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Sabbaghi H, Behbahani S, Daftarian N, Ahmadieh H. New criteria for evaluation of electroretinogram in patients with retinitis pigmentosa. Doc Ophthalmol 2021; 143:271-281. [PMID: 34191198 DOI: 10.1007/s10633-021-09843-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/25/2020] [Accepted: 05/21/2021] [Indexed: 12/01/2022]
Abstract
BACKGROUND Electroretinogram (ERG) plays an essential role in the diagnosis of retinal disease. Choosing appropriate methods could extract valuable information from ERG. In this study, a new criterion based on time-frequency domain analysis was proposed to investigate the retina in retinitis pigmentosa (RP) patients. MATERIALS AND METHODS The total number of 16 eyes from eight RP patients and 20 eyes from age-matched healthy subjects were assessed. The signals included photopic and scotopic ERGs. Continuous wavelet transform was applied to ERGs. Dominant frequencies were extracted, and the contours related to these dominant frequencies were selected. As a new criterion, the areas related to dominant frequency contours were considered a feature to differentiate the RP and normal groups. To better evaluate the proposed criterion results, the time-domain analysis characteristics of ERG were also considered. RESULTS The results showed an increase in implicit time and reduced amplitude in RP patients (P < 0.05). A significant decrease of dominant frequencies and increasing their occurrence time were seen in ERG of RP patients. Also, in RP patients, the third dominant frequency was disappeared from the three main frequencies observed in photopic ERGs of normal subjects. The area criterion showed a significant decrease in RP groups (P < 0.05). CONCLUSION RP can cause changes in the time and time-frequency components of the ERG. The area index could represent a new view of the characteristics of the ERG in the time-frequency domain. This criterion can help the ophthalmologist to have a better evaluation of retinal disease.
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Affiliation(s)
- Hamideh Sabbaghi
- Ophthalmic Epidemiology Research Center, Research Institute for Ophthalmology and Vision Science, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Soroor Behbahani
- Department of Biomedical Engineering, South Tehran Branch, Islamic Azad University, Tehran, Iran.
| | - Narsis Daftarian
- Ocular Tissue Engineering Research Center, Research Institute for Ophthalmology and Vision Science, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Hamid Ahmadieh
- Ophthalmic Research Center, Research Institute for Ophthalmology and Vision Science, Shahid Beheshti University of Medical Sciences, Tehran, Iran
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2
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Minnella AM, Barbano L, Verrecchia E, Martelli F, Pagliei V, Gambini G, Placidi G, Falsini B, Caporossi A, Manna R. Macular Impairment in Fabry Disease: A Morpho-functional Assessment by Swept-Source OCT Angiography and Focal Electroretinography. Invest Ophthalmol Vis Sci 2019; 60:2667-2675. [PMID: 31242288 DOI: 10.1167/iovs.18-26052] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Purpose Fabry disease (FD) is a multiorgan X-linked condition characterized by a deficiency of the lysosomal enzyme alpha-galactosidase A, resulting in a progressive intralysosomal deposit of globotriaosylceramide. The aim of this study was to evaluate the macular ultrastructure of the vascular network using optical coherence tomography angiography (OCTA) and to evaluate macular function using focal electroretinography (fERG) in Fabry patients (FPs). Methods A total of 20 FPs (38 eyes, mean age 57 ± 2.12 SD, range of 27-80 years) and 17 healthy controls (27 eyes, mean age 45 years ± 20.50 SD, range of 24-65 years) were enrolled in the study. Color fundus photography, swept-source optical coherence tomography (SS-OCT), OCTA and fERG were performed in all subjects. The OCTA foveal avascular zone (FAZ), vasculature structure, superficial and deep retinal plexus densities (images of 4.5 × 4.5 mm) and fERG amplitudes were measured. Group differences were statistically assessed by Student's t-test and ANOVA. Results In the FP group, the FAZ areas of the superficial and deep plexuses were enlarged (P = 0.036, t = 2.138; P < 0.001, t = -3.889, respectively), the vessel density was increased in the superficial plexus, and the fERG amplitude was reduced (P < 0.001, t = -10.647) compared with those in healthy controls. No significant correlations were found between the structural and functional data. Conclusions OCTA vascular abnormalities and reduced fERG amplitudes indicate subclinical signs of microangiopathy with early retinal dysfunction in FPs. This study highlights the relevance of OCTA imaging analysis in the identification of abnormal macular vasculature as an ocular hallmark of FD.
