Visual cortex
Fiona Rowe in Visual Fields via the Visual Pathway, 2016
The nerve fibres of the optic radiations terminate in layer 4 of the primary visual striate cortex which is located on the medial aspect of the occipital lobe, superior and inferior to the calcarine fissure. The most anterior part of the visual cortex represents the extreme nasal periphery of the retina corresponding to the monocular temporal crescent of the visual fields. Pathologies causing unilateral and/or bilateral visual field loss include migraine, trauma, primary and secondary tumours and vascular abnormalities. Visual field loss may be caused by tumour compression of the visual cortex but visual field loss may result from surgery to remove the tumour. Unilateral lesions produce colour loss in the contralateral visual hemifield and patients are less aware of colour loss than those with achromatopsia. Optic atrophy is generally absent in patients with visual cortex lesions unless there is other pathology such as papilledema due to raised intracranial pressure.
Achromatopsia
Alexander R. Toftness in Incredible Consequences of Brain Injury, 2022
This chapter discusses achromatopsia and the milder condition of colorblindness. Colorblindness occurs when a person can see light but cannot distinguish one or more colors. This condition can begin within the eyes, or, more rarely, within the brain itself. The colorblindness that the average person is familiar with is the kind that exists in the eyes and is generally genetic. There is also a type of complete colorblindness called congenital achromatopsia. Congenital achromatopsia is exceedingly rare, but because it is genetic, it can spread through families. In an analysis of cerebral achromatopsia cases, a large amount of overlap in brain damage was found in an area called the ventral occipital cortex, located near the back and bottom of the brain.
Achromatopsia: case presentation and literature review emphasising the value of spectral domain optical coherence tomography
Published in Clinical and Experimental Optometry, 2014
Xiao Xi Yu, Robert E Rego, Diana Shechtman
A literature review and case presentation are used to discuss the diagnostic value of spectral domain optical coherence tomography (SD‐OCT) in the assessment and management of congenital achromatopsia. A 24‐year‐old Hispanic man presented to the clinic with a longstanding history of decreased vision and associated possible recent progression. A comprehensive eye examination and a battery of tests including SD‐OCT, fundus photography, electroretinogram (ERG) and Farnsworth D‐15 were completed. SD‐OCT and photopic ERG confirmed the clinical diagnosis of congenital achromatopsia. There was the classic subfoveal flattened hyporeflective ‘punched out’ zone, resulting from an absence of inner segment/outer segment junction. SD‐OCT findings associated with congenital achromatopsia have been documented recently, helping in the diagnosis of the condition. The SD‐OCT findings have further expanded our knowledge of congenital achromatopsia, while also aiding in the management of the disease.
Molecular Genetics of Achromatopsia in Newfoundland Reveal Genetic Heterogeneity, Founder Effects and the First Cases of Jalili Syndrome in North America
Published in Ophthalmic Genetics, 2013
Lance Doucette, Jane Green, Coleman Black, Jeremy Schwartzentruber, Gordon J. Johnson, Dante Galutira, Terry-Lynn Young
Achromatopsia (ACHM) is a severe retinal disorder characterized by an inability to distinguish colors, impaired visual acuity, photophobia and nystagmus. This rare autosomal recessive disorder of the cone photoreceptors is best known for its increased frequency due to founder effect in the Pingelapese population of the Pacific islands. Sixteen patients from Newfoundland, Canada were sequenced for mutations in the four known achromatopsia genes CNGA3, CNGB3, GNAT2, and PDE6C. The majority (n = 12) of patients were either homozygotes or compound heterozygotes for known achromatopsia alleles, two in CNGB3 (p.T383fsX and p.T296YfsX9) and three in CNGA3 (p.R283Q, p.R427C and p.L527R). Haplotype reconstruction showed that recurrent mutations p.T383fsX and p.L527R were due to a founder effect. Aggregate data from exome sequencing, segregation analysis and archived medical records support a rediagnosis of Jalili syndrome in affected siblings (n = 4) from Family 0094, which to our knowledge is the first family identified with Jalili Syndrome in North America.
Achromatopsia: clinical features, molecular genetics, animal models and therapeutic options
Published in Ophthalmic Genetics, 2018
Nashila Hirji, Jonathan Aboshiha, Michalis Georgiou, James Bainbridge, Michel Michaelides
Achromatopsia is an autosomal recessive condition, characterised by reduced visual acuity, impaired colour vision, photophobia and nystagmus. The symptoms can be profoundly disabling, and there is no cure currently available. However, the recent development of gene-based interventions may lead to improved outcomes in the future. This article aims to provide a comprehensive review of the clinical features of the condition, its genetic basis and the underlying pathogenesis. We also explore the insights derived from animal models, including the implications for gene supplementation approaches. Finally, we discuss current human gene therapy trials.
Related Knowledge Centers
- Eye Diseases
- Optic Nerve Diseases
- Occipital Lobe
- Rod Monochromacy
- Cngb3 Gene
- Cnga3 Gene
- Chromosome