I'm legally blind, in my early 30's and I'm also considering becoming a physician... Well, more than considering. I'm taking active steps in that direction. It's not an easy decision to make -- which is why I searched your question and came across it here.
I get along well if I have technology to aid me. I can read any text that's on a screen and I use my phone's camera to read hard copies when the text is too small. Looking at the answers here, I don't understand why someone with my condition (who can use computers and read charts) is limited to just psychiatrist and can't be an endocrinologist, nephrologist or even a cardiologist. A lot of medicine these days revolves around looking at computers rather than people. I didn't think I'd be able to take care of other human beings until I became a mom and you know what? I discovered that just having a little bit of sight is a lot if you know how to use it. And if you have a good memory and are good at problem solving and logic? And if it's what you want to do? You should do it. There ARE ways. I'm not going to do it in the US, though. I've decided on Italy for my studies - there are great medicine courses in English (search Harvey Course in Pavia, Italy). It takes 6 years, the school costs close to nothing but it's still well-considered. At the end, you can be a practicing physician in Europe or do the USMLE step 1 and 2 during the 4th/5th year and try to get a residency in the US.
It's not going to be easy but since when was anything easy for us?