What are choroidal neovascular membranes?
A healthy and intact retina is the key to good vision.
Choroidal neovascular membranes are abnormal growths of blood vessels under the retina, in the so-called choroid. Such vessels grow through the barrier between the choroid and the retina, with the flow of fluid from these vessels leading to loss of vision.
Choroidal neovascular membranes are connected with a number of serious eye diseases, primarily with the wet form of age-related macular degeneration. In addition, such membranes are formed in patients with histoplasmosis, myopic macular degeneration, as well as after eye injuries.
What are the symptoms of choroidal neovascular membranes?
Choroidal neovascular membranes can cause painless vision loss. Blind (dark) spots may appear, especially in the centre of the field of vision, as well as distorted vision – straight lines will appear crooked or broken.
Other symptoms:
- different sizes of objects, when viewed with each eye in turn;
- different perception of colours for each eye or colour fading;
- flash and flicker in the centre of the field of vision.
Terms
Retina is a layer of nerve cells, located on the inner surface of the eye. The retina senses light and sends signals to the brain, with images formed out of these signals in the brain.
Sclera is the outer albuminous shell of the eye.
Choroid is the layer containing blood vessels and connective tissue located between the sclera and the retina. Nutrients and oxygen enter the eyes through the choroid.
Who is at increased risk of developing choroidal neovascular membranes?
Most often, membranes form in people over 50, with the risk increasing with age. The main reason for choroidal neovascular membranes is the wet form of age-related macular degeneration.
Choroidal neovascular membranes can form at a young age in people with existing risk factors for certain eye diseases, as well as after eye injuries.
How is choroidal neovascular membranes diagnosed?
Choroidal neovascular membranes are diagnosed by fluorescence angiography and optical coherence tomography (OCT).
Fluorescence angiography.
A yellow dye (fluorescein) is injected into a vein of an arm. Through the blood vessels, the dye enters the retina, and at this time it is photographed with a special camera.
The photo shows the vessels stained with fluorescein, and the doctor can determine if the patient has choroidal neovascular membranes.
Optical coherence tomography (OCT). A special device scans the retina and forms detailed images of the retina and macula.
The images obtained show the ophthalmologist pathological blood vessels.
How are choroidal neovascular membranes treated?
Treatment may vary depending on the cause of the membrane formation. Ophthalmologists use intravitreal injection of inhibitors of vascular endothelial growth factor (VEGF) inhibitors, laser treatment and photodynamic therapy (PDT). If the disease progresses rapidly, it is possible to combine these methods.
Inhibitors of vascular endothelial growth factor (VEGF). These medications are often prescribed to treat choroidal neovascular membranes. VEFG antagonists resist vascular endothelial growth factor (VEGF), which stimulates abnormal growth of blood vessels under the retina. There are several VEGF inhibitors. Blocking VEGF inhibits membrane growth and fluid leakage, slows down deterioration of vision, and in some cases even improves vision.
Ophthalmologists inject VEGF inhibitors into the ocular cavity. Before injecting the medication, they disinfect the outer surface of the eye and apply local anaesthesia. Sometimes VEGF inhibitors are injected repeatedly at intervals of several months. This is necessary for the long-lasting effect of the treatment.
Laser treatment. A laser is used to treat choroidal neovascular membranes. A powerful laser beam is used to inflict minor burns on the retina. As a result, pathological vessels are destroyed, their growth stops, and blood and fluid no longer leak.
After the laser procedure, vision is more blurred than before the procedure, however, vision will usually stabilize within a few weeks. In the area of the retina, which was exposed to the laser, a scar is formed, so a blind (dark) spot remains in the field of vision forever.
Usually, the laser can destroy abnormal blood vessels, but in many cases the procedure has to be repeated in several years.
Photodynamic therapy (PDT). This procedure is performed with the so-called low-power cold laser in combination with photosensitizers – medicinal substances activated by the light rays. The procedure is usually performed on an outpatient basis at the doctor’s surgery.
First, a photosensitive substance is injected into a vein of an arm. With blood, it enters the vessels of the choroid, which must be destroyed. A laser beam is directed at these vessels to activate the substance. Thus, only individual pathological vessels are damaged.
Sometimes, after PDT, pathological vessels are restored, so the procedure has to be repeated.
Treatment of choroidal neovascular membranes can stabilize vision and stop vision deterioration. However, in many cases, lost vision cannot be restored. It is imperative for such patients to learn how to use their vision as efficiently as possible.
Summary
Choroidal neovascular membranes are new abnormal blood vessels which grow under the retina and can lead to painless vision loss.
Choroidal neovascular membranes are diagnosed with special images obtained by fluorescence angiography and optical coherence tomography (OCT).
For treatment, ophthalmologists use intravitreal injections of VEGF inhibitors, laser treatment and photodynamic therapy (PDT). If the disease progresses rapidly, these methods of treatments can be combined. Treatment of choroidal neovascular membranes can stabilize vision and stop vision deterioration.
For the detailed information on visual impairment, be sure to contact an ophthalmologist. The doctor will make every effort to preserve or restore your vision.
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