Definition

A ptosis is the term given to a droop of one or both upper eyelids. The upper eyelid margin usually rests 1-2mm below the iris (coloured tissue surrounding the pupil) when a person is looking straight ahead. A severe ptosis is present if the upper eyelid is so low that it covers the pupil.

Incidence/Age

Ptosis can be congenital (present at birth) or develop later in adulthood. It is most commonly seen in people in their seventh decade or older.

Anatomy and Physiology

The eyelid is held up chiefly by the levator, a muscle that sits above the eyeball and inserts into the skin of the eyelid, usually near to the eyelashes.

Causes

A congenital ptosis is most commonly due to an abnormally weak levator muscle; the reason for the poorly functioning muscle is generally unknown and the affected child is usually otherwise healthy. Rarely a ptosis may be related to problems during pregnancy or at delivery, eg, use of forceps. A small subgroup of congenital ptosis may run in families, eg, as part of the blepharophimosis syndrome.

A ptosis which develops later in life can be due to a number of problems with the muscles or nerve supply to the upper eyelid. Ptosis can result from an acquired levator muscle weakness, eg, myotonic dystrophy, myaesthenia gravis; a problem with the nerve supply to the eyelid muscles, eg, Horner's syndrome; a disinsertion of the levator muscle from it's attachment to the eyelid skin, eg, secondary to long term contact lens wear or eyelid trauma; or a mechanical weighing down of the upper lid, eg, due to an eyelid cyst.

Symptoms and Signs

A congenital ptosis is usually first noticed by the child's parents or a health worker. Rarely a "winking" of the affected eyelid is also noticed when the child is feeding. This is called a Marcus Gunn jaw-winking ptosis and is due abnormal wiring between the eyelid and the muscles involved in chewing.

Adults tend to complain that their upper lid feels "heavy", often worse towards the end of the day and that the low upper lid is interfering with their peripheral vision. A mild ptosis can, however, occasionally be regarded as purely a cosmetic problem.

People with a moderate to severe ptosis may develop a chin up head posture to try and see more clearly, sometimes resulting in neck discomfort.

Some conditions, which cause a ptosis, can affect other structures in the region of the head and neck. Other possible symptoms may, therefore, include double vision (diplopia), different sized pupils, general muscle fatigue or difficulty swallowing.

Complications of Disorder

A marked congenital ptosis, with the upper lid covering the pupil, can result in permanently defective vision (amblyopia) if it is not treated appropriately.

In adults, the complications of having a ptosis depend largely on the severity and the underlying cause. Although ptosis is usually due to a benign cause, it can sometimes be a sign of more serious disease.

Tests

An accurate diagnosis can usually be made following a careful history and examination by an ophthalmologist (eye doctor). Additional tests may occasionally be required to find or confirm the cause. These can include specific blood tests, nerve conduction studies, X ray or CT scans of the head and/or chest or a "Tensilon" test. The latter is a test for the rare muscle disease, myaesthenia gravis. A drug is injected into a vein, under careful medical supervision, which temporarily allows the weak muscle to function normally for a few minutes.

Treatment

Medical

Ptosis is not usually amenable to medical treatment, with the exception of ptosis secondary to myaesthenia gravis, which may respond to oral anticholinesterase drugs, eg, neostigmine. Another nonsurgical treatment, occasionally useful in severe acquired levator weakness, consists of eyelid crutches ("ptosis props") that are attached to the back of a spectacle frame.

Surgical

In most cases surgery will be required to correct the ptotic eyelid, the exact operation depending on the cause. The commonest type of surgery involves reattaching or strengthening the levator muscle in the upper eyelid. This is usually achieved via an incision through the skin crease in the eyelid under local anaesthetic. When the levator muscle is very weak then a different technique is required whereby the eyelid is attached to the eyebrow muscle in the forehead.

Outcome/Prognosis

Ptosis is due to a benign cause in the majority of people. Surgical correction is often possible but even in experienced hands 10-15% of patients may require more than one operation to achieve a satisfactory eyelid height and contour.