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Oishi H, Takemura H, Amano K. Macromolecular tissue volume mapping of lateral geniculate nucleus subdivisions in living human brains. Neuroimage 2023; 265:119777. [PMID: 36462730 DOI: 10.1016/j.neuroimage.2022.119777] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2022] [Revised: 11/26/2022] [Accepted: 11/29/2022] [Indexed: 12/03/2022] Open
Abstract
The lateral geniculate nucleus (LGN) is a key thalamic nucleus in the visual system, which has an important function in relaying retinal visual input to the visual cortex. The human LGN is composed mainly of magnocellular (M) and parvocellular (P) subdivisions, each of which has different stimulus selectivity in neural response properties. Previous studies have discussed the potential relationship between LGN subdivisions and visual disorders based on psychophysical data on specific types of visual stimuli. However, these relationships remain speculative because non-invasive measurements of these subdivisions are difficult due to the small size of the LGN. Here we propose a method to identify these subdivisions by combining two structural MR measures: high-resolution proton-density weighted images and macromolecular tissue volume (MTV) maps. We defined the M and P subdivisions based on MTV fraction data and tested the validity of the definition by (1) comparing the data with that from human histological studies, (2) comparing the data with functional magnetic resonance imaging measurements on stimulus selectivity, and (3) analyzing the test-retest reliability. The findings demonstrated that the spatial organization of the M and P subdivisions was consistent across subjects and in line with LGN subdivisions observed in human histological data. Moreover, the difference in stimulus selectivity between the subdivisions identified using MTV was consistent with previous physiology literature. The definition of the subdivisions based on MTV was shown to be robust over measurements taken on different days. These results suggest that MTV mapping is a promising approach for evaluating the tissue properties of LGN subdivisions in living humans. This method potentially will enable neuroscientific and clinical hypotheses about the human LGN subdivisions to be tested.
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Affiliation(s)
- Hiroki Oishi
- Center for Information and Neural Networks (CiNet), Advanced ICT Research Institute, National Institute of Information and Communications Technology, Suita 565-0871, Japan; Graduate School of Frontier Biosciences, Osaka University, Suita 565-0871, Japan; Department of Psychology, University of California, Berkeley, Berkeley, CA 94704, United States.
| | - Hiromasa Takemura
- Center for Information and Neural Networks (CiNet), Advanced ICT Research Institute, National Institute of Information and Communications Technology, Suita 565-0871, Japan; Graduate School of Frontier Biosciences, Osaka University, Suita 565-0871, Japan; Division of Sensory and Cognitive Brain Mapping, Department of System Neuroscience, National Institute for Physiological Sciences, Okazaki 444-8585, Japan; Department of Physiological Sciences, School of Life Science, SOKENDAI (The Graduate University for Advanced Studies), Hayama 240-0193, Japan.
| | - Kaoru Amano
- Center for Information and Neural Networks (CiNet), Advanced ICT Research Institute, National Institute of Information and Communications Technology, Suita 565-0871, Japan; Graduate School of Frontier Biosciences, Osaka University, Suita 565-0871, Japan; Graduate School of Information Science and Technology, The University of Tokyo, Tokyo 113-8656, Japan
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Yuan N, Li M, Chen X, Lu Y, Fang Y, Gong H, Qian L, Wu J, Zhang S, Shipp S, Andolina IM, Sun X, Wang W. Immediate Impact of Acute Elevation of Intraocular Pressure on Cortical Visual Motion Processing. Invest Ophthalmol Vis Sci 2020; 61:59. [PMID: 32462199 PMCID: PMC7405714 DOI: 10.1167/iovs.61.5.59] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022] Open
Abstract
Purpose To physiologically examine the impairment of cortical sensitivity to visual motion during acute elevation of intraocular pressure (IOP). Methods Motion processing in the cat brain is well characterized, its X and Y cell visual pathways being functionally analogous to parvocellular and magnocellular pathways in primates. Using this model, we performed ocular anterior chamber perfusion to reversibly elevate IOP over a range from 30 to 90 mm Hg while monitoring cortical activity with intrinsic signal optical imaging. Drifting random-dot fields and gratings were used to characterize cortical population responses to motion direction and orientation in early visual areas 17 and 18. Results We found that acute IOP elevations at 50 mm Hg and above, which is often observed in acute glaucoma, suppressed cortical motion direction responses. This suppression was more profound in area 17 than in area 18, and more profound in central than peripheral visual field (eccentricities 0°–4° vs. 4°–8°) within area 17. In addition, orientation responses were more suppressed than motion direction responses for the same IOP modulation. Conclusions In contrast to human chronic glaucoma that may cause greater dysfunction in large-cell magnocellular than in small-cell parvocellular visual pathways, our direct measurement of cortical processing networks implies that the small X-cell pathway shows greater vulnerability to acute IOP elevation than the large Y-cell pathway in visual motion processing. The results demonstrate that fine discrimination mechanisms for motion in the central visual field are particularly impacted by acute IOP attacks, suggesting a neural basis for immediate visual deficits in the fine motion perception of acute glaucoma patients.
