Retinal Neovascularisation

Retinal neovascularisation involves the abnormal growth of new blood vessels in the retina—a process that attempts to help the eye but often causes serious harm. These fragile vessels can leak blood and fluid, threatening your vision if not detected and treated early.

Table of contents

• What is retinal neovascularisation?
• The retina and its blood supply
• What causes retinal neovascularisation?
• Medical conditions involving retinal neovascularisation
• Signs and symptoms
• Treatment options

What is retinal neovascularisation?

Retinal neovascularisation refers to the growth of new, abnormal blood vessels in your retina—the light-sensitive tissue at the back of your eye that enables you to see^[1]. This process happens when your body attempts to replace blood vessels that have been damaged or lost due to injury or disease^[2].

These new blood vessels are fundamentally different from healthy ones. They are fragile and lack the tight connections that normal retinal blood vessels have^[12]. Because of their weakness, they break easily, allowing fluid and blood to seep into the retina and surrounding areas^[3]. This leakage can lead to various vision problems and, if left untreated, may result in permanent vision loss^[3].

New fibrous tissues often form between these abnormal vessels, which can further decrease vision^[1]. The process may also cause inflammation and scarring in the eye^[1].

The retina and its blood supply

To understand retinal neovascularisation, it helps to know how the retina normally receives its blood supply. The retina is nourished by two separate sources of blood vessels^[4].

The first source consists of blood vessels within the inner layers of the retina itself. These vessels enter at the optic nerve and travel along the retina’s surface, sending branches that form shallow and deep networks^[4]. These vessels are located far enough in front of the light-sensing cells called photoreceptors that light can navigate around them without creating blind spots^[4].

The second source is the choroid—a spongy, pigmented layer of blood vessels and connective tissue located between the retina and the outer wall of the eye^[2]. The choroid supplies oxygen and nutrients to the outer layers of the retina^[3]. The outer portion of the retina, where photoreceptors capture light, is normally free of blood vessels^[4].

What causes retinal neovascularisation?

Retinal neovascularisation typically occurs as a protective response to injury or disease^[1]. The most common trigger is retinal ischemia—a condition where parts of the retina don’t receive enough oxygen because of damaged or blocked blood vessels^[4].

When the retina becomes starved of oxygen, it releases chemical signals to encourage new blood vessel growth^[7]. One key substance involved in this process is vascular endothelial growth factor (VEGF), a protein that stimulates the formation of new blood vessels^[4]. While this response aims to restore blood flow, the new vessels that form are abnormal and cause more harm than good^[3].

Common underlying causes of retinal ischemia include diabetes, blockages in retinal blood vessels, high blood pressure, and certain inherited blood disorders^[7].

Medical conditions involving retinal neovascularisation

Several medical conditions are associated with retinal neovascularisation. Understanding these connections is important because early detection can help preserve vision.

Diabetic retinopathy

Diabetes causes chronic high blood sugar levels that gradually weaken the tiny blood vessels in the retina^[2]. In the advanced stage known as proliferative diabetic retinopathy, neovascularisation becomes a major feature^[2]. As fluid or blood accumulates, the macula—the central part of the retina responsible for sharp, detailed vision—may swell, a condition called diabetic macular edema^[2]. This leakage increases the risk of retinal detachment, central vision loss, permanent nerve damage, and blindness^[2].

Retinal vein occlusions

The retina relies on a complex network of blood vessels, including arteries that bring oxygen-rich blood and veins that carry depleted blood away^[3]. When one of these vessels becomes blocked—a condition called occlusion—the normal blood flow is disrupted^[2]. In response, the eye attempts to restore circulation by growing new blood vessels^[3]. Unfortunately, because these vessels are fragile and abnormal, they worsen the problem and create a range of vision difficulties^[3].

Retinal detachment

Neovascularisation can lead to excessive leakage of blood and fluid into the vitreous, the clear, gel-like substance that fills the eye^[2]. This fluid buildup can pull on the retina, causing it to partially or fully detach—a serious emergency requiring immediate medical attention^[2]. Neovascularisation is especially linked to a type called tractional retinal detachment, which may result from diabetes, surgery, or fluid accumulation^[2].

Other causes

Additional conditions that may lead to retinal neovascularisation include sickle cell disease, retinopathy of prematurity (a condition affecting premature infants), severe narrowing of the carotid artery in the neck, and certain rare diseases^[7].

Signs and symptoms

Many people with retinal neovascularisation do not experience symptoms in the early stages^[7]. By the time vision problems appear, significant damage may have already occurred. This is why regular comprehensive eye exams are essential, especially for people at higher risk^[2].

When symptoms do develop, they may include:

• Blurred or distorted central vision^[1]
• Straight lines appearing wavy or bent^[6]
• A dark, gray, or empty spot in the center of your vision^[1]
• Difficulty recognizing faces or seeing fine details^[3]
• Sudden vision changes or worsening vision in one or both eyes^[1]

If you notice any of these symptoms, it’s important to contact an eye care professional right away. Early treatment can make a significant difference in preserving your vision^[6].

Treatment options

Treatment for retinal neovascularisation depends on the underlying cause, but several approaches are commonly used. The goal is to stop the abnormal blood vessel growth, prevent further leakage, and preserve as much vision as possible.

Intravitreal injections

The most common treatment is injection of anti-VEGF medications directly into the eye^[2]. These drugs work by blocking vascular endothelial growth factor, the protein that drives abnormal blood vessel growth^[3]. By inhibiting VEGF, these medications slow or stop the formation of new vessels and help prevent fluid from leaking into the eye^[2].

Several anti-VEGF drugs are available, including bevacizumab (Avastin), ranibizumab (Lucentis), aflibercept (Eylea), brolucizumab (Beovu), and faricimab (Vabysmo)^[2]. Your doctor will determine which medication is best for your specific situation.

Laser therapy

Laser treatment is another important option. The main technique, called pan-retinal photocoagulation (PRP), is often used for diabetic retinopathy and retinal vein occlusions^[2]. During this procedure, a laser is applied to the peripheral areas of the retina, destroying oxygen-starved tissue and reducing the signals that trigger new blood vessel growth^[2].

Another laser technique, called photodynamic therapy, combines light with light-sensitive medications to destroy abnormal tissue and block vessel growth^[3]. Thermal laser treatment may also be used to burn and seal off leaking blood vessels^[5].

Vitreoretinal surgery

In advanced cases, surgery may be necessary. A common procedure is vitrectomy, which involves partial or complete removal of the vitreous gel from the back of the eye^[5]. This is typically performed when extensive scarring has developed or when other treatments haven’t been successful^[5].

For retinal detachment, a technique called pneumatic retinopexy may be used, in which a gas bubble is injected into the vitreous to help seal breaks and allow the retina to reattach^[5]. Additional techniques such as photocoagulation or freezing therapy may also be performed during surgery^[5].

Importance of early treatment

The key to successful treatment is early detection. Regular dilated eye exams allow your eye care professional to identify neovascularisation before serious complications develop^[2]. If you have diabetes, high blood pressure, or other conditions that put you at risk, monitoring your vision and attending scheduled eye appointments is critical^[2].

• Retina
• Choroid
• Macula
• Vitreous
• Optic nerve