It's easy to normal saline solution for use in the lab or to rinse your mouth or nose or irrigate wounds. The concentration of the salt solution would be appropriate for use as a contact lens solution, but it's too risky to use the solution unless you have access to lab-grade salt, lab-purity water, and an autoclave. Although it's easy to obtain the salt and water, getting the solution sufficiently sterile is much harder to do. You can boil the solution practically forever, yet may not kill bacteria that encapsulate. Fungal spores, prions, and some viruses also resist boiling. Commercial rinses for home brewing and making wine can sterilize your plastic or glassware, but the saline solution may retain some infectious agents. Saline solution for contacts that you buy at a store is buffered to prevent pH changes that could harm your eyes, plus the solutions typically contain a preservative that helps keep them sterile and resist contamination longer than a simple saline solution. So, make saline and use it for lab exercises and home healthcare and first aid, but resist the temptation to use the solution in your eyes.