It is not said outright that Hikaru is blind, however the evidence adds up to it. Best case scenario is that he just has bad enough eyesight to be considered legally blind, but….more likely than not, Hikaru cannot see a thing.
This first becomes painfully apparent during his conversation walking home with Akira at the end of the episode (12).
H: Everyone seemed to have a lot of fun today.
H: Hey, what does Yukiya-kun’s smile look like? He never smiled much when I could still see.
A: It looks normal. Just like yours.
H: Really? I smile properly?
Hearing the first few lines of this dialogue part of me held onto the idea that maybe he was referring to not being able to see Yukiya smiling with Akira using his glasses. But hearing him ask if he smiles properly shut off the door to that route.
Like I said to Moeblob, there were other signs that solidify the idea that Hikaru is blind: Also in this conversation scene, Akira is leading Hikaru by the hand. Earlier, when Hikaru won the treasure hunt, he said people were kind enough to give him their stickers— as crude as it sounds, it could’ve been out of pity. Then also, giving up his glasses to Akira and saying they used to be his— chances of them having the same lens prescription is rare.
Then— oh god don’t get me started on looking back to Hikaru’s appearance in the early episodes with the fact of him being blind being in mind… He asks what the pretty nurse looked like, not only because he wasn’t there, but because he can’t see in general. Then with episode 3 and the ghost, Hikaru could sense Koichi’s presence… this factor could be what later on makes Akira go ‘Oh!’ and put the ghost-seeing megane back on to find Koichi had followed him home… Him being blind also accounts for episode 5 and him not coming to get Akira in the rain like Takuma’s brothers did…
Some people may argue and say he’s not blind, taking into account how he looks at whoever is talking and was even able to get Akira a drink in episode one, but those details just show Meganebu! handling a disabled character EXTREMELY well in my opinion, at least in his given screentime. Hikaru is nowhere near completely helpless and I appreciate that.
tl:dr version- It is safe to say that Hikaru Souma is in fact blind.