Welcome to HCM
You are Type I Diabetes
and using Lantus as you are taking 50 U it must be a 100 u/ml insulin
so volume is only 0.5ml of air in to the subcutenuous tissue ,do not worry at all this is very small volume it will not cause air embolism
It will be just absorbed.
But as you are having visual impairment
just be more careful while taking self injections.
Best of Luck.