Using contact lenses (CL:s) in a safe way doesn’t just involve not letting them stay in the eye too long – it is also important to discard the contact lens and replace it with a new one in accordance with the recommendations from the manufacturer. While the wear schedule for a CL will tell you how long you can keep the CL in the eye, the replacement schedule will tell you when it is time to discard the CL completely and never use it again.
You can for instance have a CL where the wear schedule is DW (day wear) and the replacement schedule is 30 days. This means that you should only use the CL when you are awake, since it is a DW CL and not an EW (extended wear) CL. When it is time to sleep, you take the CL out and store it in a CL case. When you wake up, you pop it in again. After 30 days of doing this, the replacement schedule tells you that it is time to discard this CL completely and start using a new one.
Replacement schedule for rigid CL:s
Rigid CL:s of the modern gas-permeable type tend to have very long replacement schedules. It is not unusual for a rigid gas-permeable CL to be replaced only after several years of daily use.
The old PMMA-style rigid CL:s were even more long-lasting and using the same CL for 10 years or more before replacing it with a new one was not uncommon. Today, PMMA rigid CL:s are exceedingly rare since they block out so much oxygen.
Replacement schedule for soft CL:s
When it comes to soft CL:s, the single-use CL has become very popular during recent years, partly because the price of CL:s has gone down. Earlier, multi-use CL:s that wasn’t discarded until after 12 months, 6 months or 3 months were much more common.
A single-use CL is discarded after its first use. This means that you never need to store it in a CL case and worry about the sanitary condition within the case. CL cases and the CL solution they are filled with can function as a breeding ground for bacteria, virus, fungi and other pathogens.
Some single-use CL:s are only meant to be kept in the eye for one day (daily wear / DW CL) while others can be kept in the eye even when you sleep (extended wear / EW CL). EW CL:s are available for a lot of different time frames, so you can pick one that suits your preferences. Some wearers like EW CL:s that are kept in the eye for one week and then discarded, others prefer two weeks, and some want to be able to keep the CL:s in for whole month. So, choosing single-use CL:s doesn’t mean that you have to discard two CL:s every day.
Always follow the instructions from the manufacturer. Just because two CL:s are made of the same material, that doesn’t mean that they have the same replacement schedule. If the replacement schedule for your CL is 6 days, don’t wait 10 days before you discard it even if it keeps giving good visual correction and your eyes are showing no signs of irritation.
Daily Disposables / Single-use DW CL:s
This is the type of CL that you put in when you wake up an discard before you go to bed. The replacement schedule and the wear schedule are identical.
Since daily disposables are used for such a short period of time (often less than 16 hours) before being discarded, they don’t have to be very durable. This means that they can be made really thin. Many lens wearers, especially novice lens wearers, find daily disposables much more comfortable than other CL:s since they are so thin.
Another advantage with discarding your CL:s so often is that not much pollen, bacteria, virus, etc will have time to build up around the CL.
Daily Disposables are usually very cheap per individual contact lens (but not necessarily a bargain when you look at the monthly cost) which means that you can afford to simply discard a CL that accidentally fell onto the floor. With a more expensive CL intended for longer use, you will find yourself hunched over, desperately searching for the dropped lens, before vigorously trying to clean it to get rid of any potentially dangerous pathogens that it picked up during its little visit to the bathroom rug, the car mat, etc.
Extended Wear Single-Use
As mentioned above, there are modern CL:s available that you can sleep with and that can be used for multiple 24-hour periods in a row while simultaneously being single-use CL:s. When you have reached the end of the wear schedule, you have also reach the end of the replacement schedule and your CL must be discarded.
Don’t forget that the replacement schedule starts ticking the minute you break the seal and take out a new CL.
Example: You have EW single-use CL:s that are to be kept in your eyes for 2 weeks straight and then discarded. This does not mean that it is okay to use them for a week, put them in a CL case for a few days, put them back into the eyes for another week, and then discard them. They are single-use and are not meant to be stored in a CL case. Once you take them out of your eyes, they are to be discarded, even if the wear schedule isn’t over yet.
Multi-use CL:s are CL:s that you can use multiple times, provided that you store them in a clean CL case with suitable CL fluid in between uses. They should also be cleaned well between uses, in accordance with the instructions from the manufacturer. Don’t forget that the CL case needs to be cleaned to, inside and outside.
Earlier, it was very common with multi-use CL:s with a replacement schedule of 12 months or 6 months. Today, most multi-use CL:s have a shorter replacement schedule, such a 1 month or 3 months. Using CL:s past the recommended replacement date is strongly advised against, even if you have been taking really good care of your CL:s.