Intravitreal injections consist of the introduction, by injection, of specific drugs into the eye, precisely in its gelatinous component known as the “vitreous body”; such injections are used to treat certain retinal diseases, such as diabetic retinopathy, the wet form of age-related macular degeneration, and retinal vein occlusion. These diseases can cause severe vision loss and their treatment must therefore be early and prompt.
The drug is injected as it is not possible to make it reach the diseased tissue, that is, the retina, in any other way.
Before the injection, the eye is treated with drops of anesthetic, so that the discomfort is minimized; the eye and the surrounding skin are disinfected and then proceeding to the actual injection that is carried out in a specific area, where the risk of damage to the internal structures is minimal. Intravitreal injections may need to be repeated many times, depending on the disease being treated.
The treatment must be carried out in an operating room that is also authorized for cataract surgery; further antibiotic prophylaxis with eye drops will also be required. After the injection, patients may feel a sensation of a foreign body or see loose bodies and rarely may experience fleeting pain, sometimes bleeding may develop on the white surface of the eye: unsightly but not dangerous. The risk of more serious complications exists as for any surgery but fortunately, it is very low: among these, for example, there are intraocular infections.
All information relating to the complications that may arise from an intravitreal injection are reported in the specific informed consent for the drug that will be delivered; we invite you to read it carefully with a family member.
Don’t forget your eyes. Get regular eye exams.
What is VEGF (Vascular Endothelial Growth Factor)
Also known as VEGF-A it plays a pivotal role in controlling both physiological and pathological angiogenesis. In the retina, specific studies have shown that VEGF can be secreted by different types of retinal cells such as EPR cells, pericytes, astrocytes, Müller cells, and endothelial cells.
Monoclonal antibodies from the anti-VEGF drug series are widely used in ophthalmology; the concept is very simple: a monoclonal antibody means that it is an antibody produced in an infinite series, therefore these antibodies can be produced starting from an antibody, multiplied by N times. We then have a molecule available that has the ability to adhere to a certain antigen, and therefore we can use them to neutralize any molecule within our body that we are interested in neutralizing.
In the case of the ischemia of the retina, the eye stimulates vasoproliferation, therefore both in the case of diabetic retinopathy and thrombosis of the central retinal vein, and in the case of maculopathies, the eye, again which has relative local ischemia, calls for new vessels to inhabit it. The retina with having no oxygen, says to the vessels next to it, “come help me and bring me some oxygen, bring me something to eat, let me breathe.”
This, which would seem like a good thing, is actually a very bad thing because the vessels that are going to form again are bad vessels, which should not exist.
We have a number of vessels in our bodies that are already sufficient in number, therefore calling for new vessels is very negative because these propagate incorrectly and go to inhabit areas that would not have been inhabited. The eye is a transparent organ, with very delicate structures and it is well understood that by putting in it vessels that grow in bulk, that pull, that move, that tear and bleed, a great mess is created.
The anti-VEGF drugs act precisely at this point in the chain of these events, therefore they are monoclonal antibodies that act on VEGF, which is the growth factor of the endothelial cells of the vessels, therefore, practically block the vasoproliferation and are a very powerful weapon that we have at our disposal, extremely widespread in the world of ophthalmology and is easy to use because the anti-VEGF is inserted directly into the vitreous cavity and let us remember that the eye has a blood-ocular barrier that causes a drug placed at inside the virtual cavity has practically no contact with the blood and therefore with the rest of the body. Thus, it is very safe because our drug has only a local action and side effects are very close to 0.
The disadvantage of these monoclonal antibodies is that they do not have eternal life and therefore when inserted inside the eye, they have an action that can last a few weeks. Hence, the need to have to perform these injections again and again.
Thanks to recent research we are now able to better understand the importance of the role that VEGF-A plays in the development of pathological angiogenesis (abnormal growth of capillaries) in some retinal diseases. In these diseases, there is intraocular neovascularization and a hyper-permeability of the endothelium with an accumulation of intra and sub-retinal fluid.
Retinal vascular diseases are characterized by edema and exudation that often affect the macular region and lead to a global reduction of central visual functions.
The Anti-VEGF Drugs
The anti-VEGF drugs are drugs that inhibit VEGF. They are used in the treatment of neovascularizations such as:
- proliferative diabetic retinopathy
- retinal vein thrombosis
- sub-retinal neovascular membrane
- neovascular glaucoma.
Numerous clinical studies have demonstrated the efficacy of these drugs for intraocular use and the total absence of drug-related adverse effects. Treatment with anti-VEGF drugs aims to prevent a further reduction in vision.
The drug cannot restore already lost vision and cannot guarantee the prevention of further loss of vision. The drug is injected into the vitreous and intravitreal injections are repeated at regular intervals (approximately every 4/6 weeks) as long as necessary.