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Affiliation(s)
- Angelo Maria Minnella
- Institute of Ophthalmology, Università Cattolica del S. Cuore, Rome, Italy.,Fondazione Policlinico Universitario A. Gemelli IRCCS, Rome, Italy
| | | | - Elena Verrecchia
- Periodic Fever and Rare Diseases Research Centre, Università Cattolica del S. Cuore, Fondazione Policlinico Universitario A. Gemelli IRCCS, Rome, Italy
| | - Francesco Martelli
- Department of Cardiovascular, Dysmetabolic and Aging-associated Diseases, National Institute of Health, Rome, Italy
| | - Valeria Pagliei
- Institute of Ophthalmology, Università Cattolica del S. Cuore, Rome, Italy
| | - Gloria Gambini
- Institute of Ophthalmology, Università Cattolica del S. Cuore, Rome, Italy
| | - Giorgio Placidi
- Institute of Ophthalmology, Università Cattolica del S. Cuore, Rome, Italy
| | - Benedetto Falsini
- Institute of Ophthalmology, Università Cattolica del S. Cuore, Rome, Italy.,Fondazione Policlinico Universitario A. Gemelli IRCCS, Rome, Italy
| | - Aldo Caporossi
- Institute of Ophthalmology, Università Cattolica del S. Cuore, Rome, Italy.,Fondazione Policlinico Universitario A. Gemelli IRCCS, Rome, Italy
| | - Raffaele Manna
- Periodic Fever and Rare Diseases Research Centre, Università Cattolica del S. Cuore, Fondazione Policlinico Universitario A. Gemelli IRCCS, Rome, Italy
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3
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Lunghi C, Galli-Resta L, Binda P, Cicchini GM, Placidi G, Falsini B, Morrone MC. Visual Cortical Plasticity in Retinitis Pigmentosa. Invest Ophthalmol Vis Sci 2019; 60:2753-2763. [PMID: 31247082 PMCID: PMC6746622 DOI: 10.1167/iovs.18-25750] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Purpose Retinitis pigmentosa is a family of genetic diseases inducing progressive photoreceptor degeneration. There is no cure for retinitis pigmentosa, but prospective therapeutic strategies are aimed at restoring or substituting retinal input. Yet, it is unclear whether the visual cortex of retinitis pigmentosa patients retains plasticity to react to the restored visual input. Methods To investigate short-term visual cortical plasticity in retinitis pigmentosa, we tested the effect of short-term (2 hours) monocular deprivation on sensory ocular dominance (measured with binocular rivalry) in a group of 14 patients diagnosed with retinitis pigmentosa with a central visual field sparing greater than 20° in diameter. Results After deprivation most patients showed a perceptual shift in ocular dominance in favor of the deprived eye (P < 0.001), as did control subjects, indicating a level of visual cortical plasticity in the normal range. The deprivation effect correlated negatively with visual acuity (r = −0.63, P = 0.015), and with the amplitude of the central 18° focal electroretinogram (r = −0.68, P = 0.015) of the deprived eye, revealing that in retinitis pigmentosa stronger visual impairment is associated with higher plasticity. Conclusions Our results provide a new tool to assess the ability of retinitis pigmentosa patients to adapt to altered visual inputs, and suggest that in retinitis pigmentosa the adult brain has sufficient short-term plasticity to benefit from prospective therapies.
