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Intravitreal injections

What to expect on the day of injection

On the day of the injection, I will clean up around your eye with some antiseptic and put some antibiotic and anaesthetic drops in your eye. I then place a spring called a speculum on your eyelids to keep them open. I will ask you to look over to 1 side and measure where I will place the injection. The injection takes only a few seconds and you may feel a mild prick as the needle goes in. You will notice some floaters in the centre of your vision like little flies. These take 2 to 3 days to clear. Afterwards I will give you some antibiotic drops to put into your eye 3 times a day for 3 days.

How Many Injections will I need?

The original trials for Lucentis involved having an injection every 4 weeks for 2 years (24 injections). Analysis of the results showed that any improvement occurred over the first 3 months. I now carry out what is called PRONTO dosing, which means having the first 3 injections 4 weeks apart. Thereafter patients have an assessment every 4 weeks, and if there are signs of activity in the blood vessels they have an injection. If there arenít signs of activity they donít. This reduces the average number of injections down to 13 or 14 with similar results.

Risks of the procedure

The main risk for an injection into the eye is infection inside the eye (called endophthalmitis). Data from the drug trials with Lucentis would suggest that this is in the order of 0.1% i.e. 1 in every 1000 injections. There are other theoretical risks including retinal detachment, cataract and rise in intraocular pressure. It is also possible to be allergic to any drug.

Risks of Anti Vascular Endothelial Growth Factor agents

There are theoretical risks from Anti-Vascular Endothelial Growth Factor drugs of Ďthrombo-embolicí events, which means heart attacks or strokes. In the large trials carried out with Lucentis, there were no more strokes or heart attacks in patients having the injection than in those who didnít have the injection.

When Avastin is given in large doses as chemotherapy for colorectal cancer, there are some of these side effects. It is not known however if they still occur with the tiny doses used for injecting into the eye. The American CATT trial did not show any increased risk of thrombo-embolic events with Avastin compared to Lucentis.

One unexpected result from the CATT trial was that patients were more likely to be admitted to hospital after Avastin, but for many different conditions such as chest infections or urinary tract infections. It is not known whether this was caused by the Avastin or just occurred by chance.

Risks of intravitreal steroid

With intravitreal triamcinolone injections there are two main specific risks; cataract and raised intraocular pressure. Cataract formation occurs in a large proportion of patients who have not already had cataract surgery.

Raised pressure inside the eye occurs in most patients to some degree, and in a small proportion of patients the pressure can be so high to require treatment usually with drops. Rarely patients can require glaucoma surgery.

The Ozurdex implant uses a different form of steroid: dexamethasone. This has been shown to have a much lower rate of cataract formation and raised pressure.