What is Buffered Saline Solution?
Our buffered saline has four ingredients: Purified water and sodium chloride PLUS two ingredients for buffering purposes: sodium borate and boric acid.
Why add buffers to saline?
The reason for buffers is to raise the pH to more closely match the pH of our natural tears, and to stabilize the pH so that it doesn’t get more acidic after opening the way simple unbuffered saline can.
What’s the pH thing all about?
The pH of the human eye tends to be around 7. Straight sodium chloride solution (i.e. unbuffered preservative free saline) is acidic, with a pH around 5.5 – or less. Furthermore, without buffers, the pH can drop lower after opening, which doesn’t necessarily matter if you’re using single-use vials and use them immediately after opening, but for larger packages or bottles, it matters more. Buffered salines aim for a pH around 7, just like the eye, on the assumption this will be more comfortable in the eye.
For some users, particularly those with dry or sensitive eyes and/or with an extensive history of corneal disease, the acidity of unbuffered saline seems to cause eye irritation, a burning sensation, and/or a tendency to lens fogging. Fogging is an especially pervasive and frustrating problem for scleral lens users.
Therefore, historically, those with the most complex medical histories have tended to prefer buffered salines for use with PROSE and full size scleral lenses. Unisol 4 and Simply Saline, both now discontinued, were buffered salines as well, with the exact same ingredients as Purilens Plus.