Choroidal Neovascularization (CNV)

What happens in CNV

The retina's center, the macula, gives sharp central vision for reading, driving and recognizing faces. Beneath it lies a support layer (the retinal pigment epithelium) and Bruch's membrane, then the choroid. When this barrier is damaged by aging, stretching or inflammation, the retina sends out signals, especially vascular endothelial growth factor (VEGF), that trigger new vessel growth. These vessels grow through breaks in Bruch's membrane, leak fluid and blood, and eventually form scar tissue that destroys central vision.

Causes

Risk factors for AMD-related CNV include older age, smoking, family history, white race and having AMD in the other eye.

Symptoms

• metamorphopsia: straight lines, door frames or text appear wavy, bent or broken
• blurred or dim central vision
• a dark, gray or empty spot in the center of vision
• objects appearing smaller or larger than they are
• reduced color brightness
• difficulty reading or recognizing faces

Side vision usually remains normal. Because the other eye compensates, many people only notice symptoms when they cover the good eye.

Diagnosis

• Visual acuity and Amsler grid testing
• Dilated retinal examination
• Optical coherence tomography (OCT): a quick, non-invasive scan that shows fluid in and under the retina. It is used at almost every visit to guide treatment.
• Fluorescein angiography: dye injected into an arm vein shows leakage from new vessels.
• OCT angiography: shows blood flow in the new vessels without dye.
• Indocyanine green angiography for certain subtypes.

Treatment

Anti-VEGF injections

Anti-VEGF medicines block the signal driving vessel growth and leakage. They are injected into the eye with a fine needle after numbing drops, a quick office procedure. Medicines include aflibercept, ranibizumab, faricimab, brolucizumab and bevacizumab (used off-label).

• Treatment usually starts with monthly injections for about 3 months.
• Intervals are then adjusted based on OCT findings, often every 4 to 16 weeks, using "treat-and-extend" schedules.
• Many people need injections for years. Stopping too early often allows leakage to return.

Most people keep their vision stable, and many gain some vision, especially when treatment starts early. Myopic CNV often needs fewer injections than AMD.

Other treatments

• Photodynamic therapy: a light-activated drug for selected cases, such as polypoidal choroidal vasculopathy.
• Port delivery system: a refillable implant releasing ranibizumab, for some patients.
• Thermal laser: now rarely used, except for vessels well away from the center.
• Treating inflammation with steroids or immunosuppressants in inflammatory CNV.

Living with CNV

• Check each eye separately with an Amsler grid weekly.
• Stop smoking.
• If you have intermediate AMD, AREDS2 vitamins can reduce the risk of progression to wet AMD.
• Low vision services, magnifiers, bright lighting and large-print or audio tools help with daily tasks.
• Ask about driving safety. Many people can still drive if the other eye has good vision.

Outlook

Before anti-VEGF drugs, CNV usually led to severe central vision loss. Now, with prompt and consistent treatment, most people maintain useful vision. Delays in treatment, large bleeds and scarring reduce the chance of recovery. Peripheral vision is preserved, so CNV does not cause total blindness.

Frequently asked questions

What is choroidal neovascularization?

Choroidal neovascularization is the growth of abnormal, leaky blood vessels from the choroid into the area under the retina. Fluid and blood from these vessels damage the macula and blur or distort central vision. It is the defining feature of wet macular degeneration.

What causes CNV?

The most common cause is wet age-related macular degeneration. Others include high nearsightedness (myopic CNV), eye inflammation such as ocular histoplasmosis, angioid streaks, long-standing central serous chorioretinopathy and eye injury. VEGF is the key chemical signal driving vessel growth.

What are the symptoms of CNV?

Typical symptoms are straight lines looking wavy or bent, blurred or dim central vision, a dark spot in the center of vision, and objects looking a different size. Symptoms often develop over days to weeks and may only be noticed when covering the other eye.

How is CNV treated?

The main treatment is anti-VEGF injections into the eye, such as aflibercept, ranibizumab or faricimab. They stop leakage and often stabilize or improve vision. Injections are usually given monthly at first, then spaced out based on scans. Photodynamic therapy is used in specific cases.

Can you go blind from choroidal neovascularization?

CNV can cause severe loss of central vision if untreated, making reading and recognizing faces difficult. It does not affect side vision, so it does not cause complete blindness. Early anti-VEGF treatment preserves useful vision in most people.