision Science, The University of New South Wales, Sydney, Australia
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Abstract
This manuscript focuses on the pathogenesis of age-related maculopathy (ARM) and the documentation of new treatments in ARM. Ischaemia will be given special consideration, as it is believed to play a central role in both early ARM and late ARM or age-related macular degeneration (AMD). Reduced choroidal and retinal blood flow causes ischaemia of Bruch's membrane, retinal pigment epithelium and neuroretina in the early course of ARM. This is thought to be the primary trigger of the condition. Chronic ischaemia upregulates vascular endothelial growth factor (VEGF), which induces abnormal vessel growth in neovascular AMD. The role of ischaemia in neovascular AMD is supported by the evidence of effective new treatments targeting VEGF.
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Affiliation(s)
- Beatrix Feigl
- Institute of Health and Biomedical Innovation and School of Optometry, Queensland University of Technology, Brisbane, Australia.
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3
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Munk MR, Beck M, Kolb S, Larsen M, Hamann S, Valmaggia C, Zinkernagel MS. Quantification of retinal layer thickness changes in acute macular neuroretinopathy. Br J Ophthalmol 2016; 101:160-165. [PMID: 27170518 PMCID: PMC5293849 DOI: 10.1136/bjophthalmol-2016-308367] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2016] [Revised: 03/08/2016] [Accepted: 04/16/2016] [Indexed: 11/26/2022]
Abstract
Purpose To quantitatively evaluate retinal layer thickness changes in acute macular neuroretinopathy (AMN). Methods AMN areas were identified using near-infrared reflectance (NIR) images. Intraretinal layer segmentation using Heidelberg software was performed. The inbuilt ETDRS -grid was moved onto the AMN lesion and the mean retinal layer thicknesses of the central grid were recorded and compared with the corresponding area of the fellow eye at initial presentation and during follow-up. Results Eleven patients were included (mean age 26±6 years). AMN lesions at baseline had a significantly thinner outer nuclear layer (ONL) (51±21 µm vs 73±17 µm, p=0.002). The other layers, including inner nuclear layer (37±8 µm vs 38±6 µm, p=0.9) and outer plexiform layer (OPL) (45±19 µm vs 33±16 µm, p=0.1) did not show significant differences between the study eyes and fellow eyes. Adjacent to NIR image lesions, areas of OPL thickening were identified (study eye: 50±14 µm vs fellow eye: 39±16 µm, p=0.005) with corresponding thinning of ONL (study eye: 52±16 µm vs fellow eye: 69±16 µm, p=0.002). Conclusions AMN presents with characteristic quantitative retinal changes and the extent of the lesion may be more extensive than initially presumed from NIR image lesions.
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Affiliation(s)
- Marion R Munk
- Department of Ophthalmology, Inselspital, Bern University Hospital, University of Bern, Switzerland.,Department of Ophthalmology, Northwestern University, Feinberg School of Medicine, Chicago, Illinois, USA.,Bern Photographic Reading Center, Inselspital, Bern University Hospital, University of Bern, Switzerland
| | - Marco Beck
- Department of Ophthalmology, Inselspital, Bern University Hospital, University of Bern, Switzerland
| | - Simone Kolb
- Department of Ophthalmology, Inselspital, Bern University Hospital, University of Bern, Switzerland
| | - Michael Larsen
- Department of Ophthalmology, Rigshospitalet-Glostrup, University of Copenhagen, Glostrup, Denmark
| | - Steffen Hamann
- Department of Ophthalmology, Rigshospitalet-Glostrup, University of Copenhagen, Glostrup, Denmark
| | | | - Martin S Zinkernagel
- Department of Ophthalmology, Inselspital, Bern University Hospital, University of Bern, Switzerland.,Bern Photographic Reading Center, Inselspital, Bern University Hospital, University of Bern, Switzerland.,Department of Clinical Research, Inselspital, Bern University Hospital, University of Bern, Switzerland
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4
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Bui BV, He Z, Vingrys AJ, Nguyen CTO, Wong VHY, Fortune B. Using the electroretinogram to understand how intraocular pressure elevation affects the rat retina. J Ophthalmol 2013; 2013:262467. [PMID: 23431417 PMCID: PMC3570935 DOI: 10.1155/2013/262467] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2012] [Accepted: 10/24/2012] [Indexed: 11/17/2022] Open
Abstract
Intraocular pressure (IOP) elevation is a key risk factor for glaucoma. Our understanding of the effect that IOP elevation has on the eye has been greatly enhanced by the application of the electroretinogram (ERG). In this paper, we describe how the ERG in the rodent eye is affected by changes in IOP magnitude, duration, and number of spikes. We consider how the variables of blood pressure and age can modify the effect of IOP elevation on the ERG. Finally, we contrast the effects that acute and chronic IOP elevation can have on the rodent ERG.