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Yu L, Xie L, Dai C, Xie B, Liang M, Zhao L, Yin X, Wang J. Progressive thinning of visual cortex in primary open-angle glaucoma of varying severity. PLoS One 2015; 10:e0121960. [PMID: 25816070 PMCID: PMC4376874 DOI: 10.1371/journal.pone.0121960] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2014] [Accepted: 01/29/2015] [Indexed: 11/26/2022] Open
Abstract
The aim of this study was to investigate possible changes of cortical thickness in the visual cortex in primary open-angle glaucoma (POAG) of varying severity. Twenty normal controls (NC), 20 mild (MP) and 17 severe (SP) POAG patients were recruited and scanned using magnetic resonance imaging. Cortical thickness analyses with regions of interest (V1, V2, ventral V3, V4 and V5/MT+) were used to assess the cortical changes among the three groups. Furthermore, the associations of cortical thickness with retinal nerve fiber layer (RNFL) thickness and mean deviation of visual field were analyzed. Compared with the NC group, decreased cortical thickness was detected in the bilateral V5/MT+ areas in the MP group and the left V1, bilateral V2 and V5/MT+ areas in the SP group. Cortical thinning of the bilateral V2 areas was detected in the SP group compared with the MP group. In addition, cortical thinning of these visual areas was related to the ophthalmologic measurements. In conclusion, POAG patients exhibit cortical thinning in the bilateral V5/MT+ in the early stage of disease. The cortical degeneration in visual areas is discrepant with disease progressing and the dorsal pathway might be selectively damaged in POAG. Therefore, the cortical thinning of these visual areas may play a key role in the progression of POAG and can serve as a novel biomarker for accurately evaluating the severity of POAG.
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Affiliation(s)
- Longhua Yu
- Department of Radiology, Southwest Hospital, Third Military Medical University, Chongqing, China
- Department of Radiology, 401st Hospital of the People’s Liberation Army, Qingdao, Shandong, China
| | - Liqi Xie
- Department of Radiology, 401st Hospital of the People’s Liberation Army, Qingdao, Shandong, China
| | - Chao Dai
- Ophthalmology research center, Southwest Hospital, Third Military Medical University, Chongqing, China
| | - Bing Xie
- Department of Radiology, Southwest Hospital, Third Military Medical University, Chongqing, China
| | - Minglong Liang
- Department of Radiology, Southwest Hospital, Third Military Medical University, Chongqing, China
| | - Lu Zhao
- McConnell Brain Imaging Centre, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada
| | - Xuntao Yin
- Department of Radiology, Southwest Hospital, Third Military Medical University, Chongqing, China
- McConnell Brain Imaging Centre, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada
- * E-mail: (XY); (JW)
| | - Jian Wang
- Department of Radiology, Southwest Hospital, Third Military Medical University, Chongqing, China
- * E-mail: (XY); (JW)
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Lamirel C, Milea D, Cochereau I, Duong MH, Lorenceau J. Impaired saccadic eye movement in primary open-angle glaucoma. J Glaucoma 2014; 23:23-32. [PMID: 22706338 DOI: 10.1097/ijg.0b013e31825c10dc] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
PURPOSE Our study aimed at investigating the extent to which saccadic eye movements are disrupted in patients with primary open-angle glaucoma (POAG). This approach followed upon the discovery of differences in the eye-movement behavior of POAG patients during the exploration of complex visual scenes. METHODS The eye movements of 8 POAG patients and 4 healthy age-matched controls were recorded. Four of the patients had documented visual field scotoma, and 4 had no identifiable scotoma on visual field testing. The eye movements were monitored as the observers watched static and kinetic targets. The gain, latency, and velocity-peak latency of the saccades recorded were then analyzed. RESULTS In POAG patients, with abnormal visual fields, watching a static target, the saccades were delayed and their accuracy was reduced, compared with those of normal observers. In POAG patients, with normal and abnormal visual fields, watching a kinetic target, a task involving precise motion analysis, the latency and accuracy of the saccades were impaired, compared with those of normal observers. CONCLUSIONS Our findings suggest that POAG alters saccade programming and execution particularly in the case of moving targets.
