Contact lenses need to be soaked in contact lens solution to be cleaned every time you take them out. There are a few alternatives you can use for contact lens solution when you are in a pinch and must take your contact lenses out, but some solutions are better than others. The best contact lens solutions are marked "multipurpose solution," or "contact lens solution," and other alternatives should only be used in an emergency.
Saline solution, which is a saltwater solution sold in pressurised cans or plastic bottles, is similar to contact lens solution in that it is a disinfectant solution that will not harm contact lenses. Saline solution is essentially only sodium combined with water, but it is sterile and usually stored under pressure, so it can clean surface smudges from contact lenses. Although it is not recommended to store contact lenses in saline solution every day, if you need to take your contact lenses out, saline solution will work until a contact lens solutions is available. As soon as possible, rinse or store your contacts in contact lens solution or multipurpose solution.
Just because contact lens solution is clear in colour does not mean that you should use plain tap water to clean your contact lenses. Tap water carries a virus known as acanthamoeba keratitis that can cause a painful and dangerous eye infection that may result in vision loss or blindness, and may require corneal transplant surgery in some cases. Distilled water should not carry acanthamoeba keratitis, although it is still possible to get an infection if the water is not sterile. Although distilled water is not a foolproof option for storing contact lenses, it is safer than regular tap water.
You are at risk for becoming infected with acanthamoeba keratitis if you use any type of water on your contact lenses, but putting a small amount of table salt in the water will eliminate more bacteria than if you use plain tap water. It is not recommended to use any of these remedies long-term, or to use them instead of regular contact lens solution or multipurpose solution. To prevent growth of bacteria, do not reuse solutions.