Can the untreated fellow eye become red after an intravitreal anti‑VEGF (vascular endothelial growth factor) injection in the other eye?

Intravitreal Anti-VEGF Injections Do Not Cause Redness in the Fellow Eye

The untreated fellow eye does not become red after intravitreal anti-VEGF injection in the contralateral eye. This is not a recognized complication of anti-VEGF therapy, and the available evidence does not support any mechanism for this occurrence.

Expected Complications of Anti-VEGF Injections

The complications of intravitreal anti-VEGF injections are well-documented and occur only in the injected eye, not the fellow eye 1:

Local Complications (Injected Eye Only)

• Infectious endophthalmitis occurs in 0.019% to 0.09% of injections, presenting within 72 hours with pain, redness, and decreased vision in the treated eye 1, 2
• Transient and sustained intraocular pressure elevation can occur in the injected eye, sometimes requiring medical or surgical intervention 1, 3
• Sterile intraocular inflammation may develop as an inflammatory adverse event specific to the injected eye 4
• Retinal detachment and cataract formation are rare complications affecting only the treated eye 1

Systemic Effects (Not Fellow Eye Redness)

• Anti-VEGF agents can escape into systemic circulation, but this has been studied primarily in retinopathy of prematurity models and does not manifest as fellow eye redness 5
• A meta-analysis found no definitive increased risk of systemic thromboembolic events, though moderate evidence suggests possible modest risk with prolonged monthly therapy 1

What the Evidence Shows About the Fellow Eye

• One study comparing injected eyes to fellow healthy eyes found no difference in ocular surface parameters, intraocular pressure, tear break-up time, or anterior segment measurements between the two eyes 6
• The only difference noted was higher subjective symptom scores (OSDI) in injected eyes, likely related to the injection procedure itself, not objective redness 6

Clinical Pitfall to Avoid

If the fellow eye becomes red after an anti-VEGF injection in the contralateral eye, this represents a separate pathological process unrelated to the injection. You must evaluate the red eye for:

• Coincidental conjunctivitis or anterior uveitis
• Underlying bilateral inflammatory disease
• Unrelated trauma or infection
• Sympathetic ophthalmia (extremely rare, typically follows penetrating trauma or intraocular surgery, not intravitreal injections)

Proper Injection Technique to Minimize Complications

• Use topical povidone iodine before all intravitreal injections, as its non-use carries unacceptably high endophthalmitis risk 1
• Do not use routine prophylactic antibiotic drops before or after injection, as they do not decrease endophthalmitis risk 1