Droopy eye lid also known as ptosis is causes when the upper eyelid muscle (levator) is weakened.  Although the exact mechanism is not known but it is believed that deep injection of the Botox above medial brow can migrate to this muscle.  Once it occurs depending on the severity several steps can be taken to treat this.  One treatment is Iodipine eye drops to stimulate a different muscle of the upper eye lid and help lift the lid.

The reported chance of ptosis is 3%, but most practices have a much lower incidence.