On a scale of one (no worries) to five (real consequences), which risks are a gamble?
Wearing Disposable Contact Lenses Past Expiration
Risk Rating: 5
Whether your lenses are supposed to last a day or a month, it's not a good idea to save a few bucks by stretching out their life span, says Thomas Steinemann, an associate professor of ophthalmology at Case Western Reserve Medical School, in Cleveland: "Even when you clean and disinfect them, lenses and lens cases become coated with germs and protein over time."
At the very least, wearing contacts past their prime can irritate your eyes, forcing you to wear clunky glasses while your eyes recover. At worst, you can develop an infectious corneal ulcer that leaves scar tissue, reducing your vision or―in extremely rare cases―causing permanent blindness. Replacing lenses with new ones as directed will ensure that you see clearly and avoid issues with your eyes.