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Affiliation(s)
- Bang V. Bui
- Department of Optometry and Vision Sciences, University of Melbourne, Parkville, VIC 3010, Australia
| | - Zheng He
- Department of Optometry and Vision Sciences, University of Melbourne, Parkville, VIC 3010, Australia
| | - Algis J. Vingrys
- Department of Optometry and Vision Sciences, University of Melbourne, Parkville, VIC 3010, Australia
| | - Christine T. O. Nguyen
- Department of Optometry and Vision Sciences, University of Melbourne, Parkville, VIC 3010, Australia
| | - Vickie H. Y. Wong
- Department of Optometry and Vision Sciences, University of Melbourne, Parkville, VIC 3010, Australia
| | - Brad Fortune
- Devers Eye Institute and Legacy Research Institute, Legacy Health, Portland, OR 97232, USA
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5
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de Souza CF, Kalloniatis M, Polkinghorne PJ, McGhee CN, Acosta ML. Functional and anatomical remodeling in human retinal detachment. Exp Eye Res 2012; 97:73-89. [DOI: 10.1016/j.exer.2012.02.009] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2011] [Revised: 02/01/2012] [Accepted: 02/15/2012] [Indexed: 10/28/2022]
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6
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Role of prostanoid production and receptors in the regulation of retinal endogenous amino acid neurotransmitters by 8-isoprostaglandin E2, ex vivo. Neurochem Res 2011; 34:2170-80. [PMID: 19513831 DOI: 10.1007/s11064-009-0013-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/21/2009] [Indexed: 12/11/2022]
Abstract
The role of enzymes and receptors of the prostanoid pathway in the inhibitory effect of 8-isoprostaglandin E2 (8-isoPGE2) on endogenous amino acid neurotransmitter levels was examined, ex vivo. Freshly isolated bovine eyeballs were injected intravitreally with IsoPs, incubated in Krebs buffer for 30 min and retina prepared for HPLC-ECD detection of amino acids. 8-isoPGE2 attenuated retinal glutamate and its metabolite, glutamine and glycine in a concentration-dependent manner. The nonselective cyclooxygenase (COX)-inhibitor, flurbiprofen, COX-2 selective inhibitor, NS-398 and thromboxane (Tx) synthase inhibitor, furegrelate had no effect on both basal amino acid levels and the inhibitory effects of 8-isoPGE2 (1-100 μM) on the retinal amino acids. Whereas the TP-receptor antagonist SQ-29548(10 μM) exhibited no effect, SC-19220(EP1; 30 μM), AH-6809(EP(1-3); 30 μM) and AH-23848(EP4; 30 μM) reversed the inhibitory effects of 8-isoPGE2 (0.01-100 μM) on glutamate, glutamine and glycine levels. We conclude that prostanoid EP-receptors regulate the inhibitory effect of 8-isoPGE2 on basal levels of endogenous amino acids in bovine retina, ex vivo.
