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Affiliation(s)
| | - Algis J Vingrys
- *Department of Optometry and Vision Sciences, The University of Melbourne
| | - Andrew J Sinclair
- †Department of Food Science, Royal Melbourne Institute of Technology
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Affiliation(s)
| | - Lgis J Vingrys
- *Department of Optometry and Vision Sciences, The University of Melbourne
| | - Andrew J Sinclair
- †Department of Food Science, Royal Melbourne Institute of Technology
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Young WM, Oh A, Williams JG, Foster ML, Miller WW, Lunn KF, Mowat FM. Clinical therapeutic efficacy of mycophenolate mofetil in the treatment of SARDS in dogs-a prospective open-label pilot study. Vet Ophthalmol 2018; 21:565-576. [DOI: 10.1111/vop.12545] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- Whitney M. Young
- Department of Clinical Sciences; North Carolina State University College of Veterinary Medicine; Raleigh NC USA
| | - Annie Oh
- Department of Clinical Sciences; North Carolina State University College of Veterinary Medicine; Raleigh NC USA
| | - Jonathan G. Williams
- Department of Clinical Sciences; North Carolina State University College of Veterinary Medicine; Raleigh NC USA
| | - Melanie L. Foster
- Department of Clinical Sciences; North Carolina State University College of Veterinary Medicine; Raleigh NC USA
| | | | - Katharine F. Lunn
- Department of Clinical Sciences; North Carolina State University College of Veterinary Medicine; Raleigh NC USA
| | - Freya M. Mowat
- Department of Clinical Sciences; North Carolina State University College of Veterinary Medicine; Raleigh NC USA
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Wong VH, Armitage JA, He Z, Hui F, Vingrys AJ, Bui BV. Chronic intraocular pressure elevation impairs autoregulatory capacity in streptozotocin-induced diabetic rat retina. Ophthalmic Physiol Opt 2014; 35:125-34. [PMID: 25529024 DOI: 10.1111/opo.12174] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2014] [Accepted: 10/23/2014] [Indexed: 02/03/2023]
Abstract
PURPOSE To assess ocular blood flow responses to acute IOP stress following 4 weeks of chronic IOP elevation in streptozotocin (STZ)-induced diabetic and control rats. We hypothesise that chronic IOP elevation for 4 weeks will further impair blood flow regulation in STZ-induced diabetic rats eyes. METHODS Two weeks following citrate buffer or STZ-injections chronic IOP elevation was induced in Long Evans rats via fortnightly intracameral injections of microspheres (15 μm) suspended in 5% polyethylene glycol. IOP was monitored daily. Electroretinography (ERG, -6.79-2.07 log cd s m(-2) ) was undertaken at Week 4 to compare photoreceptor (RmPIII ), ON-bipolar cell (Vmax ) and ganglion cell dominant ERG [scotopic threshold response (STR)] components. 4 weeks post-chronic IOP induction, ocular blood flow (laser Doppler flowmetry) was measured in response to acute IOP challenge (10-100 mmHg, in 5 mmHg steps, each 3 min). RESULTS Four weeks of chronic IOP (mean ± S.E.M., citrate: 24.0 ± 0.3 to 30.7 ± 1.3 and STZ-diabetes: 24.2 ± 0.2 to 31.1 ± 1.2 mmHg) was associated with reduced photoreceptor amplitude in both groups (-25.3 ± 2.2% and -17.2 ± 3.0%, respectively). STZ-diabetic eyes showed reduced photoreceptor sensitivity (citrate: 0.5 ± 1.8%, STZ-diabetic: -8.1 ± 2.4%). Paradoxically ON-bipolar cell sensitivity was increased, particularly in citrate control eyes (citrate: 166.8 ± 25.9%, STZ-diabetic: 64.8 ± 18.7%). The ganglion cell dominant STR was not significantly reduced in STZ-diabetic rats. Using acute IOP elevation to probe autoregulation, we show that STZ-diabetes impaired autoregulation compared with citrate control animals. The combination of STZ-diabetes and chronic IOP elevation further impaired autoregulation. CONCLUSIONS STZ-diabetes and chronic IOP elevation appear to be additive risk factors for impairment of ocular blood flow autoregulation.
