Asian Ptosis Without Double Eyelid Surgery?

An internal approach to repair will allow you to avoid a double eyelid operation while correcting the ptosis. The surgery is performed from the undersurface of the eyelid. Your normal brow position suggests you  have a reasonable muscle function, so this may be a good option for you.

Given your young age, reason 40% of your pupil is covered is likely due to lid ptosis rather than dermatochalasis (excess skin).  A posterior ptosis repair (performed on the undersurface of your eyelid with no outside incisions), would be able to address lid ptosis without creating a double eyelid.  If in fact excess skin is your issue, a conservative blepharoplasty could be performed with a low enough crease that it would look "classic Asian".  

At your age, a browlift is probably not necessary.  It sounds like you need ptosis surgery.  You are correct in that double eyelid surgery can help with ptosis.  In your case, tightening the muscles that control the position of the upper eyelid could open up your eyes and give you the appearance you want.