Dalrymple's sign is a widened palpebral (eyelid) opening, or eyelid spasm, seen in thyrotoxicosis, causing abnormal wideness of the palpebral fissure. As a result of the retraction of the upper eyelid, the white of the sclera is visible at the upper margin of the cornea in direct outward stare. It is named after British ophthalmologist, John Dalrymple (1803–1852).