Brock's most notable feature about his appearance is that his eyes naturally appear closed. The rare times people see them open are when they are forced open unnaturally: from a hit with Charmander's Flamethrower in The Ninja Poké-Showdown, when being hit in the back of the head by Arbok's tail in Who Gets to Keep Togepi?, and when he makes a face for Larvitar in A Crowning Achievement. This has been the center of fan attention for a long time.
He's not blind, his eyes are just narrow; all of his siblings have the same eyes as well.
^ His family
^ Brock with his eyes wide open