What If My Prescription Changes After Laser?

Many people considering laser eye surgery share the same worry: "What if my prescription increases afterwards — would the surgery have been for nothing?" It's a fair question, and the answer becomes clear once you understand why the laser suitability assessment exists. This article looks at the reasoning behind it, and why a stable prescription matters so much.

Why Is Laser Only Done Once Your Prescription Is Stable?

Laser surgery corrects the prescription measured at the time of treatment. If the prescription is still changing, that change can continue afterwards, and the correction may gradually fall short. That's why PRK, Femto LASIK and SMILE all share one precondition: the prescription must have been confirmed stable by measurement for the past one to two years. So the real question isn't "will my prescription increase after surgery?" but "has that risk already been ruled out?" — which is exactly what the laser suitability assessment checks, without discomfort and with same-day results.

Why Can Myopia Keep Progressing?

Myopia usually starts in the school years and can keep progressing while the eyeball is still growing, through the teens, settling once growth is complete. The longer the eyeball becomes (its axial length), the more the myopia tends to increase. When myopia is still progressing at a young age, laser waits until the prescription has stabilised — operating early risks exactly the scenario patients worry about. Even when myopia is diagnosed young, the decision rests on measured stability, not age, so younger patients are often followed more closely.

Why Is Laser Postponed Under the Age of Eighteen?

In patients under eighteen, laser is usually postponed because the prescription hasn't yet stabilised — what matters isn't age itself, but stability tracked through measurement. Even when a glasses prescription seems to have stayed the same for a while, that's an assumption rather than a confirmed fact until verified; the objective reading taken at the assessment gives an independent starting point, then weighed alongside further tests to build a clear picture of stability.

How Is Stability Confirmed at the Assessment?

The assessment includes visual acuity tests and a refraction test measuring your refractive error, compared against previous prescriptions to judge how much change there has been recently. Other parameters — corneal thickness, topography, dry eye levels and intraocular pressure — are assessed alongside it. Patients previously turned down for laser elsewhere over prescription stability can be reassessed later with up-to-date measurements; as equipment and methods improve, an old result may no longer reflect where things stand today.

Does Your Prescription Ever Change After Surgery?

Confirming stability before surgery means the decision rests on solid ground — the most important safeguard in the whole process. That said, the eye can show some natural variability over a lifetime, and this differs from person to person. Regular follow-up appointments afterwards help monitor the overall visual outcome, prescription stability included, whichever laser method was used. In short: this is surgery carried out only after stability was confirmed, not before — which is largely what removes the worry of it "being for nothing".

Is One Method Safer Than the Others Here?

A stable prescription is a shared precondition for PRK, Femto LASIK and SMILE alike — none of the three has an advantage here. What determines the choice of method comes down to other factors, such as corneal thickness, a history of dry eye and the type of refractive error; a stable prescription is simply the common starting point. Which method suits you becomes clear only once stability is confirmed, alongside decision support that weighs which laser method might be right for you.

For more detail on this topic, see Myopia on our page, covering how myopia develops and whether it's likely to progress further.