What an intravitreal injection is
The vitreous is the clear gel filling the main cavity of the eye. An intravitreal injection places medication into that gel, immediately adjacent to the retina. It is a delivery route rather than a single drug — several different medicines are given this way.
The reason it exists is simple. The eye is well protected from the bloodstream, which means drugs taken by mouth barely reach the retina, and eye drops do not penetrate to the back of the eye at all. Injecting into the vitreous is what makes an effective concentration possible where it is needed.
Conditions treated this way
- Diabetic macular oedema — swelling at the macula from diabetic retinopathy, the commonest cause of central vision loss in diabetic patients
- Wet age-related macular degeneration — abnormal vessels growing under the macula and leaking
- Retinal vein occlusion — a blocked retinal vein causing swelling and haemorrhage
- Proliferative diabetic retinopathy — to suppress abnormal new vessels, sometimes before surgery
- Other causes of macular swelling, including some inflammatory conditions
The medicines used
Anti-VEGF agents block vascular endothelial growth factor, the signal that drives abnormal vessel growth and leakage. They are the first-line treatment for wet macular degeneration and for most diabetic macular oedema.
Steroid preparations reduce inflammation and swelling, and are used where anti-VEGF response is inadequate or where the clinical picture favours them. They carry their own considerations, including a risk of raised eye pressure and cataract formation, which is why they are not simply the default.
Which agent suits you depends on your diagnosis, your previous response, your other eye conditions and cost. This is a discussion to have before the course starts.
What happens on the day
The eye is cleaned and numbed. A small speculum holds the lids open so you cannot blink during the injection. Antiseptic is applied to the surface — this step is what keeps infection rates very low, and it is why the procedure is done in a clean environment rather than a consulting room chair.
The injection itself takes seconds. Many patients see moving shapes or a dark line in the vision afterwards, which is the medicine dispersing in the vitreous, and it settles over a day or two.
You will be checked afterwards and given drops or instructions as appropriate, then sent home the same day.
Afterwards
Expect blurred vision for some hours, mild grittiness, and sometimes a red patch on the white of the eye where the needle entered. None of these are a concern on their own.
What is not expected is increasing pain, worsening redness, growing light sensitivity or falling vision over the following days. Endophthalmitis — infection inside the eye — is rare, but it is serious and time-critical, so do not wait for your scheduled appointment if these develop.
Avoid rubbing the eye and keep swimming pools and dusty environments out of the picture for a few days.
The schedule matters more than the injection
The most common reason treatment underperforms in practice is not the medicine. It is patients stopping once vision improves.
These conditions are chronic. Anti-VEGF treatment suppresses leakage; it does not cure the underlying process. When injections stop, fluid frequently returns, and the vision lost during that gap is often not fully recoverable even when treatment resumes. Attendance at the interval your surgeon sets, and the OCT scan at each visit that decides the next one, are the treatment — not an optional extra around it.
If cost or travel is making the schedule hard to keep, say so. It is a more useful conversation to have early than to have after a lapse.