Why Do Contact Lenses Have "Time Limits"?

Jesterhester · #1 (**permalink**) 02-15-2008, 12:08 PM

This is a very basic question that eye doctors probably get asked every day, but I haven't seen if here in Lens 101 yet. How come you can only wear daily contact lenses for one day? Do they become fragile and rip after that or what? Why are monthlies only good for 30 wears,and so on?

harrychiling · #2 (**permalink**) 02-16-2008, 08:24 PM

That's a great question, the daily lenses don't have any surface treatments applied to them, which means that they will build deposits (gunk, proteins, lipids, etc.) on the lens. They are basically processed less becuase they are meant to be thrown out at the end of the day. Other lenses 2 week and monthly have been treated to provide better deposit resistance or are made of materials that provide better depost resitance than dailies. Depending on the person on their wear I have seen patients that wear a two week lens monthly and have next to no depsoits on the lens and I have also seen patients that wear those same two week lenses and have deposits the first day or two. We are all built differently and the wear time is really a great way of giving patients a good idea of when to get rid of their lenses, but I have often metioned to patients that if they are a casual wearer then 2 weeks or 14 days is a good timeline for a two week disposable, but never go beyond the two week period, because the additional proteins can and will effect your comfort and ultimately your ocular health.

unclebuck · #3 (**permalink**) 06-11-2008, 04:12 PM

Quote:

Originally Posted by harrychiling

That's a great question, the daily lenses don't have any surface treatments applied to them, which means that they will build deposits (gunk, proteins, lipids, etc.) on the lens. They are basically processed less because they are meant to be thrown out at the end of the day. Other lenses 2 week and monthly have been treated to provide better deposit resistance or are made of materials that provide better deposit resistance than dailies. Depending on the person on their wear I have seen patients that wear a two week lens monthly and have next to no deposits on the lens and I have also seen patients that wear those same two week lenses and have deposits the first day or two. . .

What a great answer. Thanks.

megane_ko · #4 (**permalink**) 02-22-2009, 03:20 AM

How do you know if there are deposits on the lens?

chemist · #5 (**permalink**) 02-22-2009, 08:10 AM

what is not mentioned is that it is easy to buy weekly enzymatic cleaners that will dissolve the buildup.

note also that no mention is made of increased susceptibility to infections - which is correct.

I've been using a hydrogen peroxide based cleaner and a product called Unizyme on a weekly basis to extend the contact lens wear times.

I have no connection with any manufacturer in the contact lens business

Ricardo · #6 (**permalink**) 02-23-2009, 08:55 AM

Quote:

Originally Posted by chemist

what is not mentioned is that it is easy to buy weekly enzymatic cleaners that will dissolve the buildup.

I have a question - Do the enzymatic cleaners that dissolve the buildup have an effect on the contact lenses themselves, as in breaking down the material?

chemist · #7 (**permalink**) 02-23-2009, 12:05 PM

there is no lens degradation from enzyme cleaners

lovian05 · #8 (**permalink**) 02-24-2009, 06:30 AM

at first im wondering why do contact lenses has an expiration...now i came to realize that everything has an expiration, nothing last forever. lol!

anyway, it's simply because it will irretate our eyes...

Jesterhester · #9 (**permalink**) 04-28-2009, 11:40 AM

Quote:

Originally Posted by harrychiling

That's a great question, the daily lenses don't have any surface treatments applied to them, which means that they will build deposits (gunk, proteins, lipids, etc.) on the lens. They are basically processed less because they are meant to be thrown out at the end of the day. Other lenses 2 week and monthly have been treated to provide better deposit resistance or are made of materials that provide better deposit resistance than dailies. Depending on the person on their wear I have seen patients that wear a two week lens monthly and have next to no deposits on the lens and I have also seen patients that wear those same two week lenses and have deposits the first day or two. We are all built differently and the wear time is really a great way of giving patients a good idea of when to get rid of their lenses, but I have often mentioned to patients that if they are a casual wearer then 2 weeks or 14 days is a good time line for a two week disposable, but never go beyond the two week period, because the additional proteins can and will effect your comfort and ultimately your ocular health.

Thank you for your time, harrychilling. So it seems like it's all about deposits, then, isn't it?

You said that "2 weeks or 14 days is a good time line for a two week disposable," but I thought I heard that it's more about how many times you wear the lenses rather than the length of time. If you only put your contacts in every other day, can you wear monthly lenses for two months, in other words, you put them in and take them out thirty times before you're done with them?

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