Yes, and there are three separate clocks running at once. Most people only know about one of them, and it is not the one that matters most.
Clock 1: the blister expiry date
Every sealed blister carries a printed date, typically three to five years from manufacture.
What expires is not the plastic of the lens. It is the guaranteed sterility of the solution inside and the integrity of the foil seal. Over time that barrier stops being reliable.
Do not wear a lens from an expired blister, however perfect it looks. A lens sitting in solution no longer guaranteed sterile is precisely the starting point for a corneal infection.
This matters most if you bought a two-year supply, or have old boxes from a previous prescription in a drawer.
Clock 2: the replacement schedule — the one people get wrong
A monthly lens is monthly from the day you open the blister, not from thirty days of wear.
Wear it three days a week and it still expires on day thirty. Same for two-weeklies: fourteen calendar days.
The reason is that the lens begins accumulating protein and lipid deposits from first use, and spends every night in a case. That process runs on the calendar, not on your hours.
Stretching it is the most common false economy in lens wear: deposits, less oxygen, higher infection risk. If cost is the motive, there are better ways to reduce it — and if you wear lenses fewer than four days a week, dailies are often cheaper in practice than a monthly you keep throwing away half-used.
Clock 3: your prescription
Valid for no less than one year from issue under federal law, and longer in several states — see the state-by-state breakdown.
This clock does not affect the lens. It affects your right to buy more. And there are clinical reasons behind it: your prescription changes, the fit changes, and an exam catches things that are asymptomatic. More in when your prescription expires and ordering after it lapses.
Solution expires too
Two dates again:
- The unopened bottle date, printed on the label
- The discard period after opening — usually 90 days, marked with an open-jar symbol and a number
A bottle opened eight months ago no longer disinfects properly even with liquid left in it. Write the opening date on the bottle in marker — the simplest fix there is. See solutions compared.
And the case
No printed date, but replace it every three months. It is where biofilm forms, and it is the component most people treat as permanent furniture. Most solution packs include a new one — use it. See the case guide.
What to do with old lenses
- Expired blister — bin them. There is no sensible exception.
- In-date blister, old prescription — do not wear them “to get by”. The wrong power causes strain and headaches, and a different brand may not fit your eye at all.
- Unopened boxes still in date — if your prescription changed, many retailers accept returns on sealed boxes. Policies vary considerably: Walmart gives 90 days, ContactsDirect six months, LensDirect 30 days or 365 for a fee.
That last point is worth real money. If you bought an annual supply and your prescription changed mid-year, check the policy before writing the boxes off.
General information. Follow the instructions for your specific product and your optometrist’s advice. Reviewed by Dr. Teresita Bollar, OD.
