Causes of New Blood Vessel Growth
In the case of a retinal vein blockage or diabetic eye disease in the retina, the retina becomes “ischemic,” meaning it does not have enough oxygen flowing to it. The retina begins to release chemicals to counteract the ischemia, including vascular endothelial growth factor (VEGF).
VEGF leads to new blood vessel formation, which theoretically could bring more oxygen to the sick “ischemic” retina. However, in the case of these diseased retinas, the new blood vessels are leaky and abnormal. For example, in patients with diabetic retinopathy, there is bleeding of these abnormal vessels. Sometimes the bleeding can be so severe that the back of the eye, the vitreous cavity, fills with blood (vitreous hemorrhage). The VEGF being released by the ischemic retina also migrates to the front of the eye, where it causes new blood vessel formation on the iris and in the drainage angle.
The symptoms of a retinal vein blockage or diabetic retinopathy can include vision loss, although sometimes patients can still have good vision. These retinal diseases are often diagnosed because the patient experiences vision loss and seeks care, or they are diagnosed during a routine annual examination. Diabetic patients should have yearly dilated examinations to evaluate for diabetic retinopathy, and more often if they have mild forms of diabetic retinopathy.
The symptoms of neovascular glaucoma can include pain, redness, and decreased vision, although in early stages of the disease it is possible not to have any symptoms.
Treatment of neovascular glaucoma includes two parts:
- Treat the underlying cause of neovascular glaucoma, that is, the ischemic retina; and
- Lower the eye pressure, whether through medications, laser, surgery, or a combination of these types of treatments.
Treatment of the ischemic retina includes using a retinal laser (pan-retinal photocoagulation), which decreases the retina’s production of VEGF, and injections of anti-VEGF medications into the eye, which will cause the abnormal blood vessels to start regressing or disappearing.
It is extremely important to treat the underlying cause of neovascular glaucoma, so often your care may include several specialists, such as a glaucoma and retina specialist. It is also possible that you will be treated by a comprehensive ophthalmologist. Your primary care doctor should also be included as part of the team, as will be discussed below in the prevention section.
If glaucoma drops fail to bring the pressure down adequately, surgery is often the next step. In neovascular glaucoma, there are many considerations for what surgery to choose, including the potential of recoverable vision. Tube shunt surgery is the usual surgery recommended for patients, as it can bring down the pressure immediately and has higher rates of success than other filtering surgeries, such as trabeculectomy. If vision is very poor, some ophthalmologists may recommend a less invasive procedure such as a type of laser that destroys the ciliary body, the part of the eye that produces fluid.
Prevention should be focused on preventing the most common underlying causes of neovascular glaucoma, including retinal vein blockage and diabetic retinopathy. Risk factors for these retinal diseases include age, high blood pressure, diabetes, and heart disease. Indeed, for some types of vein occlusion, high eye pressure is a risk factor.
Controlling blood pressure and diabetes is extremely important, and patients and their ophthalmologists should work with the primary care team to ensure these goals are met. For diabetics especially, another key prevention measure is a yearly dilated exam, and for all individuals ages 65 years and older, a comprehensive eye exam every 1 to 2 years is recommended. The American Academy of Ophthalmology also recommends a baseline comprehensive eye examination at age 40.