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Affiliation(s)
- Cédric Lamirel
- *Ophthalmology Department, Fondation Ophtalmologique Adolphe de Rothschild †Ophthalmology Department, Hôpital Bichat-Claude Bernard ‡CRICM, Cogimage, Université Pierre et Marie Curie, UMR 7225, CNRS, INSERM, Paris §Ophthalmology Department, Angers University Hospital, Angers, France ∥Glostrup University Hospital, Copenhagen, Denmark
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Lai JY. Biodegradable in situ gelling delivery systems containing pilocarpine as new antiglaucoma formulations: effect of a mercaptoacetic acid/N-isopropylacrylamide molar ratio. DRUG DESIGN DEVELOPMENT AND THERAPY 2013; 7:1273-85. [PMID: 24187486 PMCID: PMC3810330 DOI: 10.2147/dddt.s53759] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Ocular drug delivery is one of the most commonly used treatment modalities in the management of glaucoma. We have recently proposed the use of gelatin and poly(N-isopropylacrylamide) (PNIPAAm) graft copolymers as biodegradable in situ forming delivery systems for the intracameral administration of antiglaucoma medications. In this study, we further investigated the influence of carrier characteristics on drug delivery performance. The carboxyl-terminated PNIPAAm samples with different molecular weights were synthesized by varying the molar ratio of mercaptoacetic acid (MAA)/N-isopropylacrylamide (NIPAAm) from 0.05 to 1.25, and were determined by end-group titration. The preparation of gelatin-g-PNIPAAm (GN) copolymers from these thermoresponsive polymers was achieved using carbodiimide chemistry. Our results showed that the carboxylic end-capped PNIPAAm of high molecular weight may lead to the lower thermal phase transition temperature and slower degradation rate of GN vehicles than its low molecular weight counterparts. With a decreasing MAA/NIPAAm molar ratio, the drug encapsulation efficiency of copolymers was increased due to fast temperature-triggered capture of pilocarpine nitrate. The degradation of the gelatin network could greatly affect the drug release profiles. All of the GN copolymeric carriers demonstrated good corneal endothelial cell and tissue compatibility. It is concluded that different types of GN-based delivery systems exhibit noticeably distinct intraocular pressure-lowering effect and miosis action, thereby reflecting the potential value of a MAA/NIPAAm molar ratio in the development of new antiglaucoma formulations.
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Affiliation(s)
- Jui-Yang Lai
- Institute of Biochemical and Biomedical Engineering, Biomedical Engineering Research Center, Molecular Medicine Research Center, Chang Gung University, Taoyuan, Taiwan
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Feng L, Zhao Y, Yoshida M, Chen H, Yang JF, Kim TS, Cang J, Troy JB, Liu X. Sustained ocular hypertension induces dendritic degeneration of mouse retinal ganglion cells that depends on cell type and location. Invest Ophthalmol Vis Sci 2013; 54:1106-17. [PMID: 23322576 DOI: 10.1167/iovs.12-10791] [Citation(s) in RCA: 99] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
PURPOSE Glaucoma is characterized by retinal ganglion cell (RGC) death and frequently associated with elevated IOP. How RGCs degenerate before death is little understood, so we sought to investigate RGC degeneration in a mouse model of ocular hypertension. METHODS A laser-induced mouse model of chronic ocular hypertension mimicked human high-tension glaucoma. Immunohistochemistry was used to characterize overall RGC loss and an optomotor behavioral test to measure corresponding changes in visual capacity. Changes in RGC functional properties were characterized by a large-scale multielectrode array (MEA). The transgenic Thy-1-YFP mouse line, in which a small number of RGCs are labeled with yellow fluorescent protein (YFP), permitted investigation of whether subtypes of RGCs or RGCs from particular retinal areas were differentially vulnerable to elevated IOP. RESULTS Sustained IOP elevation in mice was achieved by laser photocoagulation. We confirmed RGC loss and decreased visual acuity in ocular hypertensive mice. Furthermore, these mice had fewer visually responsive cells with smaller receptive field sizes compared to controls. We demonstrated that RGC dendritic shrinkage started from the vertical axis of hypertensive eyes and that mono-laminated ON cells were more susceptible to IOP elevation than bi-laminated ON-OFF cells. Moreover, a subgroup of ON RGCs labeled by the SMI-32 antibody exhibited significant dendritic atrophy in the superior quadrant of the hypertensive eyes. CONCLUSIONS RGC degeneration depends on subtype and location in hypertensive eyes. This study introduces a valuable model to investigate how the structural and functional degeneration of RGCs leads to visual impairments.
