When I get this problem I release the ball and clean the rollers of fluff. Often taking the the screw out to remove the casing. It works for my ball mouse, and done on the basis that if I mess up, a new mouse is quite cheap.
I found that with an optical mouse the ordinary mouse mat was no good I have put a clean sheet of white paper as a mouse mat. The printing on the original mat was affecting it. Once I found this did the trick I laminated it to keep it clean.