AMD Treatment Options

Treatment Modalities for Wet AMD: Treat and Extend vs. PRN (Pro Re Nata)

In the management of wet macular degeneration (neovascular AMD), intravitreal injections of anti-VEGF agents (such as ranibizumab, aflibercept, or brolucizumab) are the gold standard. However, there are two main strategies for administering them:

Treat and Extend

PRN (Pro Re Nata or As Needed)

Each approach has specific advantages, disadvantages, and selection criteria. Below, we explain both modalities in detail.

1. Treat and Extend (TAE)

What does it involve?

Initial phase: Monthly injections are given until the AMD stabilizes (no fluid on the OCT).

Extension phase: After stabilization, the interval between doses is progressively lengthened (e.g., 6, 8, 10 weeks).

If there is recurrence (new fluid), the interval is shortened.

Advantages

✔ Reduces the number of visits in stable patients.

✔ Lower risk of reactivation vs. PRN (by maintaining predefined intervals).

✔ Better adherence to treatment (predictable planning).

Disadvantages

❌ Some patients receive more injections than necessary (potential overtreatment).

❌ Requires close follow-up to adjust intervals.

Ideal for:

Patients with recurrent activity.

Those who prefer fewer visits (e.g., people who travel or live far away).

2. PRN ("Pro Re Nata" or "As Needed")

What does it consist of?

Initial phase: Same as TAE (monthly injections until stabilization).

Maintenance phase: Injections are suspended and restarted only if there is:

Loss of visual acuity.

Appearance of fluid on OCT.

New neovessels on angiography.

Advantages

✔ Minimizes the number of injections (only when there is activity).

✔ Lower cost (less medication used).

Disadvantages

❌ Higher risk of recurrence (due to delayed retreatment).

❌ More frequent visits (every 4-6 weeks for monitoring).

❌ Possible irreversible retinal damage if reactivation is not detected early.

Ideal for:

Patients with low disease activity.

Those with good self-monitoring (e.g., those who use the Amsler grid daily).

Which is Better?

Recent evidence favors "Treat and Extend" due to:

Better long-term visual acuity.

Less stress for the patient (no longer waiting for urgent checkups).

PRN may be useful in highly selected cases (patients with low disease activity and close follow-up).