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Fletcher EL, Downie LE, Hatzopoulos K, Vessey KA, Ward MM, Chow CL, Pianta MJ, Vingrys AJ, Kalloniatis M, Wilkinson-Berka JL. The significance of neuronal and glial cell changes in the rat retina during oxygen-induced retinopathy. Doc Ophthalmol 2009; 120:67-86. [PMID: 19763649 DOI: 10.1007/s10633-009-9193-6] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2009] [Accepted: 08/17/2009] [Indexed: 12/31/2022]
Abstract
Retinopathy of prematurity is a devastating vascular disease of premature infants. A number of studies indicate that retinal function is affected in this disease. Using the rat model of oxygen-induced retinopathy, it is possible to explore more fully the complex relationship between neuronal, glial and vascular pathology in this condition. This review examines the structural and functional changes that occur in the rat retina following oxygen-induced retinopathy. We highlight that vascular pathology in rats is characterized by aberrant growth of blood vessels into the vitreous at the expense of blood vessel growth into the body of the retina. Moreover, amino acid neurochemistry, a tool for examining neuronal changes in a spatially complete manner reveals widespread changes in amacrine and bipolar cells. In addition, neurochemical anomalies within inner retinal neurons are highly correlated with the absence of retinal vessels. The key cell types that link blood flow with neuronal function are macroglia. Macroglia cells, which in the retina include astrocytes and Müller cells, are affected by oxygen-induced retinopathy. Astrocyte loss occurs in the peripheral retina, while Müller cells show signs of reactive gliosis that is highly localized to regions that are devoid of intraretinal blood vessels. Finally, we propose that treatments, such as blockade of the renin-angiotensin system, that not only targets pathological angiogenesis, but that also promotes re-vascularization of the retina are likely to prove important in the treatment of those with retinopathy of prematurity.
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Affiliation(s)
- Erica L Fletcher
- Department of Anatomy and Cell Biology, The University of Melbourne, Grattan St., Parkville, VIC 3010, Australia.
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8
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Chui TYP, Thibos LN, Bradley A, Burns SA. The mechanisms of vision loss associated with a cotton wool spot. Vision Res 2009; 49:2826-34. [PMID: 19703485 DOI: 10.1016/j.visres.2009.08.017] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2009] [Revised: 08/17/2009] [Accepted: 08/19/2009] [Indexed: 11/25/2022]
Abstract
We characterized the perceptual, functional, and structural abnormalities associated with retinal ischemia during a cotton wool spot episode and its sequelae. The border of the visually salient field anomaly mirrored the quantitatively measured relative scotoma. Results of resolution perimetry and high resolution imaging indicated that there was a substantial loss of retinal ganglion cells within the affected region. A disruption in retinal nerve fiber arrangement was found at the cotton wool spot and within the arcuate relative scotoma. The presence of the arcuate relative scotoma is consistent with the hypothesis of failed signal transmission along the axons that pass through the cotton wool spot. The different levels of loss associated with the arcuate and focal scotomas indicate different underlying pathologies.
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Affiliation(s)
- Toco Y P Chui
- School of Optometry, Indiana University, 800 E. Atwater Ave., Bloomington, IN 47405, USA.
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9
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Feigl B. Age-related maculopathy – Linking aetiology and pathophysiological changes to the ischaemia hypothesis. Prog Retin Eye Res 2009; 28:63-86. [PMID: 19070679 DOI: 10.1016/j.preteyeres.2008.11.004] [Citation(s) in RCA: 101] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Affiliation(s)
- Beatrix Feigl
- Institute of Health and Biomedical Innovation, Queensland University of Technology, 60 Musk Avenue, Kelvin Grove, 4059 QLD, Australia.