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Affiliation(s)
- Vickie H Wong
- Department of Optometry and Vision Sciences, University of Melbourne, Melbourne, Australia
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Germain F, Istillarte M, Gómez-Vicente V, Pérez-Rico C, de la Villa P. Electroretinographical and histological study of mouse retina after optic nerve section: a comparison between wild-type and retinal degeneration 1 mice. Clin Exp Ophthalmol 2013; 41:593-602. [DOI: 10.1111/ceo.12046] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2012] [Accepted: 11/11/2012] [Indexed: 11/28/2022]
Affiliation(s)
- Francisco Germain
- Departamento de Fisiología; Facultad de Medicina; Universidad de Alcalá; Madrid; Spain
| | - Mirna Istillarte
- Departamento de Fisiología; Facultad de Medicina; Universidad de Alcalá; Madrid; Spain
| | - Violeta Gómez-Vicente
- Departamento de Medicina Celular y Molecular; 3D Lab, Desarrollo; Diferenciación y Degeneración; Centro de Investigaciones Biológicas; CSIC; Madrid; Spain
| | - Consuelo Pérez-Rico
- Servicio de Oftalmología; Hospital Príncipe de Asturias; Alcalá de Henares; Spain
| | - Pedro de la Villa
- Departamento de Fisiología; Facultad de Medicina; Universidad de Alcalá; Madrid; Spain
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Probing potassium channel function in vivo by intracellular delivery of antibodies in a rat model of retinal neurodegeneration. Proc Natl Acad Sci U S A 2010; 107:12710-5. [PMID: 20616020 DOI: 10.1073/pnas.0913472107] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Inward rectifying potassium (Kir) channels participate in regulating potassium concentration (K(+)) in the central nervous system (CNS), including in the retina. We explored the contribution of Kir channels to retinal function by delivering Kir antibodies (Kir-Abs) into the rat eye in vivo to interrupt channel activity. Kir-Abs were coupled to a peptide carrier to reach intracellular epitopes. Functional effects were evaluated by recording the scotopic threshold response (STR) and photopic negative response (PhNR) of the electroretinogram (ERG) noninvasively with an electrode on the cornea to determine activity of the rod and cone pathways, respectively. Intravitreal delivery of Kir2.1-Ab coupled to the peptide carrier diminished these ERG responses equivalent to dimming the stimulus 10- to 100-fold. Immunohistochemistry (IHC) showed Kir2.1 immunostaining of retinal bipolar cells (BCs) matching the labeling pattern obtained with conventional IHC of applying Kir2.1-Ab to fixed retinal sections postmortem. Whole-cell voltage-clamp BC recordings in rat acute retinal slices showed suppression of barium-sensitive Kir2.1 currents upon inclusion of Kir2.1-Ab in the patch pipette. The in vivo functional and structural results implicate a contribution of Kir2.1 channel activity in these electronegative ERG potentials. Studies with Kir4.1-Ab administered in vivo also suppressed the ERG components and showed immunostaining of Müller cells. The strategy of administering Kir antibodies in vivo, coupled to a peptide carrier to facilitate intracellular delivery, identifies roles for Kir2.1 and Kir4.1 in ERG components arising in the proximal retina and suggests this approach could be of further value in research.
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Gekeler F, Shinoda K, Blatsios G, Werner A, Zrenner E. Scotopic threshold responses to infrared irradiation in cats. Vision Res 2006; 46:357-64. [PMID: 16081127 DOI: 10.1016/j.visres.2005.06.023] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2005] [Revised: 05/06/2005] [Accepted: 06/20/2005] [Indexed: 11/15/2022]
Abstract
Infrared (IR) irradiation is frequently used in ophthalmological diagnosis and treatment. It has been used to selectively stimulate photodiode-based retinal prostheses to prove their function. Data concerning the natural IR-sensitivity of the retina are contradictory. In our experiments in dark-adapted cats an IR-laser (826 nm) and IR emitting diodes (875 nm) elicited clear scotopic threshold responses. Comparison of the two lasers (IR and a visible laser at 670 nm) using Lambs template and our experimental data revealed very similar differences in retinal sensitivity (4.28 and 3.94+/-0.29 log units, respectively). The fact that the cat retina is sensitive to IR-irradiation under certain conditions has important implications in interpreting the results from retinal prostheses and rewards further attention in its use in many ophthalmological applications.
