Skater's blind ambition; Teen who lost vision at age 2 relies on hearing, memory to skateboard

Before he hops onto his skateboard, 14-year-old Tommy Carrollcarefully taps along the lip of the 6-foot-deep concrete bowl withhis foot to find his starting point.

Once he's satisfied with his location, the Glenview teen nimblysteps onto the board, rolls down the sloping wall, then goes up andover a concrete hump in the middle of the basin before smoothlycircling high up the wall on a smaller, connected bowl.

He swoops around that bowl without a wobble, then cruises backeasily, leaning down briefly to grab his skateboard as he jumps backup to land on the deck not far from his starting point.

It's just a typical day at the Northbrook skate park. But …