Drooping of one upper lid is an important clinical sign. In ophthalmic practice, ptosis in children is usually congenital and in adults is either congenital or caused by a third cranial nerve palsy. These more common causes must always be kept in mind but there are a large number of other possible ones. When confronted with a patient whose upper lid appears to droop, the first thing to decide is whether the eyelid really is drooping or whether the lid on the other side is retracted. The upper lid might droop because the eye is small and hypermetropic or shrunken from disease. Having eliminated the possibility of such "pseudoptosis", the various other causes can be considered, beginning on the skin of the eyelid - styes, meibomian cysts - and advancing centrally through muscle - myasthenia gravis - along nerves - oculomotor palsy, Horner's syndrome - to the brainstem. Marked ptosis with the eye turned down and out and a dilated pupil is an oculomotor palsy, whereas slight ptosis, often not noticed by the patient or sometimes by the doctor, is more likely to mean Horner's syndrome. This syndrome is caused by damage to the sympathetic nervous supply to either upper or lower lids or both and is characterised by slight ptosis, small pupil, loss of sweating on the affected side of the face and slight enophthalmos (posterior displacement of the globe).

The management of ptosis depends on the cause and thus on accurate diagnosis. Surgical shortening of the levator tendon is effective in some cases of congenital ptosis and sometimes in long-standing third cranial nerve palsies. Before embarking on surgery, it is important to exclude myasthenia gravis and corneal anaesthesia. Children with congenital ptosis need to be assessed carefully before considering surgery. In young children, ptosis surgery is indicated where the drooping lid threatens to cover the line of sight and where the ptosis causes an unacceptable backwards tilt of the head. In one rather strange type of congenital ptosis, the problem disappears when the mouth is opened and the patient might literally wink unavoidably when chewing. Careful consideration is needed before making the decision for surgery in these cases.

Causes of Ptosis

• Pseudoptosis: small eye, atrophic eye, lid retraction on other side.

• Mechanical ptosis: inflammation, tumour, and excess skin.

• Myogenic ptosis: myasthenia gravis.

• Neurogenic ptosis: sympathetic - Horner's syndrome, third cranial nerve palsy, any lesion in the pathway of these, carcinoma of the lung can cause Horner's syndrome.

• Drugs: guanethidine eye drops cause ptosis.

• Congenital: ask for childhood photograph, ask for family history.

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