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Affiliation(s)
- Claudia Lunghi
- Laboratoire des systèmes perceptifs, Département d'études Cognitives, École Normale Supérieure, PSL University, CNRS, Paris, France.,Department of Translational Research and New Technologies in Medicine and Surgery, University of Pisa, Pisa, Italy
| | | | - Paola Binda
- Department of Translational Research and New Technologies in Medicine and Surgery, University of Pisa, Pisa, Italy.,Institute of Neuroscience CNR, Pisa, Italy
| | | | - Giorgio Placidi
- Department of Ophthalmology, Policlinico Gemelli, Università Cattolica del Sacro Cuore, Rome, Italy
| | - Benedetto Falsini
- Department of Ophthalmology, Policlinico Gemelli, Università Cattolica del Sacro Cuore, Rome, Italy
| | - Maria Concetta Morrone
- Department of Translational Research and New Technologies in Medicine and Surgery, University of Pisa, Pisa, Italy.,IRCCS Stella Maris, Calambrone (Pisa), Italy
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4
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Galli-Resta L, Placidi G, Campagna F, Ziccardi L, Piccardi M, Minnella A, Abed E, Iovine S, Maltese P, Bertelli M, Falsini B. Central Retina Functional Damage in Usher Syndrome Type 2: 22 Years of Focal Macular ERG Analysis in a Patient Population From Central and Southern Italy. Invest Ophthalmol Vis Sci 2019; 59:3827-3835. [PMID: 30073356 DOI: 10.1167/iovs.17-23703] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Purpose Recent studies show that patients with Usher syndrome type 2 (USH2) have abnormal cone structure and density in the central retina. This occurs in the presence of normal acuity, opening the quest for additional sensitive functional measures of central cone function in USH. We tested here whether focal macular cone electroretinogram (fERG) could be such a tool. Methods This retrospective study of central cone function loss was based on data from 47 patients with USH2 from the Ophthalmology Department of the Policlinico Gemelli/Catholic University in Rome. The analysis focused on the decrease of the fERG, obtained in response to a 41-Hz sinusoidal modulation of a uniform field presented to the central 18°, generated by red light-emitting diodes (LEDs) and superimposed on an equiluminant steady adapting background. fERG decrease was compared with the decrease of best-corrected visual acuity and Goldmann kinetic perimetry V4E field. Results fERG follow-up data document a severe and precocious loss of central cone function in USH2 patients, preceding losses in other measures of cone function. fERG is already reduced to 40% of control at the beginning of the second decade of life, and by 25 years of age, all USH2 patients have fERGs less than 30% of control values. Conclusions fERG represents a sensitive tool to evaluate central cone function in USH2, anticipating the decline of other central cone function measures, such as visual acuity and Goldmann perimetry.
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Affiliation(s)
| | - Giorgio Placidi
- Department of Ophthalmology, Policlinico Gemelli, Università Cattolica del Sacro Cuore, Rome, Italy
| | - Francesca Campagna
- Department of Ophthalmology, Policlinico Gemelli, Università Cattolica del Sacro Cuore, Rome, Italy
| | | | - Marco Piccardi
- Department of Ophthalmology, Policlinico Gemelli, Università Cattolica del Sacro Cuore, Rome, Italy
| | - Angelo Minnella
- Department of Ophthalmology, Policlinico Gemelli, Università Cattolica del Sacro Cuore, Rome, Italy
| | - Edoardo Abed
- Department of Ophthalmology, Policlinico Gemelli, Università Cattolica del Sacro Cuore, Rome, Italy
| | - Silvia Iovine
- Department of Ophthalmology, Policlinico Gemelli, Università Cattolica del Sacro Cuore, Rome, Italy
| | - Paolo Maltese
- Medical Genetics Laboratory, MAGI Euregio SCS, Bolzano, Italy
| | - Matteo Bertelli
- Medical Genetics Laboratory, MAGI Euregio SCS, Bolzano, Italy
| | - Benedetto Falsini
- Department of Ophthalmology, Policlinico Gemelli, Università Cattolica del Sacro Cuore, Rome, Italy
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5
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Ebdali S, Hashemi B, Hashemi H, Jafarzadehpur E, Asgari S. Time and frequency components of ERG responses in retinitis pigmentosa. Int Ophthalmol 2017; 38:2435-2444. [PMID: 29189947 DOI: 10.1007/s10792-017-0748-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2017] [Accepted: 10/10/2017] [Indexed: 12/01/2022]
Abstract
PURPOSE To evaluate the effects of retinitis pigmentosa (RP) on time, frequency, and time-frequency components of Xenon flash ERG signals using Fourier and wavelet transforms. METHODS Xenon flash ERG was done in 18 eyes of nine RP patients and 20 normal eyes. After examining latency and amplitude, Fourier and wavelet transforms were performed using MATLAB software. Then, we extracted the mode frequency from the Fourier transform and main frequencies and their occurrence time from the wavelet transform. Finally, mean differences were analyzed using statistical tests. RESULTS The results indicated increased latency and reduced ERG wave amplitude, no significant inter-group difference in the average mode frequency, and significant reduction in main signal frequencies and their increased occurrence times. Also one or two of the three main frequencies had disappeared in more advanced cases. CONCLUSION Retinitis pigmentosa can induce changes in ERG time and time-frequency components. Impacted areas can be identified more accurately by wavelet transform and converting scales to frequencies.
