Ptosis (eyelid)


Ptosis, also known as blepharoptosis, is a drooping or falling of the upper eyelid. 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, so it is especially important to treat the disorder in children before it can interfere with vision development.

Signs and symptoms

Ptosis can be unilateral or bilateral, and may vary in severity. Common signs and symptoms include:
  • Drooping of the upper eyelid, which may partially or completely cover the pupil.
  • Reduced vertical palpebral fissure height.
  • Compensatory frontalis overaction, leading to elevation of the eyebrows and forehead wrinkling.
  • Chin-up head posture in children or severe cases to improve the visual field.
  • Obstruction of the visual axis, especially in more severe cases.
  • Fatigability, or worsening of the ptosis as the day progresses, if the cause is a myasthenic ptosis.
  • Absent or poor upper eyelid skin 'crease formation.
  • In congenital ptosis, reduced or absent levator palpebral superioris function' is often observed.

    Complications

Ptosis can lead to various complications, including refractive errors. When ptosis obstructs the upper field of vision, affected individuals may compensate by tilting their head back or raising their eyebrows, which can result in astigmatism or other refractive errors due to the altered positioning of the eye. Additionally, ptosis can lead to eye strain and fatigue, potentially exacerbating existing refractive errors such as myopia or hyperopia. Early detection and management of ptosis, often through surgical correction, are essential to minimize these complications and ensure optimal visual health.

Causes

Ptosis occurs as the result of dysfunction of the muscles that raise the eyelid or their nerve supply. It can affect one eye or both eyes and is more common in the elderly, as muscles in the eyelids may begin to deteriorate. Babies may also exhibit ptosis at birth as the result of abnormal development of the levator muscle while the child is in the mother's womb. Congenital ptosis is hereditary in three main forms.
Causes of congenital ptosis remain unknown. Ptosis may be caused by damage to the muscle that raises the eyelid, damage to the superior cervical sympathetic ganglion or damage to the oculomotor nerve, which controls the muscle. Such damage could be a sign of an underlying disease such as diabetes mellitus, a brain tumor, a pancoast tumor and diseases that 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.
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.
Ptosis may be attributable to a myogenic, neurogenic, aponeurotic, mechanical or traumatic cause, and it usually occurs in an isolated manner. However, it may be associated with various other conditions, such as immunological, degenerative or hereditary disorders as well as tumors or infections.
Acquired ptosis is most commonly caused by aponeurotic ptosis. This can occur because of senescence, dehiscence or disinsertion of the levator aponeurosis. Moreover, chronic inflammation or intraocular surgery can lead to the same effect. Also, wearing contact lenses for long periods is thought to have a certain impact on the development of the condition.
Congenital neurogenic ptosis is believed to be caused by Horner's syndrome, in which a mild ptosis may be associated with ipsilateral ptosis, iris and areola hypopigmentation and anhidrosis caused by paresis of the superior tarsal muscle. Acquired Horner syndrome may result after trauma, neoplastic insult or even vascular disease.
Ptosis caused by trauma can ensue after an eyelid laceration with transection of the upper eyelid elevators or disruption of the neural input.
Other causes of ptosis include eyelid neoplasms, neurofibromas or cicatrization after inflammation or surgery. Mild ptosis may occur with aging. A drooping eyelid can be one of the first signals of a third-nerve palsy resulting from a cerebral aneurysm that is otherwise asymptomatic, a condition known as oculomotor nerve palsy.

Drugs

Ingestion of high doses of opioid drugs such as morphine, oxycodone, heroin or hydrocodone can cause ptosis. Pregabalin, an anticonvulsant drug, has also been known to cause mild ptosis.

Mechanism

Different trauma can cause and induce many different mechanisms. For example, myogenic ptosis results from a direct injury to the levator muscle and/or Müller's muscle. On the other hand, neurogenic ptosis is caused by closed head injuries or traumatically introduced neurotoxin or botulinum toxin due to the effect of those factors on the CNIII or the sympathetic pathway. Mechanical ptosis can also occur due to scarring tissue restricting the patient's eyelid excursion or weighing down the patient's lid. Another mechanism is the disturbance of the oculomotor nerve causing the levator palpebrae to weaken, resulting in the eyelid drooping. Ptosis can also occur in a patient with brain tumors due to pressure on the third nerve, also known as the sympathetic nerve, on the brainstem.