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Affiliation(s)
- Florian Gekeler
- University-Eye-Hospital, Schleichstrasse 12-16, D-72076 Tübingen, Germany.
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Brzezinski JA, Brown NL, Tanikawa A, Bush RA, Sieving PA, Vitaterna MH, Takahashi JS, Glaser T. Loss of circadian photoentrainment and abnormal retinal electrophysiology in Math5 mutant mice. Invest Ophthalmol Vis Sci 2005; 46:2540-51. [PMID: 15980246 PMCID: PMC1570190 DOI: 10.1167/iovs.04-1123] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE To determine how the absence of retinal ganglion cells (RGCs) in Math5 (Atoh7) mutant mice affects circadian behavior and retinal function. METHODS The wheel-running behavior of wild-type and Math5 mutant mice was measured under various light-dark cycle conditions. To evaluate retinal input to the suprachiasmatic nuclei (SCN) anatomically, the retinohypothalamic tracts were labeled in vivo. To assess changes in retinal function, corneal flash electroretinograms (ERGs) from mutant and wild-type mice were compared under dark- and light-adapted conditions. Alterations in retinal neuron populations were evaluated quantitatively and with cell-type-specific markers. RESULTS The Math5-null mice did not entrain to light and exhibited free-running circadian behavior with a mean period (23.6 +/- 0.15 hours) that was indistinguishable from that of wild-type mice (23.4 +/- 0.19 hours). The SCN showed no anterograde labeling with a horseradish peroxidase-conjugated cholera toxin B (CT-HRP) tracer. ERGs recorded from mutant mice had diminished scotopic a- and b-wave and photopic b-wave amplitudes. The scotopic b-wave was more severely affected than the a-wave. The oscillatory potentials (OPs) and scotopic threshold response (STR) were also reduced. Consistent with these ERG findings, a pan-specific reduction in the number of bipolar cells and a smaller relative decrease in the number of rods in mutant mice were observed. CONCLUSIONS Math5-null mice are clock-blind and have no RGC projections to the SCN. RGCs are thus essential for photoentrainment in mice, but are not necessary for the development or intrinsic function of the SCN clock. RGCs are not required to generate any of the major ERG waveforms in mice, including the STR, which is produced by ganglion cells in some other species. The diminished amplitude of b-wave, OPs, and STR components in Math5 mutants is most likely caused by the decreased abundance of retinal interneurons.
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Affiliation(s)
- Joseph A. Brzezinski
- From the Departments of Human Genetics and
- Internal Medicine, University of Michigan, Ann Arbor, Michigan; the
| | - Nadean L. Brown
- Divisions of Developmental Biology and
- Ophthalmology, Children’s Hospital Research Foundation, Department of Pediatrics, University of Cincinnati Medical School, Cincinnati, Ohio
| | - Atsuhiro Tanikawa
- Section for Translational Research on Retinal and Macular Degeneration, National Institute on Deafness and Other Communication Disorders, Bethesda, Maryland
| | - Ronald A. Bush
- Section for Translational Research on Retinal and Macular Degeneration, National Institute on Deafness and Other Communication Disorders, Bethesda, Maryland
| | - Paul A. Sieving
- Section for Translational Research on Retinal and Macular Degeneration, National Institute on Deafness and Other Communication Disorders, Bethesda, Maryland
- National Eye Institute, Bethesda, Maryland
| | - Martha H. Vitaterna
- Center for Functional Genomics, Northwestern University, Evanston, Illinois; and the
| | - Joseph S. Takahashi
- Center for Functional Genomics, Northwestern University, Evanston, Illinois; and the
- Department of Neurobiology and Physiology, Howard Hughes Medical Institute, Northwestern University, Evanston, Illinois
| | - Tom Glaser
- From the Departments of Human Genetics and
- Internal Medicine, University of Michigan, Ann Arbor, Michigan; the
- Corresponding author: Tom Glaser, Departments of Internal Medicine and Human Genetics, The University of Michigan, 1150 W. Medical Center Drive, 4520 MSRB I Box 0651, Ann Arbor, MI 48109;
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Parisi P, Tommasini P, Piazza G, Manfredi M. Scotopic threshold response changes after vigabatrin therapy in a child without visual field defects: a new electroretinographic marker of early damage? Neurobiol Dis 2004; 15:573-9. [PMID: 15056465 DOI: 10.1016/j.nbd.2003.12.004] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2003] [Revised: 11/20/2003] [Accepted: 12/04/2003] [Indexed: 11/18/2022] Open
