My Hb1ac was 7.4 2 months ago,recently I increased my insulin dosage to 20 Humulog x 3 & 16 Lantus x1 which reduced my insulin average on my meter to 6.6 - perhaps I injected too much ?
It's hard to really even speculate, without an awful lot more information which we don't have, and you may not have either.
One thing I would suggest would be that of this happens again you test your blood sugar and see what the numbers look like. I'd also write down whatever the number was to be able to understand any patterns.
Have you spoken to your doctor, or optician about this? Our sight really is too precious to just wait and see, when we have concerning issues.
Nobody here can diagnose you with anything - only the professionals can do that.
All the best with it. I'm sure it must be a worry for you.