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The Neuroscientist : a Review Journal... Jun 2020Color provides valuable information about the environment, yet the exact mechanisms explaining how colors appear to us remain poorly understood. Retinal signals are... (Review)
Review
Color provides valuable information about the environment, yet the exact mechanisms explaining how colors appear to us remain poorly understood. Retinal signals are processed in the visual cortex through high-level mechanisms that link color perception with top-down expectations and knowledge. Here, we review the neuroimaging evidence about color processing in the brain, and how it is affected by acquired brain lesions in humans. Evidence from patients with brain-damage suggests that high-level color processing may be divided into at least three modules: perceptual color experience, color naming, and color knowledge. These modules appear to be functionally independent but richly interconnected, and serve as cortical relays linking sensory and semantic information, with the final goal of directing object-related behavior. We argue that the relations between colors and their objects are key mechanisms to understand high-level color processing.
Topics: Agnosia; Anomia; Cerebral Cortex; Color Perception; Color Vision Defects; Humans; Visual Pathways
PubMed: 31691627
DOI: 10.1177/1073858419882621 -
Advances in Experimental Medicine and... 2016Colour vision is only achieved in the presence of healthy and functional cone photoreceptors found in the retina. It is an essential component of human vision and... (Review)
Review
Colour vision is only achieved in the presence of healthy and functional cone photoreceptors found in the retina. It is an essential component of human vision and usually the first complaint patients undergoing vision degeneration have is the loss of daylight colour vision. Therefore, an understanding of the biology and basic mechanisms behind cone death under the degenerative state of retinal dystrophies and how the activation of the apoptotic pathway is triggered will provide valuable knowledge. It will also have broader applications for a spectrum of visual disorders and will be critical for future advances in translational research.
Topics: Animals; Apoptosis; Color Vision; Color Vision Defects; Disease Models, Animal; Genetic Predisposition to Disease; Humans; Mutation; Retinal Cone Photoreceptor Cells; Retinal Degeneration
PubMed: 26427416
DOI: 10.1007/978-3-319-17121-0_31 -
Australian Health Review : a... Sep 2016
Topics: Color Vision Defects; Humans; Prejudice
PubMed: 26476553
DOI: 10.1071/AH15161 -
Journal of Pediatric Ophthalmology and... Mar 2018Achromatopsia is a complex inherited retinal disease that affects the cone cell function. It is usually an autosomal-recessive disease and is characterized by pendular... (Review)
Review
Achromatopsia is a complex inherited retinal disease that affects the cone cell function. It is usually an autosomal-recessive disease and is characterized by pendular nystagmus, poor visual acuity, lack of color vision, and marked photophobia. CNGA3, CNGB3, GNAT2, PDE6C, PDE6H, and ATF6 gene mutations have been identified as associated with this disease. New diagnostic and therapeutic tools are being studied. Optical coherence tomography and fundus autofluorescence are important imaging techniques that provide significant information about the progression of the disease. The genetic approach for these patients is a current important issue and gene therapy is an ongoing therapeutic option already being studied in clinical trials. The purpose of this review was to survey the current knowledge on diagnosis and treatment options in achromatopsia. [J Pediatr Ophthalmol Strabismus. 2018;55(2):85-92.].
Topics: Color Vision; Color Vision Defects; Disease Management; Electroretinography; Fluorescein Angiography; Fundus Oculi; Humans; Phenotype; Retinal Cone Photoreceptor Cells; Tomography, Optical Coherence
PubMed: 29257187
DOI: 10.3928/01913913-20171117-01 -
Journal of Visualized Experiments : JoVE Apr 2017Many techniques have been developed to visualize how an image would appear to an individual with a different visual sensitivity: e.g., because of optical or age...
Many techniques have been developed to visualize how an image would appear to an individual with a different visual sensitivity: e.g., because of optical or age differences, or a color deficiency or disease. This protocol describes a technique for incorporating sensory adaptation into the simulations. The protocol is illustrated with the example of color vision, but is generally applicable to any form of visual adaptation. The protocol uses a simple model of human color vision based on standard and plausible assumptions about the retinal and cortical mechanisms encoding color and how these adjust their sensitivity to both the average color and range of color in the prevailing stimulus. The gains of the mechanisms are adapted so that their mean response under one context is equated for a different context. The simulations help reveal the theoretical limits of adaptation and generate "adapted images" that are optimally matched to a specific environment or observer. They also provide a common metric for exploring the effects of adaptation within different observers or different environments. Characterizing visual perception and performance with these images provides a novel tool for studying the functions and consequences of long-term adaptation in vision or other sensory systems.
