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Wet macular degeneration

Definition


Disease: Wet macular degeneration Wet macular degeneration
Category: Eye diseases

Disease Definition:

The chronic eye disease that is marked by the deterioration of tissue in the part of the eye that's responsible for central vision is age-related macular degeneration. Blurred central vision or a blind spot may be caused in the center of the visual field because the macula gradually deteriorates in this condition. Adults age 50 and older may be affected by macular degeneration.

 

When new blood vessels grow and leak fluid underneath the macula, which is an area of densely packed light-sensitive cells in the central part of the retina, wet macular degeneration occurs. Most cases of wet macular degeneration develop from the dry type of macular degeneration.

 

The extent of vision loss may be reduced and in some instances the vision may be improved by the early detection and treatment of wet macular degeneration.
 

Work Group:


Symptoms, Causes

Symptoms:

The following signs and symptoms may appear and progress rapidly with wet macular degeneration:

 

  • Decreased central vision
  • Abrupt onset
  • Seeing nonexistent things (hallucinations), such as geometric figures, animals, unusual patterns  or even faces caused by disrupted communication between the deteriorated macula and the brain
  • Visual distortions, such as straight lines appearing wavy or crooked, a doorway or street sign looking lopsided, or objects appearing smaller or farther away than they really are
  • Rapid worsening
  • Decreased intensity or brightness of colors
  • Well-defined blurry spot or blind spot in the field of vision

 

While one eye remains fine for years, the vision of the patient may falter in the other eye. Because the good eye compensates for the eye with macular degeneration, the patient may not notice any changes or only mild changes. When this condition develops in both eyes, the vision and lifestyle of the patient are dramatically affected.

 

People should see their doctor, especially after age 50 in case:

 

  • Their ability to see colors and fine detail becomes impaired
  • They notice changes in their central vision

 

To determine if one may need to visit the eye doctor, there is one way, which is to check the vision regularly using an Amsler grid. To detect changes in one's sight that he/she otherwise may not notice, there is this simple test that may help.

 

The steps that one should follow to perform the test are the following:

 

  • Holding the grid 14 inches in front of one's self in good light. Using corrective glasses or reading glasses if one normally wears them.
  • Covering one eye
  • Looking directly at the center dot with the uncovered eye
  • While looking at this dot, one should determine whether all of the lines of the grid appear straight, uninterrupted and have the same contrast.

 

One should repeat the above steps with the other eye. If any part of the grid is missing or looks dark, blurred or wavy, an eye doctor should be immediately contacted.
 

Causes:

When abnormal new blood vessels grow from the choroid — the layer of blood vessels sandwiched between the retina and the outer, firm coat of the eye called the sclera — under and into the macular portion of the retina (a process known as choroidal neovascularization), wet macular degeneration develops. This form of macular degeneration is called "wet" because these abnormal vessels leak fluid or blood. Fluid or blood between the choroid and macula interferes with the retina's function and causes the central vision to blur. In addition to that, what the patient sees when he/she looks straight ahead becomes wavy or crooked, and blank spots block out part of the field of vision.

 

Signs of the dry form; yellow fat-like deposits (drusen) and mottled pigmentation of the retina are shown almost always in the eyes with the wet form of macular degeneration.

 

The wet form is responsible for most of the severe vision loss that people with macular degeneration experience, however, it accounts for about 15 percent of all cases. The odds of getting wet macular degeneration in the other eye increase greatly if one develops the condition in one eye.

 

A breakdown in the eye's waste-removal system may cause the wet form of macular degeneration, much like the dry form. Cones and rods, that are the light-sensitive cells in the retina, produce waste. Retinal tissue deteriorates if this waste accumulates and interrupts the retina's nutrient supply. It's not clear whether this is the mechanism that triggers the growth of abnormal blood vessels, a subject that is still under study.

 

Vision loss is usually severe and rapid with the wet form of macular degeneration, often deteriorating to 20/200 vision or worse, occurring within weeks or months. One is considered legally blind when his/her vision is 20/200 or worse in both eyes.

Retinal pigment epithelial detachment:

When fluids leak from the choroid and collects between the choroid and the next-deeper cell layer, namely the retinal pigment epithelium (RPE), then retinal pigment epithelial detachment occurs, which is another form of wet macular degeneration. When the RPE is detached, no abnormal choroidal blood vessel growth is apparent. What looks like a blister or a bump under the macula is caused by fluid beneath the RPE instead.

 

The vision of the patient can remain relatively stable for many months or even years before it deteriorates, although this kind of macular degeneration causes symptoms similar to those of typical wet macular degeneration. Anyways, RPE detachment tends to evolve to the more common wet form of macular degeneration associated with the development of newly growing abnormal choroidal blood vessels.

 

The exact causes of macular degeneration are not known, however some contributing factors were identified, those include:

Race:

White people, especially those over the age of 75, are more likely to develop macular degeneration.

Light-colored eyes:

People with light-colored eyes appear to be at a greater risk than those with darker eyes.

Family history of macular degeneration:

The odds of developing macular degeneration are higher in a person who has got someone in his/her family that had macular degeneration. Some genes that are associated with macular degeneration have been identified in recent years. For assessing early risk of the disease, genetic screening tests may be helpful in the future.

Sex:

Because women tend to live longer, they're more likely to experience the effects of severe vision loss from the disease, and are more likely to develop macular degeneration.

