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The retina is a thin film of nerve tissue located at the back of the eye and has an approximate diameter of 42 mm. Images of the world surrounding the observer are brought into focus at their retina. Through a series of complex biochemical reactions, the light focused on the retina is converted into electrical signals generated by the retina. These signals are sent to the visual cortex of the brain through the optic nerve (see also Optic Nerve Disorders). The images are then interpreted by the brain.
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Symptoms Of A Detached Retina
The retina may become separated from the back of the eye; a condition known as a detached retina. This can happen as a result of a tear, break or hole, forming within the retina. Fluid from within the eye can pass through the rift, collecting between the eye and the retina and causing the retina to partially “unpeel" from the back of the eyeball and separating it from the retinal pigment epithelium (RPE) layer that nourishes it. This type of retinal detachment, known as a rhegmatogenous detachment, is the most common form of the condition. Two other causes of retinal detachment are also encountered. Tractional retinal detachment occurs when scar tissue on the surface of the retina contracts, causing it to separate from the RPE. The third cause is exudative retinal detachment in which the condition is caused by retinal diseases, including inflammatory illnesses or direct trauma to the eye. In exudative retinal detachment, there are no breaks in the retina itself, but fluid leaks into the area beneath the retina, causing it to detach.
The disturbance of the retina will cause blurred images to be formed in the affected eye. The symptoms associated with a detached retina can involve “floaters" (little “cobwebs" or specks that float around in the field of vision), bright flashes of light or a grey veil which moves across the field of vision. The onset of symptoms can be gradual or sudden. A detached retina is considered as a medical emergency and medical treatment should be sought immediately. If it goes untreated, sight will almost certainly be lost in the affected eye.
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Detached Retina Surgery
Detached retina surgery involves reattaching the retina to the back of the eyeball to restore vision to the maximum extent possible. Detached retina surgery usually takes one of two forms: laser surgery or cryotherapy. If the problem is detected before the retina detaches, the tear or holes in the retina may be treated by laser or cryotherapy (cryopexy) alone. Both techniques can be used to “weld" the damaged section of the retina back into place. The laser is used to cauterise the damaged tissue whilst cryopexy achieves the same aim by freezing the damaged tissue into place. These procedures do not require hospitalisation and cause little or no discomfort. However, if the retina has detached, it will normally require a short stay in hospital to treat the condition.
The treatment for dealing with a detached retina in hospital may be conducted under general or local anaesthetic, depending on the details. In some circumstances a small synthetic band may be attached to the exterior of the eyeball, providing a little pressure against the detached retina; this is referred to as a scleral buckle. It may also be necessary to drain the vitreous humour from the eye in a procedure know as a viterectomy, involving an incision in the white of the eye (sclera) permitting a tool to be placed into the eye to remove the fluid. Gas will normally be inserted into the eye to push the retina back into place. As the eye heals, it will refill with vitreous humour, displacing the gas. In all of these interventions, the retina will be “welded" back into place using a laser or through a cryopexy.
Up to 90% of people presenting (in time) with a detached retina will be successfully treated, although some may require a second treatment. The exact outcome with respect to vision may take a few months to establish, but the utcome is better if treatment is commenced before the macular detaches (see also Macular Degeneration)
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- John Moran Eye Center, University of Utah: http://webvision.med.utah.edu/sretina.html
- Royal New Zealand Foundation of The Blind: http://www.rnzfb.org.nz/learnaboutblindness/eyeconditions/retinitispigmentosa/retina
- University of Michigan, Kellogg Eye Center: http://www.kellogg.umich.edu/patientcare/conditions/detached.retina.html
- National Eye Institute; Detached Retina: http://www.nei.nih.gov/health/retinaldetach/index.asp