The Experts below are selected from a list of 264 Experts worldwide ranked by ideXlab platform
Alfredo A Sadun - One of the best experts on this subject based on the ideXlab platform.
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early detection of glaucoma by means of a novel 3d computer automated visual field Test
British Journal of Ophthalmology, 2007Co-Authors: Paul P Nazemi, Alfredo A Sadun, Wolfgang Fink, Brian A Francis, Donald S. MincklerAbstract:Purpose: A recently devised 3D computer-automated threshold Amsler Grid Test was used to identify early and distinctive defects in people with suspected glaucoma. Further, the location, shape and depth of these field defects were characterised. Finally, the visual fields were compared with those obtained by standard automated perimetry. Patients and methods: Glaucoma suspects were defined as those having elevated intraocular pressure (>21 mm Hg) or cup-to-disc ratio of >0.5. 33 patients and 66 eyes with risk factors for glaucoma were examined. 15 patients and 23 eyes with no risk factors were Tested as controls. The recently developed 3D computer-automated threshold Amsler Grid Test was used. The Test exhibits a Grid on a computer screen at a preselected greyscale and angular resolution, and allows patients to trace those areas on the Grid that are missing in their visual field using a touch screen. The 5-minute Test required that the patients repeatedly outline scotomas on a touch screen with varied displays of contrast while maintaining their gaze on a central fixation marker. A 3D depiction of the visual field defects was then obtained that was further characterised by the location, shape and depth of the scotomas. The exam was repeated three times per eye. The results were compared to Humphrey visual field Tests (ie, achromatic standard or SITA standard 30-2 or 24-2). Results: In this pilot study 79% of the eyes Tested in the glaucoma-suspect group repeatedly demonstrated visual field loss with the 3D perimetry. The 3D depictions of visual field loss associated with these risk factors were all characteristic of or compatible with glaucoma. 71% of the eyes demonstrated arcuate defects or a nasal step. Constricted visual fields were shown in 29% of the eyes. No visual field changes were detected in the control group. Conclusions: The 3D computer-automated threshold Amsler Grid Test may demonstrate visual field abnormalities characteristic of glaucoma in glaucoma suspects with normal achromatic Humphrey visual field Testing. This Test may be used as a screening tool for the early detection of glaucoma.
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scotomas of age related macular degeneration detected and characterized by means of a novel three dimensional computer automated visual field Test
Retina-the Journal of Retinal and Vitreous Diseases, 2005Co-Authors: Paul P Nazemi, Wolfgang Fink, Alfredo A SadunAbstract:Purpose:We used the recently devised three-dimensional computer-based threshold Amsler Grid Test to acquire and identify typical patterns of visual field defects (scotomas) caused by age-related macular degeneration (AMD).Methods:Patients with AMD traced on a computer touch screen the borders of tho
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Three-dimensional computer-automated threshold Amsler Grid Test
Journal of biomedical optics, 2004Co-Authors: Wolfgang Fink, Alfredo A SadunAbstract:We describe a novel method for Testing a visual field that employs a computer monitor with displays of varying contrast that permits unprecedented resolution and characterization of the structure of scotomas in three dimensions. Patients are placed in front of a touch-sensitive computer screen at a fixed distance. With one eye covered, they focus on a central fixation marker and trace with their finger the areas on an Amsler Grid that are missing from their field of vision. Increasing degrees of contrast of the Amsler Grid are simulated by repeating the Test at different gray-scale levels. The results are recorded and then displayed as topographical contour rings by the computer Test program. The results can also be rendered as an immediate 3-D depiction of the central hill-of-vision. Several clinical pilot studies have been conducted at the Doheny Eye Institute and more than 200 patients have been examined with this system so far. Conditions such as optic neuritis, anterior ischemic optic neuropathy (AION), age-related macular degeneration (AMD), glaucoma, and ocular hypertension have been successfully assessed by this Test. Each condition provides unique patterns that are most evident in 3-D. The 3-D computer-automated threshold Amsler Grid Test is an innovative and noninvasive visual field Test. It provides several advantages over state-of-the-art standard automated perimetry, including: (1) additional information through 3-D depiction of scotomas, such as location, extent, slope, depth, and shape; (2) high angular resolution (1 deg compared with typically 6 deg); (3) a simple Test setup (merely a touch-sensitive computer monitor and the Test software); (4) excellent patient compliance (spending 4 to 5 min per eye). In light of its promising initial Tests, the 3-D visual field Test appears to have the potential for the early detection and monitoring of various diseases over time.
