World Library  
Flag as Inappropriate
Email this Article

Quadrantanopia

Article Id: WHEBN0011207545
Reproduction Date:

Title: Quadrantanopia  
Author: World Heritage Encyclopedia
Language: English
Subject: Anopsia, Optic papillitis, Positional alcohol nystagmus, Band keratopathy, Fourth nerve palsy
Collection:
Publisher: World Heritage Encyclopedia
Publication
Date:
 

Quadrantanopia

Quadrantanopia
Classification and external resources
Right homonymous superior quadrantanopia. The areas of the visual field lost in each eye are shown as black areas. This visual field defect is characteristic of damage to Meyer's loop on the left side of the brain.
ICD-10 H53.4
ICD-9 368.46

Quadrantanopia, quadrantanopsia, or quadrant anopia refers to an anopia affecting a quarter of the field of vision.

It can be associated with a lesion of an optic radiation.[1] While quadrantanopia can be caused by lesions in the temporal and parietal lobes, it is most commonly associated with lesions in the occipital lobe.[2] If Meyer's loop (temporal pathway) is lesioned, the vision loss is superior (colloquially referred to as "pie in the sky"); if Baum's loop (parietal pathway) is lesioned, the vision loss is inferior.[3]

Homonymous inferior/superior quadrantanopia

Homonymous (denotes a condition which affects the same portion of the visual field of each eye) inferior quadrantanopia and Homonymous superior quadrantanopia are a loss of vision in the same lower or upper quadrant of the visual field in both eyes - either the left lower/upper quadrant - left homonymous inferior/superior quadrantanopia - or the right lower/upper quadrant - right homonymous inferior/superior quadrantanopia.[4]

Homonymous binasal/bitemporal quadrantanopia

NB Homonymous means 'affecting the same side on each eye'. You cannot have a homonymous binasal anopia. This is just 'binasal anopia'. Binasal (either inferior or superior) quadrantanopia affects the inner visual quadrants closer to the nasal cavity in both eyes. Bitemporal (either inferior or superior) quadrantanopia affects the outer visual quadrants in both eyes.

Characteristics of quadrantanopia

An interesting aspect of quadrantanopia is that there exists a distinct and sharp border between the intact and damaged visual fields, due to an anatomical separation of the quadrants of the visual field. For example, information in the left half of visual field is processed in the right occipital lobe and information in the right half of the visual field is processed in the left occipital lobe.[2]

Example of the sharp division between the blind and intact fields (for someone with hemianopsia, rather than quadrantanopia, in this case)

In a quadrantonopia that is partial, there also exists a distinct and sharp border between the intact and damaged field within the quadrant. The sufferer is able to detect light within the damaged visual field.

The prospects of recovering vision in the affected field are bleak. Occasionally, patients will spontaneously recover vision in the affected field within the first three months after the brain injury; however, vision loss remaining after this period of spontaneous recovery is traditionally thought to be permanent, certain companies now claim to be able to induce recovery of vision after this three month period.[5]

Compensatory behaviors

Individuals with quadrantanopia often modify their behavior to compensate for the disorder, such as tilting of the head to bring the affected visual field into view.[6] Drivers with quadrantanopia, who were rated as safe to drive, drive slower, utilize more shoulder movements and, generally, corner and accelerate less drastically than typical individuals or individuals with quadrantanopia who were rated as unsafe to drive. The amount of compensatory movements and the frequency with which they are employed is believed to be dependent on the cognitive demands of the task; when the task is so difficult that the subject's spatial memory is no longer sufficient to keep track of everything, patients are more likely to employ compensatory behavior of biasing their gaze to the afflicted side.[7] Teaching individuals with quadrantanopia compensatory behaviors could potentially be used to help train patients to re-learn to drive safely.

References

  1. ^ Yale- Cranial Nerve 2, pg. 11
  2. ^ a b Kolb, B & Whishaw, I.Q. Human Neuropsychology, Sixth Edition, p.361; Worth Publishers (2008) ISBN 978-0-7167-9586-5
  3. ^ Central Visual Pathways
  4. ^ William J. Weiner: Neurology for the Non-Neurologist, p.526; Lippincott Williams & Wilkins (July 2010) ISBN 1605472395
  5. ^ Rehabilitation for Homonymous Hemianopia and Quadrantanopia
  6. ^ Visual Fields in Brain Injury - Hemianopsia.net Everything you need to know about Hemianopsia
  7. ^ http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3101691/
  • Quadrantanopsia Visual Fields Teaching Case from MedPix
This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and USA.gov, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for USA.gov and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
 
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
 
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.
 


Copyright © World Library Foundation. All rights reserved. eBooks from Project Gutenberg are sponsored by the World Library Foundation,
a 501c(4) Member's Support Non-Profit Organization, and is NOT affiliated with any governmental agency or department.