There are different types of solutions that people use to clean and store their contact lenses. These include 

• multipurpose fluids, 
• saline solutions, and 
• hydrogen peroxide based solutions. 

None of these solutions can be recycled, but it is safe to pour them down the sink.

Can they be reused?

No. Do not reuse old solutions for other purposes (eg disinfection,  watering plants). They often contain preservatives or salts that are detrimental to plant health, and are also not optimized for disinfection purposes beyond cleaning of contact lenses. 

Ingredients

Contact lens solutions usually have several types of ingredients. 

• Disinfectants are included to stop bacteria, fungus, and other tiny living things from growing on the lens or causing protein buildup. 
• Wetting agents are added to prevent dry eyes, 
• Buffers help to maintain healthy levels of salt and pH for the lens and the eyes. 
• Preservatives are also used to make sure the solution can last for a while without going bad. 

More info on ingredients here

Do these solutions really expire?

Yes. 

• Expired solutions can be harmful to the eyes as they may contain bacteria, especially if they have been opened or their seals are loosened. 
• The acidity of the solution can also change over time, making it less effective at disinfecting. 
• Additionally, other active ingredients in the solution can degrade, reducing its overall effectiveness. 

Therefore, it's important to avoid using solutions that have expired to ensure proper disinfection and eye health. These are your eyes!

Exception:

Pure saline solutions, if unopened, are safe to use for wound irrigation past the expiry date. Over time, the solution may dry out slightly increasing the concentration of salt. But when used for wound irrigation such solutions remain safe as long as they have no other additives which would make them unsuitable for this use.