How long is a glasses prescription valid?

For ordering lenses, roughly two years for adults in most of Europe — less for children and less for contact lenses. For understanding your own eyes, a prescription never expires.

Typical limits

• United Kingdom — a spectacle prescription is normally valid for two years; sooner if the optometrist specifies, and typically one year for children under 16 and for people over 70.
• Spain — commonly one to two years in practice, at the prescriber's discretion; opticians will generally ask for a recent test before dispensing.
• Germany — similar, with the Brillenpass and the clinical prescription serving different purposes; retailers usually want a current measurement.
• Contact lenses — shorter almost everywhere, often a year, because the fit and eye-surface health need re-checking, not just the vision.

These are conventions rather than physics: the number on an expired prescription is not wrong, it is just no longer recent enough for a dispenser to rely on.

Why the limit exists

An eye test is not only a refraction. It is also a check of eye pressure, the retina, and the health of the front of the eye — several of which change silently. Time-limiting the prescription is how the system makes sure the rest of that examination happens too.

Expired does not mean useless

You cannot order lenses from a five-year-old prescription. But it is the only evidence of where your eyes were five years ago, and that context is what makes today's measurement interpretable: stable, drifting, or changed suddenly. Optometrists routinely ask what your last prescription was — and almost nobody knows.

Keep them all, dated. The expired ones are the history; only the newest one is the prescription.