I mention an opthamologist because my son has visual tracking problems related to lazy eye (amblyopia.) It's taken awhile for him to be able to read a line in a book without a guide, but it still takes longer. To extend that same notion down, if there is a visual processing (rather than just a classic lens/focus) issue it could play out in not being able to process a whole word at once. I'd imagine there would be other indicators, though, such as not being able to catch a ball, perhaps issues with mazes, searching like when assembling puzzles, etc.
