Editing Visual system (section)

===Balance===
Along with [[proprioception]] and [[vestibular function]], the visual system plays an important role in the ability of an individual to control balance and maintain an upright posture.  When these three conditions are isolated and balance is tested, it has been found that vision is the most significant contributor to balance, playing a bigger role than either of the two other intrinsic mechanisms.<ref>{{cite journal |vauthors=Hansson EE, Beckman A, Håkansson A |title=Effect of vision, proprioception, and the position of the vestibular organ on postural sway |journal=Acta Otolaryngol. |volume=130 |issue=12 |pages=1358–63 |date=December 2010 |pmid=20632903 |doi=10.3109/00016489.2010.498024 |s2cid=36949084 |url= http://lup.lub.lu.se/search/ws/files/5263076/1671500.pdf}}</ref> The clarity with which an individual can see his environment, as well as the size of the visual field, the susceptibility of the individual to light and glare, and poor depth perception play important roles in providing a feedback loop to the brain on the body's movement through the environment.  Anything that affects any of these variables can have a negative effect on balance and maintaining posture.<ref>{{cite journal |vauthors=Wade MG, Jones G |title=The role of vision and spatial orientation in the maintenance of posture |journal=Phys Ther |volume=77 |issue=6 |pages=619–28 |date=June 1997 |pmid=9184687 |doi= 10.1093/ptj/77.6.619|doi-access=free }}</ref> This effect has been seen in research involving elderly subjects when compared to young controls,<ref>{{cite journal |vauthors=Teasdale N, Stelmach GE, Breunig A |title=Postural sway characteristics of the elderly under normal and altered visual and support surface conditions |journal=J Gerontol |volume=46 |issue=6 |pages=B238–44 |date=November 1991 |pmid=1940075 |doi=10.1093/geronj/46.6.B238 }}</ref> in [[glaucoma]] patients compared to age matched controls,<ref name="Shabana, 2005">{{cite journal |vauthors=Shabana N, Cornilleau-Pérès V, Droulez J, Goh JC, Lee GS, Chew PT |title=Postural stability in primary open angle glaucoma |journal=Clin. Experiment. Ophthalmol. |volume=33 |issue=3 |pages=264–73 |date=June 2005 |pmid=15932530 |doi=10.1111/j.1442-9071.2005.01003.x |s2cid=26286705 }}</ref> [[cataract]] patients pre and post surgery,<ref name="Schwartz, 2005">{{cite journal |vauthors=Schwartz S, Segal O, Barkana Y, Schwesig R, Avni I, Morad Y |title=The effect of cataract surgery on postural control |journal=Invest. Ophthalmol. Vis. Sci. |volume=46 |issue=3 |pages=920–4 |date=March 2005 |pmid=15728548 |doi=10.1167/iovs.04-0543 |doi-access=free }}</ref> and even something as simple as wearing safety goggles.<ref>{{cite journal |vauthors=Wade LR, Weimar WH, Davis J |title=Effect of personal protective eyewear on postural stability |journal=Ergonomics |volume=47 |issue=15 |pages=1614–23 |date=December 2004 |pmid=15545235 |doi=10.1080/00140130410001724246 |s2cid=22219417 }}</ref> [[Monocular vision]] (one eyed vision) has also been shown to negatively impact balance, which was seen in the previously referenced cataract and glaucoma studies,<ref name="Shabana, 2005"/><ref name="Schwartz, 2005"/> as well as in healthy children and adults.<ref>{{cite journal |vauthors=Barela JA, Sanches M, Lopes AG, Razuk M, Moraes R |title=Use of monocular and binocular visual cues for postural control in children |journal=J Vis |volume=11 |issue=12 |page= 10|year=2011 |pmid=22004694 |doi=10.1167/11.12.10 |doi-access=free }}</ref>

According to Pollock et al. (2010) [[stroke]] is the main cause of specific visual impairment, most frequently visual field loss ([[Homonymous hemianopsia|homonymous hemianopia]], a visual field defect). Nevertheless, evidence for the efficacy of cost-effective interventions aimed at these visual field defects is still inconsistent.<ref>{{cite journal | doi = 10.1111/j.1747-4949.2010.00516.x | volume=5 | title=Vision | year=2010 | journal=International Journal of Stroke | issue=3_suppl | page=67}}</ref>