The witness was allegedly suffering from advanced glaucoma at the time of the crime, severely limiting visibility. Surveillance video from the scene also revealed the eyewitness was much farther away than he initially claimed to be, according to the Exoneration Project.
Found this definition;
You can be legally blind with tunnel vision, i.e. you can see directly ahead, but nothing out of the corner of your eye.
That sound dangerous when doing something other than reading. Even walking could be a problem without having peripheral view.