Abstract
Vigabatrin (VGB) has been widely used in patients affected by drug-resistant epilepsy and West syndrome. Following reports of visual field loss associated with vigabatrin therapy, some authors have investigated retinal electrophysiologic variables to identify early electrophysiologic markers and pathogenetic mechanisms of retinal damage. There are no previous reports of a scotopic threshold response (STR) reduction associated with vigabatrin therapy. A 13-year-old male child was submitted to a complete electroretinographic study before and after the start of vigabatrin therapy. Of the electroretinographic responses analyzed, only the scotopic threshold response was altered. The scotopic threshold response is a corneal-negative wave in the electroretinogram (ERG) of a fully dark-adapted eye. In cat, this response has been shown to be mediated by K+ spatial buffer currents that flow from proximal to distal retina in retinal glia as a result of elevated concentration of K+ in proximal retina following depolarization of local neurons in response to light onset. The prospective nature of the study in a previously untreated patient on vigabatrin monotherapy allows us to speculate on the underlying pathogenetic mechanisms and level of action of vigabatrin therapy-related retinal damage. If the predictive value of the scotopic threshold response changes is documented, this ERG response could be used to perform a preliminary evaluation of drugs, which modify gamma-aminobutyric acid (GABA) receptors and/or GABA levels.
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Affiliation(s)
- Pasquale Parisi
- Child Neurology, Department of Pediatrics, La Sapienza 2 University, c/o Sant'Andrea Hospital, Via di Grottarossa, 1035-1039 Rome, Italy.
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Abstract
The purpose of this study was to determine what contributions are made to the rat full-field electroretinogram (ERG) by ganglion cells (GCs). To that end, the ERG was assessed longitudinally following optic nerve transection (ONTx). Additional studies were conducted using intravitreal injections of pharmacologically active substances. The ERG was recorded simultaneously from both eyes of anaesthetized adult Brown-Norway rats (ketamine: xylazine: acepromazine, 55: 5: 1 mg kg(-1)) using custom silver chloride electrodes. Stimuli were brief, white xenon discharges delivered via a Ganzfeld under dark-adapted and light-adapted conditions (150 cd m(-2)). ERGs were obtained 1, 2, 3, 4 and 9 weeks after ONTx (n = 8) or sham (n = 8) operations. ONTx reduced both positive and negative components of the scotopic threshold response (pSTR and nSTR). Scotopic ERG responses to brighter flashes, including a-waves, b-waves and oscillatory potentials (OPs) were unaffected by ONTx. ONTx reduced the photopic b-wave and OPs. TTX (6 microM) reduced the pSTR and nSTR, but not the scotopic a-wave, b-wave or OPs. TTX had dramatic effects on the photopic ERG, surpassing the effects of ONTx. TTX application 9 weeks post-ONTx had little additional effect on the STR. Inhibition of inner retinal responses using GABA (10 mM) or NMDA (0.8 mM) reduced the nSTR substantially. Similar results were obtained with antagonists of AMPA/KA ionotropic glutamate receptors 6-cyano-7-nitroquinoxaline-2,3(1H,4H)-dione (CNQX, 0.2 mM) or cis-2,3-piperidinedicarboxylic acid (PDA, 5 mm); however, both also reduced the scotopic b-wave by approximately 40 %. By contrast, the NMDA receptor antagonist D(-)-2-amino-7-phosphonoheptanoic acid (D-AP7, 0.2 mM) had no effect alone, but the combination of D-AP7 and CNQX completely abolished the STR. The results of this study indicate that: (1) both pSTR and nSTR components in the rat depend directly upon intact GC responses, and that amacrine cell contributions to these components are relatively small; (2) scotopic ERG response components to brighter flashes receive little influence from GCs; (3) the rat photopic ERG also reflects GC signals and may serve as an additional useful test of GC function; (4) TTX had dramatic effects on the rat photopic ERG that were not attributable to GC currents, but rather to voltage-gated sodium currents in amacrine or interplexiform cells; (5) a small residual negative STR persisted after ONTx that was likely to be generated by graded responses of third-order retinal cells, most likely amacrine cells.
