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Ophthalmic Plastic and Reconstructive... Dec 2023Dysthyroid optic neuropathy (DON) is a sight-threatening complication of thyroid eye disease (TED). This review provides an overview of the epidemiology, pathogenesis,... (Review)
Review
PURPOSE
Dysthyroid optic neuropathy (DON) is a sight-threatening complication of thyroid eye disease (TED). This review provides an overview of the epidemiology, pathogenesis, diagnosis, and current therapeutic options for DON.
METHODS
A literature review.
RESULTS
DON occurs in about 5% to 8% of TED patients. Compression of the optic nerve at the apex is the most widely accepted pathogenic mechanism. Excessive stretching of the nerve might play a role in a minority of cases. Increasing age, male gender, smoking, and diabetes mellitus have been identified as risk factors. Diagnosis of DON is based on a combination of ≥2 clinical findings, including decreased visual acuity, decreased color vision, relative afferent pupillary defect, visual field defects, or optic disc edema. Orbital imaging supports the diagnosis by confirming apical crowding or optic nerve stretching. DON should be promptly treated with high-dose intravenous glucocorticoids. Decompression surgery should be performed, but the response is incomplete. Radiotherapy might play a role in the prevention of DON development and may delay or avoid the need for surgery. The advent of new biologic-targeted agents provides an exciting new array of therapeutic options, though more research is needed to clarify the role of these medications in the management of DON.
CONCLUSIONS
Even with appropriate management, DON can result in irreversible loss of visual function. Prompt diagnosis and management are pivotal and require a multidisciplinary approach. Methylprednisolone infusions still represent first-line therapy, and surgical decompression is performed in cases of treatment failure. Biologics may play a role in the future.
Topics: Humans; Male; Glucocorticoids; Graves Ophthalmopathy; Methylprednisolone; Optic Nerve; Papilledema
PubMed: 38054987
DOI: 10.1097/IOP.0000000000002555 -
The British Journal of Ophthalmology May 2022Normal foveal development begins at midgestation with centrifugal displacement of inner retinal layers (IRLs) from the location of the incipient fovea. The outer... (Review)
Review
Normal foveal development begins at midgestation with centrifugal displacement of inner retinal layers (IRLs) from the location of the incipient fovea. The outer retinal changes such as increase in cone cell bodies, cone elongation and packing mainly occur after birth and continue until 13 years of age. The maturity of the fovea can be assessed invivo using optical coherence tomography, which in normal development would show a well-developed foveal pit, extrusion of IRLs, thickened outer nuclear layer and long outer segments. Developmental abnormalities of various degrees can result in foveal hypoplasia (FH). This is a characteristic feature for example in albinism, aniridia, prematurity, foveal hypoplasia with optic nerve decussation defects with or without anterior segment dysgenesis without albinism (FHONDA) and optic nerve hypoplasia. In achromatopsia, there is disruption of the outer retinal layers with atypical FH. Similarly, in retinal dystrophies, there is abnormal lamination of the IRLs sometimes with persistent IRLs. Morphology of FH provides clues to diagnoses, and grading correlates to visual acuity. The outer segment thickness is a surrogate marker for cone density and in foveal hypoplasia this correlates strongly with visual acuity. In preverbal children grading FH can help predict future visual acuity.
Topics: Child; Color Vision Defects; Eye Abnormalities; Fovea Centralis; Humans; Tomography, Optical Coherence; Vision Disorders; Visual Acuity
PubMed: 33148537
DOI: 10.1136/bjophthalmol-2020-316348 -
Handbook of Clinical Neurology 2022The ventral temporal cortex hosts key regions for the high-level visual processing of object shape and color. These areas represent nodes of large-scale neural circuits... (Review)
Review
The ventral temporal cortex hosts key regions for the high-level visual processing of object shape and color. These areas represent nodes of large-scale neural circuits dedicated to object recognition. In the language-dominant hemisphere, some of these regions communicate with the language systems; by assigning verbal labels to percepts, these circuits speedup stimulus categorization, and permit fast and accurate interindividual communication. By impairing the functioning of these circuits, neurological damage may provoke disabling disorders of the processing of visual objects and of their colors. Brain damage of vascular, degenerative, toxic, or traumatic origin can induce deficits at different levels of visual processing, from the building of shape- or wavelength-invariant percepts, to their connections with semantic knowledge and with the appropriate lexical entry. After an overview of the neuroimaging of domain-preferring regions for object shape and color in the ventral temporal cortex, this chapter reviews evidence from historical and recent cases of acquired visual agnosia and color processing deficits. A recurrent motif emerging from patients' patterns of performance and lesion locations is the existence of caudo-rostral gradients in the ventral occipito-temporal cortex, spanning from more perceptual to more cognitive stages of processing.
Topics: Agnosia; Color; Humans; Language; Temporal Lobe; Visual Perception
PubMed: 35964971
DOI: 10.1016/B978-0-12-823493-8.00022-5 -
Acta Clinica Croatica Apr 2023Acute optic neuritis is often associated with multiple sclerosis. It is considered to be the most common ocular symptom of multiple sclerosis. In addition to acute optic...
