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Macula
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==Clinical significance== {{multiple image | direction = horizontal | width = 150 | footer = [[Fundus photographs]] of the right eye (left image) and left eye (right image), seen from front so that left in each image is to the person's right. The gaze is into the camera, so in each picture the macula is in the center of the image, and the [[optic disc]] is located towards the nose. | image1 = Fundus photograph of normal right eye.jpg | alt1 = | caption1 = | image2 = Fundus photograph of normal left eye.jpg | alt2 = | caption2 = }} The clinical macula is seen when viewed from the pupil, as in ophthalmoscopy or retinal photography. Whereas loss of [[peripheral vision]] may go unnoticed for some time, damage to the macula will result in loss of central vision, which is usually immediately obvious. The progressive destruction of the macula is a [[disease]] known as [[macular degeneration]] and can sometimes lead to the creation of a macular hole. Macular holes are rarely caused by trauma, but if a severe blow is delivered it can burst the blood vessels going to the macula, destroying it.<ref name="Macular Degeneration"/> Visual input from the macula occupies a substantial portion of the brain's visual capacity. As a result, some forms of [[visual field loss]] that occur without involving the macula are termed '''macular sparing'''. (For example, [[visual field testing]] might demonstrate ''[[homonymous hemianopsia]] with macular sparing''.) In the case of occipitoparietal ischemia owing to occlusion of elements of either [[posterior cerebral artery]], patients may display cortical [[blindness]] (which, rarely, can involve blindness that the patient denies having, as seen in [[Anton-Babinski syndrome|Anton's Syndrome]]), yet display sparing of the macula. This selective sparing is due to the collateral circulation offered to macular tracts by the [[middle cerebral artery]].<ref>{{cite web|last=Helseth|first=Erek|title=Posterior Cerebral Artery Stroke|url=http://emedicine.medscape.com/article/1160677-overview#aw2aab6b2|work=Medscape Reference|publisher=Medscape|access-date=23 October 2011}}</ref> Neurological examination that confirms macular sparing can go far in representing the type of damage mediated by an infarct, in this case, indicating that the caudal visual cortex (which is the principal recipient of macular projections of the optic nerve) has been spared. Further, it indicates that cortical damage rostral to, and including, [[lateral geniculate nucleus]] is an unlikely outcome of the infarction, as too much of the lateral geniculate nucleus is, proportionally, devoted to macular-stream processing.<ref>{{cite book|last=Siegel|first=Allan|title=Essential Neuroscience|url=https://archive.org/details/essentialneurosc0000sieg|url-access=registration|year=2006|publisher=Lippincott Williams & Wilkins|location=Baltimore, Maryland|isbn=978-0-7817-9121-2|edition=First Revised|author2=Sapru, Hreday N.|editor=Betty Sun}}</ref>
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