Intravitreal injections for the treatment of retinal diseases

[24/04/2012]

Intravitreal injections for the treatment of retinal diseases

This may seem like an obscure topic to the lay person but it has become a big part of the treatment armamentarium of the retinal specialist in the management of retinal diseases! It is therefore my aim to provide a basic understanding of what this involves so that individuals who may require this treatment can be better prepared.



What exactly is an intravitreal injection?

As shown in the image above, it involves "sticking a needle" into the eye and releasing specific drugs into the vitreous cavity. It is used for the treatment of a variety of eye diseases but in recent years, it has revolutionized the management of retinal diseases and has a significant impact not just on affected patients but also on retinal surgeons' lives!!

The "Revolution"?

The rise of intravitreal injections started in 2004 when intravitreal Macugen was first used in the management of age related macular degeneration (AMD). This drug was developed to inhibit vascular endothelial growth factor (VEGF) which is a growth factor involved in the development of blood vessels. This had modest effect on the disease but the following year when Avastin (another inhibitor of VEGF) was first used to treat AMD, the revolution truly took off!

This was the first time there was any treatment that could actually improve vision in people with wet AMD. From Avastin, another drug came into the market in 2006 - Lucentis. This was a designer drug specifically manufactured to treat VEGF driven eye diseases as compared to Avastin (which was a cancer drug for metastatic bowel cancer).

The impact of this 'revolution' extended beyond its positive effects on patients but also the increased workload for retinal surgeons as these injections had to be given every month in order to maintain its efficacy. There was also far reaching consequences for healthcare services in some countries as reimbursement for this very expensive drug burned very large holes in the healthcare budget!

What conditions are treated with intravitreal injections?

The anti-VEGF drugs (Avastin & Lucentis) were initially used to treat wet AMD. However, it's use has extended to many other retinal diseases which all have a common association - the blockade of VEGF would result in a positive impact on the disease. Aside from wet AMD, other diseases would include diabetic retinopathy, retinal vein occlusions (or eye stroke), neovascular glaucoma and even retinopathy of prematurity.

So far, I have mentioned only anti-VEGF drugs which has resulted in an exponential increase in the number of intravitreal injections in recent years. In actual fact, this technique of drug delivery is not at all new. We have been giving antibiotics (in cases of severe eye infections), anti-virals (in patients with AIDS) and steroids (for inflammatory eye diseases) for a long time. This mode of drug delivery allows for a good amount of drug getting to the intended target without having large amounts in the body (when taken orally or through a vein) and giving unwanted side effects.

The Future of intravitreal injections?

More drugs are being developed to treat these retinal diseases - some which can last longer and would therefore, reduce the frequency of injection. Other techniques are being researched i.e. different ways of storing and releasing the active drug in a gradual and controlled manner could mean even less frequent injections.

I leave you with a well made video about intravitreal injections from a lay person's point of view.