Pathology

is a common neurogenic ptosis that could also be classified as neuromuscular ptosis because the site of pathology is at the neuromuscular junction. Studies have shown that up to 70% of myasthenia gravis patients present with ptosis, and 90% of these patients will eventually develop ptosis. In this case, ptosis can be unilateral or bilateral, and its severity tends to be oscillating during the day, because of factors such as fatigue or drug effect. This particular type of ptosis is distinguished from the others with the help of a Tensilon test and blood tests. Also specific to myasthenia gravis is the fact that coldness inhibits the activity of cholinesterase, which makes it possible to differentiate this type of ptosis by applying ice onto the eyelids. Patients with myasthenic ptosis are likely to experience a variation in the drooping of the eyelid at different hours of the day.
Ptosis caused by oculomotor palsy can be unilateral or bilateral, as the subnucleus to the levator muscle is a shared midline structure in the brainstem. In cases where the palsy is caused by the compression of the nerve by a tumor or aneurysm, it is highly likely to result in an abnormal ipsilateral papillary response and a larger pupil. Surgical third nerve palsy is characterized by a sudden onset of unilateral ptosis and an enlarged or sluggish pupil to the light. In this case, imaging tests such as CTs or MRIs should be considered. Medical third nerve palsy, contrary to surgical third nerve palsy, usually does not affect the pupil and tends to improve in several weeks slowly. Surgery to correct ptosis due to medical third nerve palsy is normally considered only if the improvement of ptosis and ocular motility are unsatisfactory after half a year. Patients with third nerve palsy tend to have a diminished or absent function of the levator.
When caused by Horner's syndrome, ptosis is usually accompanied by miosis and anhidrosis. In this case, the ptosis is due to interruption innervations to the sympathetic, autonomic Muller's muscle rather than the somatic levator palpebrae superioris muscle. The lid position and pupil size are typically affected by this condition, and the ptosis is generally mild, no more than 2 mm. The pupil might be smaller on the affected side. While 4% cocaine instilled in the eyes can confirm the diagnosis of Horner's syndrome, Hydroxyamphetamine eye drops can differentiate the location of the lesion.
Chronic progressive external ophthalmoplegia is a systemic condition that usually affects only the lid position and the external eye movement without involving the movement of the pupil. This condition accounts for nearly 45% of myogenic ptosis cases. Most patients develop ptosis due to this disease in their adulthood. A characteristic of ptosis caused by this condition is that the protective uprolling of the eyeball when the eyelids are closed is very poor.

Diagnosis

A doctor will first perform a physical exam with questions about the patient's medical history to distinguish whether the condition may be hereditary. A slit lamp exam is performed with a high-intensity light that allows a close look at the patient's eyes. The doctor can also perform a test in which edrophonium is injected into a vein, and the eyelids are monitored for resulting signs of improvement.
A visual field test may be performed, which assesses the degree to which the ptosis affects the superior vision. Because nerve damage is among the possible causes of ptosis, the ophthalmologist will check the patient's pupil for abnormalities. The doctor will also check muscle function.
The ophthalmologist may also measure the degree of the eyelid droop by measuring the marginal reflex distance, which is the distance between the center of the pupil and the edge of the upper lid, as well as the strength and function of the patient's levator muscle. This test entails holding the frontalis muscle to measure how far the eyelid travels when the patient is gazing downward.
Through these tests, the ophthalmologist may properly diagnose ptosis and identify its classification, and a determination may be made regarding the course of treatment, which may involve surgery.

Classification

Depending upon the cause, ptosis may be classified into:
File:Thom Yorke Glastonbury Festival 2010.jpg|thumb|English musician and Radiohead lead vocalist Thom Yorke has a milder left-eye ptosis