Contact Lens Solution in Goggles keeps them clear

A guy I swim with at the lake had some contact lens solution that he put inside his goggles (about a teaspoon in each eyepiece). The solution swirls around and keeps the inside of the lens nice and clear. He offered me some, so I tried it. It really worked great, and didn’t sting my eyes.

It should be a plain saline solution, not the disinfectant kind.

keywords: swimming goggles, fog, anti-fog