Intravitreal Injections: Anti-VEGF and Steroid Therapies

More than 6 million intravitreal injections are administered annually in the United States alone, making this the single most commonly performed procedure in ophthalmology (American Academy of Ophthalmology). That number reflects a genuine transformation in how retinal diseases are managed — conditions that once led to irreversible blindness can now be stabilized, and in many cases meaningfully improved, through a needle no thicker than a human hair delivered directly into the vitreous cavity of the eye.

How Intravitreal Injections Work

The eye, by design, is remarkably good at keeping substances out. The blood-retinal barrier blocks most systemically administered drugs from reaching the posterior segment in therapeutic concentrations. Intravitreal injection bypasses that barrier entirely. A 30-gauge needle penetrates the pars plana — the relatively safe zone about 3.5 to 4.0 mm behind the limbus — and deposits a small volume of medication (typically 0.05 mL) directly into the vitreous humor, placing the drug in immediate proximity to the retina, macula, and choroid.

The procedure itself takes roughly 15 to 30 seconds. Topical anesthetic and antiseptic preparation with povidone-iodine are standard. Post-injection, patients may notice floaters (the drug bolus itself) and mild discomfort, both of which typically resolve within hours.

Anti-VEGF Therapies

Vascular endothelial growth factor (VEGF) is the central molecular villain in a range of retinal diseases. Overexpression of VEGF drives abnormal blood vessel growth (neovascularization) and vascular permeability, leading to fluid leakage, hemorrhage, and retinal damage. Anti-VEGF agents bind and neutralize this protein before it can reach its receptors.

Approved Anti-VEGF Agents

• Ranibizumab (Lucentis) — FDA-approved in 2006 for neovascular age-related macular degeneration (nAMD). A monoclonal antibody fragment specifically designed to penetrate retinal tissue. The landmark MARINA and ANCHOR trials demonstrated that monthly ranibizumab injections improved visual acuity by an average of 6.6 to 11.3 letters on the ETDRS chart at 12 months (NEI/NIH).

• Aflibercept (Eylea) — Approved in 2011, this fusion protein acts as a decoy receptor that binds VEGF-A, VEGF-B, and placental growth factor. The VIEW 1 and VIEW 2 trials showed non-inferiority to monthly ranibizumab with dosing every eight weeks after an initial loading phase. A higher-dose formulation, aflibercept 8 mg (Eylea HD), received FDA approval in 2023 and permits dosing intervals up to 16 weeks in some patients.

• Bevacizumab (Avastin) — Originally approved for metastatic colorectal cancer, bevacizumab is used off-label for retinal indications at roughly 1/40th the cost of ranibizumab. The CATT trial, funded by the National Eye Institute, found bevacizumab equivalent to ranibizumab for visual acuity outcomes in nAMD at two years (NEI/NIH CATT Study).

• Brolucizumab (Beovu) — A single-chain antibody fragment approved in 2019, notable for its small molecular size and potential for extended dosing (every 12 weeks). Post-marketing surveillance revealed cases of retinal vasculitis and occlusive retinal arteritis, prompting updated safety labeling.

• Faricimab (Vabysmo) — Approved in 2022, faricimab is the first bispecific antibody in ophthalmology, targeting both VEGF-A and angiopoietin-2 (Ang-2). The TENAYA and LUCERNE trials demonstrated that approximately 80% of patients with nAMD could be maintained on intervals of 12 weeks or longer.

Key Indications for Anti-VEGF

Anti-VEGF injections are FDA-approved or widely used for neovascular AMD, diabetic macular edema (DME), macular edema following retinal vein occlusion, diabetic retinopathy, and myopic choroidal neovascularization. DME alone affects approximately 750,000 people in the United States (CDC Diabetes and Vision Loss Data).

Intravitreal Steroid Therapies

Where anti-VEGF agents target a single molecular pathway, corticosteroids suppress inflammation broadly — downregulating cytokines, prostaglandins, and VEGF simultaneously. This makes them particularly useful for conditions with a strong inflammatory component.