Wolfgang Fink - One of the best experts on this subject based on the ideXlab platform.
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early detection of glaucoma by means of a novel 3d computer automated visual field Test
British Journal of Ophthalmology, 2007Co-Authors: Paul P Nazemi, Alfredo A Sadun, Wolfgang Fink, Brian A Francis, Donald S. MincklerAbstract:Purpose: A recently devised 3D computer-automated threshold Amsler Grid Test was used to identify early and distinctive defects in people with suspected glaucoma. Further, the location, shape and depth of these field defects were characterised. Finally, the visual fields were compared with those obtained by standard automated perimetry. Patients and methods: Glaucoma suspects were defined as those having elevated intraocular pressure (>21 mm Hg) or cup-to-disc ratio of >0.5. 33 patients and 66 eyes with risk factors for glaucoma were examined. 15 patients and 23 eyes with no risk factors were Tested as controls. The recently developed 3D computer-automated threshold Amsler Grid Test was used. The Test exhibits a Grid on a computer screen at a preselected greyscale and angular resolution, and allows patients to trace those areas on the Grid that are missing in their visual field using a touch screen. The 5-minute Test required that the patients repeatedly outline scotomas on a touch screen with varied displays of contrast while maintaining their gaze on a central fixation marker. A 3D depiction of the visual field defects was then obtained that was further characterised by the location, shape and depth of the scotomas. The exam was repeated three times per eye. The results were compared to Humphrey visual field Tests (ie, achromatic standard or SITA standard 30-2 or 24-2). Results: In this pilot study 79% of the eyes Tested in the glaucoma-suspect group repeatedly demonstrated visual field loss with the 3D perimetry. The 3D depictions of visual field loss associated with these risk factors were all characteristic of or compatible with glaucoma. 71% of the eyes demonstrated arcuate defects or a nasal step. Constricted visual fields were shown in 29% of the eyes. No visual field changes were detected in the control group. Conclusions: The 3D computer-automated threshold Amsler Grid Test may demonstrate visual field abnormalities characteristic of glaucoma in glaucoma suspects with normal achromatic Humphrey visual field Testing. This Test may be used as a screening tool for the early detection of glaucoma.
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scotomas of age related macular degeneration detected and characterized by means of a novel three dimensional computer automated visual field Test
Retina-the Journal of Retinal and Vitreous Diseases, 2005Co-Authors: Paul P Nazemi, Wolfgang Fink, Alfredo A SadunAbstract:Purpose:We used the recently devised three-dimensional computer-based threshold Amsler Grid Test to acquire and identify typical patterns of visual field defects (scotomas) caused by age-related macular degeneration (AMD).Methods:Patients with AMD traced on a computer touch screen the borders of tho
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Three-dimensional computer-automated threshold Amsler Grid Test
Journal of biomedical optics, 2004Co-Authors: Wolfgang Fink, Alfredo A SadunAbstract:We describe a novel method for Testing a visual field that employs a computer monitor with displays of varying contrast that permits unprecedented resolution and characterization of the structure of scotomas in three dimensions. Patients are placed in front of a touch-sensitive computer screen at a fixed distance. With one eye covered, they focus on a central fixation marker and trace with their finger the areas on an Amsler Grid that are missing from their field of vision. Increasing degrees of contrast of the Amsler Grid are simulated by repeating the Test at different gray-scale levels. The results are recorded and then displayed as topographical contour rings by the computer Test program. The results can also be rendered as an immediate 3-D depiction of the central hill-of-vision. Several clinical pilot studies have been conducted at the Doheny Eye Institute and more than 200 patients have been examined with this system so far. Conditions such as optic neuritis, anterior ischemic optic neuropathy (AION), age-related macular degeneration (AMD), glaucoma, and ocular hypertension have been successfully assessed by this Test. Each condition provides unique patterns that are most evident in 3-D. The 3-D computer-automated threshold Amsler Grid Test is an innovative and noninvasive visual field Test. It provides several advantages over state-of-the-art standard automated perimetry, including: (1) additional information through 3-D depiction of scotomas, such as location, extent, slope, depth, and shape; (2) high angular resolution (1 deg compared with typically 6 deg); (3) a simple Test setup (merely a touch-sensitive computer monitor and the Test software); (4) excellent patient compliance (spending 4 to 5 min per eye). In light of its promising initial Tests, the 3-D visual field Test appears to have the potential for the early detection and monitoring of various diseases over time.
