Good morning, This is a great question, and one that I get asked about a lot. Ptosis is when the eyelid position is low. Imagine taking a light and flashing it at your eyes. You will see a light reflex in the middle of your pupil. The distance between that light and the eyelid margin (area where eyelashes are coming out) is called the margin to reflex distance 1 (MRD1). When that distance is small (the eyelid margin is close to the center of the pupil), you have some degree of eyelid ptosis. Ptosis can be mild, moderate, or severe, and the treatment options depend on the individual findings. Alternatively, you can also have eyelid asymmetry from other things such as excess skin on the surface of the eye, differences in fat distribution in the eyelid causing relative differences in hollows, or you can have differences in the way the eyelid skin folds. The treatment options depend on a case by case basis. An in person consultation is always best to determine what is the right treatment. I hope this helps.