| 释义 |
age-related macular degeneration
Thesaurus| Noun | 1. | age-related macular degeneration - macular degeneration that is age-relatedAMDmacular degeneration - eye disease caused by degeneration of the cells of the macula lutea and results in blurred vision; can cause blindness |
EncyclopediaSeemacular degenerationage-related macular degeneration
macular degeneration breakdown of cells in the macula lutea" >macula lutea, resulting in a loss of central vision in the affected eye; peripheral vision is not affected. There are several varieties; most appear in persons 50 to 60 years of age (age-related macular degeneration), but one variety is congenital and is seen in younger people (stargardt's disease or Stargardt's macular degeneration). In about 75 per cent of cases the cause is not known, and nothing can be done to prevent, arrest, or reverse the process.Patient Care. Since a large majority of cases of macular degeneration cannot be arrested or treated, care is aimed at making the most of the vision that the patient has. The condition does not progress to total blindness and usually is self-limiting. The inability to perceive detail can be compensated for in part by using large-type books and magazines and a magnifying lens for reading, and having adequate lighting whenever detail work is necessary.
Patients with macular degeneration are given a sheet of paper on which is printed a grid of horizontal and vertical lines. They are instructed to look at this grid daily and note whether there is any change in distortion of lines in the center of vision. This same technique can be used as a screening test to evaluate central vision. However, seeing distorted lines in the grid is not necessarily symptomatic of macular degeneration. Further examination by an ophthalmologist is necessary for a definitive diagnosis. Grid for evaluating macular degeneration.age-related macular degeneration (ARMD) a type having its onset between the ages of 50 and 60, the leading cause of blindness in persons over the age of 65. There are two main types, involutional and exudative age-related macular degeneration.
The involutional (dry or non-exudative) type accounts for 90 per cent of cases and is characterized by the gradual wearing out of the cells in the retinal pigment epithelium, resulting in a slow, progressive loss of central vision. Although visual acuity loss usually does not progress beyond the 20/200 level, this is a significant disability. Treatment is not generally available.
The exudative (neovascular or wet) type is characterized by the growth of a neovascular membrane within or very close to the macula, resulting in distorted and blurred vision. The vision loss from this type of macular degeneration may be only of hand movements. Laser photocoagulation of this form of macular degeneration is aimed at destroying the neovascular membrane; if diagnosed and treated very early when the membrane is small, significant loss of central vision may be avoided.Patient Care. Health care providers can be of great help for early diagnosis of this devastating disease through ongoing patient education programs. After laser treatment, which is performed under a retrobulbar anesthetic, the patient should be instructed to leave the patch in place for at least six hours. Any increase in distortion or blurred vision should be immediately reported and followed up by an urgent outpatient exam. Low vision aids and services can improve quality of life for persons with this disorder.Stargardt's macular degeneration Stargardt's disease.age-re·lat·ed mac·u·lar de·gen·er·a·tiona common macular degeneration beginning with drusen of the macula and pigment disruption and sometimes leading to severe loss of central vision.age-related macular degeneration See Macular degeneration. mac·u·lar de·gen·er·a·tion (mak'yū-lahr dě-jen'ĕr-ā'shŭn) A progressive deterioration of the macula lutea resulting in the loss of central vision.
Synonym(s): age-related macular degeneration. age-related macular degeneration (AMD, ARMD) A disorder affecting the central and most important part of the RETINA in elderly people and causing progressive loss of central vision. Peripheral vision is retained. AMD may be dry or wet. The dry form is due to degenerative changes in the tissues under the retina; the wet form is caused by the development of a CHOROIDAL NEOVASCULAR MEMBRANE which leaks fluid under the retina with progressive destruction of the rods and cones and connecting nerves. Mutation of the gene for complement factor H is an impotant risk factor. A proportion of cases are thought to be attributable to cigarette smoking. Antioxidant vitamin supplements slightly reduce the risk. The anti-angiogenic drug anecortave acetate, injected close to the posterior sclera, appears to be of value. Progress of the condition can sometimes be stopped by laser burns to seal the leakage, but established disciform degeneration is irremediable, short of MACULAR TRANSLOCATION. See also VASCULAR ENDOTHELIAL GROWTH FACTOR.Age-related macular degeneration (ARMD)Degeneration of the macula (the central part of the retina where the rods and cones are most dense) that leads to loss of central vision in people over 60.Mentioned in: Cataract Surgerymacular degeneration, age-related (ARMD, AMD)A common, chronic degenerative condition found in a large percentage of elderly patients (and sometimes middle-aged ones) characterized by loss of central vision. There are two main forms of the condition: non-neovascular (dry, atrophic) AMD, which is the most common, and exudative (wet, neovascular) AMD in which the loss of vision is the most severe. The main features of dry AMD are the presence in the macular region of small, yellowish-white spots (hard drusen) and large, poorly defined, coalescing soft drusen, focal hyperpigmentation of the retinal pigment epithelium (RPE) and at a later stage geographic atrophy of the RPE and depigmentation exposing choroidal vessels. Visual acuity becomes markedly reduced, there is metamorphopsia and the condition usually becomes bilateral over several years. The condition is managed essentially by the use of low vision aids.Exudative AMD has a similar clinical picture initially but is followed by choroidal neovascularization (CNV), which gives rise to subretinal fluid, haemorrhages, exudation, RPE detachment and subretinal fibrosis in the macular region resulting in severe loss of central vision. If detected early (usually with an Amsler chart), treatment with laser photocoagulation will reduce the risk of further visual loss. Photodynamic therapy (PDT) is another method of reducing the risk of visual loss. It allows selective destruction of the choroidal neovascularization with minimal damage to the overlying retinal tissue. It consists of injecting a photosensitizing agent (e.g. verteporfin) that is taken up by the abnormal vessels and when activated by a laser light of a given wavelength (e.g. 689 nm) it damages and shrivels up the vessels. Recent drug therapies, such as the anti-VEGF ranibizumab and bevacizumab, which are injected intravitreally at regular intervals and designed to stop the leakage and the growth of blood vessels, not only reduce loss of vision but improve visual acuity in a significant percentage of cases of wet AMD. Syn. senile macular degeneration. See fluorescein angiography; disciform scar; drusen; macular dystrophy; lipofuscin; age-related maculopathy; oxidative stress; macular pigment; Kollner's rule; photostress test; VEGF.See ARMD
See AMDage-related macular degeneration
Related to age-related macular degeneration: glaucoma, diabetic retinopathySynonyms for age-related macular degenerationnoun macular degeneration that is age-relatedSynonymsRelated Words |