Intravitreal Injection for Diabetic Retinopathy: When Is It Needed and How to Choose the Right Medication

If you or someone in your family has diabetes, chances are you've already heard the term "diabetic retinopathy" from your eye doctor. What you may not know is how the actual treatment works once retinopathy starts affecting your vision — and why your retina specialist picks one injection over another. At Claritas Eye and Retina, this is one of the most common questions patients ask Dr Mayank Bansal during a consultation: "Doctor, why this injection and not that one? And how many will I actually need?"

This blog tries to answer that in plain language — when intravitreal injections are actually needed for Diabetic Retinopathy, how the different anti-VEGF drugs (Eylea, Razumab, Vabysmo) compare, when a steroid implant like Ozurdex makes more sense, how long each option keeps working, and roughly how many injections a person should expect.

What Is Diabetic Retinopathy, and Why Do We Inject the Eye at All?

Diabetic retinopathy (DR) develops when years of elevated blood sugar quietly damage the tiny blood vessels feeding the retina, the light-sensitive layer at the back of the eye. Early on, it's called non-proliferative diabetic retinopathy (NPDR) — this stage often has no or minimal symptoms. Left uncontrolled, it can progress to proliferative diabetic retinopathy (PDR), where the retina starts growing abnormal, fragile new blood vessels that can bleed or pull on the retina.

Alongside this, fluid can leak from damaged vessels into the central part of the retina — the macula — causing diabetic macular edema (DME), which is swelling that directly blurs central vision. DME can occur at any stage of retinopathy, and it's usually DME, not DR itself, that brings patients to a retina clinic complaining of blurred or distorted vision.

The swelling and abnormal vessel growth are largely driven by a protein called vascular endothelial growth factor (VEGF), which the stressed retina produces in excess when it isn't getting enough oxygen. Injecting a medicine directly into the vitreous cavity of the eye — an "intravitreal injection" — lets us deliver a concentrated dose of anti-VEGF medication, or occasionally a steroid, right where it's needed, largely avoiding the side effects of systemic treatment.

When Should Intravitreal Injections Actually Be Given?

Not every patient with diabetic retinopathy needs an injection. Injections are generally recommended when:

• Centre-involving diabetic macular edema is present — meaning the swelling has reached the very center of the macula and is affecting reading or detailed vision.

• Proliferative diabetic retinopathy has developed, with new, abnormal vessels at risk of bleeding into the eye.

• Vitreous hemorrhage or early tractional changes are present alongside active leaking vessels.

Dr Mayank Bansal typically bases the decision on a combination of visual acuity testing, dilated retinal examination, and an OCT (optical coherence tomography) scan. The OCT, in particular, tells us exactly how thick the central retina is and whether the fluid is sitting under or within the retinal layers — details that shape not just the decision to treat, but which drug is likely to work best.

Choosing the Right Anti-VEGF: Eylea vs Razumab vs Vabysmo

Anti-VEGF therapy is the first-line treatment for center-involving DME and is also used to regress abnormal vessels in proliferative disease. But "anti-VEGF" isn't a single drug — it's a class, and the three names' patients hear most often at a retina clinic in India are Eylea, Razumab, and the newer Vabysmo. Here's how the team at Claritas Eye and Retina generally thinks through the choice.

Eylea (Aflibercept)

Eylea has been a workhorse anti-VEGF agent for over a decade. It works by mopping up not just VEGF-A but also VEGF-B and placental growth factor, giving it a broader binding profile than some older agents. Large trials have shown it works well for DME and, notably, is approved to treat diabetic retinopathy even in patients who don't yet have macular edema, since it can reduce the risk of the disease progressing to the proliferative stage.

Standard Eylea dosing usually starts with monthly injections for the first three months (a "loading phase"), after which the interval is typically stretched to once every two months. A newer high-dose formulation, Eylea HD, has extended this further, with some patients maintained on three- to four-month intervals, and in certain cases even five-month intervals, cutting down significantly on clinic visits (however, it has not been yet introduced in India).

Razumab (Biosimilar Ranibizumab)

Razumab is India's own biosimilar version of ranibizumab, developed to bring down the cost of anti-VEGF treatment without compromising on safety or effectiveness. Multiple Indian real-world studies comparing Razumab against the original ranibizumab molecule have found comparable improvements in vision and comparable reduction in retinal thickness, which is reassuring for patients who are budget-conscious but still want a well-studied, biologically similar drug.

Razumab is usually given as three initial monthly loading doses, followed by further injections as needed, guided by OCT findings and vision response — a "treat and extend" or "when required" approach rather than a fixed long interval. Because its effect tends to last on the shorter side compared with some newer molecules, patients on Razumab may need slightly more frequent monitoring and, at times, more frequent injections over a year than those on longer-acting drugs.

Vabysmo (Faricimab)

Vabysmo is the newest of the three and works differently — it's a bispecific antibody, meaning it blocks two separate pathways at once: VEGF-A and a second protein called angiopoietin-2, which is involved in blood vessel instability and inflammation. The idea is that hitting two targets together produces more durable control of swelling than blocking VEGF alone.