Acute optic neuritis is often associated with multiple sclerosis. It is considered to be the most common ocular symptom of multiple sclerosis. In addition to acute optic neuritis, in patients with multiple sclerosis, subclinical optic neuritis is also described. It is characterized by slow progression and bilateral involvement, thus being unnoticed by the patient. The purpose of the present study was to assess vision impairment in multiple sclerosis patients without a history of acute optic neuritis, using a number of functional tests including visual field testing by Octopus 101 perimetry N1 program, contrast sensitivity testing by Pelli Robson chart, and color vision by Ishihara pseudoisochromatic plates. The study included 35 multiple sclerosis patients aged 18-50 years, without subjective signs of vision impairment and visual acuity 1.0 according to Snellen. Visual field defects were found in 28 patients. The most common defects of visual fields were retinal sensitivity depression in peripheral zone and nerve fiber bundle defect. Reduced contrast sensitivity was found in 30 (86%) patients. Study results indicated multiple sclerosis patients free from signs of optic neuritis to suffer vision function impairment, as demonstrated by Octopus perimetry and contrast sensitivity testing with Pelli Robson charts.
Topics: Humans; Visual Acuity; Visual Fields; Vision Tests; Multiple Sclerosis; Optic Neuritis
PubMed: 38304362
DOI: 10.20471/acc.2023.62.01.24 -
Journal of Medical Ethics Nov 2023
Topics: Humans; Color; Color Vision Defects; Medicine
PubMed: 37871944
DOI: 10.1136/jme-2023-109634 -
Vision Research Jul 2023Blue cone monochromacy (BCM) is a congenital vision disorder characterized by complete loss or severely reduced long- and middle-wavelength cone function, caused by... (Review)
Review
Blue cone monochromacy (BCM) is a congenital vision disorder characterized by complete loss or severely reduced long- and middle-wavelength cone function, caused by mutations in the OPN1LW/OPN1MW gene cluster on the X-chromosome. BCM patients typically suffer from poor visual acuity, severely impaired color discrimination, myopia, and nystagmus. In this review, we cover the genetic causes of BCM, clinical features of BCM patients, genetic testing, and clinical outcome measurements for future BCM clinical trials. However, our emphasis is on detailing the animal models for BCM and gene therapy using adeno-associated vectors (AAV). We describe two mouse models resembling the two most common causes of BCM, current progress in proof-of-concept studies to treat BCM with deletion mutations, the challenges we face, and future directions.
Topics: Animals; Mice; Color Vision Defects; Mutation; Genetic Therapy; Retinal Cone Photoreceptor Cells; Rod Opsins
PubMed: 37001420
DOI: 10.1016/j.visres.2023.108221 -
International Ophthalmology May 2021Color vision deficiencies are a group of vision disorders, characterized by abnormal color discrimination. They include red-green color blindness, yellow-blue color... (Review)
Review
BACKGROUND
Color vision deficiencies are a group of vision disorders, characterized by abnormal color discrimination. They include red-green color blindness, yellow-blue color blindness and achromatopsia, among others. The deficiencies are caused by mutations in the genes coding for various components of retinal cones. Gene therapy is rising as a promising therapeutic modality. The purpose of this review article is to explore the available literature on gene therapy in the different forms of color vision deficiencies.
METHODS
A thorough literature review was performed on PubMed using the keywords: color vision deficiencies, gene therapy, achromatopsia and the various genes responsible for this condition (OPN1LW, OPN1MW, ATF6, CNGA3, CNGB3, GNAT2, PDE6H, and PDE6C).
RESULTS
Various adenovirus vectors have been deployed to test the efficacy of gene therapy for achromatopsia in animals and humans. Gene therapy trials in humans and animals targeting mutations in CNGA3 have been performed, demonstrating an improvement in electroretinogram (ERG)-investigated cone cell functionality. Similar outcomes have been reported for experimental studies on other genes (CNGB3, GNAT2, M- and L-opsin). It has also been reported that delivering the genes via intravitreal rather than subretinal injections could be safer. There are currently 3 ongoing human clinical trials for the treatment of achromatopsia due to mutations in CNGB3 and CNGA3.
CONCLUSION
Experimental studies and clinical trials generally showed improvement in ERG-investigated cone cell functionality and visually elicited behavior. Gene therapy is a promising novel therapeutic modality in color vision deficiencies.
Topics: Animals; Color Vision Defects; Cyclic Nucleotide-Gated Cation Channels; Electroretinography; Genetic Therapy; Humans; Mutation; Retinal Cone Photoreceptor Cells
PubMed: 33528822
DOI: 10.1007/s10792-021-01717-0 -
Biomedicines Jan 2023The visual process begins with the absorption of photons by photopigments of cone and rod photoreceptors in the retina. In this process, the signal is first amplified by... (Review)
Review
The visual process begins with the absorption of photons by photopigments of cone and rod photoreceptors in the retina. In this process, the signal is first amplified by a cyclic guanosine monophosphate (cGMP)-based signaling cascade and then converted into an electrical signal by cyclic nucleotide-gated (CNG) channels. CNG channels are purely ligand-gated channels whose activity can be controlled by cGMP, which induces a depolarizing Na/Ca current upon binding to the channel. Structurally, CNG channels belong to the superfamily of pore-loop cation channels and share structural similarities with hyperpolarization-activated cyclic nucleotide (HCN) and voltage-gated potassium (KCN) channels. Cone and rod photoreceptors express distinct CNG channels encoded by homologous genes. Mutations in the genes encoding the rod CNG channel ( and ) result in retinitis-pigmentosa-type blindness. Mutations in the genes encoding the cone CNG channel ( and ) lead to achromatopsia. Here, we review the molecular properties of CNG channels and describe their physiological and pathophysiological roles in the retina. Moreover, we summarize recent activities in the field of gene therapy aimed at developing the first gene therapies for CNG channelopathies.
PubMed: 36830806
DOI: 10.3390/biomedicines11020269