Dr. Julio Armando Anguiano Peña
Dra. Peggy Chang
MULTIMEDICA VISTA HERMOSA
Age-related macular degeneration (AMD) is a disease associated with aging that gradually destroys sharp, central vision. Central vision is needed for seeing objects clearly and for common daily tasks such as reading and driving. AMD affects the macula, the part of the eye that allows you to see fine detail. AMD causes no pain. In some cases, AMD advances so slowly that people notice little change in their vision. In others, the disease progresses faster and may lead to a loss of vision in both eyes. AMD is a leading cause of vision loss in Americans 60 years of age and older. It two forms: wet and dry.
Macular Degeneration Causes
No one knows the etiology, or cause, of age-related macular degeneration. Causes are likely to be genetically inherited, but environmental factors may also contribute. Macular degeneration often runs in families. There may be a wide variety of different genes and proteins associated with dry and wet macular degeneration. Studies of twins showed that genetic factors play a significant role in the cause.
Many of the following risk factors have been found to be associated with age-related macular degeneration:
- Age: The likelihood of developing macular degeneration increases with age.
- Race: Macular degeneration is more common in whites but occurs in all races.
- Pigmentation: Macular degeneration is more common in lightly pigmented people.
- Iris color: As a corollary of skin pigmentation, people with a more lightly colored iris are more likely to develop some forms of macular degeneration.
- Gender: Women seem to be at greater risk.
- Smoking is a well-established risk factor for both forms of macular degeneration.
- Obesity and syndrome X, or metabolic syndrome, are also associated with the condition.
- Sleep apnea may be associated with macular degeneration independent of the obesity risk factor.
- Exposure to sunlight: Those with lifelong outdoor careers or hobbies as well as those living near the equator and at high altitudes are at greater risk.
- Medications: Some medications like Fosamax for osteoporosis may predispose to macular degeneration.
- High degrees of myopia may be associated with age-related macular degeneration or a similar condition called myopic degeneration.
- Family history is perhaps the most important risk factor other than age
Age-related macular degeneration begins with characteristic yellow deposits in the macula (central area of the retina, which provides detailed central vision, called the fovea) called drusen between the retinal pigment epithelium and the underlying choroid. Most people with these early changes (referred to as age-related maculopathy) have good vision. People with drusen can go on to develop advanced AMD. The risk is considerably higher when the drusen are large and numerous and associated with disturbance in the pigmented cell layer under the macula. Recent research suggests that large and soft drusen are related to elevated cholesterol deposits and may respond to cholesterol-lowering agents.
Central geographic atrophy, the “dry” form of advanced AMD, results from atrophy to the retinal pigment epithelial layer below the retina, which causes vision loss through loss of photoreceptors (rods and cones) in the central part of the eye. No medical or surgical treatment is available for this condition, however vitamin supplements with high doses of antioxidants, lutein and zeaxanthin, have been suggested by the National Eye Institute and others to slow the progression of dry macular degeneration and, in some patients, improve visual acuity.
Neovascular or exudative AMD, the “wet” form of advanced AMD, causes vision loss due to abnormal blood vessel growth (choroidal neovascularization) in the choriocapillaris, through Bruch’s membrane, ultimately leading to blood and protein leakage below the macula. Bleeding, leaking, and scarring from these blood vessels eventually cause irreversible damage to the photoreceptors and rapid vision loss if left untreated.
Symptoms of age-related macular degeneration include the following:
- Blurred or decreased central close-up and distance vision, which is often delayed because patients subconsciously ignore the eye with worst vision prior to development of the condition in the previously good eye.
- Blind spots, or scotomas, are a direct result of lost macular function.
- Straight lines look irregular or bent, called metamorphopsia, and objects appear a different color or shape in each of the eyes.
- Objects appearing smaller in one eye than the other, called micropsia, may also indicate a swelling and bulging of the macula, leading to a greater distance between the individual photoreceptors, which in turn causes the brain to interpret the object as smaller than seen by the good eye.
