Functions and pathologies of the posterior segment of the eye
It is a simple surgical procedure, the purpose of which is to inject drugs directly into the eyeball (vitreous cavity).
This enables very high concentrations of medication to enter at intraocular level that would not reach via another route (oral or intravenous) as the eye is an organ isolated from the rest of the organism and that makes it difficult for drugs not administered by intravitreous route to reach high enough concentrations inside in the eye.
They are used as treatment for retina or vitreous issues. Depending on the indications, we can chose different kinds of intravitreal drugs: anti-angiogenics, corticoids, antibiotics, etc.
At present, the injections that are most commonly used are anti-angiogenics, of which we have 2 drugs, Ranibizumab and Aflibercept, which have been used for intraocular use and a third, Bevacizumab, which is only for compassionate use and in exceptional cases, where other medications have not been effective enough for controlling the disease.
The administration of these drugs is widespread for exhumative or wet age-associated mascular degeneration, and for the treatment of choroidal neovascular membrane secondary to other causes (for example, myopia magna). They are also the treatment of choice for cases of macular oedema (swelling of the central retina) associated with vascular diseases of the retina (for example, retinal vein obstruction, diabetic retinopathy, etc.).
We are currently participating in various state-of-the-art anti-angiogenic studies, with greater efficacy in the control of these diseases and a lower frequency and number of injections.
In the near future, we will also begin clinical trials to administer intravitreal injections in order to slow or even stop the evolution of atrophic senile macular degeneration.
A special mention must be made of intravitreal corticoids, such as the dexamethasone intravitreal implant, the effects of which last 4 to 6 months and the indications for which include treatment of vascular macular oedema and inflammatory oedema, in the context of either ocular inflammation (uveitis) or after intraocular surgery (cystoid macular oedema).
For a short time now, we have also had a Fluocinolone intraocular implant for very select cases of refractory diabetic macular oedema (which recurs after multiple treatments), the pharmacological effects of which may last up to 3 years without requiring reinjections.
Another disease for which we use intravitreal injections is endophthalmitis (an infection of the intraocular content), in this case with antibiotics. The choice will depend on the micoorganism causing the disease.
Although they are not medications themselves, intraocular silicone, gas and air can be used to treat very select cases of retinal detachment.
For the safety and comfort of patients, intravitreal injections should be administered in an operating theatre or clean room, and, therefore, under strict sterility conditions.
No pre-operative period is required and it is an outpatients technique (no hospital admission needed). It is simple to administer: under topical anaesthetic (use of anaesthetic drops). It is well tolerated by patients.
The risk of complications is extraordinarily low if we follow these intructions.
The patient will barely feel any irritation during or after the injection, but if they do, it is limited to a feeling of grit in the eye, stinging and a slightly red eye.
On few occasions, a small red spot may appear in the place of the injection (hyposphagma) which is reabsorbed on its own. Seeing black bubbles after the injection is not uncommon, they could be leftover air; they usually disappear in 24 to 48 hours without any effect on the treatment.
The most feared complication, and luckily it is very uncommon, is endophthalmitis. To prevent it, the patient should apply antibiotic drops on the days after the procedure.
Frequently asked questions
Administration of the injection is practically painless, as we instill some anaesthetic eyedrops into your eye prior to the procedure. It shouldn't be painful afterwards either, but if it is, the eye is very red or your eye sight becomes poorer than normal, you should see an ophthalmologist.
The number of injections each patient needs cannot be predicted. This will depend on the type of disease, the progression thereof and the patient's response to medication among other reasons.