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Affiliation(s)
- Liang Feng
- Department of Ophthalmology, Northwestern University, Evanston, IL, USA
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Lai JY. Biocompatibility of chemically cross-linked gelatin hydrogels for ophthalmic use. JOURNAL OF MATERIALS SCIENCE. MATERIALS IN MEDICINE 2010; 21:1899-1911. [PMID: 20238149 DOI: 10.1007/s10856-010-4035-3] [Citation(s) in RCA: 112] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2009] [Accepted: 02/22/2010] [Indexed: 05/27/2023]
Abstract
Biocompatibility is a major requirement for the development of functional biomaterials for ophthalmic applications. In this study, we investigated the effect of cross-linker functionality on ocular biocompatibility of chemically modified gelatin hydrogels. The test materials were cross-linked with glutaraldehyde (GTA) or 1-ethyl-3-(3-dimethyl aminopropyl)carbodiimide (EDC), and were analyzed using in vitro and in vivo assays. Primary rat iris pigment epithelial cultures were incubated with various gelatin discs for 2 days, and the cellular responses were monitored by cell proliferation, viability, and pro-inflammatory gene and cytokine expression. The results demonstrated that the cells exposed to EDC cross-linked gelatins had relatively lower lactate dehydrogenase activity, cytotoxicity, and interleukin-1beta and tumor necrosis factor-alpha levels than did those to GTA treated samples. In addition, the gelatin implants were inserted in the anterior chamber of rabbit eyes for 12 weeks and characterized by clinical observations and scanning electron microscopy studies. The EDC cross-linked gelatin hydrogels exhibited good biocompatibility and were well tolerated without causing toxicity and adverse effects. However, a significant inflammatory reaction was elicited by the presence of GTA treated materials. It was noted that, despite its biocompatibility, the potential application of non-cross-linked gelatin for local delivery of cell and drug therapeutics would be limited due to rapid dissolution in aqueous environments. In conclusion, these findings suggest ocular cell/tissue response to changes in cross-linker properties. In comparison to GTA treatment, the EDC cross-linking is more suitable for preparation of chemically modified gelatin hydrogels for ophthalmic use.
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Affiliation(s)
- Jui-Yang Lai
- Institute of Biochemical and Biomedical Engineering, Chang Gung University, 33302, Taoyuan, Taiwan, Republic of China.
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Local motion processing limits fine direction discrimination in the periphery. Vision Res 2008; 48:1719-1725. [PMID: 18558417 DOI: 10.1016/j.visres.2008.05.003] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2008] [Revised: 05/05/2008] [Accepted: 05/07/2008] [Indexed: 11/24/2022]
Abstract
Visual sensitivity is reduced in the periphery for many discrimination tasks. Previously it has been reported that motion coherence thresholds are higher for dot stimuli presented in the periphery, a finding that could arise either from (a) impaired motion integration or (b) from motion integrators inheriting more noisy local directional signals. We sought to disentangle these factors using an equivalent noise paradigm. We report a deterioration in discrimination thresholds in the periphery that does not result from reduced visibility and is fully accounted for by an increase in local directional uncertainty with no change in sampling efficiency. Changes in motion coherence thresholds with stimulus eccentricity, measured using similar stimuli, exhibit a high degree of inter-subject variability.