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Affiliation(s)
- Bang V Bui
- Discoveries in Sight, Legacy Clinical Research & Technology Centre, 1225 NE 2nd Avenue, Portland, OR 97232, USA
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Kremers J. The assessment of L- and M-cone specific electroretinographical signals in the normal and abnormal human retina. Prog Retin Eye Res 2003; 22:579-605. [PMID: 12892643 DOI: 10.1016/s1350-9462(03)00049-1] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Electroretinography (ERG) is a non-invasive method that can contribute to a description of the functional organization of the human retina under normal and pathological circumstances. The physiological and pathophysiological processes leading to an ERG signal can be better understood when the cellular origins of the ERG are identified. The ERG signal recorded at the cornea is initiated by light absorption in the photoreceptors which leads to activity in the photoreceptors and in their post-receptoral pathways. Light absorption in distinct photoreceptor types may lead to different ERG responses caused either by differences between the photoreceptors or between their post-receptoral pathways. The description of contributions of the different photoreceptor types to the ERG may therefore give more detailed insight in the origins of the ERG. Such a description can be obtained by isolating the responses of a single photoreceptor type. Nowadays, careful control of differently colored light sources together with the relatively well-known cone and rod fundamentals enables a precise description and control of photoreceptor excitation. Theoretically, any desired combination of photoreceptor excitation modulation can be achieved, including conditions in which the activity in only one photoreceptor type is modulated (silent substitution). In this manner the response of one photoreceptor type is isolated without changing the state of adaptation. This stimulus technique has been used to study the contribution of signals originating in the different photoreceptor types to the human ERG. Furthermore, by stimulating two or more photoreceptor types simultaneously, the interaction between the different signals can be studied. With these new techniques results of measurements in healthy subjects and patients with retinal diseases can be compared. This approach should ultimately help to develop better diagnostic tools and result in a fuller description of the changes and the pathophysiological mechanisms in retinal disorder. Finally, data obtained with cone and rod specific stimuli may lead to a reinterpretation of the standard ERG used in a clinical setting.
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Affiliation(s)
- Jan Kremers
- Department of Experimental Ophthalmology, University of Tübingen Eye Hospital, Röntgenweg 11, D-72076 Tübingen, Germany.
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Sugawara T, Sieving PA, Bush RA. Quantitative relationship of the scotopic and photopic ERG to photoreceptor cell loss in light damaged rats. Exp Eye Res 2000; 70:693-705. [PMID: 10870528 DOI: 10.1006/exer.2000.0842] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In order to use the ERG to track the effects of potential photoreceptor rescue treatments, we have compared retinal histology to the ERG in light damage. Male albino CD rats (40) were purchased at 7 weeks of age and reared in 50 lx cyclic light until 8 week old. They were exposed to a range of light intensities using white fluorescent light (1000, 1500, 2000, 2500 or 3000 lx) for 24 or 48 hr (n = 5 per group). Controls remained in dim cyclic light. Seven days after exposure, dark and light adapted ERGs were recorded from threshold up to 200 cd m-2 using 50 ms Ganzfeld white light stimuli. The STR, and scotopic and photopic b-wave thresholds and amplitudes were measured. After recording the ERG, the eyes were removed from the animals in each of the five 48 hr light exposed groups and control group for histological measurements. These included: (1) outer nuclear layer width in rod photoreceptor cell number (cell count) and micrometers, and (2) outer + inner segment layer width along the vertical meridian in the inferior retina. The product of cell count and outer + inner segment length was calculated. All histological measures showed a statistically significant linear relationship to light exposure intensity (P < 0.0001): r2 = 0.94 (cell count), 0.90 (outer nuclear layer width), 0.77 (outer + inner segment length). The log of the scotopic b-wave threshold and log amplitude showed a significant linear correlation to all histological parameters (P < 0.0001) and there was no significant difference between b-wave threshold and amplitude for any one of the histology measures used. However, overall, log b-wave threshold was significantly better correlated to histology P < 0.02. Only log b-wave amplitude showed a significant increase in variability in light damaged retinas (P < 0.02). The b-wave threshold intensity increased 0.33 log cd m-2 and the maximum amplitude decreased 0.23 log microV with each 10% decrease in cell number in the outer nuclear layer. The sensitivity of the scotopic threshold response, which originates from third order neurons, changed much more slowly with cell loss, than did the b-wave (P < 0.0005) and was well fit by a linear relationship to cell loss. The increase in photopic b-wave threshold was not significant for a cell loss of less than 70-80%. Neither the photopic or scotopic b-wave could be reliably recorded with more than 80% cell loss, but the scotopic threshold response remained. Both the scotopic and photopic ERG showed similar waveform changes near the threshold, including loss of the positive going b-wave and the predominance of a negative going response. Outer nuclear layer cell counts in this study showed the same relationship to log b-wave threshold elevation, as has been previously shown for whole retinal rhodopsin content in light damage, indicating that regional histology measurements can be good indicators of overall cell survival. Both the b-wave threshold and amplitude can be reliably used to track photoreceptor cell loss due to the damaging effects of constant light, but the scotopic threshold response may be more useful in severe damage.
