Intravitreal eye injections: what to expect, risks and aftercare

Some eye medicines only work if they reach the inside of the eye, and drops or tablets cannot do that. The Milton Keynes leaflet explains that the most commonly used are anti-VEGF drugs, which in wet macular degeneration and diabetes slow or stop the growth of abnormal, leaky blood vessels in the retina. They are also used after a blocked retinal vein. A steroid implant or injection may be chosen to reduce swelling of the retina or inflammation inside the eye.

The aim is to stabilise or improve vision. The leaflet is frank that the injections may not restore sight already lost, and that vision may still worsen because of the underlying disease. That is worth knowing at the start, because the injections hold a condition in check more often than they reverse it.

For many conditions of this type the alternatives are laser treatment, observation with scans, or in some cases surgery, depending on the diagnosis. Your retinal team will explain which applies to you. It is worth asking what is likely to happen to your vision if you decide to wait.

The Scottish leaflet adds that treatment is put off if you have had a stroke, transient ischaemic attack or heart attack within the last three months, and that you should ring the unit if you have cold sores, shingles, chickenpox, any infection or are about to start antibiotics. The Milton Keynes leaflet also asks you to mention uncontrolled blood pressure or angina and any blood thinner.

Preparation is simple but specific. The Milton Keynes leaflet asks you not to wear eye make-up, false lashes or contact lenses that day, to bring someone with you, who will not be allowed in the procedure room, and to avoid driving. The Scottish leaflet adds that clean glasses and eyelid hygiene help reduce infection risk, especially if you have blepharitis, and that an unopened supply of any prescribed drops should be to hand.

Neither leaflet mentions fasting. Follow whatever your unit's letter says about eating and about your usual medicines.

• Bring a list of eye drops and tablets, including any blood thinner.

• Allow time: expect most of a morning or afternoon even though the injection is brief.

• Arrange transport; if both eyes are treated on the same day the Scottish leaflet suggests someone should accompany you home.

You lie down and local anaesthetic drops are put in. The skin around the eye is cleaned with an iodine-based antiseptic and further antiseptic drops go on the eye surface. A small drape covers the face, a speculum holds the lids open and you are asked to look in a particular direction and keep still.

The injection site is marked with a measuring device and the medicine is given. The Scottish leaflet says the whole procedure normally takes 20 minutes, the injection itself about 20 seconds, and that a vision check or a scan may be done on the day. Because you are asked to look away, you are very unlikely to see the needle. Most of the discomfort people report comes from the antiseptic rather than the needle, according to the same leaflet.

Common effects are an ache, a gritty or sore eye, redness that can look dramatic but is harmless, a corneal scratch and floaters or dots that last a couple of days. The Scottish leaflet says a bruise on the white of the eye can take up to two weeks to clear.

Serious but rare problems include raised pressure, inflammation, cataract, retinal detachment, bleeding inside the eye, severe infection and loss of vision. The Milton Keynes leaflet gives severe infection as 1 in 2,000 cases, and the Scottish leaflet as one in 1,000, so quote neither as definitive and ask your unit for its own figure.

Do not rub the eye for the rest of the day while the numbing drops are working. Avoid make-up, water in the eye and swimming for the period your unit specifies, and continue any existing drops. Over-the-counter painkillers help the ache. The Scottish leaflet also advises waiting 24 hours before flying and avoiding gardening for two to three days.

The Milton Keynes leaflet says that an eye that becomes progressively red, painful, sensitive to light or swollen, or that develops discharge or sudden loss of vision, should be seen at accident and emergency without delay. Call the eye unit on the number you were given where it is open, and use A&E or NHS 111 out of hours.

Ask which drug is planned, how often you will be seen at first, what the scans measure and when the team would consider changing or stopping treatment. Ask who gives the injection and what happens if an appointment has to move, since the Milton Keynes leaflet says you must keep to scheduled treatment and monitoring visits.

Both NHS and private units offer the same type of injection. Differences tend to be in waiting time, choice of appointment slot and how monitoring is arranged, not in the technique, and a long course means the practicalities matter.