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Karwatsky P, Bertone A, Overbury O, Faubert J. Defining the nature of motion perception deficits in glaucoma using simple and complex motion stimuli. Optom Vis Sci 2006; 83:466-72. [PMID: 16840871 DOI: 10.1097/01.opx.0000225107.38719.0d] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
PURPOSE The purpose of this study is to determine the nature of motion perception deficits in primary open-angle glaucoma by measuring the sensitivity of simple (luminance-defined) and complex (texture-defined) motion, the latter requiring supplementary neural processing to be resolved. These findings will help address the possible extent of the cortical damage in glaucoma that has been recently demonstrated by anatomic and physiological studies. They also serve the purpose of establishing which motion paradigms would be most appropriate for assessing glaucoma-related functional loss. METHODS Direction-identification thresholds for first-order and second-order motion were measured for 26 patients with primary open-angle glaucoma (for both phakic and pseudophakic) and 18 nonglaucomatous observers. RESULTS The glaucomatous observers showed significantly increased motion thresholds for both first- and second-order motion conditions when compared with nonglaucomatous observers. However, the relative increase in threshold for first-order motion did not differ significantly from that of second-order motion. CONCLUSIONS These findings imply that there is no measurable higher-level cortical function damage caused by the glaucomatous process because no greater loss in second-order motion was observed. Based on the results, we suggest that motion paradigms used to assess functional loss in primary open-angle glaucoma should consist of simple, first-order type stimuli to minimize potential confounds such as those introduced by both the normal and pathologic aging process on complex motion processing (i.e., perimetry using complex motion stimuli).
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Affiliation(s)
- Peter Karwatsky
- Visual Psychophyiscs and Perception Laboratory, Ecole d'Optométrie, Université de Montréal, Montréal, Quebec, Canada
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Dakin SC, Mareschal I, Bex PJ. Local and global limitations on direction integration assessed using equivalent noise analysis. Vision Res 2005; 45:3027-49. [PMID: 16171844 DOI: 10.1016/j.visres.2005.07.037] [Citation(s) in RCA: 90] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2004] [Revised: 06/28/2005] [Accepted: 07/30/2005] [Indexed: 11/24/2022]
Abstract
We used an equivalent noise (EN) paradigm to examine how the human visual system pools local estimates of direction across space in order to encode global direction. Observers estimated the mean direction (clockwise or counter-clockwise of vertical) of a field of moving band-pass elements whose directions were drawn from a wrapped normal distribution. By measuring discrimination thresholds for mean direction as a function of directional variance, we were able to infer both the precision of observers' representation of each element's direction (i.e., local noise) as well as how many of these estimates they were averaging (i.e., global pooling). We estimated EN for various numbers of moving elements occupying regions of various sizes. We report that both local and global limits on direction integration are determined by the number of elements present in the display (irrespective of their density or the size of region they occupy), and we go on to show how this dependence can be understood in terms of neural noise. Specifically, we use Monte Carlo simulations to show that a maximum-likelihood operator, operating on pooled directional signals from visual cortex corrupted by Poisson noise, accounts for psychophysical data across all conditions tested, as well as motion coherence thresholds (collected under similar experimental conditions). A population vector-averaging scheme (essentially a special case of ML estimation) produces similar predictions but out-performs subjects at high levels of directional variability and fails to predict motion coherence thresholds.
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Affiliation(s)
- Steven C Dakin
- Department of Visual Science, Institute of Ophthalmology, University College London, 11-43 Bath Street, London EC1V 9EL, UK.
