Eye injections (anti-VEGF): why we need them, how they are given, and what to watch for

When we tell a patient they need "an injection in the eye," the first reaction is usually worry: "An injection into the eye itself? Does it hurt? Will I need it once, or for the rest of my life?" This worry is completely understandable. In this article we explain what these injections are, why they have become one of the most important treatments for retinal disease, how the injection is given step by step, what the real risks are and how big they are, and why keeping appointments is part of the treatment itself.

What are these injections, and how do they work?

In some retinal diseases, the eye produces large amounts of a substance called vascular endothelial growth factor (VEGF). This substance makes the blood vessels of the retina leak fluid, causing swelling of the macula, and it also stimulates the growth of abnormal new vessels that bleed easily.

The injections we use are medicines that block this substance. Leakage decreases, the swelling gradually dries up, and the abnormal vessels stop growing. But the effect of each injection is temporary, because the eye keeps producing VEGF as long as the disease is active. That is why most patients need a series of injections at intervals set by the doctor, rather than a single injection.

When are these injections used?

Wet age-related macular degeneration: one of the main causes of loss of central vision in older people. In one large clinical trial, monthly injections preserved vision in about 95% of patients after one year, compared with about 62% in the group that did not receive the medicine, and the benefit continued to the end of the second year (Rosenfeld et al., 2006). In another trial, the injections clearly outperformed the treatment used before them (Brown et al., 2006). A large review of many trials confirmed that these injections preserve or improve vision compared with no treatment (Solomon et al., 2019).

Diabetic macular edema that affects vision (Wells et al., 2015; Virgili et al., 2023). We explain when to start treatment and when monitoring is enough in our articles on diabetic retinopathy and diabetic macular edema.

Retinal swelling caused by a blocked retinal vein: injections are the preferred treatment for this condition in European guidelines (Schmidt-Erfurth et al., 2019).

Sometimes in proliferative diabetic retinopathy, as an alternative to laser or together with it, depending on the patient's circumstances.

How is the injection given?

The injection is usually given in an equipped, sterile room. All the steps take a few minutes, and the injection itself takes seconds. Experts of the European Society of Retina Specialists agreed on recommendations for safe injection, because many details of this procedure have not been studied in comparative trials (Grzybowski et al., 2018). The steps are usually:

1. Anesthetic drops in the eye.
2. Cleaning the eye and eyelids with an antiseptic solution, the most important step for preventing infection.
3. A small device that keeps the eyelids open, so the lashes do not touch the injection site.
4. The injection into the white of the eye, from the side, with a very fine needle.

Some details may differ from one center to another.

You may feel slight pressure during the injection, and many patients feel little or no pain. Afterwards you may notice a red patch on the white of the eye at the injection site, or black spots moving in your vision for a short time. Both are common and usually disappear within days without treatment.

What are the risks, and how big are they really?

It is important for patients to know the risks at their real size, without playing them down and without exaggerating them.

Infection inside the eye (endophthalmitis): this is the most serious complication, but it is rare. In an analysis of more than 350,000 injections, the rate was about 1 case per 1,800 injections (Fileta et al., 2014). In a French study of more than five million injections, the rate was about 1 case per 4,000 injections (Baudin et al., 2022). But a patient may receive dozens of injections over several years, so it is very important to know the warning signs listed at the top of this article and to act quickly if they appear.

Other complications inside the eye: such as a temporary rise in eye pressure after the injection, inflammation inside the eye that is not caused by infection, and minor bleeding under the conjunctiva (Solomon et al., 2019).

General complications in the body (such as heart attack or stroke): the available data are not conclusive, and large reviews have not shown a clear increase in these risks (Solomon et al., 2019; Virgili et al., 2023). Even so, tell your doctor if you have recently had a heart attack or a stroke.

What about antibiotic drops after the injection?

Many patients expect them to be necessary. But in the large French study, antibiotic drops after the injection did not reduce the risk of infection (Baudin et al., 2022). Real prevention comes from good antisepsis before the injection. In all cases, follow your own doctor's instructions.

How many injections will I need, and why do appointments matter?

There is no single schedule that suits everyone. There are monthly injections, injections as needed after each examination, and the "treat-and-extend" approach, which gradually lengthens the interval between injections as the eye becomes stable. Treatment often starts with several monthly injections, after which the intervals are set according to how the eye responds on examination and OCT scans (Lanzetta et al., 2024).

Keeping to the schedule is not a detail. A British trial found that reducing how often treatment is given may slightly reduce its benefit (Chakravarthy et al., 2013). The disease does not pause because an appointment was missed.

Are the different medicines the same?

There are several medicines in this group. In comparative clinical trials, the effects on vision were similar between the commonly used medicines in many situations (Martin et al., 2011; Solomon et al., 2019; Virgili et al., 2023). In diabetic macular edema, one medicine showed an advantage in patients who started with poorer vision during the first year (Wells et al., 2015).

Newer medicines have been designed to allow longer intervals between injections in some patients, with vision results that were not worse than the older medicines in trials (Heier et al., 2022; Wykoff et al., 2022; Lanzetta et al., 2024). Biosimilar medicines have also appeared: scientifically equivalent copies of the original medicine, with results equivalent to it in trials (Bressler et al., 2023).

The medicine and the schedule are chosen after discussion with the patient, according to the type of disease, how the eye responds, the patient's ability to attend, and the cost. The aim is to choose the most suitable treatment for each case, not necessarily the "newest" medicine.

Questions patients often ask

Does the injection hurt?

Most patients feel only slight pressure, thanks to the anesthetic drops.

Will I need injections for life?

That depends on the disease and on how the eye responds. In some patients injections can be reduced or stopped once the condition is stable; others need long-term follow-up.

Does the injection treat the underlying cause of the disease?

No. The injection controls the leakage and the abnormal vessels. In diabetes, control of blood sugar and blood pressure remains essential.

Can I drive after the injection?

Vision is often blurred for several hours because of the drops and the antiseptic, so arrange a way to get home.

Summary

These injections have changed the results of treatment for many retinal diseases, making it possible to preserve vision in large numbers of patients who used to lose their central vision. But they are a long-term treatment that needs patience and commitment. We discuss with each patient the treatment options that suit their case, and explain that the risks are rare but real, and that knowing the warning signs and keeping appointments are an essential part of successful treatment.

This information is for health education and does not replace a medical examination.