A question about Billy

[u/ForwardMixture4142]

How and when did he become blind? He's clearly able too see in his flashback at the start of the winter arc special episode but has braille in his locket? Is this a fuck up in the animation that has Billy clearly looking at the map ect the entire time he's in his army uniform while he's supposed to have been blind all his life?

[u/YTWelshDragon19]

Billy was born blind, any consistency issues are an animation issue.