A drooping eyelid can be the first clue to a hidden aneurysm
Ptosis, a sagging upper eyelid, is often just a sign of ageing muscles. But it can also flag diabetes, a tumour pressing on a nerve, a silent brain aneurysm or myasthenia gravis. One bedside test for that last cause is surprisingly low-tech: doctors hold ice against the eyelid and watch whether it lifts.
The upper lid is raised by the levator palpebrae superioris, wired to the oculomotor nerve, with help from the smaller superior tarsal muscle supplied by sympathetic nerves. Damage anywhere along that chain can let the lid fall, on one side or both, sometimes far enough to cover the pupil. People compensate by raising their eyebrows, wrinkling the forehead or tipping the chin up to see beneath the lid.
Children are a special concern. Some babies are born with ptosis because the levator muscle developed abnormally in the womb, and three hereditary forms are known, though the ultimate causes of congenital cases remain unclear. Left untreated, a heavy lid can block vision during a critical window and lead to amblyopia or astigmatism, which is why early treatment matters. The condition is sometimes nicknamed lazy eye, though that term properly belongs to amblyopia.
In adults the commonest acquired form comes from the tendon-like sheet of the levator stretching or detaching with age, chronic inflammation, eye surgery and possibly long-term contact lens wear. Other culprits include trauma, lid tumours, high doses of opioids such as morphine or heroin, and snake venoms like the black mamba's. A sudden one-sided droop with an enlarged or sluggish pupil points to compression of the third cranial nerve by a tumour or aneurysm and calls for CT or MRI; when the pupil is spared, the palsy often improves over weeks, and surgery is usually delayed about six months.
Myasthenia gravis deserves its own mention. Up to 70 percent of patients show ptosis at first, and 90 percent eventually do. Its hallmark is fluctuation: the lid tires and drops as the day wears on. Cold slows the enzyme cholinesterase, so an ice pack can briefly improve the droop, helping separate it from other causes alongside blood tests and the Tensilon test. A small 2025 study found that surgically lifting the lid reshaped the outer corneal layer within six months.
Source: Ptosis (eyelid)
