| Peripheral Vision |
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Peripheral vision is weak in Human s, especially at distinguishing Color and shape. This is because the density of receptor cells on the Retina is greatest at the center and lowest at the edges (see Visual System for an explanation of these concepts). In addition, there are two types of receptor cells, Rod Cell s and Cone Cell s; rod cells are unable to distinguish color and are predominant at the periphery, while cone cells are concentrated mostly in the center of the retina (the Macula ). Peripheral vision is good at detecting motion (a feature of rod cells), however, and is relatively strong at night or in the dark, when the lack of color cues and lighting makes cone cells far less useful. This makes it useful for avoiding predators, who tend to hunt at night and may attack suddenly from ambush. Peripheral vision loss may occur due to a number of ocular or neurological diseases or disorders. Glaucoma , Stroke , Branch Retinal Vein Occlusion , Branch Retinal Artery Occlusion , Ischemic Optic Neuropathy , and transient Migraine are some of the more common causes, whereas Retinitis Pigmentosa , Choroideremia , Gyrate Atrophy , Pituitary Tumor s, optic disc drusen, Brain Tumor s and Aneurysms , and tilted Optic Disc s are uncommon or rare {Link without Title} . TESTING PERIPHERAL VISION See Also: Visual field test # Close one eye. Extend your arms straight out to your sides # Slowly swing your arms to your front, noting when you first see your hands. # Do you see your hand opposite the closed eye hand 90 degrees from your nose? # Do you see your hand on the same side as the closed eye 30 degrees from your nose? # If yes, the test is normal.
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