How do I prepare a collyre of chlorhexidine 0.02%?

R/chlorhexidinedigluconate 20% Solution   106 mg; mannitol 1 g; Water for injections AD 100 ml  

for 10 ml: chlorhexidinedigluconate 20% Solution 10.6 mg; mannitol 100 mg and water for injections AD 10 ml.  

One hundred mg of mannitol weighing is on the edge but of chlorhexidinedigluconate 20% solution you will have to dilute 1 g with sterile water up to 20 g and of these 10, 6x 20 = 212   mg weigh.   The mixture mannitol and chlorhexidinedigluconate 1% solution is supplemented with water for injections up to 10 ml. This solution is filtered on a sterilized membrane filter 0.2 micrometer in a sterilised collyrevial.    

I have my doubts about the prescribed concentration. I found as collyrium with chlorhexidine 0.1%! And the activity of this is still being questioned. It would help with bacterial conjunctivitis but the effictivity has never been proven with a large number of patients.