Retinal neovascularization describes the growth of new, abnormal blood vessels within the retina, the light-sensitive tissue. These vessels are often fragile and can significantly impact vision, leading to severe visual impairment. This condition represents the body’s attempt to compensate for insufficient oxygen supply, but the resulting vessel growth is dysfunctional.
Understanding Retinal Neovascularization
The retina is a layer of tissue in the back of the eye, containing photoreceptor cells that convert light into electrical signals for the brain. Directly beneath the retina, the choroid is a vascular layer rich in blood vessels that supplies oxygen and nutrients. When parts of the retina experience a lack of oxygen (ischemia), the body responds by releasing growth factors, such as vascular endothelial growth factor (VEGF).
These growth factors stimulate the formation of new blood vessels. However, the vessels that form are often weak, leaky, and prone to bleeding. They can grow from the choroid into the retina or extend into the vitreous. Leakage from these vessels can cause fluid and blood to accumulate within the retina, leading to swelling and distortion of vision. Over time, these abnormal vessels can lead to scar tissue formation, pulling on the retina and potentially causing retinal detachment.
Common Causes of Retinal Neovascularization
Retinal neovascularization is often a complication of eye conditions that disrupt retinal blood supply. Age-related Macular Degeneration (AMD), particularly its “wet” form, is a common cause. In wet AMD, abnormal blood vessels, often originating from the choroid, grow under the macula, the central retina responsible for sharp vision. This growth is driven by high levels of VEGF produced by the retina in individuals with AMD.
Diabetic Retinopathy, a diabetes complication, is another prevalent cause. Chronic high blood glucose levels damage retinal blood vessels, leading to poor circulation and oxygen deprivation. In the advanced stage, known as proliferative diabetic retinopathy (PDR), the retina releases growth factors in response to this oxygen shortage, triggering new, fragile blood vessel formation on the retinal surface or into the vitreous. Other less common causes include retinal vein occlusions, where blocked retinal veins lead to ischemia and neovascularization, and ocular histoplasmosis syndrome, an eye infection causing choroidal neovascularization.
Identifying the Signs
Early recognition of retinal neovascularization is important for intervention. Individuals may notice a gradual or sudden blurring of their central vision, ranging from mild to severe. Distorted vision, where straight lines appear wavy or bent, is another common symptom. Some people report dark spots or blind spots appearing in their central field of vision, making reading or face recognition difficult.
The sudden appearance of new floaters, small specks or cobweb-like shapes drifting across the field of vision, can indicate bleeding from the abnormal vessels into the vitreous. Flashes of light may also occur. Vision may decrease, especially in low light. These symptoms can affect one or both eyes, and their severity varies with the extent and location of abnormal vessel growth, bleeding, or fluid leakage.
Diagnosis and Treatment
Diagnosing retinal neovascularization begins with a comprehensive dilated eye exam to view the retina directly. Specialized imaging tests provide detailed information. Optical Coherence Tomography (OCT) is a non-invasive scan that captures cross-sectional images of the retina, revealing fluid accumulation, swelling, and abnormal vessels within or beneath the retinal layers. Fluorescein Angiography (FA) involves injecting a dye into a vein, which travels to the eye’s blood vessels. A special camera highlights leaky or abnormal vessels as the dye flows.
Treatment for retinal neovascularization focuses on inhibiting the growth of these abnormal vessels and managing their complications. Anti-VEGF injections are the current standard of care. Medications like ranibizumab (Lucentis), aflibercept (Eylea), and bevacizumab (Avastin) are injected directly into the eye. These drugs work by blocking vascular endothelial growth factor (VEGF), a protein promoting blood vessel growth, reducing leakage and preventing new vessel formation. Injections are administered monthly initially, with frequency adjusted based on patient response.
Other treatments may be considered for specific situations. Laser photocoagulation can seal off leaking blood vessels or destroy abnormal vessels, especially away from the macula. Photodynamic therapy (PDT) involves injecting a light-sensitive drug followed by activation with a specific laser to close abnormal vessels. In severe cases, such as significant vitreous hemorrhage or retinal detachment from scar tissue, vitrectomy surgery may be necessary to remove blood or repair the retina. Early detection and consistent management are important to preserving vision.