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10
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Du Y, Hirooka K, Miyamoto O, Itano T, Tokuda M, Shiraga F. Both amacrine and bipolar cells release glutamate in the rat retina after ischemia/reperfusion insult in vitro. Curr Eye Res 2008; 33:782-8. [PMID: 18798081 DOI: 10.1080/02713680802334600] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
PURPOSE To investigate which cells in the inner nuclear layer release glutamate after exposure through the use of a model mimicking rat retina ischemia/reperfusion induced by glucose/oxygen deprivation in vitro. METHODS An in vitro retinal ischemia model was used to monitor the release of glutamate by staining with diaminobenzidine hydrochloride. Immunocytochemistry was used to identify the cells releasing glutamate during ischemic/reperfusion injury. RESULTS On immunocytochemistry, double-labeling of some amacrine and bipolar cells was observed, with somata being stained blue by GABA and two portions of the processes labeled brown due to glutamate reactivity. Some somata of amacrine cells were double-labeled with calbindin, while horizontal cells were single-labeled with calbindin. CONCLUSIONS During ischemia/reperfusion injury in vitro, both amacrine and bipolar cells release glutamate. These results may be related to the patterns of apoptotic cell death seen in the inner retina.
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Affiliation(s)
- Yinghua Du
- Department of Ophthalmology, Kagawa University Faculty of Medicine, Kagawa, Japan
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11
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Sun D, Vingrys AJ, Kalloniatis M. Metabolic and functional profiling of the ischemic/reperfused rat retina. J Comp Neurol 2008; 505:114-30. [PMID: 17729266 DOI: 10.1002/cne.21481] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
We quantitatively tracked the recovery in amino acid labeling and cation channel functionality within distinct retinal elements for up to 2 weeks after an ischemic insult. Pattern recognition analysis of multiple amino acid and agmatine (a cation channel probe; 1-amino-4-guanidobutane; AGB) immunocytochemical patterns was used to classify all neural elements within the retina. This classification was spatially complete and with single-cell resolution. By 48 hours of reperfusion the amino acid labeling pattern of virtually all cell populations had returned to near preischemic levels, with the exception of glutamine and alanine levels, which remained significantly higher in many cell populations. Classification resulted in a total of 18 statistically separable theme classes (including neurons, glia, and extraretinal classes), a reduction of 10 theme classes from the normal retina (Sun et al. [ 2007a, b] J Comp Neurol, this issue). In addition to the known selective losses of amacrine cell types within the inner nuclear layer, we now demonstrate a selective loss of theme classes representing cone bipolar cells within the bipolar cell population. While there was a recovery in the amino acid labeling pattern, there were persistent cation channel gating anomalies (as reflected by AGB labeling) within several theme classes, including the theme class representing all the remaining rod bipolar cells, suggesting aberrant neuronal function secondary to metabolic insult.
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Affiliation(s)
- Daniel Sun
- Department of Optometry and Vision Science, University of Auckland, New Zealand
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12
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Downie LE, Pianta MJ, Vingrys AJ, Wilkinson-Berka JL, Fletcher EL. Neuronal and glial cell changes are determined by retinal vascularization in retinopathy of prematurity. J Comp Neurol 2007; 504:404-17. [PMID: 17663451 DOI: 10.1002/cne.21449] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
We have characterized the vascular, neuronal, and glial changes in oxygen-induced retinopathy, a model of retinopathy of prematurity (ROP). Newborn Sprague-Dawley rats were exposed to either 80% +/- 2% oxygen to postnatal day P11 and then room air until P18 (ROP) or room air for the entire duration (controls). Retinal structure was examined under the light microscope and following postembedding immunocytochemistry in central, midperipheral, and peripheral regions. Müller cells were evaluated immunocytochemically with glial fibrillary acidic protein. The extent of vascularization was established histologically. ROP caused significant thinning of the inner cellular and plexiform layers, which became more pronounced in the peripheral inner nuclear layer of ROP animals (11.3% loss vs. 25.4% loss). Amacrine cell amino acid levels were particularly vulnerable in the peripheral retina; bipolar cells showed similar but less prominent changes. Müller cells had elevated glutamine levels and were most gliotic in the periphery. The vasculature extended to peripheral retinal regions at P18 in controls but not in ROP rats. The most striking pattern of change was evident in the midperipheral "transition zone" of ROP animals. Areas close to blood vessels showed neurochemical properties that were similar to those of the central retina, indicating a local protective effect of the inner retinal blood supply. We find that ROP produces complex vascular, neural, and glial changes that relate to the proximity of inner retinal blood vessels.