Paul P Nazemi - One of the best experts on this subject based on the ideXlab platform.
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early detection of glaucoma by means of a novel 3d computer automated visual field Test
British Journal of Ophthalmology, 2007Co-Authors: Paul P Nazemi, Alfredo A Sadun, Wolfgang Fink, Brian A Francis, Donald S. MincklerAbstract:Purpose: A recently devised 3D computer-automated threshold Amsler Grid Test was used to identify early and distinctive defects in people with suspected glaucoma. Further, the location, shape and depth of these field defects were characterised. Finally, the visual fields were compared with those obtained by standard automated perimetry. Patients and methods: Glaucoma suspects were defined as those having elevated intraocular pressure (>21 mm Hg) or cup-to-disc ratio of >0.5. 33 patients and 66 eyes with risk factors for glaucoma were examined. 15 patients and 23 eyes with no risk factors were Tested as controls. The recently developed 3D computer-automated threshold Amsler Grid Test was used. The Test exhibits a Grid on a computer screen at a preselected greyscale and angular resolution, and allows patients to trace those areas on the Grid that are missing in their visual field using a touch screen. The 5-minute Test required that the patients repeatedly outline scotomas on a touch screen with varied displays of contrast while maintaining their gaze on a central fixation marker. A 3D depiction of the visual field defects was then obtained that was further characterised by the location, shape and depth of the scotomas. The exam was repeated three times per eye. The results were compared to Humphrey visual field Tests (ie, achromatic standard or SITA standard 30-2 or 24-2). Results: In this pilot study 79% of the eyes Tested in the glaucoma-suspect group repeatedly demonstrated visual field loss with the 3D perimetry. The 3D depictions of visual field loss associated with these risk factors were all characteristic of or compatible with glaucoma. 71% of the eyes demonstrated arcuate defects or a nasal step. Constricted visual fields were shown in 29% of the eyes. No visual field changes were detected in the control group. Conclusions: The 3D computer-automated threshold Amsler Grid Test may demonstrate visual field abnormalities characteristic of glaucoma in glaucoma suspects with normal achromatic Humphrey visual field Testing. This Test may be used as a screening tool for the early detection of glaucoma.
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scotomas of age related macular degeneration detected and characterized by means of a novel three dimensional computer automated visual field Test
Retina-the Journal of Retinal and Vitreous Diseases, 2005Co-Authors: Paul P Nazemi, Wolfgang Fink, Alfredo A SadunAbstract:Purpose:We used the recently devised three-dimensional computer-based threshold Amsler Grid Test to acquire and identify typical patterns of visual field defects (scotomas) caused by age-related macular degeneration (AMD).Methods:Patients with AMD traced on a computer touch screen the borders of tho
Werner J Schmidt - One of the best experts on this subject based on the ideXlab platform.