Topics: Adaptation, Physiological; Aging; Color Perception; Color Perception Tests; Color Vision; Color Vision Defects; Humans; Retina; Visual Cortex
PubMed: 28518063
DOI: 10.3791/54038 -
Investigative Ophthalmology & Visual... Feb 2021Emmetropization is the process of adjusting ocular growth to the focal plane in order to achieve a clear image. Chromatic light may be involved as a cue to guide this...
PURPOSE
Emmetropization is the process of adjusting ocular growth to the focal plane in order to achieve a clear image. Chromatic light may be involved as a cue to guide this process. Achromats are color blind and lack normal cone function; they are often described as being hyperopic, indicating a failure to emmetropize. We aim to describe the refraction and refractive development in a population of genetically characterized achromats.
METHODS
Refractive error data were collected retrospectively from 28 medical records of CNGB3 c.1148delC homozygous achromats. The distribution of spherical equivalent refractive error (SER) and spherical error was analyzed in adults. The refractive development in children was analyzed by documenting astigmatic refractive error and calculating median SER in 1-year age groups and by analyzing the individual development when possible.
RESULTS
The distribution of SER and spherical error resembled a Gaussian distribution, indicating that emmetropization was disturbed in achromats, but we found indication of some decrease in SER during the first years of childhood. The prevalence of refractive errors was high and broadly distributed. Astigmatic refractive errors were frequent but did not seem to increase with age.
CONCLUSIONS
Refractive development in achromats is more complicated than a complete failure to emmetropize. The spread of refractive errors is larger than previously documented. Results presented here support the theory that chromatic cues and cone photoreceptors may play a role in emmetropization in humans but that it is not essential.
Topics: Accommodation, Ocular; Adolescent; Adult; Aged; Color Vision Defects; Cyclic Nucleotide-Gated Cation Channels; Female; Follow-Up Studies; Humans; Male; Middle Aged; Refraction, Ocular; Refractive Errors; Retrospective Studies; Time Factors; Young Adult
PubMed: 33560291
DOI: 10.1167/iovs.62.2.10 -
International Ophthalmology Mar 2020As proven in studies dating back to the eighteenth century, color vision changes may occur early in the course of glaucoma. Our aim was to reevaluate the incidence of...
PURPOSE
As proven in studies dating back to the eighteenth century, color vision changes may occur early in the course of glaucoma. Our aim was to reevaluate the incidence of acquired color vision deficiency in glaucoma patients of the University hospital Zürich by using the Panel D-15 test.
METHODS
Inclusion criteria of the study involved a diagnosis of glaucoma, age equal or greater than 18 years with no upper limit and a best-corrected visual acuity (BCVA) smaller than ≤ 0.7 logMAR. All volunteers were tested twice monocularly for color vision with (1) the Ishihara color plate test and (2) the Farnsworth and Lanthony Panel D-15 test by one examiner (L.B.). Using the Moment of Inertia Method of Vingrys and King-Smith (Investig Ophthalmol Vis Sci 29(1):50-63, 1988), we measured the color defect type (blue-yellow, red-green or non-selective).
RESULTS
One hundred and fifty-one eyes of 87 glaucoma patients were included in this study. Nine eyes showed a deficient result in the Ishihara test, which proves a congenital red-green weakness. Fifty-one (33.8%) eyes showed color vision anomalies in the desaturated test and 24 (15.9%) eyes in the saturated Panel D-15 test. A total of 25.2% and 8.6% of eyes in the desaturated and saturated test were diffuse dyschromatopsia, respectively. The second most prevalent deficiencies were blue-yellow defects with 4.0% and 4.6% of saturated and desaturated results. Just the covariate visual acuity had a significant influence on the Panel D-15 result, whereas other variables like age, sex or intraocular pressure did not show any impact.
CONCLUSION
This study ascertains that the long-known theory of color vision defects in patients with glaucoma is also relevant in our sample of 151 eyes, providing continuity to claims firstly reported many years ago. Despite our results highlighting more diffuse dyschromatopsia than other similar experiments, we have also proven that the tritanomalous defects occur more frequently than other color defects.
