Ptosis is the partial or complete drooping of the upper eyelid due to the incomplete or loss of function of the levator and Müller smooth muscles, partially covering the pupil in mild cases or completely covering the pupil in severe cases. In order to overcome the visual impairment, bilateral ptosis results in a special posture in which the head is tilted and the forehead is wrinkled because of the need to look up.
Etiology
1. Congenital
The majority of cases are caused by hypoplasia or deficiency of the levator muscle, or a deficiency of the nerve that governs the levator muscle. It is a congenital developmental malformation, mostly bilateral, sometimes unilateral, and can be autosomal dominant or recessive. Zhang Key, Ophthalmology Department, Jinyang People’s Hospital
2.Acquired
The causes are traumatic, neurogenic, myogenic and mechanical, among which myogenic is caused by myasthenia gravis.
3. Hysterical
It is caused by hysteria, with sudden drooping of both upper eyelids or with hysterical pupillary dilatation, and sometimes compression of the supraorbital nerve can cause the drooping to disappear suddenly.
Clinical manifestations
1. Paralytic ptosis
This is caused by paralysis of the articular nerve. It is mostly unilateral and often combined with paralysis of other extraocular or intraocular muscles innervated by the motoneurotic nerve.
2. Sympathetic ptosis
This is caused by dysfunction of the Müller muscle or by damage to the cervical sympathetic nerve. In the latter case, there is also ipsilateral pupillary narrowing, sunken eyes, flushing and an absence of sweating, which is called Horner syndrome.
3. Myogenic ptosis
This is often seen in myasthenia gravis and is often associated with generalized fatigue of the random muscles. This type of ptosis is characterized by improvement after rest, immediate aggravation during continuous transients, light in the morning and heavy in the afternoon, and temporary relief of symptoms after 15 to 30 minutes of subcutaneous or intramuscular injection of neostigmine.
4.Other
(1) Traumatic injury to the actinic nerve or the levator muscle or Müller muscle can cause traumatic ptosis.
(2) Diseases of the eyelid itself, such as severe trachoma and lid tumors, increase the weight of the eyelid and cause mechanical ptosis.
(3) Pseudophakic ptosis can be caused by anophthalmia, microphthalmia, ocular atrophy, and various causes of reduced orbital fat or orbital contents.
Examination
To estimate the function of the levator muscle, the position of the upper lid margin during extreme upward and downward gaze of the eye can be measured with the frontalis muscle contraction force offset, respectively. A difference of less than 4 mm between the front and back indicates severe insufficiency of the levator muscle.
Treatment
The main goal is to prevent vision loss and improve appearance, and treatment should be directed at the cause. Congenital ptosis should be surgically corrected early if it interferes with vision development. If the ptosis is mild and does not affect visual development, surgery can be performed at a later date to improve appearance. In cases of unilateral ptosis that obscures the pupil, early surgery should be sought, preferably before age 6, to prevent amblyopia. For myogenic or paralytic ptosis, adenosine triphosphate, vitamin B1, or neostigmine may be used. Surgery should be carefully considered when prolonged treatment is not effective.