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morphine induced catalepsy is augmented by nmda receptor antagonists but is partially attenuated by an ampa receptor antagonist
European Journal of Pharmacology, 1996Co-Authors: Thomas M Tzschentke, Werner J SchmidtAbstract:High doses of morphine produce a state of behavioural inactivity and muscular rigidity. This type of ‘catalepsy’ is clearly different from the state which is produced by the administration of neuroleptics, e.g. haloperidol. While haloperidol-induced catalepsy can easily be antagonised by NMDA receptor antagonists, there has been a report that the non-competitive NMDA receptor antagonist (+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine (MK-801) potentiates morphine-induced catalepsy. The aim of this study was to further examine the role of glutamate receptors in the mediation of morphine-induced catalepsy. To this end we coadministered morphine (20, 40, 60 mg/kg i.p.) with MK-801 (0.1 and 0.3 mg/kg i.p.), the competitive NMDA receptor antagonist dl-(E)-2-amino-4-methyl-5-phosphono-3-pentoic acid (CGP 37849) (2 and 6 mg/kg i.p.), or 1-(4-aminophenyl)-4-methyl-7,8-methylen-dioxy-5H-2,3-benzodiazepine (GYKI 52466) (2 and 4 mg/kg), an antagonist of the AMPA type of glutamate receptors, respectively. The degree of catalepsy was assessed using two different methods, the ‘bar/podium/Grid’ Test which is commonly used to measure neuroleptic-induced catalepsy, and a Test for the presence or absence of righting reflexes after turning the animals into a supine position. It was found that in the ‘bar/podium/Grid’ Test coadministration of both NMDA receptor antagonists significantly and dose-dependently augmented morphine-induced catalepsy. The results using the AMPA receptor antagonist were less clear since the lower dose of GYKI 52466 tended to attenuate the morphine effect whereas the higher dose augmented morphine-induced catalepsy in some cases. While placing the animals on the bar and on the podium produced essentially the same results, the Grid was found to be inapplicable for the measurement of morphine-induced catalepsy since the animals did not cling to the Grid and fell off almost immediately after being released from the experimenter's hand. With respect to the righting reflexes it was found that the number of animals not showing these responses increased when MK-801 or CGP 37849 was coadministered with morphine. In contrast, most of the animals treated with GYKI 52466 and morphine displayed intact righting reflexes. It is concluded that glutamatergic transmission plays an important role in the mediation of morphine-induced catalepsy, though different to that of haloperidol-induced catalepsy, and that NMDA and AMPA receptors are differentially involved in different aspects of the associated behavioural state.
Samuel N. Markowitz - One of the best experts on this subject based on the ideXlab platform.
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Scotoma size reduction as an adaptive strategy in age-related macular degeneration.
Canadian Journal of Ophthalmology, 2010Co-Authors: Kevin K. Lee, Samuel N. MarkowitzAbstract:Abstract Objective: Retinal areas with reduced sensitivity to light stimuli represent the true scotoma size in patients with age-related macular degeneration (AMD), whereas the perceived visual field defect area that covers a specific target of regard may represent an effective size of the same scotoma. This study was designed to highlight the conceptual difference between the "true scotoma size" and its "effective scotoma size" counterpart. Design: Prospective nonrandomized observational case series. Participants: Ten adults with documented AMD, low vision, and best-corrected visual acuity of 20/50–20/200 in the better eye. Methods: Effective scotoma size and true scotoma size were calculated from measurements with the macular Grid Test performed with automated perimetry and from microperimetry performed with the Nidek MP-1, respectively. Results: Ten patients aged 70–92 years (mean 81 years) met the inclusion criteria. Mean effective scotoma size measured with the macular Grid Test was 40.19 (SD 34.88) deg 2 . Mean true scotoma size measured with microperimetry was 75.17 (SD 56.08) deg 2 ( p ≤ 0.003). The log unit change in scotoma size, defined as scotoma utility score, was −55.91%. The effect size observed for the scotoma utility score was 0.74. Conclusions: Effective scotoma size experienced by patients with AMD is significantly smaller than true scotoma size. This reduction may be explained by adaptive variability in eye positions during any single fixation stability attempt, which ultimately results in enhanced visual field perception.
