Wet Macular Degeneration is Choroidal Neovascularization (CNV) – The Unwanted Blood Vessels

wet amd vision lossIn the case of choroidal neovascularization (CNV, also known as “wet” macular degeneration), new blood vessels are the cause of the problem. Yet normally when new blood vessels are created in the body, it is a good sign. For example, it is part of the way the body heals wounds. But with CNV, the blood vessels pose a problem because they originate in the choroid layer of the eye and pass through a weak part of the Bruch’s membrane, the innermost layer of choroid, then pass into the subretinal pigment epithelium (sub-RPE) or subretinal space. These blood vessels aren’t supposed to exist in this part of the eye, are weak and tend to leak, potentially substantially impairing vision.

Oxygen and nutrients are provided to the eye by the choroid. The choroid layer already contains a large number of blood vessels, and these extra blood vessels also cause cramped conditions and impair normal functioning. In some cases, CNV can even lead to blindness.

CNV is also known as “wet” macular degeneration  (AMD). Approximately 10-15% of the cases of AMD are CNV. The rest are “dry” AMD.

CNV can be secondary to both infectious and noninfectious inflammation of the uvea, the middle layer of the eye.

Diagnosis

This condition can develop suddenly, and people can find that their central vision has deteriorated within a few weeks. Sometimes they may also notice that their vision is distorted (metamorphopsia), and colors do not look normal.

If these new blood vessels start hemorrhaging, the onset of CNV can be accelerated.

An accurate examination is necessary in order to identify the correct diagnosis. Preferential hyperacuity perimetry can be used to detect CNV. But as CNV can often originate from the rear of the pole lesions, it can be difficult to identify. A fluorescein angiography (FA) can be used to confirm if the CNV lesion complex is “classic” or “occult”. Classic CNV is indicated by well-demarcated areas with early hyperfluorescence and intense late leakage. Occult CNV areas are not as clearly defined. Leakage appears in the early to middle phase, and the leaks are less intense.

Indocyanine-green angiography (ICGA) can be used to obtain relevant information about the choroidal status. Optical coherence tomography (OCT) may also be useful to determine the clinical characteristics of the CNV.

Causes

Choroidal neovascularization causes vary. For example, it can occur when there are defects in the Bruch’s membrane. Excessive quantities of vascular endothelial growth factor (VEGF) are associated with the development of CNV.

It can occur with the rare genetic disease pseudoxanthoma elasticum. In rare cases it also appears with optic disc drusen, which is a relatively common disease caused by the calcification of globules of mucoproteins and mucopolysaccharides in the optic disc.

CNV can occur in the cracks within the retinal macular tissue (known as “lacquer cracks”) caused by extreme myopia or malignant myopic degeneration.

The Wisconsin Beaver Dam Study funded by the NIH showed that 1.2% of adults (aged 43-86 years) with age-related macular degeneration (ARMD) also developed CNV. This study also indicated that 5-10% of people suffering from myopia also developed CNV. Myopia is an eye disease condition in people resulting in being nearsighted.

CNV can also be found in patients with ocular histoplasmosis syndrome (OHS), a disease caused by granulomatous fundus lesions. CNV caused by OHS can cause severe vision loss in people who are only in their thirties and forties.

Eye injuries may also be a factor in the development of CNV. New studies* have shown high levels of expression of the proteins CD40 and its ligand CD40L in people with CNV diseases. CD40 is thought to stimulate the secretion of vascular endothelial growth factors (VEGF) and other fibroblast growth factors, but the exact mechanism causing CNV has not been fully determined.

Prognosis

As with many diseases, early detection can lead to better results.

Although the current standard treatments of CNV described below are effective in the sense that they improve vision, the problem often reoccurs. People suffering from CNV are also more likely (25%) to develop CNV in their other eye, according to the American Academy of Ophthalmology. This outcome is also supported by reports from physicians.

Treatment

Intravitreal injections of anti-VEGF drugs such as Avastin, Macugen and Lucentis are the most common treatment modality for CNV. These drugs bind to and inactivate vascular endothelial growth factor, thereby controlling the neovascularization and lessening the spread of fluids below the retinal pigment epithelium.

When CNV is present alongside neovascular (“wet”) age-related macular degeneration, it is generally treated with a combination of photodynamic therapy and intravenous photosensitive drugs. The non-damaging laser light activates the drug, which then destroys the new blood vessels. It also inhibits the development of new blood vessels by forming fibrous clots.

The use of surgery in the treatment of CNV is controversial. Some patients with subfoveal CNV appear to benefit from surgical removal. Only rarely do eyes with ARMD improve. Longer-term follow-up and refined case selection are required before this approach can be widely recommended.

Other Treatments

As with any part of the body that is not functioning normally, diet and lifestyle changes can help prevent and maybe even reverse the impairment.

The new research shows the expression of proteins may play a part in the development of this disease. Obviously essential nutrients, both as part of a normal healthy diet and as supplements, can help the body restore balance so that the correct proteins are expressed, rather than ones that could be having a detrimental effect.

Organic foods are a good way to obtain some of these essential nutrients. These can be taken in the form of a daily juice mixture of ingredients such as ginger, garlic, greens (e.g. kale), apples, grapes, raspberries, lemon, chlorophyll, wheat grasses, beets, cabbage, carrots and celery. It’s best not to use too many fruits, as excess sugar is not healthy either. Learn more about juicing.

See research on macular degeneration vitamins and supplements.

What caused the initial defect in the Bruch’s membrane which allowed the blood vessels to pass into the subretinal space? This isn’t known, but as with any organ in the body, all parts must be kept in good working condition through exercise. See these free eye exercises.

If you notice a difference in your vision, it is important to visit an ophthalmologist as soon as you can in order to prevent potentially serious damage to your eyes.

 

* http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3931637/

More research: http://europepmc.org/search/?page=1&query=%22ARMD%22

Summary
Article Name
Choroidal Neovascularization or Wet AMD - The Unwanted Blood Vessels
Description
Choroidal neovascularization (CNV) causes visual impairment that can in some cases lead to blindness. Its causes are unclear. Treatments and prognosis.
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