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What is Choroidal Neovascularization (CNV)?

Choroidal neovascularization (CNV) is the medical term for growth of new blood vessels beneath the eye’s retina (subretinal). It can be painless, but can lead to macular degeneration, a major cause of vision loss. This condition may respond to treatment, while being incurable. CNV is diagnosed by an eye specialist, an ophthalmologist, who will make a diagnosis by taking pictures of your eyes using advanced medical imaging.

How does the eye work?

In simple terms, when light passes through the cornea at the front of the eye it is focused by the lens onto the retina. The retina lines the inside of the eye. It transforms the light into electrical signals that travel through the optic nerve directly to the brain where they are interpreted as images. The macula is the part of the eye in the central area of the retina that focuses central vision, what we would typically see that is directly in front.1 It affects how we see to read and watch TV and how we handle actions such as typing, chopping and sewing, tasks requiring fine detail.

What is macular degeneration?

The leading cause of vision loss in the United States, there are several types of macular degeneration, the deterioration of the macula. It primarily affects the clarity of our central vision by causing blurry or blind spots. Some people with severe macular degeneration can be considered legally blind.2

Age, genetics and the environment can all play a role in the development of macular degeneration. It affects millions people, commonly over age 55. Routine eye exams are important to clinically diagnose, monitor, and manage these conditions because the specific choice of clinical treatment will vary.

Dry AMD

Dry age-related macular degeneration (AMD) is the most common form of macular degeneration, accounting for around 90% of cases.2 It is also called non-neovascular and non-exudative AMD because the vessels of the eye do not leak. It is caused by a continual thinning of the retina and results in color changes of the macula. Eye cells give off waste product that can accumulate as yellowish spots on the retina. These are called drusen. They can cause the breakdown or shrinking of the retina and are very common even in those without AMD.

Wet AMD

10-15% of the population has “wet” AMD.2 This is when new blood vessels, known as CNV, grow beneath the retina. If these blood vessels ooze or leak they can disrupt the normally smooth macula, causing it to bulge or move, distorting or obliterating some or all of a person’s central vision. You may experience these as spots or blotches in the middle of what your eye sees. It can also cause straight lines to appear wavy. It generally does not affect peripheral vision.

What is myopic macular degeneration (MMD)?

Myopia is the condition of being short-sighted, what we generally refer to as nearsightedness.1 This means you can see things clearly and sharp close up, but items may be blurry in the distance. A common condition, it is generally managed through the use of corrective lenses. Myopic macular degeneration generally affects nearsighted people, those who have an elongation of the eye, or an increase in the distance between the cornea and the retina. When the retina thins it can tear causing bleeding underneath. This causes anatomical changes in the eyeball that impact the ability to focus incoming light. It can also impair the ability to see detail making it difficult to read, look at fine art, or interpret facial expressions. Some people also experience altered or restricted color perception.1

CNV in MMD

Myopic macular degeneration differs from AMD. It has a genetic component and often runs in families. It can also be worsened by long-term close-up work such as sewing or other craft or technical skills.3 In some people, new blood vessels grow under the retina from vessels in the choroid layer of the eye. This can cause the retina to stretch and cells in the macula to shrink (atrophy) or die, causing the development of a blind spot in the middle of the visual field.3 This CNV can be delicate, with cell walls that may leak or ooze beneath the retina, causing scarring resulting in partial vision loss.

Treatment approaches

There is no known cure for macular degeneration. For Dry AMD there is also no FDA approved treatment. There are steps you can take to care for your general health like diet and exercises, as well as wearing sunglasses. These steps can benefit other kinds of macular degeneration that also have other medical options to slow their progression.

Anti-VEGF

When CNV vessels leak it is generally due to the presence of a protein called vascular endothelial growth factor (VEGF). It can be treated with anti-vascular endothelial growth factor (anti-VEGF), a drug that is injected into the eye (intravitreal) that can prevent or slow new vascular growth (CNV).1,4

Eye injections

Administered by an ophthalmologist, these shots are first given once a month for 3 months. Then done on a maintenance basis determined individually for each person. It is hard to get full compliance with anti-VEGF because people are reluctant to get shots directly into the jelly of their eyeballs, even though they are generally quick and not painful.1,3,4 Anti-VEGF is used based on the location of the leak. If it is not centered near the macula alternative treatment using laser photocoagulation may be used to stop leaking blood vessels.

Laser surgery

Wet AMD and myopic macular degeneration can both be treated with anti-VEGF injections.3 Laser treatment is now a less common approach; it was more widespread before the development of anti-VEGF. The lasers use light to destroy or seal (close off) new blood vessels thus preventing leakage. Laser use can leave scars, leaving permanent damage in the visual field.2,4

There are drugs used to treat wet AMD that are aimed at reducing new blood vessel growth. Other approaches include Photodynamic Therapy or PDT, which combines the use of drugs and light therapy.2

Talk to your doctor

Ophthalmologists treat all of these degenerative conditions. A clear diagnosis will help inform the recommended treatments associated with any macular degeneration. Eat right, exercise and protect your eyes from the sun. Report any ongoing visual changes to your doctor right away.

Linda Minton | February 2019
  1. Myopic Macular Degeneration. Available at: https://www.mdfoundation.com.au/content/myopic-macular-degeneration. Accessed 2.21.19.
  2. Haddrill, M. What is Macular Degeneration? Available at: https://www.allaboutvision.com/conditions/amd.htm. Accessed 2.19.19
  3. Dunaief, J. Myopic Macular Degeneration. Available at: https://www.brightfocus.org/macular/article/myopic-macular. Accessed 2.21.19
  4. Turbert, D. Choroidal Neovascular Membranes Treatment. Available at: https://www.aao.org/eye-health/diseases/choroidal-neovascular-membranes-treatment. Accessed 2.20.19.