First, you should consider writing an optional essay to explain your circumstances.
Second, you will want to marshall as much evidence as possible showing that you are currently aware of the impact your situation can have and how you are able to manage well despite it. Strong performance in courses these days that do have a lot of reading can help mitigate weaker performance in earlier years of school.
The key is really this: an MBA program can involve a lot of reading for some courses. So, if you really are concerned about reading for long periods of time, you should: a) seriously consider whether an MBA program makes sense for you at this time; and b) explore what support opportunities or accommodations each program may be able to offer.
Not to sound insensitive, but it is easy to say that, "if only for XYZ, I would have had a perfect GPA." Part of the challenge for all people is moving away from excuses and focusing on how one can succeed in spite of various challenges or obstacles. If you focus too much on providing an excuse, you will only hinder yourself from realizing your full potential. Obstacles are there and deserve to be recognized, but keep in mind that you are certainly not the first person who is legally blind and others surely have managed to achieve a "perfect GPA" in spite of their condition. So, the key is to show that you currently have the same attributes that may have made those folks successful - and that that is who you are today, as opposed to in the past (i.e. - demonstrating growth).