Age-related macular degeneration
Age-related macular degeneration: Excerpt from Professional Guide to Diseases (Eighth Edition)
Macular degeneration is the atrophy or degeneration of the macular region of the retina. Two types of age-related macular degeneration occur. The dry or atrophic form is characterized by atrophic pigment epithelial changes and is most often associated with a slow, progressive, and mild vision loss. The wet, exudative form causes progressive visual distortion leading to vision loss. It’s characterized by subretinal neovascularization that causes leakage, hemorrhage, and fibrovascular scar formation, which produce significant loss of central vision.
Causes and incidence
Age-related macular degeneration results from underlying pathologic changes that occur primarily at the level of the retinal pigment epithelium, Bruch’s membrane, and the choriocapillaris in the macular region. Drusen (bumps), which are common in elderly people, appear as yellow deposits beneath the pigment epithelium and may be prominent in the macula. No predisposing conditions have been identified; however, some forms of the disorder are hereditary.
Macular degeneration is the most common cause of legal blindness in adults, accounting for about 12% of blindness cases in the United States and for about 17% of new blindness cases. It’s also one of the causes of severe irreversible loss of central vision in elderly people — by age 75, almost 15% of people have this condition. Whites have the highest incidence. Other risk factors are family history and cigarette smoking.
Signs and symptoms
The patient notices a change in central vision. Initially, straight lines (for example, of buildings) become distorted; later, a blank area appears in the center of a printed page (central scotoma).
Diagnosis
❑ Indirect ophthalmoscopy — fundus examination through a dilated pupil may reveal gross macular changes.
❑ I.V. fluorescein angiography — sequential photographs may show leaking vessels as fluorescein dye flows into the tissues from the subretinal neovascular net.
❑ Amsler’s grid — used to monitor visual field loss.
Treatment
Laser photocoagulation reduces the incidence of severe vision loss in the patient with subretinal neovascularization, turning serous age-related macular degeneration to the dry form.
Photodynamic therapy, which can be performed in a physician’s office, is an option for the patient with wet macular degeneration. In this procedure, verteporfin (a light-sensitive medication) is injected into a vein in the patient’s arm and allowed to circulate to the eyes. The physician then shines a laser into the eyes, and the verteporfin produces a chemical reaction that destroys abnormal blood vessels. If the vessels regrow, the procedure can be repeated.
Special considerations
❑ Inform the patient with bilateral central vision loss of the visual rehabilitation services available to him.
❑ Special devices, such as low-vision optical aids, are available to improve the quality of life in the patient with good peripheral vision.
Book Source Details
- Book Title: Professional Guide to Diseases (Eighth Edition)
- Author(s): Springhouse
- Year of Publication: 2005
- Copyright Details: Professional Guide to Diseases (Eighth Edition), Copyright © 2005 Lippincott Williams & Wilkins.
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Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.
» Next page: Scotoma (Professional Guide to Signs & Symptoms (Fifth Edition))
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