Garrett was blind in the beginning
A lot of people on this board think that there is a plothole where Garrett isn't blind during the opening of the movie. Reasons why he is blind:
Look at his eyes. Here is a picture of him before he was blind: http://i.imgur.com/xJiFE.jpg Dark eyes.
Picture from beginning of movie when people think that he isn't blind: http://i.imgur.com/Rudo0.jpg Gray eyes.
And of course, picture of him as adult: http://i.imgur.com/dL6N6.jpg Identical to the 2nd picture.
Also, at the beginning of the movie he is training using the stick he uses throughout the movies. The girl's father gave him the stick after he was blinded and can be seen at around 45 minutes in the movie.
The purpose of him being in the beginning is for people who watch the movie more than once and seeing him as a younger person right after he was blinded and add something for the 2nd viewing.