Topics: Adult; Aged; Aged, 80 and over; Color Perception Tests; Color Vision; Color Vision Defects; Female; Glaucoma; Humans; Incidence; Intraocular Pressure; Male; Middle Aged; Switzerland; Visual Acuity
PubMed: 31705359
DOI: 10.1007/s10792-019-01218-1 -
Ophthalmology Oct 2023
Topics: Humans; Color Vision Defects; Macula Lutea; Electroretinography; Cyclic Nucleotide-Gated Cation Channels
PubMed: 36682978
DOI: 10.1016/j.ophtha.2022.11.001 -
Progress in Retinal and Eye Research Sep 2014Hereditary cone disorders (CDs) are characterized by defects of the cone photoreceptors or retinal pigment epithelium underlying the macula, and include achromatopsia... (Review)
Review
Hereditary cone disorders (CDs) are characterized by defects of the cone photoreceptors or retinal pigment epithelium underlying the macula, and include achromatopsia (ACHM), cone dystrophy (COD), cone-rod dystrophy (CRD), color vision impairment, Stargardt disease (STGD) and other maculopathies. Forty-two genes have been implicated in non-syndromic inherited CDs. Mutations in the 5 genes implicated in ACHM explain ∼93% of the cases. On the contrary, only 21% of CRDs (17 genes) and 25% of CODs (8 genes) have been elucidated. The fact that the large majority of COD and CRD-associated genes are yet to be discovered hints towards the existence of unknown cone-specific or cone-sensitive processes. The ACHM-associated genes encode proteins that fulfill crucial roles in the cone phototransduction cascade, which is the most frequently compromised (10 genes) process in CDs. Another 7 CD-associated proteins are required for transport processes towards or through the connecting cilium. The remaining CD-associated proteins are involved in cell membrane morphogenesis and maintenance, synaptic transduction, and the retinoid cycle. Further novel genes are likely to be identified in the near future by combining large-scale DNA sequencing and transcriptomics technologies. For 31 of 42 CD-associated genes, mammalian models are available, 14 of which have successfully been used for gene augmentation studies. However, gene augmentation for CDs should ideally be developed in large mammalian models with cone-rich areas, which are currently available for only 11 CD genes. Future research will aim to elucidate the remaining causative genes, identify the molecular mechanisms of CD, and develop novel therapies aimed at preventing vision loss in individuals with CD in the future.
Topics: Animals; Color Vision Defects; Disease Models, Animal; Eye Proteins; Humans; Mutation; Retinal Cone Photoreceptor Cells; Retinal Degeneration
PubMed: 24857951
DOI: 10.1016/j.preteyeres.2014.05.001 -
Expert Opinion on Biological Therapy Jan 2018The eye is a target for investigational gene therapy due to the monogenic nature of many inherited retinal and optic nerve degenerations (IRD), its accessibility, tight... (Review)
Review
INTRODUCTION
The eye is a target for investigational gene therapy due to the monogenic nature of many inherited retinal and optic nerve degenerations (IRD), its accessibility, tight blood-ocular barrier, the ability to non-invasively monitor for functional and anatomic outcomes, as well as its relative immune privileged state.Vectors currently used in IRD clinical trials include adeno-associated virus (AAV), small single-stranded DNA viruses, and lentivirus, RNA viruses of the retrovirus family. Both can transduce non-dividing cells, but AAV are non-integrating, while lentivirus integrate into the host cell genome, and have a larger transgene capacity.
AREAS COVERED
This review covers Leber's congenital amaurosis, choroideremia, retinitis pigmentosa, Usher syndrome, Stargardt disease, Leber's hereditary optic neuropathy, Achromatopsia, and X-linked retinoschisis.
EXPERT OPINION
Despite great potential, gene therapy for IRD raises many questions, including the potential for less invasive intravitreal versus subretinal delivery, efficacy, safety, and longevity of response, as well as acceptance of novel study endpoints by regulatory bodies, patients, clinicians, and payers. Also, ultimate adoption of gene therapy for IRD will require widespread genetic screening to identify and diagnose patients based on genotype instead of phenotype.
Topics: Choroideremia; Clinical Trials as Topic; Color Vision Defects; Dependovirus; Genetic Therapy; Genetic Vectors; Humans; Lentivirus; Macular Degeneration; Nerve Degeneration; Stargardt Disease; Usher Syndromes; cis-trans-Isomerases
PubMed: 29057663
DOI: 10.1080/14712598.2018.1389886