In large international trials, a majority of patients treated with Vabysmo were able to be extended to injections every 12 to 16 weeks by the end of the first year, while achieving vision gains at least as good as those on standard aflibercept dosing. For patients who find frequent clinic visits difficult — because of travel, work commitments, or simply injection fatigue — Vabysmo's ability to stretch the treatment interval is a genuine practical advantage, though it typically costs more than Razumab and is priced closer to, or above, Eylea.

So Which Intravitreal Injection to Choose for Diabetic Retinopathy?

There's no single "best" anti-VEGF for every patient — the right choice depends on several factors that Dr Mayank Bansal weighs at Claritas Eye and Retina:

• Severity and pattern of the swelling on OCT — some patterns respond better to broader-binding molecules like aflibercept.

• Budget and affordability — Razumab often becomes the practical starting point for patients who need effective treatment at a lower recurring cost.

• How far the patient travels for follow-up — someone commuting long distances may benefit more from a longer-acting drug like Vabysmo or Eylea HD, even at higher upfront cost.

• Response to the first few injections — a patient not responding adequately to one anti-VEGF agent is often switched to another with a different mechanism, which is one of the reasons faricimab (Vabysmo) is particularly useful in eyes that have "plateaued" on aflibercept or ranibizumab.

• Systemic health — patients with recent stroke or cardiovascular events need an individualized risk discussion before starting any anti-VEGF agent.

When Do We Use a Steroid Implant Like Ozurdex Instead?

Anti-VEGF injections are the default first choice, but they're not right for everyone. Ozurdex is a tiny, biodegradable rod containing 0.7 mg of dexamethasone, a steroid, that's injected into the vitreous and slowly releases medication over several months. Dr Mayank Bansal considers Ozurdex over anti-VEGF therapy in situations such as:

• DME that hasn't responded adequately to multiple anti-VEGF injections — a fairly common scenario, since studies suggest a meaningful proportion of DME patients remain swollen even after a year of good anti-VEGF therapy.

• Pseudophakic patients (those who have already had cataract surgery), since the cataract-related side effects of steroids are no longer a major concern.

• Patients who cannot commit to frequent monthly visits, since Ozurdex's effect lasts considerably longer than a typical anti-VEGF injection.

• Eyes with a significant inflammatory component to their swelling, where the anti-inflammatory action of a steroid may work better than VEGF blockade alone.

• Patients with recent cardiovascular events such as a heart attack or stroke, where retina specialists are sometimes more cautious about repeated anti-VEGF exposure and prefer a non-VEGF-targeting option.

The trade-off is that steroids can raise eye pressure and accelerate cataract formation, so Ozurdex is used more selectively and with closer monitoring of intraocular pressure, especially in patients who still have their natural lens.

How Long Does the Effect of Each Treatment Last?

This is one of the most practical questions patients ask, since it directly affects how often they'll need to visit the clinic.

• Eylea (aflibercept): Typically, effective for about 8 weeks between injections after the initial loading phase; the high-dose formulation can extend this to 12–20 weeks in suitable patients.

• Razumab (biosimilar ranibizumab): Generally, has a shorter duration of action, with many patients' needing reassessment around every 4–6 weeks during the active treatment phase, though intervals can be extended once the disease stabilizes.

• Vabysmo (faricimab): Designed for durability — a large proportion of patients in clinical trials were successfully extended to dosing every 12–16 weeks by the end of the first year.

• Ozurdex (dexamethasone implant): The anti-inflammatory effect typically peaks within the first month and provides meaningful benefit for roughly 4 to 6 months

How Many Injections Are Usually Needed?

There's no fixed number, because diabetic eye disease behaves differently from patient to patient, and Dr Mayank Bansal doesn't believe in putting every patient through a rigid, one-size-fits-all schedule. A fixed monthly "loading dose" isn't mandatory for everyone — instead, the approach at Claritas Eye and Retina is to treat based on what the eye actually needs.

In practice, this means an injection is given when there's active swelling or leakage confirmed on examination and OCT. Once the retina responds and the swelling settles, the patient is simply monitored at regular intervals rather than being brought back for injections on autopilot. If, during follow-up, the swelling recurs — what we call "re-swelling" — that's when the next injection is considered. Each time, the decision to repeat the injection (and which medicine to use) is reassessed on its own merit, based on how the eye is behaving at that visit, not on a pre-fixed calendar.

This as-needed philosophy keeps treatment tailored to the individual rather than over-treating an eye that's already stable, or under-treating one that needs closer attention. Alongside this, Dr Mayank Bansal always stresses that the injections are only one part of the picture — keeping blood sugar and blood pressure well controlled, sticking to regular retina check-ups, and following general precautions such as timely diabetes management and a healthy lifestyle make a real difference to how well the eye holds on to its improvement and how infrequently injections are eventually needed.

A Final Word from Claritas Eye and Retina

Choosing between Eylea, Razumab, Vabysmo, and Ozurdex isn't about picking the "strongest" drug — it's about matching the right molecule to the right eye, the right stage of disease, and the right patient's practical circumstances. If you or a family member has diabetes and hasn't had a retina check-up recently, don't wait for symptoms to show up; diabetic retinopathy can progress silently. A dilated eye examination and an OCT scan can tell you exactly where things stand, and if treatment is needed, the team at Claritas Eye and Retina, under Dr Mayank Bansal, can walk you through which option fits your eye and your life best.