There is a lot of "explanations" for drop eye, but I personally believe it is mostly genetics, and the fact that arowanas are not meant to be in a tank.
There are also many ways or trick to help prevent or cure drop eye, but none are 100% effective (or proven to be effective). You can try:
- ping pong balls
- flashing lights (xmas lights)
- painting the bottom or putting gravel (so that the bottom does not reflect, avoiding the aro to look down)
- putting the aro in a pond
Personally, I don't mind a little drop eye, I guess you have to learn to live with it.
I just realised that my aro has drop-eye syndrome. I know there's no cure for this, but what could I do so that it doesn't get worse.
In my tank I have 6 african cichlids, 4 indo tiger, and 4 different plecos. The tank is a 220g, granit bottom, no sand, just a few silk plants.