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Affiliation(s)
- Laura E Downie
- Department of Anatomy and Cell Biology, The University of Melbourne, Parkville, Victoria, Australia
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Feigl B, Stewart I, Brown B. Experimental hypoxia in human eyes: Implications for ischaemic disease. Clin Neurophysiol 2007; 118:887-95. [PMID: 17307390 DOI: 10.1016/j.clinph.2006.12.012] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2006] [Revised: 11/14/2006] [Accepted: 12/11/2006] [Indexed: 11/24/2022]
Abstract
OBJECTIVE This study investigated neuroretinal activity under normoxic and hypoxic conditions with the multifocal electroretinogram (mfERG). METHODS We used two mfERG paradigms, the fast flicker and slow flash stimulation modes, to measure neuroretinal activity in five healthy participants who breathed room air and a reduced oxygen mixture (14% oxygen, balance nitrogen). We analysed concentric ring N1P1 and P1N2 response density amplitudes, the P1 implicit times as well as the local scalar product (SP) response densities. RESULTS During hypoxia there was a significant reduction of the scalar product response density for the fast flicker (p<0.001) and for the slow flash mfERG (p<0.001). The N1P1 and P1N2 response densities were lower especially for the central three rings; although these reductions were not significant between the two oxygen conditions, they indicated an overall distortion of the mfERG waveform. CONCLUSIONS It is demonstrated that a post-receptoral, primarily ON and OFF bipolar cell deficit is evident in the central retina of healthy young people during short term hypoxia. SIGNIFICANCE Our findings suggest that persons with pre-existing ischaemic eye disease may be at risk when exposed to hypoxic conditions.
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Affiliation(s)
- Beatrix Feigl
- Institute of Health and Biomedical Innovation, Queensland University of Technology, Australia.
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Feigl B, Brown B, Lovie-Kitchin J, Swann P. The rod-mediated multifocal electroretinogram in aging and in early age-related maculopathy. Curr Eye Res 2006; 31:635-44. [PMID: 16877272 DOI: 10.1080/02713680600762739] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
PURPOSE To measure function with the rod-mediated multifocal electroretinogram (mfERG) in younger and older subjects with normal vision and with early age-related maculopathy (ARM). METHODS Thirty subjects were studied: 10 healthy subjects with a mean age of 31 years (young group), 10 healthy subjects with a mean age of 71 years (old group), and 10 early ARM subjects with a mean age of 71 years (early ARM group). The influence of cataract was approximated by retesting five subjects of the young group through an 0.3 neutral density filter (ND filter group). We analyzed first-order N1P1-amplitude and P1-implicit time (P1-IT) mfERG responses and correlated them with funduscopic changes as defined by the Age-Related Eye Disease Study (AREDS) group. RESULTS Averaged concentric ring P1-ITs were significantly delayed in the old (p = 0.02) and early ARM (p < 0.001) compared with the young group and in the early ARM group compared with the old and ND group (p < or = 0.01). There were no significant differences in N1P1-amplitudes between groups, but there was a significant location effect for all groups with highest mean amplitudes for the most peripheral ring of hexagons (p < 0.01). Significantly delayed overall P1-ITs (p < 0.05) were correlated with progressive funduscopic changes. CONCLUSIONS Aging and early ARM affects the rod-mediated mfERG, and there is good correlation with funduscopic changes. Although a lens effect cannot be excluded, a neuronal transmission alteration at the postreceptoral level is suggested.
