Contact Lenses Forum

Why do contact lenses have an expiration date? If I have some 1 Day Acuvue For Astigmatism and it's a year past the expiration date on the package, what would be the risks? Will the solution be stinky? Will it be dried up? Can bacteria somehow make their way into the sealed package if they have a year or two to work on it?

You've got one-day contact lenses that have been sitting around for a year? After all that time the lenses will probably by dried out. If somehow they're still in liquid, they may disintegrate if you try to pick them up. One-day contacts are very thin. Finally, after sitting so long is possible that their shape may have changed and they won't be the same prescription any more.
Nakchura suggested that the chemicals might have mutated into something harmful, but what usually happens with chemicals is they become weaker with the passage of time. Remember the Second Law of Thermodynamics: entropy increases. That means the longer you try to keep things together, the more they fall apart.