Most people are advising to do medical research for realistic approaches- which in general is important regardless of the possible abuse your characters are going to endure. But its going to take more than that. Even if you write about something that happens all the time in real life that doesn't stop things from feeling too coincidental or too fake. It doesn't matter that in real life anyone can drop dead from an aneurysm- in the world of fiction it can feel like a cheap attempt to make the audience feel sad.
Amortelito has the right approach in general. Action-consequence. A shared idea that also explores this is known as the Domino Effect, if you want to look into that. What is the purpose of the blindness? What else is suppose to happen in this story? Can any other big factors help foreshadow or lead up to the moment?
On the flip side, its not always bad to have multiple coincidences happen. A lot of guilty-pleasure stories are about shamelessly rolling with it and people still love them for it. It doesn't have to be shameless though, even if one day he just went blind -which is a thing- how you explore the contrast of someone having to adjust to that doesn't have to be cheap. Just don't make it a quick montage of, "this is my life now!".
While you do this research, I beg you to look into and study blind life so you don't fall into the stereotypical abled-romanticisms that tend to plague such characters. In fact, you might just find the right inspiration for your character reading other's experiences. I recommend this research first and foremost before just diving in and writing as Yansusu states. No first draft is perfect!