Intravitreal Injections

In the last decade and a half, there have been great advances in the treatment of diseases of the retina. Understanding of diseases is greatly enhanced by revolutionary technologies like Optical Coherence Tomography (OCT), OCT Angiography (OCTA), fluorescein angiography, and Autofluorescence imaging at eye clinics as well as research that has taken place in various institutions across the world.
Retinal diseases like wet age-related macular degeneration (AMD) that would have led to definite blindness just 15 years back, can be treated successfully with the recent advances. The use of different types of injections given inside the vitreous cavity is a giant leap in the treatment of these diseases.
There are mainly 2 types of injections, Anti VEGF injections and steroid injections.

What are the diseases where these injections are used?
They are used for the treatment of wet AMD, retinal vein occlusion (RVO) with macular edema, proliferative diabetic retinopathy (PDR), and diabetic macular edema (DME). They are used in certain cases of retinopathy of prematurity (ROP)

What are AntiVEGF injections?
Vascular endothelial growth factor (VEGF) is a protein that gets raised to higher levels in retinal diseases mentioned above. They facilitate the development of abnormal blood vessels under the retina ( wet AMD) or on the surface of the retina ( PDR). They bind to receptors on vessel walls and lead to increased leakage. It may also lead to the development of Cystoid changes causing macular edema. Anti VEGF injections are monoclonal antibodies that mimic the VEGF molecules. They act by blocking these receptors and preventing VEGF from causing damage. This results in constriction of abnormal blood vessels that grow under or over the retina and reduces their chances of regenerating and growing. It also helps in drying the macular edema and improving vision.

How long do these injections last? How many injections are required for a particular pt?
These injections typically act for 4-6 weeks before their action starts reducing. Hence at the beginning of treatment 3 to 6 injections, one per month, are given. This is known as the loading dose. After this, the patients have to be examined at 4 to 6weekly intervals. If disease pathology seems to be worsening again, injections have to be given again. It is impossible to predict exactly how many injections a patient will need at the beginning of treatment as it needs to be repeated till the disease process is resolved completely. However recent studies have shown that in the first year a patient typically needs 8-9 injections, in the second year 4-5, in the third year 3-4, and 1-2 injections per year from the 4th year onwards if the patient continues with treatment on a regular basis.

How are these injections given?
These injections are given in the vitreous cavity in the operation theatre under complete sterile precautions. The procedure is performed inside the operation theatre under sterile precautions to avoid infection.
At the beginning of the procedure parts around the eye are cleaned with an antiseptic solution. A sterile drape is applied. Eyelids are separated by a clip-like instrument known as a speculum. Anesthetic drops are applied. The injection is given using a very thin and sharp needle. Usually, the procedure is painless and a patient only feels a slight prick. The procedure typically takes 7-10 minutes though injection takes less than 30 seconds.

What precautions have to be taken after the injections?
Antibiotic eye drops are prescribed for a period of 5-7 days postoperatively. Face and head wash should be avoided for a period of a week. Splashing water in the eyes is to be strictly avoided. It is advisable to use protective eyewear if there is a lot of dust in the environment. Patients are asked to come for evaluation after 24 hours to make sure that there is no infection or inflammation in the postoperative period.
A patient must report back immediately if she develops severe redness of the eye, watering, pain, and drop in vision. It’s quite common to have a small amount of bleeding at the site of injection, causing redness (Subconjunctival hemorrhage). However other signs like pain and watering are not associated with it. Sometimes patients notice black spots inside the eye caused by air bubbles injected along with the drug. They resolve in 2 to 3 days

What types of AntiVEGF injections are available?
Currently there are 4 types of injections available. Bevacizumab (Avastin), Ranibizumab (Razumab and Accentrix), Brolicizumab ( Pagenax) and Aflibercept (Eylea).

Of these, Avastin injection is primarily used in cancer therapy. But since 2005, the injection has been widely used in retinal disorders. There have been many studies around the world on the effectiveness of Avastin in many retinal diseases. However, the use of this injection in eye diseases is considered off-label. This means that the government’s relevant authority has only allowed the use of this drug in cancer patients. Theoretically, there are higher chances of infection as well as thromboembolic phenomena like a stroke with Avastin.
It is mandatory to provide this information to patients with retinal disorders before giving these injections inside the eye. This information is available on the website of the Vitreoretinal Society of India (VRSI). (http://vrsi.in/wp-content/uploads/2018/02/Avastin_Guidlines_Book.pdf)
The other 3 types of injections are designed for retinal disorders and are approved by the relevant government authorities for ophthalmic treatment.

(Related Video: https://youtu.be/Qce6MBuZfHI)

B) Steroids: These are very effective drugs when used to treat macular edema caused by diabetic retinopathy or retinal vein occlusion. They are usually not used for the treatment of AMD or hemorrhage in the vitreous cavity.
Two types of steroids are commonly used in clinical practice. Triamcinolone acetonide and Ozurdex implant.

Triamcinolone acetonide: This drug is present in powder format.It is used in various diseases in various specialties. Use in ophthalmology is off label. It is a very potent and cost-effective treatment option. However, the likelihood of developing high intraocular pressure causing glaucoma and rapid progression of cataracts are common complications. Effect of injection tends to last for 1-2 months, after which reinjection might be necessary. The risk of complications increases with subsequent injections. Postoperatively patients might see a shower of black or white dots/floaters inside the eye for a few days.
Ozurdex: This is a sustained release drug delivery for dexamethasone. A small tablet of the drug is injected into the vitreous cavity, where it slowly dissolves over a period of 3-4 months. The action of the drug lasts for 3-4 months. It is much less likely to cause glaucoma and progression of cataracts than triamcinolone. It is approved for the treatment of ophthalmic diseases

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