There are a lot of suggestions on how to PREVENT drop eye on arowanas but there is only one reliable way of getting rid of it : operating on the fish to remove the extra fat. I have heard that putting aros in a pond works too but i have not confirmed that
Using a PingPong ball i believe is part of the prevention. They do this , like Nealy said, to keep the aros eye pointing upwards..
Also, please take note that Drop Eye is not a disease but a condition that affects only aros kept in aquariums.
PM me if you want links on how to operate on your arowana to remove the fat that causes drop eye.