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Affiliation(s)
- T Sugawara
- Kellogg Eye Center, University of Michigan, Ann Arbor 48105, USA
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Kommonen B, Kylmä T, Karhunen U, Dawson WW, Penn JS. Impaired retinal function in young labrador retriever dogs heterozygous for late onset rod-cone degeneration. Vision Res 1997; 37:365-70. [PMID: 9135869 DOI: 10.1016/s0042-6989(96)00123-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Xenon-flash d.c.-electroretinograms were recorded from dark adapted, rod-cone degenerate homozygote affected (n = 6), heterozygote carrier (n = 3) and control retinas (n = 4) at 3 and 4 months of age, starting at 0.6 log units below control PII threshold. One log unit higher stimuli were necessary to evoke PII in heterozygote and affected retinas compared to controls. Unique to the heterozygotes, double peaked PII responses that were evoked by -2 log relative units intensity stimulation were significantly (P = 0.028) lower in amplitude than those of controls. PII amplitudes of homozygotes were significantly (P = 0.005) lower in amplitude than those of controls at both ages examined in response to -2 and 0 log relative intensity stimulation. No differences were found in scotopic threshold response amplitudes or times to peak between the three groups. Homozygote affected PII times to peak were significantly (P = 0.005) shorter in relation to controls at -2 log units. Findings suggest that heterozygotes exhibit an impaired retinal function which can be demonstrated at 3 and 4 months in this mutant.
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Affiliation(s)
- B Kommonen
- Department of Clinical Sciences/Surgery, Faculty of Veterinary Medicine, University of Helsinki, Finland.
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14
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Graham SL, Goldberg I, Buckland L, Hollows FC. Flash and pattern electroretinogram changes with optic atrophy and glaucoma. Exp Eye Res 1995; 60:697-706. [PMID: 7641852 DOI: 10.1016/s0014-4835(05)80011-9] [Citation(s) in RCA: 56] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
We investigated recent reports that, contrary to common belief, glaucoma can affect flash as well as pattern electroretinograms. An extensive flash and pattern electroretinogram test protocol was used in a large sample of glaucoma patients and age-matched controls who were either visually normal or had other optic nerve diseases. All electroretinogram parameters were reduced and delayed in normal people > 55 years of age. The effect did not increase in later decades. In patients aged < or = 55 years, flash electroretinograms showed mild reductions and delays from optic atrophy alone. Glaucomatous ERG changes were larger and increased with disease severity. Pattern electroretinograms and oscillatory potentials were almost equally reduced in optic atrophy and all degrees of glaucoma. Mildly affected patients > 55 years of age had similar electroretinogram change to age-matched normals in most conditions. Advanced glaucoma patients showed similar differences from normal irrespective of age. This suggests that direct diagnostic application of these results to older patients will be difficult, that the ERG changes in glaucoma cannot be attributed simply to optic atrophy and that additional widespread outer retinal damage occurs in glaucoma.
