This is the first time I have used Evo Tears. I normally purchase Hycosan, Shield which is exactly the same product, but it was not available. So I feel lucky to have found Evo Tears on this site since perflourohexyloctane is the only eye drop that relieves my symptoms. I see that it is now out of stock so I hope you are able to have it available in the future. I will definitely buy again.