Sodium chloride in lid spray?

[Pinky]

Hi DrG,
You wrote that sodium chloride in ointments have no place in dry eye treatment, but what about sodium chloride in a lid spray? I have been using Tears Again Liposome Lid Spray for the past couple of days and it has brought me a lot of relief. I would hate to have to give it up! The ingredients are: Purified water, Lecithin, Ethanol 1%, Vitamin A, Vitamin E, Sodium Chloride, Phenoxyethanol 0.5%.

Thanks for your input.

[DrG]

Dear Pinky,

Salt is important. Our natural tears contain sodium chloride. I am sure that the liposome spray contains just enough sodium chloride to make the spray compatible with your ocular tissues. The term for this is isotonic, and amounts to 9 grams of salt per liter of solution, or 0.9%.

The salt content in Muro 128 is typically 5 times greater, or 5%. Having a higher tonicity - hypertonic - than the surrounding tissues causes water to be pulled out of the intracellular spaces, thereby having a dehydrating effect.

I noted that someone posted a question to DrL concerning the use of one-half teaspoon of salt in a quart of water as a lid scrub. This is 2.5 grams in slightly less than 1 liter, for a concentration of 0.3%, which is quite hypotonic.