How to prepare an ophthalmological solution of EDTA 3%?

A solution of 4.4% is isotoon. So with a 3% solution we get about 70% of the required isotonicity. Of the prescribed 5 ml is 3.5 ml isotone. You can optionally add 30mg of borax for 5ml solution. Given that there is a small amount of 5 ml, I would not add a preservative. But use sterilized water and filter germ-free with sterilized filters in a sterilized vial.