Not to try and speak as the GM (anything but that) I have three things to say.
[hider=First]The physical effects of Susac's Syndrome - at least from what I read in your link - are minimal. It's been explicitly stated in canon of Katawa Shoujo that Yamaku only accepts those with physical disabilities, with some exceptions (see: Misha and maybe Hanako). Of course, I may have missed something.[/hider]
[hider=Second]There's no way to not be sure about a character. One way to go about it is to ask questions from your perspective, then answer from Elmo's. Does he get along with others? What kinds of pastimes does he enjoy? What pet peeves - if any - does he have? You'd be surprised what your character can teach you about them sometimes.[/hider]
[hider=Third][youtube]nZBKFoeDKJo[/youtube]
...I had to. I'm sorry.[/hider]

EDIT: ...ninja'd by the GM. Disregard everything I just said.