What is ptosis?

Abnormal drooping of the upper eyelid is called ptosis. Normally upper eyelid covers about one-sixth of the cornea that is 2 millimeters. Ptosis is said to be present if the upper eyelid covers more than 2 millimeters of the cornea.

Levator palpebrae superioris is the muscle, which is responsible in elevating the upper eyelid. Any defect in the muscle per se or the nerve (third cranial nerve) innervating the muscle may lead to ptosis.

What are the different types of ptosis?

Congenital ptosis: It is the common form of eyelid ptosis present since childbirth. It may involve one or both upper eyelids and vary in severity from mild to severe. This form of eyelid ptosis is often the result of lack of development of the levator muscle.

Acquired ptosis: This is a type of upper eyelid ptosis. The tendon of the levator muscle may loosen or detach, causing ptosis. This process is similar to a knee ligament sprain or tear. It is not uncommon for one to develop a droopy upper eyelid following cataract surgery. The cataract surgery may be the ‘last straw’ that causes a weak tendon to finally give way.

Ptosis is determined by the cause of the drooping eyelid.

Myogenic ptosis means that the lid sags because of a problem with the muscle that raises the eyelid. An example of a muscle condition that causes ptosis is Myasthenia Gravis. This is a disease in which the voluntary muscles in the body weaken due to abnormalities within the muscles, themselves. 
Neurogenic ptosis refers to the condition where the nerve supply to the muscle is affected. 
Mechanical ptosis occurs when the weight of the eyelid is too great for the muscles to lift. 
Aponeurotic ptosis or levator dehiscence occurs primarily in people more than 30 years of age and the incidence increases with age. 
What are the symptoms?

Drooping eyelids is the principal sign in ptosis. 
Children with congenital ptosis often tilt their heads back or raise their eyebrows to lift the eyelids. 
Adults have the same symptoms, but they also notice a loss of vision, especially in the upper field. 
How is it diagnosed?

In order to diagnose ptosis, it is imperative to know the history of the patient in terms of:

Age of onset. 
Family history. 
History of trauma. 
History of eye surgeries. 
Any variability in the degree of ptosis. 
Besides, it is examined by:

Inspecting eyes for presence of local causes. 
Ptosis in one or both the eyes. 
Checking the function of various extra ocular muscles and levator 
palpebrae superioris, a muscle of the eyelids. 
Assessment of amount /degree of ptosis. 
Assessment of levator function. 
Looking for other concomitant diseases, which may be a cause of ptosis. 
Checking the photographic record of the face of the patient. 
How is it treated?

Congenital ptosis: It almost always needs a surgical correction. In severe degrees of ptosis, surgical correction must be performed as soon as possible after birth to prevent stimulus deprivation ‘amblyopia’ (functional blindness). In mild to moderate degrees of ptosis, surgery may be deferred up to 3-4 years of age when more appropriate measurements of degree of ptosis and levator function be made.

Acquired ptosis: The underlying cause should be looked for and an attempt be made to treat it medically/surgically. The amount of resection required is always lesser than that required in cases of congenital ptosis and prognosis is usually good.

Myogenic ptosis: Myasthenia Gravis must be controlled with measures such as corticosteroids, immunosuppresives, plasmapheresis and by surgical removal of the thymus. 
Neurogenic ptosis: In all cases of neurogenic ptosis, the patient must be reviewed periodically on conservative management to allow for any spontaneous recovery and for defect to stabilise. In complete paralysis of the third nerve, surgery is often contraindicated unless the strabismus is corrected as when the lid is raised the diplopia becomes manifest. Surgery for neurogenic ptosis seldom gives good results. 
Mechanical ptosis: Treatment should be of the cause. 
Aponeurotic ptosis: Surgical resection of levator gives good results.