The upper eyelid skin is usually some of the best healing skin on the body, at least from the standpoint of scar quality. Sadly, you seem to have had difficulty despite that.
From your description, I suggest that you have the scar revised. Perhaps you had a tight eyelid early in the healing process which put tension on the scar. During a revision, only the scar will be removed and this will likely not lead to much tension.
The first goal of a revision is too have a smooth scar. In other words, not dented in. During the early parts of healing the scar may be mounded up a little, this is normal and should resolve. A dented in scar is not going to fill in on its own and would need further work. Aside from trying surgery again, fillers like Restylane or Juvederm could be used.
The second goal of a revision is a scar that is as narrow as possible.
The final goal of a revision is a scar without visible color problems. If you tend to scar very white, there is little that surgery can offer to correct this.
If your scar ends up dented after the revision, it may be your genetics, or it could be the technique. You may consider a second opinion. A wide or white scar is amendable to make-up and is not as severe a problem. You could also look into permanent cosmetics (specially qualified tattoo artists do this) to blend the color. Be sure to pick someone highly skilled in this because it is not easy.