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The visual pathway consists of structures that carry visual information from the retina to the brain.Lesions in that pathway cause a variety of visual field defects. In the visual system of human eye, the visual information processed by retinal photoreceptor cells travel in the following way:
Macular sparing can be determined with visual field testing.The macula is defined as an area of approximately + 8 degrees around the center of the visual field. [3] During examination, vision in an area of greater than 3 degrees must be preserved for a patient to be considered to have macular sparing because there is involuntary eye movement within 1 to 2 degrees.
This results in an image of the light being focused on the periphery of the retina. Light from this spot then casts shadows of the blood vessels (which lie on top of the retina) onto unadapted portions of the retina. Normally the image of the retinal blood vessels is invisible because of adaptation. Unless the light moves, the image disappears ...
Proliferative retinopathy is the result of aberrant blood flow to the retina due to blood vessel overgrowth, or neovascularization. These pathologically overgrown blood vessels are often fragile, weak, and ineffective at perfusing the retinal tissues. [ 13 ]
In neuroanatomy, the optic radiation (also known as the geniculocalcarine tract, the geniculostriate pathway, and posterior thalamic radiation) are axons from the neurons in the lateral geniculate nucleus to the primary visual cortex. The optic radiation receives blood through deep branches of the middle cerebral artery and posterior cerebral ...
These diseases often cause sudden rapid visual loss in one eye. Inflammatory diseases of the blood vessels, like giant-cell arteritis, polyarteritis nodosa, eosinophilic granulomatosis with polyangiitis, granulomatosis with polyangiitis, and rheumatoid arthritis can cause arteritic AIONs (AAION). The vast majority of AIONs are nonarteritic ...
AAION is due to temporal arteritis (also called giant-cell arteritis), an inflammatory disease of medium-sized blood vessels (Chapel-Hill-Conference) that occurs especially with advancing age. In contrast, NAION results from the coincidence of cardiovascular risk factors in a patient with "crowded" optic discs.
Abnormal blood vessels can form in the back of the eye of a person with diabetes. These new blood vessels are weaker and prone to breaking and causing hemorrhage. [2] Diabetic retinopathy accounts for 31.5–54% of all cases of vitreous hemorrhage in adults in the United States. [1]