How can I reduce the scar tissue on my bottom eyelid left from chalazion surgery? (photos)

Tough to tell much from the pictures.  If you have a scar right at the lid margin, you could have an excision of the scar full thickness through the lid.  If just on the skin, this could be re-excised. These will give you a new scar, but hopefully would look better than what you have.  See an oculoplastic surgeon since they specialize in this sort of work. 

The picture is a bit out of focus, so it is difficult to see the details of the lid margin. I am concerned that the surgery was 4 years ago, and the eyelid has not thinned or returned to normal appearance. It is also difficult to tell whether you have lashes there, and whether the normal lid margin microanatomy is present. An oculoplastic surgeon could confirm the diagnosis and help you determine your next steps. If you were my patient, I would want to be sure of the diagnosis - i.e., scar, inflammation, neoplasm. Please have this checked out. Best wishes.