How Can You Tell if One's Eyelid Droops Because of Ptosis or Too Much Eyelid Skin?

The two commonly recognized reason eyelids appear to be different is extra eyelid skin or drooping of the eye lifting muscle.

Frequently unappreciated is the difference in set of the eyeball in the eye socket (orbital dystopia).  the eye is an oblong sphere, and differences in "set" of the eye can cause profound differences in the appearance of the eye with respect to the eyelid as well as the cheekbone.  There is often flatness on the side of the deeper set of the eyeball.

It takes an artistic eye to appreciate the differences between the two sides, and design a solution that does not create absolute symmetry of the eyelids or cheekbones, for example, only to have the ultimate result look very odd because the main reason for the two sides being different was a difference in set of the globe within the eye socket.

Sometimes it is difficult to tell the difference between ptosis and extra skin. Ptosis comes from a weak or torn eyelid muscle. The edge of the eyelid sits too close to the pupil. Extra skin alone can mimic this but when the skin or eyebrow is lifted up the lid either is in a normal position or stays too low.

The easiest way to tell the difference between ptosis and dermatochalasis (excess eyelid skin) is by lifting the excess skin off of the upper eyelid. If the actual lid margin itself is cutting across the black pupil portion of the eye, then you may have ptosis. If the eyelid is raised above the pupil all the time even with the excess skin on top of the lid, you just have simple dermatochalasis. For many examples of cosmetic eyelid surgery, please see the link and the video below

As you are now probably aware, upper eyelid ptosis is a condition that causes the upper eyelid to appear to be droopy or give a person that sleepy-eye appearance.  With this condition, the upper eyelid is lower than it should be (it either covers part of the iris or is very close to covering the iris) and this is caused by a weak eyelid muscle.  You may have two problems - excess eyelid skin and a weakened muscle.  If it is just excess skin then you should no longer notice the droopy appearance once the excess skin is removed. The procedure for removing excess upper eyelid skin is called an Upper Blepharoplasty.  If it is both then you will still have the same appearance after removing the excess upper eyelid skin as the ptosis will not have been corrected by doing a blepharoplasty alone.  Removal of the excess skin will not change the position of the upper eyelid.

You mentioned going to an expert and he said you had ptosis.  My feeling is that you either did not trust the diagnosis of this person or would be more comfortable in having a second opinion.  No one will be able to give you the answer you are seeking without actually examining you.  My advice is to get a second opinion from a Board Certified Facial Plastic surgeon, Occuplastic surgeon, or an Ophthalmologist.  A qualified physician will know exactly what is causing the droopy appearance.