Question: What stops blind people from seeing?

Indi Ghangrekar answered on 12 Mar 2012:

You can break up the process of seeing, or vision, into a few separate processes and there is the possibility for any of these processes to not work properly.

So, what are they? Well, 1) vision is a result of a specialised group of proteins called opsins that can detect the light coming off objects. 2) These proteins are present in specailised cells in the eye called rods and cones (there are 3 types of cones). 3) The rods and cones send the light information detected by the opsin proteins to some other cells in the eyes called ganglion cells that process that information a bit – they try to make a little more sense of the information. 4) They pass the information to the brain via the optic nerve. 5) The part of the brain that gets this visual information is near the back.

So any of those processes from 1-5 can go wrong, so, for example, the opsin protein genes may not work properly; or the rod, cone or ganglion cells may not work very well; there may be problems with the optic nerve; or there may be damage to the part of the brain that makes sense of what we see. I don’t actually know what the most likely problem is for it going wrong though, sorry!