What Are the Side Effects of Eye Injections?

Most people who receive an eye injection walk away with nothing worse than temporary redness, mild soreness, and a few hours of blurry vision. Intravitreal injections, the standard delivery method for drugs that treat conditions like wet age-related macular degeneration and diabetic eye disease, are among the most frequently performed procedures in ophthalmology. The side-effect profile ranges from fleeting annoyances that resolve on their own to rare but serious complications that can threaten sight, and the specific drug being injected matters quite a bit in determining which risks apply to you.

The Common, Short-Lived Effects

The most frequently reported complaint after an intravitreal injection is surface-level eye discomfort: a gritty or burning sensation, watery eyes, and redness at or around the injection site. A small patch of bright-red bleeding on the white of the eye, called subconjunctival hemorrhage, is extremely common and looks alarming but is harmless in most people, clearing up within a week or two. In rare cases involving bleeding disorders, that hemorrhage can be more extensive and require treatment.¹

The type of anesthesia used before the injection affects how you feel afterward. Topical anesthetic drops (the most common approach) can cause temporary burning. Subconjunctival anesthesia, where a small amount of numbing agent is injected under the eye’s surface membrane, provides better pain control during the procedure but comes with a significantly higher chance of subconjunctival hemorrhage compared to topical drops alone.² Some clinics use lidocaine gel, which can reduce injection pain but occasionally causes surface-level keratitis (irritation of the cornea).³

Needle size also plays a role in how much pain you feel. Studies comparing different gauges found that thinner needles (29- or 30-gauge) cause significantly less pain than thicker ones (26- or 27-gauge), with no correlation between pain and needle length or the patient’s age.⁴ However, the thinnest needles bring their own trade-off: reflux of fluid back out of the injection site occurs more often with 30-gauge needles (about half of injections) compared to 32-gauge needles (about one in eight).⁵

Floaters That Appear After Injection

Many patients notice new floaters, small specks or strands drifting across their vision, in the hours or days following an injection. These are typically tiny air bubbles or drug particles suspended in the gel-like vitreous fluid inside the eye. In one controlled study, about one in five patients reported floaters a week after their injection. The study also found that older patients and those who already had posterior vitreous detachment (a common age-related separation of the vitreous from the retina) were more likely to notice them.⁶

A less obvious source of persistent floaters is silicone oil. The syringes used to draw up and deliver many intravitreal drugs have silicone-lubricated barrels, and tiny droplets of that silicone can get deposited into the eye with each injection. Research has shown that standard polycarbonate syringes release significantly more silicone oil into the eye than prefilled or silicone-free syringes, and the droplets accumulate with repeated injections, especially with more viscous drugs.⁷ These droplets are harmless in most people but can become noticeable floaters over time, particularly for patients who receive dozens of injections over the course of their treatment.

Pressure Spikes Inside the Eye

Every intravitreal injection temporarily raises the pressure inside your eye, simply because you have added a small volume of fluid to an enclosed space. The spike is immediate and dramatic. A systematic review and meta-analysis found that pressure jumps by roughly 24 mmHg within seconds of injection, from a normal baseline of around 15 mmHg to a peak that can exceed 40 mmHg.⁸ A separate study measuring peak pressures after both aflibercept and ranibizumab injections recorded average spikes to roughly 43–46 mmHg.⁹

The good news is that the eye’s natural drainage systems bring the pressure back down quickly. Within half an hour, the excess pressure drops to only a couple of mmHg above baseline in most patients.⁸ For healthy eyes, these brief spikes are well tolerated. In extreme cases, though, the acute pressure surge has been estimated to be enough to cause structural damage in eyes that already have compromised drainage, such as one case report describing rupture of a filtering bleb in a post-surgical eye.¹⁰ If you have glaucoma or are a glaucoma suspect, your doctor will typically monitor your pressure more carefully after each injection.

