Can daily disposable contact lenses be safely re-used?

Question

It is recommended that "daily" contact lenses are to be disposed of after about 8 hours of use. I understand that daily lenses are made from a different material than, say, monthly ones; they are softer and apparently not suitable for cleaning.

However, what stops me from buying a lens case, some sterilising lens liquid and simply storing them in the case for a couple more days?

I asked a salesperson at the opticians today, but they declined to answer, and have a financial bias.

I have tried it once before (I kept some of the solution the lenses came in, placed the lenses in it after a day's wear and used them the next day) and it I didn't feel that my eyes were irritated, though I did notice that they became drier faster than usual.

Why I shouldn't do this; what happens to the material/my eyes?

Answer 1

Truth be told, all contacts are prone to buildup of biological materials. I could find no data on whether temporary lenses are more prone to buildup, or are more difficult to clean. To get FDA approval, the companies must have their product tested for the duration of usage, frequency of replacement, and conditions treated. A full list of approved contact lens products and what the FDA has certified them for can be found here. The FDA definition of "disposable" contact lenses is for them to be used once and discarded, but sellers are also allowed to market extended use contacts as "disposable". Any use past that period is not FDA-approved usage of the product and thus is outside of the usual scope of safety.

Reuse of temporary lenses is shown to cause problems for users.

Thirty-nine percent (154/398) had some qualifying criterion: reduced comfortable wearing time (CWT), 20%; dryness, 20%; irritation, 5%; corneal staining, 8%; and hyperaemia, 7%. After refitting with [daily dispoables (DDs)], the prevalence of reduced CWT was decreased from 65% to 51% (P=0.0039), dryness from 60% to 41% (P<0.0001) and corneal staining from 28% to 21% (P=0.04). There was no significant change in the prevalence of irritation, or hyperaemia. Some differences were noted between the two lens materials.

Ultimately, it's a matter of risk-benefit. Some people don't produce as much build-up. Some people are less susceptible to infections. But when it comes to your eye health, consider that the risks could be serious including permanent blindness. Is that worth saving a few bucks even if that's the rare worst case?