Cigarette smoking:

The risk of macular degeneration doubles in the case of exposure to cigarette smoke. The single most preventable cause of macular degeneration is cigarette smoking.

Obesity:

The chance that early or intermediate macular degeneration will progress to the more severe form of the disease can be increased by being severely overweight.

Cardiovascular diseases:

These include high blood pressure, stroke, heart attack and coronary artery disease with angina.

Exposure to sunlight:

Only a small percentage of ultraviolet (UV) light actually reaches the retina despite the fact that the retina is more sensitive to shorter wavelengths of light, including ultraviolet light. By the transparent outer surface of the eye (cornea) and the natural crystalline lens in the eye, most ultraviolet light is filtered. The risk of developing macular degeneration is believed to be increased by long-term exposure to ultraviolet light; however, this risk remains controversial and it hasn’t been proved yet.

Low levels of nutrients:

This includes low blood levels of minerals, such as zinc, and of antioxidant vitamins, such as A, C and E. Antioxidants may protect the cells from oxygen damage (oxidation), which may be partially responsible for the effects of aging and for the development of certain diseases such as macular degeneration.
 

Complications

Complications:

None

Treatments:

Stopping further progression of the disease is what the treatment of wet macular degeneration focuses on.

 

The treatments for wet macular degeneration include:

Laser therapy (photocoagulation):

A high-energy laser beam is used in this treatment to destroy abnormal, leaky blood vessels located under the macula called choriodal neovascularizations (CNVs). This procedure is used to prevent further damage to the macula and stop continued vision loss for as long as possible.

 

As a treatment for wet macular degeneration, laser therapy has major limitations. If the patient has CNV directly under the center of the macula, this treatment isn't used. Additionally, the more damaged the macula is, the lower the likelihood of success. Only a small percentage of people who have wet macular degeneration are good candidates for laser therapy because of these restrictions.

 

Dark or gray spots that are already completely and permanently blank won't be replaced by laser treatment. But with time, the patient may stop being aware of this spot, especially when using both eyes. The laser surgery needs to be repeated in about half of those who seem likely to have a good result. But people can’t always repeat their laser treatment. 

 

The patient may retain more sight if his/her vision is closely monitored and he/she has frequent follow-ups with the doctor than if he/she goes untreated.

Photodynamic therapy (PDT):

Photodynamic therapy is usually used for treating CNV directly under the fovea that lies at the center of the macula and provides the sharpest vision in healthy eyes. All or part of the central vision could be destroyed in case conventional hot-laser surgery is used at this location. The chances of preserving some of that vision increase by PDT. It may halt the loss of the patient's vision or at least slow down the rate of vision loss, but it won't bring back any of the vision that's lost.

 

A cold laser and a light-sensitizing drug called verteporfin that's injected into the bloodstream of the patient are combined in this procedure. In the CNV under the macula, is where the drug concentrates. the drug releases substances that can theoretically close off the abnormal blood vessels without damaging the macula, and the CNV transforms into a thin scar when the doctor directs cold-laser light at the macula.

 

There's a better chance that the patient will preserve some of his/her vision with this procedure than if he/she had hot-laser surgery or no treatment at all, as the overlying rods and cones are largely preserved. If the CNV doesn't close or if it reopens after initial closure, the therapy can be repeated. After the procedure and until the drug wears off about five days after treatment, the patient will need to avoid direct sunlight and intensely bright lights.

Macular translocation surgery:

In certain circumstances when abnormal blood vessels are located directly under the fovea, macular translocation is used. The surgeon detaches the retina, shifts the fovea away from the CNV and relocates it over healthy tissue to perform the procedure. With tiny forceps or using a hot laser to destroy blood vessels without damaging the fovea, the surgeon can remove the exposed CNV. This surgery can preserve vision and in some cases even improve vision in case the vision loss is recent, the extent of CNV is limited and the tissue around the fovea is healthy. However, this surgery is not commonly used.

Vascular endothelial growth factor antagonists (anti-VEGF medications):

By blocking the effects of a growth factor these blood vessels need to thrive, these drugs help stop the growth (proliferation) of new CNV. For treating wet macular degeneration, these drugs are commonly used and are among the most effective therapies.

 


The formation of new blood vessels can be stopped and the leakage from existing blood vessels can be decreased by both ranibizumab and bevacizumab, which is a colon and rectal cancer treatment drug that's closely related to ranibizumab. As the blood vessels shrink and the fluid under the retina absorbs allowing retinal cells to regain some function, the patient may partially recover his/her vision in some instances. Although other anti-VEGF medications aren’t available for clinical use, but many of them are currently under study. 

 

These medications are injected directly into the eye. To maintain the beneficial effect of the medication, the patient may need repeat injections every four weeks. Whether anti-VEGF medications might prove more effective when used in combination with other therapies, such as PDT or injections of steroid drugs (glucocorticoids), or not, is still being investigated. The optimal timing of the intervals between injections of anti-VEGF medications is also being investigated.

Implantable optical devices:

The objects in the central part of the patient’s visual field may be enlarged in case the patient undergoes surgery to implant a miniature telescopic device into his/her eye. This method may improve visual acuity and quality of life in people with very advanced macular degeneration.
 

Prognosis:

Not available

Expert's opinion

Expert's Name:
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Clinical Trials:

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