<P> Ptosis is a drooping or falling of the upper eyelid . The drooping may be worse after being awake longer when the individual's muscles are tired . This condition is sometimes called "lazy eye", but that term normally refers to the condition amblyopia . If severe enough and left untreated, the drooping eyelid can cause other conditions, such as amblyopia or astigmatism . This is why it is especially important for this disorder to be treated in children at a young age, before it can interfere with vision development . </P> <P> The term is from Greek πτῶσις "a fall, falling". </P> <P> Ptosis occurs due to dysfunction of the muscles that raise the eyelid or their nerve supply (oculomotor nerve for levator palpebrae superioris and sympathetic nerves for superior tarsal muscle). It can affect one eye or both eyes and is more common in the elderly, as muscles in the eyelids may begin to deteriorate . One can, however, be born with ptosis . Congenital ptosis is hereditary in three main forms . Causes of congenital ptosis remain unknown . Ptosis may be caused by damage / trauma to the muscle which raises the eyelid, damage to the superior cervical sympathetic ganglion or damage to the nerve (3rd cranial nerve (oculomotor nerve)) which controls this muscle . Such damage could be a sign or symptom of an underlying disease such as diabetes mellitus, a brain tumor, a pancoast tumor (apex of lung) and diseases which may cause weakness in muscles or nerve damage, such as myasthenia gravis or Oculopharyngeal muscular dystrophy . Exposure to the toxins in some snake venoms, such as that of the black mamba, may also cause this effect . </P> <P> Ptosis can be caused by the aponeurosis of the levator muscle, nerve abnormalities, trauma, inflammation or lesions of the lid or orbit . Dysfunctions of the levators may occur as a result of autoimmune antibodies attacking and eliminating the neurotransmitter . </P>

Damage to this nerve can cause a drooping eyelid