What Is An Intravitreal Injection Procedure Risks?

An intravitreal injection is a procedure where medication is delivered directly into the vitreous humor, the clear gel that fills the space between the lens and the retina at the back of the eye. It is one of the most common ophthalmic procedures performed worldwide, primarily used to treat conditions like age-related macular degeneration, diabetic retinopathy, and macular edema. The procedure itself is quick, but it carries a specific set of risks including infection, bleeding, and increased eye pressure, though serious complications are relatively rare.

Why Are Intravitreal Injections Performed?

The eye has a natural barrier that prevents many oral or topical medications from reaching the retina. Injecting medication directly into the vitreous cavity bypasses this barrier. This allows for a high concentration of the drug to sit precisely where it is needed, maximizing the therapeutic effect while limiting systemic side effects.

Most injections deliver anti-VEGF medications. VEGF, or vascular endothelial growth factor, is a protein that promotes the growth of abnormal blood vessels. In diseases like wet age-related macular degeneration, these vessels leak fluid and blood, destroying central vision. Anti-VEGF drugs block this protein, halting the growth and leakage.

Other injections may contain steroids to reduce inflammation or antibiotics to treat internal eye infections. The specific drug used depends entirely on the underlying condition being treated.

How Is the Procedure Performed?

An intravitreal injection is typically performed in an outpatient clinic or office setting. It is not performed in an operating room. The entire process usually takes less than 15 minutes, with the injection itself lasting only a few seconds.

The eye is first numbed with topical anesthetic drops. The eye and eyelids are then cleaned with an antiseptic, usually povidone-iodine. This step is critical for preventing infection. A small speculum is used to hold the eyelids open so you cannot blink during the injection.

The doctor will then insert a very fine needle through the sclera, the white part of the eye, at a specific angle. The medication is delivered, and the needle is removed. You may see a small bubble or shadow in your vision afterward, which is normal and typically resolves within a day. You will be monitored briefly before being sent home.

What Are the Most Common Risks and Side Effects?

Most side effects are mild and temporary. They are the body’s normal response to having a needle enter the eye. These are not considered complications, but rather expected reactions.

Common side effects include:

• Redness or subconjunctival hemorrhage (a small bruise on the white of the eye)
• A gritty or scratchy sensation
• Watery eyes
• Floaters, which are often tiny gas bubbles or medication particles
• Mild discomfort or pressure

These symptoms usually improve within 24 to 48 hours. Over-the-counter artificial tears can help with the gritty feeling, but you should always ask your doctor before using any additional drops.

What Are the Serious Complications?

Serious complications are rare, occurring in less than 1% of injections, but they do happen. You must be able to recognize the warning signs.

Endophthalmitis is the most feared complication. It is a severe infection inside the eye that can cause permanent vision loss. Symptoms include increasing pain, redness, swelling of the eyelid, and a sudden decrease in vision. This typically occurs within the first few days after the injection. It is a medical emergency requiring immediate treatment.

Retinal detachment is another serious risk. The needle can occasionally tear the retina, leading to a detachment. Symptoms include a sudden increase in floaters, flashes of light, or a curtain-like shadow moving across your vision.

Elevated intraocular pressure is common immediately after the injection. The added fluid volume temporarily raises pressure inside the eye. For most people, this normalizes within minutes to hours. However, in patients with glaucoma or those receiving repeated injections, pressure spikes can become problematic and may require monitoring or treatment.

Traumatic cataract is possible if the needle touches the lens of the eye. This is more common in certain anatomical situations but remains a rare event.

How Likely Are These Complications?

Clinical evidence consistently shows that the rate of endophthalmitis is very low, generally estimated at around 1 in 1,000 to 1 in 10,000 injections. The exact rate varies by study and technique, but it is consistently under 0.1%.

The risk of retinal detachment is similarly low. Research indicates that the incidence is less than 1% per injection. The risk of a traumatic cataract is also below 1%. These figures are important for context. While the risks are real, the likelihood of a serious complication from a single injection is extremely small.

The benefit of treatment usually far outweighs these risks. Untreated wet macular degeneration or diabetic macular edema leads to progressive, often irreversible, vision loss. The injections are designed to prevent that outcome.

What Does Recovery Look Like?

Most people return to normal activities the same day. You should not rub your eye. Rubbing increases the risk of introducing bacteria into the injection site.

Your doctor will likely advise you to avoid swimming, hot tubs, or getting dirty water in your eye for a few days. This reduces the risk of infection. You may also be given antibiotic drops to use for several days after the procedure.

You should not fly or engage in heavy lifting immediately after unless cleared by your doctor. The gas bubble used in some procedures can expand at altitude, causing dangerous pressure spikes. This applies specifically to injections that include a gas bubble, which is more common in retinal detachment repair than in standard anti-VEGF therapy.

Vision may be blurry for the first day or two. The medication itself can cause this. Many patients notice improvement within a week, but this varies depending on the condition being treated and the specific drug used.

When Should You Call Your Doctor Immediately?

Do not wait for a routine follow-up if you experience severe symptoms. Call your eye doctor or go to the emergency room right away if you have:

• Significant eye pain that does not subside
• Sudden loss of vision or a shadow in your field of view
• Increasing redness and swelling of the eyelid
• Nausea or vomiting associated with eye pain
• Discharge or pus coming from the eye

These symptoms could indicate endophthalmitis or retinal detachment. Both require urgent intervention. Time is vision. Do not delay seeking care.

What Is An Intravitreal Injection Procedure Risks Compared to Alternatives?

For many retinal diseases, the main alternative to intravitreal injections is laser therapy or surgery. Laser photocoagulation can seal leaking blood vessels but often causes permanent scarring and is less effective for many conditions.

Vitrectomy surgery involves removing the vitreous gel entirely. It is a much more invasive procedure performed in an operating room under anesthesia. It carries higher risks of bleeding, infection, and cataract formation.

Systemic medications, taken orally or intravenously, are rarely effective for retinal disease because they do not reach sufficient concentrations in the eye. They also carry significant systemic side effects.

When compared to these alternatives, intravitreal injections are generally considered the safest and most effective option for many posterior segment diseases. They are minimally invasive, repeatable, and can be performed quickly without general anesthesia.

Are There Long-Term Risks of Repeated Injections?

Many patients require injections every four to eight weeks for months or years. This raises the question of cumulative risk.

Research suggests that repeated injections are generally safe. The risk of endophthalmitis does not appear to increase with each injection. The risk is per procedure, not cumulative in a linear fashion.

However, long-term steroid injections can increase the risk of glaucoma and cataract formation. Anti-VEGF injections have not been shown to cause these issues to the same degree. Some evidence suggests that chronic, repeated injections may slightly increase the risk of retinal atrophy or geographic atrophy over many years, but this is an area of ongoing research and the evidence is not conclusive.

One practical concern is the cumulative risk of elevated eye pressure. Some patients develop sustained ocular hypertension after many injections. Your doctor should monitor your eye pressure at each visit to manage this risk.