In medicine, dilute salt water is very useful. For example, we can use it to scrub wound, diminish inflammation and so on. Just as you have said, saline solution is good for eyes. Therefore, it is commonly used in eye drops and cleaning contact lenses. However, you maybe overlook something, that is, they are produced by strict formula ratio, a series of production and inspection. Therefore, suggest you don't jump to use it without any adding consider, if like this, you may go into trouble.
Nope, it's harmful for your eyes, because the saline solution is diluted salt water that is common used for eye drops as well as wash contact lenses. It's good for your eyes because your tears are naturally a little salty. However, the salt water means water contains salt, you can't make it by yourself at home due to it could cause dry eyes and other unexpected eye problems.
The doctor of traditional Chinese medicine thinks the salt has the effect of eliminating the dryness. And the most powerful function of salt is to scrub wound to diminish inflammation. That is to say, drinking salt water can be good for sore eyes. But about the replacing use to clean contact lenses, I think you'd better use the solution to clean the contact lenses.