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Shabana N, Cornilleau-Pérès V, Droulez J, Goh JCH, Lee GSM, Chew PTK. Postural stability in primary open angle glaucoma. Clin Exp Ophthalmol 2005; 33:264-73. [PMID: 15932530 DOI: 10.1111/j.1442-9071.2005.01003.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
BACKGROUND This study evaluated the visual contribution to postural steadiness in primary open angle glaucoma (POAG), in correlation with the mean deviation (MD) measured through conventional perimetry, and with the Advanced Glaucoma Intervention Study (AGIS) score, which quantifies the extent of losses in the visual field. METHODS In 35 POAG patients and 21 age-matched normal subjects, the sway of the centre of pressure of the feet, on a firm or foam support, was recorded. The subjects stood on a force-plate with eyes closed, or with one or two eyes open. RESULTS For all subjects, the sway velocity was lower with vision than without vision, indicating the existence of a visual contribution to posture at all stages of glaucoma. This contribution was significantly lower for POAG patients than for normals in monocular and binocular vision, and decreased with the MD, or as the AGIS score increased. Among the maximum, minimum and average values of the two monocular MD, the MD of the worse eye presented the most significant negative correlation with the visual contribution to posture. The somatosensory contribution to postural steadiness was larger in POAG patients, as compared to normals, in monocular or binocular vision. CONCLUSION Primary open angle glaucoma induces a deficit in the visual contribution to postural steadiness, which should be taken into account for the prevention of falls.
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Affiliation(s)
- Noor Shabana
- Department of Ophthalmology, National University of Singapore, Singapore
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Abstract
Visual acuity is an essential component of the routine ophthalmic examination and the most common measure of visual function. There is increasing recognition, however, of the need to evaluate visual function beyond the limited extent afforded by visual acuity. The primary objective of this article is to introduce a variety of new and lesser-used techniques for measuring visual function that complement visual acuity assessment, each of which has been shown to detect visual dysfunction in patients with normal visual acuity.
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Affiliation(s)
- Gary L Trick
- Visual Diagnostic Service, Department of Eye Care Services, Henry Ford Health Center, 2799 West Grand Boulevard, Detroit, MI 48202, USA.
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Shabana N, Cornilleau Pérès V, Carkeet A, Chew PTK. Motion perception in glaucoma patients: a review. Surv Ophthalmol 2003; 48:92-106. [PMID: 12559330 DOI: 10.1016/s0039-6257(02)00401-0] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Most of the histopathological and psychophysical studies in glaucoma reveal a preferential damage to the magnocellular (M) pathway although a few of them support a damage to the parvocellular (P) pathway as well. In glaucoma, the visual fields are usually evaluated by conventional perimetry. However, it has been demonstrated that 20-40% of ganglion cells are lost before field defects are detected using conventional perimetry. Therefore, new psychophysical tests have recently been designed in order to specifically isolate and evaluate the visual mechanisms that are impaired at the early stages of glaucoma. In this context, several authors have addressed the issue of motion perception under the hypothesis of a predominant damage of the M pathway in glaucoma, and that motion perception is mediated mainly by M pathway. The results of these studies depict a large variation in the percentage of patients showing anomalous motion perception. Overall, motion thresholds are elevated in both glaucoma and ocular hypertensive patients as compared to control subjects, irrespective of the stimulus size and eccentricity. The test which discriminates best between patients and normal subjects is motion perimetry. The visual field defects in glaucoma patients identified by conventional perimetry and motion perimetry are similar, but the sizes of the defects are usually larger with motion perimetry. However, motion tests in central vision have no correlation with visual field defect on conventional perimetry. In glaucoma, loss of performance on motion perception tests does not necessarily support the existence of a specific deficit in the M pathway, because some behavioral studies suggest that the P pathway can also mediate motion perception. It is also difficult to conclude that motion perception is specifically affected in glaucoma because most of these studies do not yield a comparison with other visual functions. Despite these difficulties, localized motion perception tests at eccentricities of more than 15 degrees can be considered as a promising diagnostic tool.
