The retina is the nerve layer which lines the back of the eye. It senses light and sends signals to the brain which in turn interprets these signals and converts them to images resulting in vision. As one ages, the vitreous gel inside the eye contracts and as a result can pull on the retina. This can lead to a retinal tear. Vitreous fluid can then leak through the tear and accumulate beneath the retina causing the retina to detach from the back wall of the eye. Once detached, the retina stops functioning. Left untreated, a retinal detachment can lead to blindness.
Early symptoms of a retinal tear include new floaters (particles floating in the vision) and the onset of flashing lights. As symptoms progress, the vision may be obscured by a shadow or gray curtain-like feature which may signal a retinal detachment. Typically there is no pain or discomfort associated with a retinal tear or detachment.
The most common cause of a retinal tear and subsequent detachment is the contraction of the vitreous gel inside the eye exerting tension on the retina. This tension may cause a retinal hole to form through which fluid can pass. The fluid can then lift the retina off of the back wall of the eye. Other conditions that may contribute to a retinal tear include nearsightedness, severe eye trauma, intraocular surgery, family history of retinal detachment, weak areas in the retina known as lattice degeneration or a history of retinal detachment in the other eye.
Retinal tears are treated with laser surgery or cryotherapy which seal the retina and prevent it from detaching. If a retinal detachment is present a more complex surgical procedure is required to repair and reposition the retina. Depending on the clinical findings, your doctor may recommend a pneumatic retinopexy, a scleral buckling procedure or a vitrectomy. Most surgical repairs are successful but visual recovery may take months. In some cases only partial vision is restored. Retinal detachments occur that cannot be repaired in which case visual loss is permanent.
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Age-Related Macular Degeneration
Age-related macular degeneration (AMD) is the most common cause of severe vision loss in the elderly population. It affects the central area of the retina called the macula, which is responsible for crisp, detailed vision required for activities such as reading and driving. It usually does not affect peripheral vision. There are two forms of the condition, the earlier dry (non-neovascular) and more advanced wet (neovascular) macular degeneration. Ninety percent of people with macular degeneration have the dry form and experience gradual loss of vision, while ten percent of individuals with macular degeneration have the wet form and experience rapid, severe vision loss. Deposits known as drusen form under the retina which, over time, can grow in size and number leading to visual symptoms. Abnormal blood vessel growth (neovascularization) can eventually develop in the macula and lead to significant loss of vision.
Visual symptoms are variable in the early stages and can affect one eye more than the other. Central vision can become blurry, distorted, wavy or dark as the disease progresses. Increased presence of drusen and development of neovascularization in the retina are associated with the progression of the visual symptoms.
Oxidative stress appears to play a major role in the development of macular degeneration. Elements produced by the environment can damage human cells. This damage combined with a genetic tendency or family history of macular degeneration increases the risk for developing this condition. Other risk factors include smoking and high cholesterol levels. AMD is diagnosed based on the findings of a dilated eye exam and retinal imaging studies.
Currently, nutritional supplements are used to treat dry or non-neovascular AMD. Antioxidant vitamins, zinc and lutein have been shown in large scientific studies to lower the risk of progression to the more advanced form of the condition by about twenty-five percent. The most current treatments for wet or neovascular AMD involve injections of medications into the eye that stop blood vessel growth and bleeding. These medications are called VEGF blockers or anti-VEGF agents. They target a chemical known as Vascular Endothelial Growth Factor which is responsible for the abnormal blood vessel growth characteristic of AMD. Other long established, yet effective treatments which are used in selected cases include thermal laser and photodynamic therapy.
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