What is the difference between daily, fortnightly, monthly, and yearly replacement contact lenses?

The main difference is how long you should wear the lenses before they expire!

Daily contact lenses are worn for one day and then discarded. The next day you put a new contact lens on the eye, ensuring you always have a clean contact lens every day. They also don't involve the use of contact lens maintenance and cleaning solutions, drastically reducing problems associated with eye infections.

Scheduled replacement lenses (fortnightly, monthly, yearly) need cleaning and disinfection every day. They are discarded in accordance with the manufacturer's recommendations, and your ophthalmologist will guide you about the right time. Generally, this happens after two weeks for fortnight-replacement contact lenses or a month (for monthly-replacement lenses).

The validity of contact lenses starts from the moment the contact lenses are opened, regardless of whether or not you use them. As soon as you open the blister of a monthly lens, the validity is 30 days, even if you only use it one day. In the packaging, the contact lenses are stored in a preservation solution which is not the same as the one used in maintenance liquids, so it loses its validity after being opened.

Extending the use of contact lenses, even if they appear to be in good condition, is one of the main mistakes made by contact lens wearers and is the main cause of eye infections.

For your eye health, do not extend the validity of your contact lenses!