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Affiliation(s)
- Noor Shabana
- Department of Ophthalmology, National University of Singapore, Singapore
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Ansari EA, Morgan JE, Snowden RJ. Psychophysical characterisation of early functional loss in glaucoma and ocular hypertension. Br J Ophthalmol 2002; 86:1131-5. [PMID: 12234893 PMCID: PMC1771332 DOI: 10.1136/bjo.86.10.1131] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
AIM The psychophysical evaluation of selective cell loss in early glaucoma and ocular hypertension. METHODS Contrast sensitivity was measured for the detection of luminance modulated gratings at a range of spatial (0.5, 2, 8 c/deg) and temporal (0, 16 Hz) frequency combinations in three groups of age matched patients (primary open angle glaucoma, ocular hypertension, normal controls; n=16). Stimuli of 5 degrees were presented foveally and at 15 degrees along the nasal horizontal meridian under photopic conditions. RESULTS Fovea: Compared to the normal group, the thresholds for the glaucoma patients were significantly elevated at all spatial and temporal frequencies (p<0.0001), but this reduction was not significantly different at any particular spatial or temporal frequency (p>0.1). There was no difference in contrast sensitivity between the normals and OHTs (p>0.10). Periphery: The thresholds of the glaucoma patients were elevated compared to the normal controls (p<0.01). The loss of sensitivity was slightly greater at the higher spatial frequencies for both stationary and flickering patterns but this did not reach significance (p=0.09). The contrast sensitivity in normal and OHT groups was not significantly different (p>0.10). CONCLUSIONS In early glaucoma, the reduction in contrast sensitivity to stimuli which isolate the magnocellular pathway (0.5 c/deg, 16 Hz) was not significantly different compared with the reduction in contrast sensitivity to stimuli that isolate the parvocellular pathway. These findings are not consistent with the hypothesis that the magnocellular pathway is selectively damaged in early glaucoma.
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Affiliation(s)
- E A Ansari
- Department of Ophthalmology, University of Wales College of Medicine, Cardiff, UK
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Abstract
Advances in our understanding of the pathophysiology of retinal ganglion cell death in glaucoma are providing important insights into the functional changes occurring in retinal ganglion cells in the early stages of the disease. These exciting new findings may help us develop psychophysical tests to monitor early retinal ganglion cell damage, possibly before neurons are committed to the process of cell death.
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Affiliation(s)
- E A Ansari
- Department of Ophthalmology, University Hospital of Wales, Cardiff, UK
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Culham J, He S, Dukelow S, Verstraten FA. Visual motion and the human brain: what has neuroimaging told us? Acta Psychol (Amst) 2001; 107:69-94. [PMID: 11388143 DOI: 10.1016/s0001-6918(01)00022-1] [Citation(s) in RCA: 80] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Recently, neuroimaging techniques have been applied to the study of human motion perception, complementing established techniques such as psychophysics, neurophysiology and neuropsychology. Because vision, particularly motion perception, has been studied relatively extensively, it provides an interesting case study to examine the contributions and limitations of neuroimaging to cognitive neuroscience. We suggest that in the domain of motion perception neuroimaging has: (1) revealed an extensive network of motion areas throughout the human brain, in addition to the well-studied motion complex (MT+); (2) verified and extended findings from other techniques; (3) suggested extensive top-down influences on motion perception; and (4) allowed experimenters to examine the neural correlates of awareness. We discuss these contributions, along with limitations and future directions for the neuroimaging of motion.
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Affiliation(s)
- J Culham
- Department of Psychology, University of Western Ontario, London, Ont., Canada N6A 5C2.
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Velten IM, Korth M, Horn FK, Budde WM. Temporal contrast sensitivity with peripheral and central stimulation in glaucoma diagnosis. Br J Ophthalmol 1999; 83:199-205. [PMID: 10396199 PMCID: PMC1722936 DOI: 10.1136/bjo.83.2.199] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
AIMS To evaluate temporal contrast sensitivity with full field, peripheral, and central stimulation and to determine the most sensitive corresponding retinal area for glaucoma damage. METHODS Temporal contrast sensitivity was determined either with a full field, a peripheral annular area from 30 degrees to 90 degrees, or a central area from 0 degree to 30 degrees at a frequency of 37.1 Hz. 232 eyes of 232 subjects were included. They were classified into four groups: eyes with ocular hypertension (OHT, n = 54), "preperimetric" glaucomas (n = 73) with glaucomatous optic disc abnormalities but no visual field loss, "perimetric" glaucomas (n = 53) with visual field loss, and 52 normals. RESULTS In all four groups, temporal contrast sensitivity was almost equal with full field and peripheral, but significantly higher than with central stimulation (p < 0.001). With regard to the diagnostic power of the three different stimulus areas, OHTs and glaucomas were found to be best discriminated from normals by peripheral stimulation. CONCLUSIONS According to these results, temporal contrast sensitivity seems to be determined by peripheral retinal areas. As the diagnostic power of the three different stimulus areas was best with the peripheral stimulation, this condition should be used for early glaucoma diagnosis.
