Do unopened contact lenses expire? If so, how?

Question

I know that when contact lenses are purchased they have an expiration date printed on them. But how long of a shelf life do they have? I mean really? They're not food, so I don't really understand why they would "expire". Perhaps a chemical reaction? But what reaction? Aren't most polymers non-reactive?

The reason I'm asking is that I wear glasses, but it might be nice to have contacts for certain things like paintball, SCUBA diving, water sports, etc. If I were to do that though, I would only use contacts for those things, which means that they'd be on the shelf for a while.

Answer 1

I know this is terrible for my eyes, but I usually wear a pair of contacts for a long time without taking them out at all. I usually have to rub my eyes and use eye drops because of it, but it results in the rest of them just sitting there for a while. When I put them in, they work fine, don't burn or anything.

Answer 2

They are in salt water in the package.  If you let one sit around for years unopened, the water eventually evaporates and leaves the salt.  Same thing happens but a lil quicker opened in a case.

I would suggest getting disposable contacts.  One box of Acuvue Oasis, which contains 6 contacts, or 3 pairs cost me 25$ at Costco and Sams both, and there are some that are cheeper.  If your eyes are different strengths, then you would have to get 2 boxes, one for each eye at a time, but it would give you a total of 6 pair.  So, its a good price, even for very limited use.

I have a feeling though, once you get into wearing contacts, you will start wearing them more often.  They feel a lil weird the very first time, and I have about a 24 hour adjustment period when changing from glasses to contacts or vice versa, but after you get used to it you never know they are there.  I even sleep in mine.  I take them out once a week to clean over night, and replace once a month.  THey are very convientent.