Commodore Amiga 500 User Manual page 200

With your thumbs , push firmly in the direction of the arrows to
open the cover for the mouse ball. With the mouse upside
down, lift off the cover with a fingernail :
Put your hand over the opening, turn the mouse upside down ,
and catch the ball:
In the opening, you 'll see three small metal rollers . Moisten a
cotton swab with alcohol or head cleaning fluid and gently swab
the surface of each roller. Turn each roller as you swab to clean
it all the way around .
With the cloth , wipe off the mouse ball. (Don't use any liquid
when cleaning the mouse ball.) When you 're done, blow gently
into the opening to remove any dust, replace the ball , and slide
the cover for the ball back into place.
9-4 Caring for the Amiga