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Hemianopsia is a medical condition in which vision is partially lost in one or both eyes. The word is from Greek origins, in which “hemi” means half, “an” means without, and “opsia” means sight. The occurrence is more associated with the brain and the optic fibers than with the eye itself. The main causes are traumatic brain injury, stroke, or brain tumors. These incidents can result in insufficient blood flow, hemorrhage, or a change in blood flow, all of which can disable the optic fibers from receiving or transmitting complete visual information to the brain.
The difference between hemianopsia and total blindness is light perception, in that the former still permits the brain to recognize light, and images are seen in a hazy manner. A person suffering from hemianopsia can easily tell which hemisphere of the brain is damaged. If vision loss is experienced on the left eye, then the damage is on the right hemisphere, because optic fibers travel through the brain in an intersecting manner. Correspondingly, left-hemisphere damage can cause a vision loss in the right eye. There are also cases where this visual condition affects both eyes.
Hemianopsia in both eyes can be classified in two types: homonymous and heteronymous. Patients with the homonymous type experience visual problems on the same sides of the eyes. For instance, only the left sides of each eye can perfectly see the image, while the right sides of the eyes will only see a blur. In contrast, the heteronymous kind can result in a visual loss on opposite sides of both eyes.
Heteronymous hemianopsia can be further categorized as either bitemporal or binasal. Bitemporal hemianopsia is experienced when the outer sides of the eyes have loss of vision. This occurs when the brain injury is located where the optic nerves intersect. A person can suffer from binasal hemianopsia when the inner sides of the eyes experience visual problems, while the outer sides can see clearly. This can occur if a patient suffers from hydrocephalus or an injury in the central nervous system.
Hemianopsia, in general, can be difficult to cure, as brain injuries tend to be permanent. Treatments and rehabilitations, however, are available to teach patients to cope with their condition and learn to be more aware of their surroundings. Eyeglasses have also been made available to alleviate the effects of hemianopsia. Another treatment still in its experimental stages is “Vision Restoration Therapy” that involves brain stimulation.
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