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Frishman LJ, Sieving PA. Evidence for two sites of adaptation affecting the dark-adapted ERG of cats and primates. Vision Res 1995; 35:435-42. [PMID: 7892737 DOI: 10.1016/0042-6989(94)00165-i] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The present study compared the effects of full-field steady adapting backgrounds on the sensitivity of the scotopic threshold response (STR) of the dark-adapted ERG and scotopic PII (b-wave and d.c.-component) to Ganzfeld flashes in cats (n = 4), macaque monkeys (n = 2), and one human subject. In cats, the sensitivity of the STR was reduced by a factor of 2 by backgrounds that were 500 times weaker than backgrounds reducing PII; and for the primates, the STR was reduced by backgrounds almost 100 times weaker than those reducing PII. Since the STR is generated more proximally in the retina than PII, these results provide evidence for proximal and more distal retinal sites of postreceptoral light adaptation. A practical implication is that dim scattered room light can remove the STR from the ERG while hardly affecting PII.
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Affiliation(s)
- L J Frishman
- Department of Ophthalmology, University of Michigan, Ann Arbor 48109
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Zeumer C, Hanitzsch R, Mättig WU. The c-wave of the electroretinogram possesses a third component from the proximal retina. Vision Res 1994; 34:2673-8. [PMID: 7975304 DOI: 10.1016/0042-6989(94)90223-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
ERG and light-induced extracellular potassium ([K+]o) changes have been measured in isolated retinas of both Rana esculenta and Rana temporaria. The conditions of the preparations have been varied. Isolated frog retinas kept receptor side-upward in a moist chamber without perfusion showed the well-known slow PIII in the ERG. Retinas superfused from the receptor side, with O2 enrichment at their vitreal surface, however, exhibit a slow cornea-positive potential in the ERG. The slow ERG-potentials relate to different light-induced potassium changes in the proximal retina. There was a long lasting and larger proximal potassium increase in adequately maintained retinas but a smaller and shorter one in preparations lacking superfusion and oxygen. There was no significant difference between the size of potassium decrease around receptors of retinas superfused from their vitreal side and those superfused from receptor side. A reduction of slow PIII should therefore not be responsible for the slow cornea-positive potential. The long lasting and larger (by 59%) potassium increase in the proximal retina may counteract the potential in the Müller cells caused by the potassium decrease around receptors and thereby cancel slow PIII and generate a third component of the electroretinogram c-wave.
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Affiliation(s)
- C Zeumer
- Carl-Ludwig-Institute of Physiology, Leipzig, Germany
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Hood DC, Birch DG. A computational model of the amplitude and implicit time of the b-wave of the human ERG. Vis Neurosci 1992; 8:107-26. [PMID: 1558823 DOI: 10.1017/s0952523800009275] [Citation(s) in RCA: 119] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
To improve the usefulness of the ERG in identifying the sites and mechanisms of adaptation, development, and disease processes, a theoretical framework based upon Granit's analysis of the ERG was evaluated. The framework assumes that the ERG is the sum of two potentials, one, P3, generated by the receptors and the other, P2, generated by the cells of the INL. Hood and Birch (1990a, b) demonstrated that the leading edge of the a-wave can be quantitatively described by a model used to describe the response from single rod receptors. This model provides P3(t), a theoretical receptor response as a function of time, for any given flash intensity. The ERGs from normal observers and patients with retinal diseases were analyzed in this framework, first by deriving P2 by computer subtracting the predicted P3(t) responses. This analysis was successful and a computational model of the ERG was then derived. The model of P2(t) was constructed with linear filters and a static nonlinearity and using P3(t) as the input. The ERG for any given flash intensity is then P3(t) + P2(t). The model describes (1) the change both in implicit times and in trough-to-peak b-wave amplitudes with flash intensity for the normal, dark-adapted observers; and (2) the changes in b-wave implicit times and amplitudes for three patients with retinal diseases. Among the implications drawn from these analyses were as follows: (1) The fits of the Naka-Rushton equation to trough-to-peak b-wave amplitudes must be interpreted with great care. (2) When the INL is affected by retinal disease, the b-wave may be a very poor reflection of INL activity. (3) The implicit time of the b-wave can provide a measure of receptor sensitivity.
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Affiliation(s)
- D C Hood
- Department of Psychology, Columbia University, New York, NY 10027
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Steinberg RH, Frishman LJ, Sieving PA. Chapter 6 Negative components of the electroretinogram from proximal retina and photoreceptor. ACTA ACUST UNITED AC 1991. [DOI: 10.1016/0278-4327(91)90011-p] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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