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Affiliation(s)
- I M Velten
- Department of Ophthalmology, University of Erlangen-Nürnberg, Germany
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18
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Westcott MC, Fitzke FW, Crabb DP, Hitchings RA. Characteristics of frequency-of-seeing curves for a motion stimulus in glaucoma eyes, glaucoma suspect eyes, and normal eyes. Vision Res 1999; 39:631-9. [PMID: 10341990 DOI: 10.1016/s0042-6989(98)00187-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
This study compared frequency-of-seeing curves for a line displacement test in glaucoma patients and normals. Probit analysis of the frequency-of-seeing curves provided the motion thresholds and the slopes of the frequency-of-seeing curves, represented by the interquartile range. The thresholds and interquartile ranges were significantly elevated in the glaucoma eyes and suspect eyes, compared to controls. A logistic regression model incorporating both the interquartile range and threshold significantly improved the sensitivity of the motion test in the suspects. Abnormal shallowing of the slope of the motion frequency-of-seeing curve may represent one of the earliest changes in glaucoma.
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Affiliation(s)
- M C Westcott
- Institute of Ophthalmology, Department of Visual Science, London, UK
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19
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Westcott MC, Fitzke FW, Hitchings RA. Abnormal motion displacement thresholds are associated with fine scale luminance sensitivity loss in glaucoma. Vision Res 1998; 38:3171-80. [PMID: 9893824 DOI: 10.1016/s0042-6989(98)00038-8] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
This study tests the hypothesis that abnormal motion displacement thresholds coexist with scotomas on a finer spatial scale than is measurable by conventional Humphrey perimetry. Eighteen patients with primary open angle glaucoma in one eye, and 18 age matched normal controls underwent motion displacement threshold testing and high spatial resolution perimetry. The motion displacement thresholds were significantly elevated in the glaucoma eyes, in 73% this exceeded normal limits. Ten glaucoma eyes had normal Humphrey 24-2 field nearest the motion test site: of these seven had abnormally elevated motion displacement thresholds and six had fine scale threshold depressions detected with high spatial resolution perimetry. This result suggests that glaucomatous elevations of motion displacement threshold may be present in areas of normal Humphrey 24-2 field, and this may coexist with measurable scotomas beyond the resolution of conventional Humphrey perimetry in some, but not all patients.
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Affiliation(s)
- M C Westcott
- Department of Visual Science, Institute of Ophthalmology, London, UK
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20
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Herse P, Coveney D, Pham L. Factors influencing short wavelength automated perimetry in normal subjects. Clin Exp Optom 1998. [DOI: 10.1111/j.1444-0938.1998.tb06631.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Affiliation(s)
- Peter Herse
- School of Optometry, The University of New South Wales
| | - David Coveney
- School of Optometry, The University of New South Wales
| | - Linh Pham
- School of Optometry, The University of New South Wales
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21
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Abstract
The processing of visual input depends on the position of the visual stimuli in the visual field. Based on the anatomical structure of the retina and the cortex, the function and perception vary with the location in the visual field. Due to the low signal-to-noise ratio, electrophysiological recordings in human subjects commonly have to use large stimuli and, therefore, yield poor spatial resolution. The combination of the method of quasi-simultaneous stimulation of many small (1.5 degrees x 1.5 degrees squares) visual field elements by binary m-sequences and topographical recordings allowed us to reconstruct the potential maps elicited at each of 54 visual field locations independently. Twenty-two normal subjects participated in the experiments and observed monocularly a stimulation field of 13.5 degrees x 9 degrees filled with the 54 squares. Mean luminance was 6.5 cd/m2 and contrast was 95%. The EEG was recorded in 30 channels with a dense array of electrodes over the occipital brain areas. Individual noise levels of the subjects were estimated and significant signals were analyzed quantitatively. We determined three components between 90 ms and 220 ms latency. Both global field power (GFP) and topography of the components were affected by retinal stimulus location, showing a significant decline of GFP with retinal eccentricity. Our data demonstrate that even small retinal targets may evoke brain activity which can be recorded simultaneously. Scalp field topography depends critically on the exact stimulus location within the foveal and parafoveal retinal areas while response strength mainly depends on eccentricity.
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Affiliation(s)
- A Jedynak
- Institute of Physiology, Justus-Liebig University, Giessen, Germany
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