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Affiliation(s)
- Beatrix Feigl
- Institute of Health and Biomedical Innovation, Queensland University of Technology, Kelvin Grove, Australia.
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Feigl B, Brown B, Lovie-Kitchin J, Swann P. Functional loss in early age-related maculopathy: the ischaemia postreceptoral hypothesis. Eye (Lond) 2006; 21:689-96. [PMID: 16680100 DOI: 10.1038/sj.eye.6702389] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
We review proposed models and psychophysical and electrophysiological tests performed in many studies for early age-related maculopathy (ARM). We suggest that ischaemia is the trigger for impaired retinal pigment epithelium function causing imbalance of secretion of vascular growth factors, reduced disc degradation capability and reduced metabolic activity and possible inflammatory response. This results in increased deposition of cell debris, such as drusen and thickens Bruch's membrane causing even more ischaemia of the overlying neurosensory retina. The photoreceptors are more resistant to ischaemia given their proximity to the choroid. Furthermore, being 'upstream' from the inner retinal layers, they act as an oxygen sink depriving retinal layers further from the choroid. Postreceptoral cell layers and especially parts of the inner nuclear layer that are located in the watershed zone between two sources of blood supply are preferentially vulnerable to ischaemia. Based on psychophysical and electrophysiological findings we propose that most of the function impairment in early ARM starts postreceptorally.
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Affiliation(s)
- B Feigl
- Institute of Health and Biomedical Innovation, School of Optometry, Queensland University of Technology, Brisbane, Queensland, Australia.
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16
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Feigl B, Brown B, Lovie-Kitchin J, Lee L. Dynamics of Retinal Function after Multiple Photodynamic Therapies in Age-Related Macular Degeneration: A Report of Cases. Doc Ophthalmol 2006; 111:135-48. [PMID: 16523231 DOI: 10.1007/s10633-005-5319-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/15/2005] [Indexed: 10/24/2022]
Abstract
PURPOSE To monitor retinal function after multiple laser treatments by photodynamic therapy (PDT) with the multifocal electroretinogram (mfERG) in age-related macular degeneration (AMD). METHODS Five eyes of five subjects with AMD were investigated before the first and 1 month after each of three PDT treatments. Function was assessed using the cone- and rod-mediated mfERG, high-contrast distance visual acuity, central visual fields and contrast sensitivity. For each subject the local first-order mfERG results before treatment were used as a template and fitted against the local post-treatment results (Matlab, Mathworks). RESULTS We found transient reduction of the cone- and rod-mediated amplitudes between the first and second treatments but stable or improved mfERG function in four of five eyes for the cone-mediated mfERG and in all eyes for the rod-mediated mfERG after three treatments. Visual acuities and contrast sensitivities remained stable between treatments in four and two eyes respectively, whereas visual fields showed substantially higher mean defects in two subjects after all treatments. CONCLUSION As found in previous studies of the cone-mediated mfERG after one PDT treatment, objective function was stabilized after multiple treatments in this case report. Similarly, although poor at baseline, rod-mediated function was not further compromised. Transiently reduced amplitudes after 1 month possibly reflected choroidal hypoperfusion. A larger sample size is needed to confirm if additional evaluation using electrophysiological criteria might be helpful in re-treatment decisions during PDT.
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Affiliation(s)
- Beatrix Feigl
- Centre for Health Research, School of Optometry, Queensland University of Technology, Brisbane, Australia.
