Congenital Ptosis
Congenital ptosis occurs because of abnormal development of the muscle that lifts the eyelid (levator palpebralis).  This can be associated with certain syndromes.    One of the hallmarks of congenital ptosis is that the affected lid doesn’t come all the way down when a child looks down—it “lags” behind the normal lid in a relatively elevated position.    Also, the upper eyelid crease is not as well defined in people with congenital ptosis -- the ptotic lid is relatively "smooth" as compared to the normal one.

Neurologic Ptosis
All muscles in the body, when functioning properly, will “do as they are told” by the nerve that supplies them with information from the brain.   This applies to the muscles that move the eye (extraocular muscles) and lifts the eyelid (levator muscle); the levator muscle shares a common nerve supply with the pupil and some of the extraocular muscles.  If an insult has occurred to the nerve supply of the levator – and ptosis results – it will typically (but not always) be accompanied by abnormal function of the pupil and the extraocular muscles.  In some cases the pupil will be dilated and the eyes will be misaligned (strabismus). 

In addition to nerve impairment causing ptosis (plus variable degrees of strabismus and pupillary abnormality), there can be chemical abnormalities at the junction between the nerve and the levator (myasthenia gravis).  Myasthenia gravis is very rare in childhood.  

Timing of surgery
Ptosis can cause amblyopia if the lid completely covers the pupil.  In these cases, the ptosis must be repaired as soon as possible so as to prevent worsening of amblyopia and allow for its treatment.  Another indication for surgery is if the ptosis is causing high astigmatism (which will produce amblyopia).  Finally, if a child is lifting their chin all of the time they should have their ptosis repaired without significant delay.

If the ptosis is not severe enough to cause amblyopia, it is acceptable to wait until a child is 4 or 5 years old before surgical repair.  Children younger than this are don’t typically notice their different appearance and are unlikely to be teased by other children.

Surgery
There are two major methods for repairing ptosis: tightening the levator or lifting the lid mechanically.   To “tighten” the levator an incision is made one of two ways – either on the skin of the eyelid or, under certain circumstances, on the undersurface of the eyelid.  There are indications and benefits (and risks) to each of these approaches, and each case needs to be determined individually.  In general, if the levator function is good, the preferred method is to use one of these techniques.

Lifting the eyelid mechanically involves placing material under the skin, just in front of the skull, to suspend the lid.   There are many different materials used and every one of them has worked well, and failed, at some time.  Synthetic materials are most commonly used but we can also use tissue harvested from a person who has died and made a gift of tissue from their thigh (fascia lata); fascia lata is tested for all known transmissible diseases and then irradiated – over many, many years there have been no cases of disease transmission reported.

The greatest risk of surgery is the need for reoperation.  Everybody heals differently.  While some children require just one surgical repair – and this is what everyone would like – some need another operation (or operations) at some point.   It is impossible to absolutely predict who will need more than one surgery or the interval between surgeries.  Basically, some children need just one repair and others need more. 

There is also a risk of infection, though this is uncommon.  A very aggressive infection could cause vision loss or systemic infection, but this would require a failure to detect the infection or a failure of the infection to respond to antibiotics; this is very, very rare.  To minimize infection risk, antibiotic drops or ointments are used after surgery for the first week or so, and the patient is examined during the first week after surgery (when the risk of infection is greatest).

Just after surgery the eyelid will be higher than its final position.  This can cause dryness of the eye surface, especially when the patient is sleeping, so it is important to keep the eye lubricated in the post-operative period.  As noted above, people with congenital ptosis have a problem with the lid coming down normally, as well – you might have noticed that the eye appears open when your child sleeps.  All ptosis repair techniques have a tendency to exacerbate this inability to close the lid – this will be noticeable when the patient is asleep and, sometimes, when she blinks. This is especially so when a suspension procedure is performed.  However, the trade off is permanent vision loss – or an abnormal appearance all of the time – as opposed to an eyelid that stays open a little more than it did prior to surgery.