Sustained Pressure Elevation Over Many Injections

Beyond the immediate spike, a small percentage of patients develop chronically elevated eye pressure after months or years of repeated injections. A large Japanese study found that about 7% of patients treated for age-related macular degeneration developed elevated pressure over an average follow-up of roughly four years. The strongest predictors were a history of glaucoma, a higher number of total injections, and a particular treatment schedule (treat-and-extend rather than as-needed). Most of those cases were controlled with pressure-lowering eye drops, and a few resolved on their own without medication.¹¹

The risk is higher with steroid-based injections. Dexamethasone implants, which slowly release medication inside the eye over months, produce a more sustained pressure increase that peaks around two months after the injection and can linger for several months before returning to baseline by about a year.⁸ Triamcinolone acetonide injections carry a similar risk, and in some cases the pressure rise can be difficult to control with drops alone.¹²

Cataracts From Steroid Injections

If you are receiving a corticosteroid rather than an anti-VEGF drug, cataract formation is a well-recognized side effect that does not apply to the anti-VEGF class at all. Steroids promote a specific type of clouding called posterior subcapsular cataract. In one case, a posterior subcapsular opacity that appeared one week after a dexamethasone implant progressed to a fully mature cataract within just three weeks.¹³ A separate series documented 22 patients who needed cataract surgery after receiving triamcinolone acetonide injections, the majority of whom were being treated for macular degeneration or diabetic macular edema.¹⁴ These cataracts are treatable with standard surgery, but they add a procedure (and recovery time) on top of the ongoing injection schedule.

Infection Inside the Eye

Endophthalmitis, a full-blown infection inside the eye, is the most feared complication of any intravitreal injection. Fortunately it is also one of the rarest. The reported rate varies by study, but large reviews place it somewhere between about 0.02% and 0.2% per injection.¹⁵ One hospital-based study analyzing over 7,000 injections found 15 cases, an incidence of 0.2%, with the most common bacteria being enterococci.¹⁶ Staphylococcal species are also commonly implicated.¹⁷

Symptoms typically appear within a few days: worsening pain, significant vision loss, and a red, swollen eye. If you experience these warning signs after an injection, treating it as an emergency is critical, because delay worsens the visual outcome. Prevention protocols revolve around meticulous antiseptic technique, with povidone-iodine applied to the eye surface before the injection being the single most important step. The use of prophylactic antibiotic eye drops before and after the procedure remains debated among ophthalmologists, and practice patterns continue to shift.

Sterile Inflammation Without Infection

Not every inflammatory reaction after an injection means an infection has taken hold. Sterile (non-infectious) inflammation is actually more common and comes in two flavors. The first is a mild, subclinical anterior chamber reaction, essentially a low-grade inflammation in the front of the eye that occurs at rates as high as 19% after anti-VEGF injections but usually causes no symptoms and resolves on its own. The second is more noticeable sterile uveitis or sterile endophthalmitis, which occurs in roughly 0.05% to 4.4% of injections depending on the drug used.¹⁸

A recent study of the higher-dose aflibercept formulation found sterile inflammation in about 4% of injections and 12% of patients over the observation period, with symptoms like blurred vision, floaters, and mild pain appearing one to three days after the injection. None of these cases involved severe inflammation such as a visible collection of pus in the front of the eye.¹⁹ Distinguishing sterile inflammation from true infection is one of the trickier judgment calls in ophthalmology, because the early symptoms overlap. Severe pain, a pronounced pus layer in the front of the eye, and major vision loss all tilt the diagnosis toward infection.

Retinal Vasculitis With Brolucizumab

One anti-VEGF drug, brolucizumab, stands apart from the others in its association with a specific and serious complication: retinal vasculitis and retinal vascular occlusion, where blood vessels inside the eye become inflamed and can close off. A post-hoc analysis of the drug’s pivotal trials reported inflammatory vasculitis in about 3.3% of injections.¹⁸ A systematic review of real-world reports gathered data on 63 patients (70 eyes) who developed these events after brolucizumab. Nearly half experienced the event after just one injection, and about 88% of events occurred within 30 days. Roughly a third of eyes with available follow-up data suffered significant vision loss.²⁰ This risk profile has significantly limited brolucizumab’s clinical uptake, and many retina specialists reserve it for patients who have not responded to other anti-VEGF options.

Retinal Tears and Detachment

The needle itself can, on very rare occasions, cause mechanical damage to the retina. A study tracking complications across thousands of injections found retinal breaks or detachments at a rate of about 0.08% per injection and 0.3% per eye over time.²¹ These are genuine emergencies that typically require surgical repair, but their rarity means they do not factor heavily into the risk-benefit calculation for most patients. Sudden flashes of light, a curtain-like shadow in your peripheral vision, or a sudden shower of new floaters after an injection all warrant an immediate call to your eye doctor.

