Lens cases can be a significant source of microbial contamination- replace at least monthly. Do not rinse your lens case with water. Water can harbor microorganisms that can lead to severe infection. Only use fresh- multi-purpose solution (or sterile saline solution) to prevent contamination of your lens case. If your case comes in contact with water- replace it with a new case. It is essential that you follow your doctor's directions and all labeling instructions for proper use of your lenses and lens care products.