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Affiliation(s)
- Samira Ebdali
- Medical Physics Department, Faculty of Medical Sciences, Tarbiat Modares University, Jalal Ale Ahmad Highway, P.O. Box: 14115-111, Tehran, Iran
| | - Bijan Hashemi
- Medical Physics Department, Faculty of Medical Sciences, Tarbiat Modares University, Jalal Ale Ahmad Highway, P.O. Box: 14115-111, Tehran, Iran.
| | - Hassan Hashemi
- Noor Ophthalmology Research Center, Noor Eye Hospital, Tehran, Iran
| | | | - Soheila Asgari
- Department of Epidemiology and Biostatistics, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran
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6
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Todorova MG, Türksever C, Schötzau A, Schorderet DF, Valmaggia C. Metabolic and functional changes in retinitis pigmentosa: comparing retinal vessel oximetry to full-field electroretinography, electrooculogram and multifocal electroretinography. Acta Ophthalmol 2016; 94:e231-41. [PMID: 26490228 DOI: 10.1111/aos.12846] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2015] [Accepted: 08/03/2015] [Indexed: 11/30/2022]
Abstract
PURPOSE To determine a relationship between the retinal vessel saturation alterations and the residual retinal function measured by means of full-field electroretinography (full-field ERG), electrooculogram (EOG) and multifocal electroretinography (mfERG) in patients with retinitis pigmentosa (RP). METHODS Retinal vessel oximetry (RO), full-field ERG, EOG and mfERG were performed on 43 eyes of 22 patients suffering from RP and were compared to those of 26 eyes of 13 healthy controls. The oxygen saturation in the first and second branch retinal arterioles (A-SO2 ) and venules (V-SO2 ) was measured, and their difference (A-V SO2 ) was calculated. Full-field ERG amplitudes, EOG parameters and averaged mfERG response amplitudes (within central 3°, between 3° and 8°, 8° and 15°, 15° and 24°) were evaluated in relation to the RO measurements. RESULTS V-SO2 correlated negatively with the full-field ERG and EOG values, with increasing functional damage the V-SO2 was higher. The RP group was well distinguished from the controls when the RO measurements were correlated to the averaged N1 (baseline to trough), but also to the N1P1 (trough-to-peak) mfERG response amplitudes. Receiver operating characteristic (ROC) curve of V-SO2 , compared to those of N1 and N1P1 mfERG response averages (15-24°), presented a high differential margin between RP and controls (p < 0.001), shown by an area under the ROC curve of 0.912 (95% CI: 0.840-0.984). CONCLUSION Retinal vessel saturation showed a significant relation to full-field ERG, EOG and mfERG. Thus, retinal vessel oximetry could potentially complement electrophysiological tests in monitoring disease progression in patients with RP.
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Affiliation(s)
| | - Cengiz Türksever
- Department of Ophthalmology; University of Basel; Basel Switzerland
| | - Andreas Schötzau
- Department of Ophthalmology; University of Basel; Basel Switzerland
| | - Daniel F. Schorderet
- IRO- Institute for Research in Ophthalmology; Sion Switzerland
- Department of Ophthalmology; University of Lausanne; Lausanne Switzerland
- School of Life Sciences; Federal Institute of Technology; Lausanne Switzerland
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7
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Falsini B, Iarossi G, Chiaretti A, Ruggiero A, Manni L, Luigi M, Galli-Resta L, Corbo G, Abed E. NGF eye-drops topical administration in patients with retinitis pigmentosa, a pilot study. J Transl Med 2016; 14:8. [PMID: 26748988 PMCID: PMC4707001 DOI: 10.1186/s12967-015-0750-3] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2015] [Accepted: 12/07/2015] [Indexed: 11/17/2022] Open
Abstract
Background
Preclinical trials have shown beneficial effects of nerve growth factor (NGF) administration on visual function in animal models of retinitis pigmentosa (RP). The aim of this pilot study was to explore the potential efficacy of short term NGF eye drops treatment in patients affected by RP. Methods
The trial consisted in 10 days daily administration of murine NGF as eye-drops for a total dose of 1 mg NGF/pt. Eight RP patients at an advanced stage of the disease were included in the trial. To monitor safety and potential adverse effects subjects underwent standard clinical measures and were requested to report any general or topic alterations following NGF assumption. Retinal function was assessed at baseline and after treatment by best-corrected visual acuity measurement (BCVA), macular focal electroretinogram (fERG) recording and Goldmann visual field testing. Results A transient tolerable local corneal irritation was the only adverse effect reported. fERG and BCVA remained within the limits determined by test–retest analysis of a large cohort of RP patients. Three patients reported a subjective feeling of improved visual performance. This was associated to a temporary enlargement of the visual field in all three patients and to improved fERG in two of the three. Conclusions Short-term administration of NGF eye-drops caused neither significant adverse effects nor visual function losses in the tested RP patients. A minority of patients experienced an improvement of visual performance as shown by Goldmann visual field and fERG. This study supports the safety and possible efficacy of NGF eye-drops administration in RP patients. Trial registration: EudraCT n. 2008-004561-26
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Affiliation(s)
- Benedetto Falsini
- Institute of Ophthalmology, Policlinico Gemelli, Catholic University of Sacro Cuore, Rome, Italy.