Cardiovascular Concerns and Systemic Effects

Anti-VEGF drugs work by blocking a growth factor that stimulates new blood vessel formation. That same growth factor plays roles throughout the body, which raises a natural question: can a drug injected into the eye affect the heart or brain? Small amounts of anti-VEGF drugs do enter the bloodstream after intravitreal injection, and they can temporarily lower systemic VEGF levels.²²

The reassuring finding from large studies is that, overall, the risk of heart attack, stroke, or death does not appear meaningfully increased. A nationwide study comparing patients who received intravitreal anti-VEGF to matched controls found identical rates of stroke, heart attack, or death (0.2% in both groups) during the 28 days after injection, with no statistically significant association in adjusted analyses.²³ One possible exception emerged in a case-crossover study that found no overall increased stroke risk with ranibizumab but did find a signal for hemorrhagic stroke specifically, though the numbers were small and the overall stroke association was not statistically significant.²⁴ In practice, most ophthalmologists consider the systemic cardiovascular risk low enough to continue treatment in patients with heart disease or stroke history, but they discuss it as part of informed consent.

Macular Atrophy and Long-Term Anti-VEGF Use

One of the more unsettling areas of ongoing research is whether the anti-VEGF drugs themselves contribute to gradual thinning and death of cells in the macula, the central part of the retina responsible for sharp vision. Several lines of evidence suggest an association. Retrospective analysis of a major clinical trial (CATT) found that patients receiving monthly injections over two years had a 59% higher risk of developing macular atrophy compared to those injected only as needed, who received fewer total injections.²⁵

A more recent study looked specifically at patients whose wet macular degeneration was in remission (the disease was stable) and compared those who continued receiving maintenance injections to those who took a treatment break. Eyes receiving ongoing injections showed a small but statistically significant increase in the rate of atrophy progression, roughly 0.3 square millimeters per year more than the group on a treatment holiday.²⁶ Whether this represents a direct toxic effect of anti-VEGF drugs on retinal cells, or simply an unmasking of atrophy that the disease itself would have caused, remains genuinely unresolved.²⁷ For patients, the practical implication is that your doctor may periodically reassess whether continued injection is providing enough benefit to justify the cumulative exposure.

Side Effects Specific to Complement Inhibitors

A newer class of intravitreal drugs targets the complement system, part of the immune response, for the treatment of geographic atrophy (advanced dry macular degeneration). Pegcetacoplan and avacincaptad pegol fall into this category. Many of their common side effects overlap with anti-VEGF injections: conjunctival hemorrhage, eye pain, increased pressure, and occasional endophthalmitis. Pressure spikes above 30 mmHg occurred in roughly 1% to 8% of cases in clinical trials but were manageable with medication.²⁸

The unique concern with complement inhibitors is the development of new wet macular degeneration (exudative AMD) in eyes that previously had only the dry form. Across pooled trial data, about 5% of treated eyes developed this complication compared to roughly 2% in sham-treated controls, a statistically significant difference.²⁸ In rare instances, the inflammatory reaction can be severe: one case report describes a patient who lost all vision in the treated eye within 12 days of a single pegcetacoplan injection due to presumed occlusive retinal vasculitis.²⁹

Anxiety, Treatment Burden, and Adherence

Something that does not show up in clinical-trial adverse-event tables but profoundly affects real patients is the psychological burden of repeated eye injections. The idea of a needle entering your eye is inherently anxiety-provoking, and that anxiety does not always diminish with experience. Pain and anxiety around injections are frequently reported despite anesthesia, and they can reduce patients’ willingness to stay on their treatment schedule.³⁰ Missing or delaying injections because of anxiety is a real clinical problem, since many of these conditions require consistent treatment to prevent vision loss. If injection anxiety is affecting you, it is worth raising with your doctor; techniques like distraction, music, guided breathing, and gentle conversation during the procedure have all been studied and can help.

Pregnancy and Intravitreal Anti-VEGF

Because anti-VEGF drugs can enter the bloodstream and VEGF plays a critical role in fetal blood vessel development, there is genuine concern about using these drugs during pregnancy or breastfeeding. The evidence base consists mostly of small case series rather than controlled trials, for obvious ethical reasons. Current expert opinion holds that intravitreal anti-VEGF should be given during pregnancy only when the potential benefit to the mother’s sight clearly outweighs the theoretical risk to the developing fetus, with careful attention to the timing of exposure relative to developmental windows.³¹ Some researchers have recommended that clinics routinely check pregnancy and breastfeeding status in women of childbearing age before each injection cycle, a practice that is not yet universal.³²

1
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