i think otis is a lot more affected by his disability than he lets on... i really doubt he'd want anyone to perceive him as "weak", so he goes without a lot of the aids he would realistically need. he just brute forces through them lol... which only makes them worse. in terms of vision, i imagine part of the reason his artwork is done so boldly is partially due to the fact that it helps him see it better. i headcanon him as having 20/100 vision, aka, very very impaired sight. on the border of legally blind. (for those who do not know, no shame if you dont, legal blindness does not mean you see nothing. there are different degrees of blindness and some see more than others, although its usually incredibly hard to make out what an object is). i dont think his eyesight was always so awful, but it certainly got worse due to his negligence of his health. i imagine he has little things around his room that help him, although he keeps them hidden and only uses them when no one else will be able to see him. he likes to keep his room set up in a way that he can move without bumping into things; he keeps larger items in different parts of his room so he can identify them easier on days where his nystagmus is more intense. generally speaking though, he has the layout of the house memorized. he hates when the fireflys bring in random junk or move things, because then he has to rely on his vision more.
i think his paintings also help with this. for more detail-oriented work like his taxidermy, he has some shitty magnifying eye glasses that he sometimes wears when he cant put up with his eye pain any longer, or it becomes too hard to see what hes doing. i think for the most part though, he relies on texture rather than sight when it comes to these projects. he can feel where stitches are, what part of the body hes working on, mistakes, etc.
otis loves reading; i imagine books are very important to him, but as he gets older, it becomes harder and harder to read. it pisses him off, so he finds excuses to get others to read for him. he hates doing this though, utterly despises it. makes him feel weak. maybe he'll get baby to read for him, but thats the last resort. otherwise, he'll use his magnifying glasses and just... take a really long time to figure out the words.
books get aggravating for him, so he prefers to write his own. generally speaking, he knows the words hes written, and he can write it in a way that is readable to him. i dont think otis has easy access to braille, and he never learned to read it either, but if he were given the access and the time to learn, i think he would find it exceptionally helpful. he'd read a hell of a lot more.
when it comes to navigating, otis is generally able to get around just fine. however, he almost always has to have his hand on something to steady himself, whether it be a railing or a piece of furniture. he never asks for help when he needs it, but baby and gloria learn to catch onto when he needs help. otis might make a snide comment, but he loves them too much to really be upset at them. baby doesnt really know how to help, but she tries... to some degree. she reads out loud and acts out scripts, knowing that otis is secretly grateful to some degree. gloria helps in her own ways... very early on she drilled it into otis's head that he needed to be protecting his skin from the sun. she doesnt mind that otis doesnt stay downstairs too often. she knows he prefers the dimly lit or completely dark upstairs.
otis was not taught how to care for his skin as a child. he wasnt taught to care for himself at all, really. until he met the fireflys, his skin was in pretty awful condition. gloria and baby helped him take better care of it, and gave him new clothes to help protect his skin. gloria taught otis how to sew and mend clothes, so otis started making his own clothing, usually hand-me-downs from the fireflys or clothing he found on victims. wow so cute