At 1.9% w/v concentration will boric acid also act as a preservative in eyewash?

Is 1.9% w/v too strong ? Article herein suggests 1.5% strength.
Where else can I research acceptable concentration?
Formula under consideration also contains sodium chloride USP (tonicity) and sodium borate USP (pH adjuster).
On one listing the purpose of the boric acid reads buffering agent.
On another listing it indicates both buffering and preservative, at the same concentration.
Question arises since the boric acid USP 1.9% w/v is indicated as dual purpose- a buffering agent and a preservative.
21CFR349.20 calls for a preservative and I do not know the chemistry to know if that is possible in this combination/concentration.
If, at 1.9% concentartion, is it effective as a preservative?
Is it safe when used as an eyewash when exceeding the 1.5% guideline ?
Thanks very much.