Available Steroid Options

• Triamcinolone acetonide — Used off-label, typically at doses of 1 to 4 mg. Provides potent anti-inflammatory and anti-edema effects but carries well-documented risks of elevated intraocular pressure (IOP) and cataract acceleration. Studies suggest approximately 30% to 40% of patients experience clinically significant IOP elevation.

• Dexamethasone intravitreal implant (Ozurdex) — A biodegradable polymer implant releasing dexamethasone over approximately six months. FDA-approved for macular edema due to retinal vein occlusion, non-infectious posterior uveitis, and DME. The sustained-release design reduces injection frequency compared with soluble steroids.

• Fluocinolone acetonide implant (Iluvien) — Designed for continuous microdose delivery over up to 36 months, FDA-approved for DME in patients previously treated with corticosteroids without clinically significant IOP rise. The FAME trials showed that 33% of patients gained 15 or more ETDRS letters at 24 months (ClinicalTrials.gov — FAME Study).

Risks and Complications

The most feared complication is endophthalmitis — an intraocular infection that can be devastating. The incidence per injection sits at approximately 0.02% to 0.05%, a reassuringly low number that still adds up given the sheer volume of injections performed globally. Strict antiseptic technique, particularly the use of 5% povidone-iodine applied to the conjunctival surface, remains the primary preventive measure.

Other risks include retinal detachment (rare), vitreous hemorrhage, and — specific to steroids — IOP elevation and posterior subcapsular cataract formation. Patients receiving steroids require regular tonometry monitoring.

Treatment Burden and Evolving Strategies

The elephant in the exam room is treatment burden. Monthly or bimonthly injections, sustained over years, impose significant logistical and psychological costs on patients and caregivers. Treat-and-extend protocols, which gradually lengthen the interval between injections based on individual disease activity, have become the dominant dosing strategy, aiming to minimize injection frequency without sacrificing outcomes.

Newer agents with extended durability — aflibercept 8 mg, faricimab — represent one path forward. The Port Delivery System (Susvimo), a surgically implanted reservoir that releases ranibizumab continuously for up to six months, earned FDA approval in 2021 before being voluntarily withdrawn from the market in 2023 due to commercial and manufacturing considerations rather than safety signals. Gene therapy approaches that would enable the eye to produce its own anti-VEGF protein are under active investigation, with RGX-314 and ABBV-RGX-314 in Phase III trials (ClinicalTrials.gov).

Frequently Asked Questions

How painful is an intravitreal injection?

Most patients report feeling pressure rather than sharp pain. Topical anesthesia — typically proparacaine drops or a lidocaine-soaked pledget — numbs the eye surface effectively. Post-procedure discomfort is generally mild and brief.

Can anti-VEGF and steroid injections be combined?

Combination therapy is sometimes employed, particularly in refractory DME where inflammation plays a significant role alongside VEGF-driven pathology. The decision involves weighing the additive benefit against the steroid-related risk of IOP elevation and cataract progression.

How long do the effects of a single injection last?

Duration varies by agent. Bevacizumab and ranibizumab typically require retreatment every 4 to 6 weeks. Aflibercept and faricimab can extend to 8–16 weeks. The dexamethasone implant (Ozurdex) lasts roughly 4 to 6 months, and fluocinolone acetonide (Iluvien) delivers drug for up to 36 months.

What happens if treatment is stopped too early?

Discontinuation before disease stabilization risks recurrence of macular edema or neovascularization, with potential for irreversible vision loss. Long-term follow-up data from the CATT and IVAN trials showed that inconsistent treatment was associated with worse visual outcomes at five years.

References

• American Academy of Ophthalmology — Anti-VEGF Treatments
• National Eye Institute — Age-Related Macular Degeneration
• National Eye Institute — CATT Study
• CDC — Diabetes and Vision Loss Data
• ClinicalTrials.gov — FAME Study (NCT00344968)
• ClinicalTrials.gov — RGX-314 Gene Therapy (NCT04832724)

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