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Kalloniatis M, Sun D, Foster L, Haverkamp S, Wässle H. Localization of NMDA receptor subunits and mapping NMDA drive within the mammalian retina. Vis Neurosci 2005; 21:587-97. [PMID: 15595182 DOI: 10.1017/s0952523804214080] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Glutamate is a major neurotransmitter in the retina and other parts of the central nervous system, exerting its influence through ionotropic and metabotropic receptors. One ionotropic receptor, the N-methyl-D-aspartate(NMDA) receptor, is central to neural shaping, but also plays a major role during neuronal development and in disease processes. We studied the distribution pattern of different subunits of the NMDA receptor within the rat retina including quantifying the pattern of labelling for all the NRI splice variants, the NR2A and NR2B subunits. The labelling pattern for the subunits was confined predominantly in the outer two-thirds of the inner plexiform layer. We also wanted to probe NMDA receptor function using an organic cation, agmatine (AGB); a marker for cation channel activity. Although there was an NMDA concentration-dependent increase in AGB labelling of amacrine cells and ganglion cells, we found no evidence of functional NMDA receptors on horizontal cells in the peripheral rabbit retina, nor in the visual streak where the type A horizontal cell was identified by GABA labelling. Basal AGB labelling within depolarizing bipolar cells was also noted. This basal bipolar cell AGB labelling was not modulated by NMDA and was completely abolished by the use of L-2-amino-4-phosphono-butyric acid,which is known to hyperpolarize retinal depolarizing bipolar cells. AGB is therefore not only useful as a probe of ligand-gated drive, but can also identify neurons that have constitutively open cationic channels. In combination,the NMDA receptor subunit distribution pattern and the AGB gating experiments strongly suggests that this ionotropic glutamate receptor is functional in the cone-driven pathway of the inner retina.
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Affiliation(s)
- Michael Kalloniatis
- Department of Optometry and Vision Science, University of Auckland, Auckland, New Zealand.
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18
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Bui BV, Vingrys AJ, Wellard JW, Kalloniatis M. Monocarboxylate transport inhibition alters retinal function and cellular amino acid levels. Eur J Neurosci 2004; 20:1525-37. [PMID: 15355319 DOI: 10.1111/j.1460-9568.2004.03601.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We assessed the effect of the in vivo application of monocarboxylate transport inhibitors on retinal function and amino acid immunocytochemistry. We wanted to determine the impact that altered aerobic metabolite availability has on retinal function and the characteristics of amino acid shunting into metabolic pools. Electroretinograms were collected from anaesthetized rats at various times after intravitreal injection of the monocarboxylate transport inhibitors alpha-cyano-4-hydroxycinnamate (4-CIN; 2 micro L, 0.1-10 mm) or p-(dipropylsulphamoyl)benzoic acid (probenecid; 1-10 mm). Changes in retinal function were compared with quantitative amino acid immunocytochemical changes in retinas harvested 20 and 40 min after either 4-CIN or vehicle treatment. The injection of 4-CIN resulted in a dose-dependent reduction of the ON-bipolar cell P2 wave amplitude (20-80%) and delay in its implicit time. The phototransduction sensitivity was mildly reduced whereas the ON-bipolar cell P2 sensitivity was unaffected. Probenecid induced functional changes similar to those observed with 4-CIN. We also mapped the amino acid alterations within specific cell classes induced by 4-CIN application. All neurones displayed a reduced glutamate content averaging 48%; reduced GABA (31%) and glycine (28%) were found within amacrine cells and glutamine was reduced in all cell classes except photoreceptor and Müller cells. All cell classes in the retina demonstrated increases in aspartate (57%), whereas leucine (24%) and ornithine (21%) were only significantly increased in photoreceptor and bipolar cells. The reduction in glutamate immunolabelling in specific retinal cell classes was mirrored by an increase in aspartate levels at these locations. In addition, attenuated glutamine immunolabelling also closely matched the spatial pattern observed for glutamate. Our immunocytochemical analysis provides evidence that monocarboxylate transport inhibition induces a shift in the equilibrium of glutamate transamination reactions involving aspartate throughout the retina whereas photoreceptor and bipolar cells also use glutamate transamination reactions involving ornithine and leucine. The distribution pattern of glutamine secondary to monocarboxylate inhibition suggests that this amino acid is a major precursor for glutamate throughout the retina.
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Affiliation(s)
- Bang V Bui
- Department of Optometry and Vision Sciences, University of Melbourne, Victoria, Australia
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