One of my characters goes blind in one eye from a car crash. I would like to know what could've exactly happened to him to cause his blindness. Basically, he's knocked out from hitting his head during the crash, and when he wakes up in the hospital, he can't see out of one eye. So does anyone know what could've happened to him? Just a side note, he doesn't lose his eye. I am open to it being discolored or something though, if that could've possibly happened.
Not really sure about vehicle accidents, but I did lose vision in one eye temporarily after taking a particularly bad hit in a boxing match. Officially it's called Post Tramautic Visual Loss and may affect one or both eyes, and can be from a result of different injuries. It may be temporary, but it is far more frequently permanent. With mine, I didn't actually start to experience any vision loss until a a few minutes after the match ended. I was then rushed to the hospital and given all kinds of head scans, including x-rays and a CAT scan and not allowed to sleep for at least 24 hours. Apparently my vision loss was due to swelling around the optic nerve just in behind the eye and when the swelling went down, my vision returned in a few days. I, however, was ridiculously lucky. Aside from having the usual symptoms an eye generally has from a boxing match, though, there was no real discoloration or damage. From what I remember being explained to me, you can also lose vision from a head injury by bruising the vision centres of your brain and they stop working properly, or you if you get hit hard enough your retinas could detach. Either of these would also leave the eye looking relatively normal. Also, just as a weird side note, for a few weeks after this, it was almost impossible to read. Whenever I tried it was like words didn't really seem real and sorta changed themselves while I was reading them. Kind of an odd side effect that hasn't entirely left and shows up some times when I'm under-slept and over-caffeinated.
A detached retina can cause blindness, i believe, if it's not treated. the detachment can be caused by blunt force trauma
Is the cause of the blindness something you plan to reveal to the reader, or is it just a detail of your backstory? I say this without knowing the context (especially how the accident fits in the overall plot), but I love the idea of the cause being a mystery, as well as its permanence.
Head injuries can lead to a few vision problems, including permanent blindness, but these problems are usually treatable if treatment is administered immediately. Detached retina and optical nerve damage are the two most likely causes of blindness. In your case, I would look up traumatic optic neuropathy, but it might be simpler to just go with severe physical damage.
Though it could be changed in editing later, the reader finds out about this character being blind in one eye in the first chapter, but it's not said why he's blind. Right now what's going to probably happen is the MC will end up telling another character about the accident, which will bring up his twin's blindness. Then the reader will know the accident caused it.