Head Lamps

My head laps are full of dirt. Im sure its in the inside because it wont comeoff even if you scrub w/ alot of soap on the outside. Is there a special way to clean the head lamps? and if so what is it? I drive a 2000 cavy and its getting harder to see at night. Any thing would help thanks.

Just pull 'em off the car & use a bottle brush to clean the insides.