| | - Giancarlo Iarossi
- Ophthalmology Department, Ospedale "Bambin Gesù", 00165, Rome, Italy.
| | - Antonio Chiaretti
- Institute of Pediatrics, Policlinico Gernelli, Catholic University, Rome, Italy.
| | - Antonio Ruggiero
- Institute of Pediatrics, Policlinico Gernelli, Catholic University, Rome, Italy.
| | - Luigi Manni
- Institute of Translational Pharmacology, CNR, Rome, Italy.
| | | | | | - Giovanni Corbo
- Institute of Ophthalmology, Policlinico Gemelli, Catholic University of Sacro Cuore, Rome, Italy.
| | - Edoardo Abed
- Institute of Ophthalmology, Policlinico Gemelli, Catholic University of Sacro Cuore, Rome, Italy.
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8
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Lopez Torres LT, Türksever C, Schötzau A, Orgül S, Todorova MG. Peripapillary retinal vessel diameter correlates with mfERG alterations in retinitis pigmentosa. Acta Ophthalmol 2015; 93:e527-33. [PMID: 25809154 DOI: 10.1111/aos.12707] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2014] [Accepted: 02/06/2015] [Indexed: 12/25/2022]
Abstract
PURPOSE To investigate relationship between the peripapillary retinal vessel diameter and the residual retinal function, measured by mfERG, in patients with retinitis pigmentosa (RP). PATIENTS AND METHODS A cross-sectional study based on 23 patients with RP (43 eyes) and 20 controls (40 eyes) was performed. Retinal vessel diameters were measured using a computer-based program of the retinal vessel analyser (RVA; IMEDOS Systems UG, Jena, Germany). We evaluated the mean diameter in all four major retinal arterioles (D-A) and venules (D-V) within 1.0-1.5 optic disc diameters from the disc margin. The data were compared with the N1 amplitudes (measured from the baseline to the trough of the first negative wave), with the N1P1 amplitudes (measured from the trough of the first negative wave to the peak of the first positive wave) of the mfERG overall response and with the mfERG responses averaged in zones [zone 1 (0°-3°), zone 2 (3°-8°), zone 3 (8°-15°) and zone 4 (15°-24°)]. RESULTS Mean (±SD) D-A and D-V were narrower in patients with RP [84.86 μm (±13.37 μm) and 103.35 μm (±13.65 μm), respectively] when compared to controls [92.81 μm (±11.49 μm) and 117.67 μm (±11.93 μm), respectively; the p-values between groups were p = 0.003 for D-A and p < 0.001 for D-V, linear mixed-effects model]. The RP group revealed clear differences compared to the controls: D-A and D-V became narrower with reduced mfERG responses. D-V correlated significantly with the overall mfERG N1 amplitudes (p = 0.013) and with N1P1 amplitudes (p = 0.016). D-V correlated with the mfERG amplitudes averaged in zones: (zone 2, 3 and 4; p ≤ 0.040) and N1P1 mfERG amplitudes (zones 1, 2, 3 and 4; p ≤ 0.013). CONCLUSIONS Peripapillary retinal vessel diameter is reduced in RP proportionally to functional alterations.
