Treat-and-Extend Anti-VEGF Regimen Explained
Last updated: October 2026
Short answer: in a treat-and-extend (T&E) regimen, the patient receives an anti-VEGF injection at every visit. If the macula is dry, the next interval is extended, typically by 2 weeks; if there is disease activity, it is shortened. This individualises treatment, reducing visits while maintaining vision better than many as-needed (PRN) approaches in real-world practice.
The three common regimens
| Regimen | How it works | Strengths | Weaknesses |
|---|---|---|---|
| Fixed (monthly or bimonthly) | Injections at fixed intervals | Proven in pivotal trials; predictable | Over-treats some patients; high visit and injection burden |
| PRN (as needed) | Monthly monitoring; inject only when active | Fewer injections | Many monitoring visits; real-world under-treatment and vision loss |
| Treat-and-extend | Inject every visit; adjust the interval by activity | Fewer visits; individualised; good vision maintenance | Some patients receive more injections than they strictly need |
A typical T&E protocol (nAMD)
- Loading phase: usually three monthly injections.
- Assess activity at each visit with vision, examination and OCT.
- If inactive (dry): inject and extend the next interval, commonly by 2 weeks.
- If active: inject and shorten the interval, commonly by 2 weeks (or return to the last dry interval).
- Continue up to a maximum interval (often 12–16 weeks with current agents).
Protocols differ between units and drugs, so follow local guidance.
What counts as disease activity?
- New or increased intraretinal fluid
- New or increased subretinal fluid
- New macular haemorrhage
- Vision loss attributed to disease activity
- Some studies have shown that tolerating a small amount of stable subretinal fluid did not compromise vision, but intraretinal fluid is generally treated as activity.
Longer-acting agents
- Newer agents and higher-dose formulations (for example, faricimab and high-dose aflibercept) have allowed many patients to reach intervals of up to 16 weeks in trials.
- Switching agents can be considered in patients who respond poorly or need very frequent injections.
Frequently asked questions
What is a treat-and-extend regimen?
An anti-VEGF regimen in which the patient is injected at every visit, and the interval to the next visit is lengthened if the macula is dry or shortened if the disease is active.
How much is the interval extended in treat-and-extend?
Commonly by 2 weeks at a time when the disease is inactive, up to a maximum interval of about 12–16 weeks, depending on the drug and local protocol.
Is treat-and-extend better than PRN?
In real-world practice, treat-and-extend often maintains vision better than PRN, because PRN tends to lead to under-treatment. It also usually needs fewer clinic visits.
Related: AMD notes, landmark anti-VEGF trials and OCT reading tips.
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