The distance between the upper and lower eyelid margins is called the palpebral fissure, which is about 9 mm in Westerners and 7-8 mm in Easterners. Ptosis (upper eyelid ptosis).
Etiology: The main muscle that lifts the upper lid is the levator palpebrae, with the other synergistic muscles being the frontalis and Müller muscles. The levator aponeurosis is innervated by the ophthalmic nerve, and the Müller muscle is innervated by the sympathetic nerve. Various degrees of ptosis can result from the loss of function of the levator and Müller muscles for various reasons. Patients with ptosis tend to contract the frontalis muscle excessively or look up to get rid of visual impairment. Ptosis not only affects appearance and appearance, but also visual function such as visual field and vision development. The ophthalmology department of the Ninth People’s Hospital of Shanghai Jiaotong University School of Medicine, Jing Ji
Classification: There are several ways to classify ptosis. It is classified as mild, moderate or severe depending on the height of the lid margin or the degree to which the pupil is obscured. If the frontalis muscle is removed and the upper lid margin is located at the superior pupil margin, it is mild; if it is located at the superior pupil margin and obscures 1/2 of the pupil, it is moderate; and if it obscures more than 1/2 of the pupil, it is severe. The etiologic classification is more helpful in the overall understanding, diagnosis and treatment of the disease. The following is a comprehensive classification of the room.
I. Congenital ptosis. This is the most common type of ptosis and is most often due to hypoplasia of the levator muscle or a disorder of the nerves (peripheral and central) that innervate it. There are four clinical types of ptosis, depending on whether they are accompanied by abnormalities of the eye or other areas.
1. Simple ptosis. This is the most common type of ptosis, and is caused by the developmental abnormalities of the levator aponeurosis that lead to a decrease in function or loss of function, and is not associated with extraocular muscle dysfunction or other abnormalities.
2. Ptosis with extraocular muscle paralysis. This is reported in the literature to account for 12% of congenital ptosis and is associated with paralysis of the superior rectus or inferior oblique muscles in addition to ptosis, resulting in limited upturn of the eyeball. This is mostly due to central neurodevelopmental disorders.
3. Ptosis syndrome. This syndrome is characterized by ptosis, small lid fissures, inverted canthus, and widening of the medial canthus, also known as komoto syndrome.
4. Synergistic ptosis. Mandibular-transient syndrome (Macus-Gunn syndrome), manifests as ptosis on one side at rest, and when chewing, opening the mouth, or moving the jaw to the opposite side, the ptosis suddenly lifts to normal, or even exceeds the normal eyelid height on the opposite side. This is a specific type of congenital ptosis, which may be caused by an abnormal connection between the extra-parietal nerve portion of the trigeminal nucleus and the nucleus accumbens region of the levator muscle, or by an abnormal connection of the motor branch occurring between the trigeminal nerve and the motoneurotic nerve. The condition has a tendency to heal on its own, and some patients return to normal ptosis after developmental maturity.
Acquired ptosis
1. ptosis with paralysis of the motoneurone nerve. Ptosis occurs when the peripheral or central part of the nerve is damaged, sometimes with extraocular muscle paralysis and pupillary changes. The cause can be tumor, trauma, inflammation, or vascular disease.
2. Sympathetic ptosis. Sympathetic ptosis is a type of ptosis that results from sympathetic nerve palsy that leads to dysfunction of the Müller muscle, such as the appearance of an entropion of the eyeball on the side of the lesion, a narrow pupil, a smaller lid fissure, and syndromes.
3. Myogenic ptosis. The most common is myasthenia gravis. The earliest symptom in patients with systemic myasthenia gravis is ptosis, with the typical “morning lightness and evening heaviness” phenomenon. In addition, chronic progressive extraocular muscle paralysis, progressive myotonic dystrophy, and myotonic syndrome are all associated with myogenic ptosis.
4. Tendonoplegic ptosis. Ptosis is caused by damage to the levator aponeurosis due to various causes. It is also the more common type of ptosis. It is classified as traumatic, geriatric, medical and atrophic.
5. Mechanical ptosis. Ptosis is caused by lesions of the eyelid itself, such as upper eyelid tumors, inflammation, scarring, and tissue proliferation that cause the eyelid itself to increase in weight.
III. Pseudopelvic ptosis
The appearance shows a drooping upper eyelid, but objective examination reveals that the levator muscle strength is normal, the upper eyelid margin is in a normal position, or the lid margin is in a lower than normal position due to a lack of eyelid support, and the levator muscle strength is basically normal. The main causes of pseudopalpebral ptosis are as follows.