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Affiliation(s)
| | - Cengiz Türksever
- Department of Ophthalmology; University of Basel; Basel Switzerland
| | - Andreas Schötzau
- Department of Ophthalmology; University of Basel; Basel Switzerland
| | - Selim Orgül
- Department of Ophthalmology; University of Basel; Basel Switzerland
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9
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A new interpretation of components in the ERG signals to sine wave luminance stimuli at different temporal frequencies and contrasts. Vis Neurosci 2010; 27:79-90. [DOI: 10.1017/s0952523810000179] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
AbstractFull-field electroretinograms were recorded from five normal human subjects using white light (mean luminance: 250 cd/m2) sine wave stimuli at different frequencies and contrasts. In agreement with previous studies, we found that the amplitude of the fundamental component displayed a dip at about 12 Hz, coinciding with a maximum in the second harmonic component, indicating frequency doubling of the responses. By including measurements at different contrasts, we were able to recognize two (sine-like and transient) response components. We found that the waveform of the transient response was relatively frequency independent. An algorithm to separate the two components was developed. The interaction between these two components can explain the frequency-doubled responses around 12 Hz. The sine-like component is more linear and prominent in the low-frequency region, whereas the transient seems to be more nonlinear and prominent in the high-frequency region.
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10
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Riva CE, Logean E, Falsini B. Visually evoked hemodynamical response and assessment of neurovascular coupling in the optic nerve and retina. Prog Retin Eye Res 2005; 24:183-215. [PMID: 15610973 DOI: 10.1016/j.preteyeres.2004.07.002] [Citation(s) in RCA: 181] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The retina and optic nerve are both optically accessible parts of the central nervous system. They represent, therefore, highly valuable tissues for studies of the intrinsic physiological mechanism postulated more than 100 years ago by Roy and Sherrington, by which neural activity is coupled to blood flow and metabolism. This article describes a series of animal and human studies that explored the changes in hemodynamics and oxygenation in the retina and optic nerve in response to increased neural activity, as well as the mechanisms underlying these changes. It starts with a brief review of techniques used to assess changes in neural activity, hemodynamics, metabolism and tissue concentration of various potential mediators and modulators of the coupling. We then review: (a) the characteristics of the flicker-induced hemodynamical response in different regions of the eye, starting with the optic nerve, the region predominantly studied; (b) the effect of varying the stimulus parameters, such as modulation depth, frequency, luminance, color ratio, area of stimulation, site of measurement and others, on this response; (c) data on activity-induced intrinsic reflectance and functional magnetic resonance imaging signals from the optic nerve and retina. The data undeniably demonstrate that visual stimulation is a powerful modulator of retinal and optic nerve blood flow. Exploring the relationship between vasoactivity and metabolic changes on one side and corresponding neural activity changes on the other confirms the existence of a neurovascular/neurometabolic coupling in the neural tissue of the eye fundus and reveals that the mechanism underlying this coupling is complex and multi-factorial. The importance of fully exploiting the potential of the activity-induced vascular changes in the assessment of the pathophysiology of ocular diseases motivated studies aimed at identifying potential mediators and modulators of the functional hyperemia, as well as conditions susceptible to alter this physiological response. Altered hemodynamical responses to flicker were indeed observed during a number of physiological and pharmacological interventions and in a number of clinical conditions, such as essential systemic hypertension, diabetes, ocular hypertension and early open-angle glaucoma. The article concludes with a discussion of key questions that remain to be elucidated to increase our understanding of the physiology of ocular functional hyperemia and establish the importance of assessing the neurovascular coupling in the diagnosis and management of optic nerve and retinal diseases.
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Affiliation(s)
- Charles E Riva
- Institut de Recherche en Ophtalmologie, 1950 Sion, Switzerland.
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11
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Strettoi E, Pignatelli V, Rossi C, Porciatti V, Falsini B. Remodeling of second-order neurons in the retina of rd/rd mutant mice. Vision Res 2003; 43:867-77. [PMID: 12668056 DOI: 10.1016/s0042-6989(02)00594-1] [Citation(s) in RCA: 163] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
This is a brief review of data obtained by analyzing the morphology and the physiology of the retinas in rd/rd and normal, wt mice, aged 10-90 days. Second-order neurons of the rd/rd show abnormalities that start with the anomalous development of rod bipolar cells around P10 and culminate with the atrophy of dendrites in cone bipolar cells, mostly evident at P90. Horizontal cells remodel considerably. Cone-mediated ERGs, (recorded between 13 and 16 days of age) have reduced a-wave and b-wave amplitudes and longer b-wave latency and duration. B-wave abnormalities indicate specific postreceptoral dysfunction. Morphological and ERG changes in rd/rd retinas are consistent with substantial inner retinal remodeling associated to photoreceptor degeneration.
