4. Nerve Damage
Sometimes, ptosis is caused by nerve damage. The honest truth is that there are nerves traveling throughout your body and multiple nerves throughout each body part. That includes your eyes and your eyelids. When those nerves are damaged, then you have to find a way to get around them because the nerve impulses are not getting to the brain and vice versa to tell the eyelid to move all the way up.
The nerve that is controlling the eyelid muscles can become damaged anywhere along the path, and when that happens, the nerve impulses are going to have a really hard time getting from point A to point B. Nerve damages much rarer than other causes of droopy eyelids, but it does happen.
If this is the cause of your ptosis, then someone may have to go in surgically and repair the nerve. There might be a few other options that your doctor has available.