There is a natural tarsal crease at the upper eyelid which deepens when raising and opening the upper eyelids, thus forming a double eyelid which is a typical feature in non Asians. However this upper eyelid crease may be partially or totally absent in East Asian people due to certain anatomic features like weaker or missing upper eyelid skin adhesion to the levator palpebrae superioris muscle and to the tarsal plate, thus leading to a single or mono upper lid, to distinguish it from double upper eyelids shown by other ethnicities. The single upper eyelid may be commonly associated to the presence of an epicanthic fold covering the caruncle (lacrimal lake).
Creating the double eyelid crease is best accomplished by means of incisional techniques to build up the adhesions between upper eyelid skin and the eyelid elevator muscle and the palpebral tarsus (cartilage).