Editing Visual system (section)

==Clinical significance==

[[File:Hemianopsia en.jpg|thumb|350px|right|'''[[Visual pathway lesions]]''' <br />
From top to bottom: <br /> 1. Complete loss of vision, right eye <br /> 2. [[Bitemporal hemianopia]] <br /> 3. [[Homonymous hemianopsia]] <br /> 4. [[Quadrantanopia]] <br /> 5&6. Quadrantanopia with [[macular sparing]]]]

Proper function of the visual system is required for sensing, processing, and understanding the surrounding environment. Difficulty in sensing, processing and understanding light input has the potential to adversely impact an individual's ability to communicate, learn and effectively complete routine tasks on a daily basis.

In children, early diagnosis and treatment of impaired visual system function is an important factor in ensuring that key social, academic and speech/language developmental milestones are met.

[[Cataract]] is clouding of the lens, which in turn affects vision. Although it may be accompanied by yellowing, clouding and yellowing can occur separately. This is typically a result of ageing, disease, or drug use.

[[Presbyopia]] is a visual condition that causes [[Far-sightedness|farsightedness]]. The eye's lens becomes too inflexible to [[Accommodation (eye)|accommodate]] to normal reading distance, focus tending to remain fixed at long distance.

[[Glaucoma]] is a type of blindness that begins at the edge of the visual field and progresses inward. It may result in [[tunnel vision]]. This typically involves the outer layers of the optic nerve, sometimes as a result of buildup of fluid and excessive pressure in the eye.<ref name="Publications">{{cite book|author=Harvard Health Publications|title=The Aging Eye: Preventing and treating eye disease|url=https://books.google.com/books?id=6cwilvu0CXQC&pg=PA20|access-date=15 December 2014|publisher=Harvard Health Publications|isbn=978-1-935555-16-2|page=20|year=2010}}</ref>

[[Scotoma]] is a type of blindness that produces a small [[Blind spot (vision)|blind spot]] in the visual field typically caused by injury in the primary visual cortex.

[[Homonymous hemianopia]] is a type of blindness that destroys one entire side of the visual field typically caused by injury in the primary visual cortex.

[[Quadrantanopia]] is a type of blindness that destroys only a part of the visual field typically caused by partial injury in the primary visual cortex. This is very similar to homonymous hemianopia, but to a lesser degree.

[[Prosopagnosia]], or face blindness, is a brain disorder that produces an inability to recognize faces. This disorder often arises after damage to the [[fusiform face area]].

[[Visual agnosia]], or visual-form agnosia, is a brain disorder that produces an inability to recognize objects. This disorder often arises after damage to the [[ventral stream]].