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Affiliation(s)
- Enrica Strettoi
- Laboratorio di Neurofisiologia, Istituto di Neuroscienze del CNR, Area della Ricerca, Via G. Moruzzi 1, 56100, Pisa, Italy.
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12
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Khan NW, Jamison JA, Kemp JA, Sieving PA. Analysis of photoreceptor function and inner retinal activity in juvenile X-linked retinoschisis. Vision Res 2001; 41:3931-42. [PMID: 11738458 DOI: 10.1016/s0042-6989(01)00188-2] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Thirteen retinoschisis males with genotyped XLRS1 gene mutations were examined by electroretinogram (ERG) techniques to determine photoreceptor involvement and ON-pathway and OFF-pathway sites of dysfunction. Parameters R(max) and logS determined by fitting the mathematical model of the activation phase of phototransduction to the scotopic and photopic a-wave responses, were not significantly different from normal. However, the XLRS photopic a-wave amplitudes were significantly lower than normal across all intensities, consistent with defective signaling in the OFF pathway. Long flash (150 ms) ON-OFF photopic responses showed reduced b-wave amplitude but normal d-wave amplitude, giving a reduced b/d ratio of <1.32 Hz photopic flicker ERG fundamental frequency responses showed reduced amplitude and delayed phase, consistent with abnormal signaling by both the ON- and OFF-pathway components. These results indicate that the XLRS1 protein appears not to affect photoreceptor function directly for most XLRS males, and that ERG signaling abnormalities occur in both the ON- and OFF-pathway components that originate in the proximal retina.
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Affiliation(s)
- N W Khan
- Department of Ophthalmology and Visual Sciences, W. K. Kellogg Eye Center, University of Michigan, 1000 Wall Street, Ann Arbor, MI 48105, USA
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13
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Abstract
Within the retina, the Müller cells and photoreceptors are in close physical proximity and are metabolically coupled. It is unknown, however, whether Müller cells affect photoreceptor differentiation and outer segment membrane assembly. The objective of this study was to determine whether targeted disruption of Müller cell metabolism would induce photoreceptor dysmorphogenesis. Intact isolated Xenopus laevis embryonic eyes were cultured in medium with or without Müller cell-specific inhibitors (i.e., alpha-aminoadipic acid and fluorocitrate). To assess Müller cell injury, the gross retinal morphology was examined along with immunocytochemical assessment of Müller cell-specific protein expression patterns. The steady-state levels of opsin were quantified to determine whether the Müller cell inhibitors negatively affected photoreceptor protein synthesis. Müller and photoreceptor cell ultrastructure was scrutinized and the organization of the outer segment membranes was graded. In control retinas, there was no swelling of Müller cell cytoplasm. Glial fibrillary acidic protein (GFAP) was undetectable, whereas glutamine synthetase was abundant. The steady-state level of opsin was high and photoreceptors elaborated properly folded outer segments. Exposure to both Müller cell-specific inhibitors induced swelling of Müller cell endfeet, cytoplasmic paling and alterations of Müller cell-specific protein expression patterns. The steady-state level of opsin in retinas exposed to alpha-aminoadipic acid was unchanged compared with control eyes, whereas, in eyes exposed to fluorocitrate, opsin levels were slightly reduced. The most significant finding was that targeted disruption of Müller cell metabolism adversely affected photoreceptor outer segment membrane assembly, causing dysmorphogenesis of nascent outer segments. These results suggest that the termination signal(s) necessary for proper outer segment folding were disrupted by targeted inhibition of Müller cells and support the hypothesis that Müller cells interact with photoreceptors through mechanisms that may regulate, at least in part, the assembly of photoreceptor outer segment membranes.
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Affiliation(s)
- M M Jablonski
- Retinal Degeneration Research Center, Department of Ophthalmology, University of Tennessee, Memphis, Tennessee 38163, USA.
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