1. laxity of the upper lid skin. In older adults, laxity of the upper lid skin obscures part or all of the pupil, obscuring the visual field and affecting vision in severe cases, but the lid margin position is seen to be normal after lifting the upper lid skin and the function of the levator muscle is checked as normal. The symptoms can be improved by surgically removing the loose skin.
2. Lack of upper lid support. Conditions such as microphthalmia, entropion, and atrophy of the eyeball can cause the eyelid to lose support, resulting in a collapsed eyelid with a lower than normal lid margin position.
3. Protective pseudo-epicanthalmoplegia. Pseudophakic ptosis with protective eye closure can occur with corneal inflammation, changes in luminosity, reflexive half-closed eyes, or half-closed eyes in wind and dust blowing.
4. Eye position abnormalities. In patients with upward obliquity, excessive eye upward pupillary rotation is obscured by the eyelid and mistaken for the presence of ptosis; clinical differentiation should be noted against the function of the levator muscle in normal eyes.
Pathogenesis. There are four main types of ptosis in terms of the mechanism of onset: neurogenic, myogenic, tenosynovial, and mechanical. Neurogenic ptosis mainly refers to ptosis caused by dysfunction of the motoneurotic and sympathetic nerves that innervate the levator and Müller muscles, including motoneurotic nerve palsy, oculomotor palsy, mandibular-transient syndrome, and Horner’s syndrome. Myogenic ptosis mainly refers to hypoplasia of the levator muscle alone or with hypotony of the extraocular muscles and includes congenital ptosis, microphthalmos syndrome, and myasthenia gravis. Tendonoplegia refers to ptosis caused by lesions of the levator aponeurosis, including age-related ptosis and lid laxity. Mechanical ptosis refers to ptosis caused by eyelid tumors or scarring.
Treatment]
Treatment is chosen based on the cause of ptosis, the degree of ptosis, the strength of the levator muscle, and the time of onset. For ptosis caused by myasthenia gravis, inflammation, tumors, endocrine, neurological, and vascular factors, aggressive pharmacologic treatment and treatment of the primary cause are advocated first. Two major issues are included in surgical treatment: the choice of the timing of surgery and the choice of surgical method.
I. Timing of surgery
（Surgical treatment is the only option for congenital ptosis, and the timing of surgery varies depending on the condition.
1. Simple ptosis: Depending on the severity of the ptosis and the impact on vision, the timing of surgery can vary. In general, surgery is chosen at the age of 3-5 years, while severe ptosis can be operated at the age of 1-2 years.
2. Patients with extraocular muscle dysfunction should undergo ptosis correction surgery after strabismus correction.
3, Ptosis syndrome: Patients with small lid fissures are generally advocated to be operated on in stages so as not to compromise the surgical results.
4. Synergistic ptosis: Macus-Gunn syndrome has a tendency to heal on its own. If the ptosis is not very severe, it is observed on follow-up and can be treated surgically if the ptosis is still present by maturity. If the ptosis is severe at an early age and has the potential to interfere with the development of visual function, surgery is performed at age 3 to 5 years. Surgery may also be considered to improve the appearance if the ptosis is not severe, but the patient and parents strongly request treatment.
(ii) Acquired ptosis The timing of surgery is related to the cause.
1. Ptosis caused by systemic disease: Surgery should be considered only after active treatment of the primary disease and after the condition has been stable for more than 6-12 months.
Patients with other extraocular muscle paralysis should have their diplopia corrected before surgery is performed.
3, Traumatic ptosis: usually performed more than 1 year after trauma, but if confirmed to be caused by a tear or dissection of the levator muscle, it should be surgically repaired immediately.
4. Ptosis of the levator aponeurosis: surgery can be considered when vision is affected.
5. Myogenic ptosis: Patients with severe myasthenia gravis should take surgery when medication is poor, the ptosis has been stable for more than 1 year, and there is no other extraocular muscle paralysis or generalized muscle paralysis.
II. Surgical method selection
The preoperative examination includes a routine eye examination, determination of the cause, determination of the muscle strength of the levator muscle, determination of the amount of ptosis, and determination of the function of the extraocular muscles. A detailed preoperative examination not only determines the choice of surgical method and the amount of surgery performed, but is also the basis for making judgments about the prognosis and the occurrence of complications.
The common surgical methods used to correct ptosis include frontalis surgery, levator muscle surgery and Müller muscle surgery, and the surgical method used depends on the strength of the patient’s levator muscle.
1. Frontalis flap suspension: When the muscle strength of the levator muscle is less than 4 mm, surgery that utilizes the strength of the frontalis muscle is chosen. Currently the most commonly used procedure is the frontalis flap suspension.
2. Epiglottis shortening: chosen when the strength of the levator muscle is 4-9 mm.