Fluorescein angiography allows for the identification and localization of abnormal vascular processes. Optical coherence tomography is now used by most ophthalmologists in the diagnosis and the followup evaluation of the response to treatment by using either Avastin or Lucentis, which are injected into the vitreous of the eye at various intervals.
No one has found a treatment or a cure for the dry form of age-related macular degeneration.
- Antioxidants: Deficiencies in antioxidants (specifically zinc and vitamins A, C, and E, selenium, copper, lutein, and zeaxanthine) have been noted in some people with age-related macular degeneration. Antioxidants may protect against age-related macular degeneration by preventing free radicals or unstable oxygen from damaging the retina.
The wet form of age-related macular degeneration is more likely than the dry form to cause significant vision loss. Different treatments of the wet form are available and may help decrease the amount of vision that is lost.
- Laser treatment: Clinical trials have demonstrated the value of laser treatment for some people with the wet form.Laser treatment may stop or lessen vision loss in early stages of the disease. It is performed with a specific wavelength designed to cauterize the abnormal blood vessels. Argon and krypton lasers are most commonly used for treating macular degeneration.
- A laser beam destroys existing blood vessels and may stop the growth of new ones.
- A scar forms after the laser treatment. This produces a permanent loss of vision in that area of the retina, sacrificed in order to preserve the rest of the eye layer. This is analogous to chopping down living trees in the path of a forest fire in order to stop the continued inevitable spread of that fire.
- Vision usually does not improve after laser treatment. It works in about half the cases, and only a small number of people meet the criteria for laser treatment. Its limitations have prompted a search for other forms of therapy.
- Photodynamic therapy: In April 2000, the U.S. Food and Drug Administration (FDA) approved this treatment. A light-activated drug called verteporfin (Visudyne) is given intravenously, and a specially designed laser is used to close the abnormal vessels while leaving the retina intact. You may need several treatments over one to two years because closed blood vessels can reopen within the treated area. Because Verteporfin is activated by light, exposure to sunlight must be avoided for five days after treatment. This laser treatment is vastly different from standard Argon laser treatment in that a broad beam of laser light covers the entire macula, while Argon laser treatment is precisely controlled by the ophthalmologist to cauterize specific leaking vessels under the biomicroscope.
- Antioxidants: Deficiencies in antioxidants have been noted in some people with age-related macular degeneration. Antioxidants may protect against age-related macular degeneration by preventing free radicals or unstable oxygen from damaging the retina. Due to the findings of the AREDS, it is recommended that all patients with macular degeneration receive antioxidant supplements.
- A variety of drugs that block vascular endothelial growth factor (VEGF) are being evaluated as a treatment option. These treatments for the first time have produced actual improvements in vision, rather than simply delaying or arresting the continued loss of vision characteristic of macular degeneration.
Until recently, no effective treatments were known for wet macular degeneration. However, new drugs, called anti-angiogenics or anti-VEGF (anti-Vascular Endothelial Growth Factor) agents, can cause regression of the abnormal blood vessels and improvement of vision when injected directly into the vitreous humor of the eye. The injections have to be repeated on a monthly or bi-monthly basis. Examples of these agents include ranibizumab (trade name Lucentis), bevacizumab (trade name Avastin, a close chemical relative of ranibizumab) and pegaptanib (trade name Macugen). Only ranibizumab and pegaptanib are approved by the FDA for AMD as of April 2007. Bevacizumab is approved, but for other indications. Pegaptanib (Macugen) has been found to have benefits in neovascular AMD. Worldwide, bevacizumab has been used extensively despite its “off label” status. The cost of ranibizumab (Lucentis) is approximately US$2000 per treatment while the cost of bevacizumab (Avastin) is approximately US$150 per treatment.
Macular Degeneration Vision with age-related emerging
Macular Degeneration Vision with advanced age