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Chapter 4: Lids, Lacrimal Apparatus, & Tears
ANATOMIC DEFORMITIES OF THE LIDS
ENTROPION
Entropion-turning inward of the lid (Figure 4-3)-may be involutional (spastic, senile), cicatricial, or congenital. Involutional entropion is most common and by definition occurs as a result of aging. It always affects the lower lid and is the result of a combination of laxity of the lower lid retractors, upward migration of the preseptal orbicularis muscle, and buckling of the upper tarsal border.
Cicatricial entropion may involve the upper or lower lid and is the result of conjunctival and tarsal scar formation. It is most often found with chronic inflammatory diseases such as trachoma.
Congenital entropion is rare and should not be confused with congenital epiblepharon, which usually afflicts Asians. In congenital entropion, the lid margin is rotated toward the cornea, whereas in epiblepharon the pretarsal skin and muscle cause the lashes to rotate around the tarsal border.
Trichiasis is impingement of eyelashes on the cornea and may be due to entropion, epiblepharon, or simply misdirected growth. It causes corneal irritation and encourages ulceration. Chronic inflammatory lid diseases such as blepharitis may cause scarring of the lash follicles and subsequent misdirected growth.
Distichiasis is a condition manifested by accessory eyelashes, often growing from the orifices of the meibomian glands. It may be congenital or the result of inflammatory metaplastic changes in the glands of the eyelid margin.
Surgery to evert the lid is effective in all kinds of entropion. Useful temporary measures in involutional entropion are to tape the lower lid to the cheek, with tension exerted temporally and inferiorly, or to inject botulinum toxin. Trichiasis without entropion can be temporarily relieved by plucking the offending eyelashes. Permanent relief may be achieved with electrolysis, laser or knife surgery, or cryosurgery.
ECTROPION
Ectropion (sagging and eversion of the lower lid) (Figure 4-4) is usually bilateral and is a frequent finding in older persons. Ectropion may be caused by relaxation of the orbicularis oculi muscle, either as part of the aging process or following seventh nerve palsy. The symptoms are tearing and irritation. Exposure keratitis may occur.
Involutional ectropion is treated surgically by horizontal shortening of the lid. Cicatricial ectropion is caused by contracture of the anterior lamella of the lid. Treatment requires surgical revision of the scar and often skin grafting. Minor degrees of ectropion can be treated by several fairly deep electrocautery penetrations through the conjunctiva 4-5 mm from the lid margins at the inferior aspect of the tarsal plate. The fibrotic reaction that follows will often draw the lid up to its normal position.
COLOBOMA
Congenital coloboma is the result of incomplete fusion of fetal maxillary processes. The consequence is a lid margin cleft of variable size. The medial aspect of the upper lid is most often involved, and there is often an associated dermoid tumor. Surgical reconstruction can usually be delayed for years but should be done immediately if the cornea is at risk. A full-thickness eyelid defect from any cause is sometimes referred to as a coloboma.
EPICANTHUS
Epicanthus (Figure 4-5) is characterized by vertical folds of skin over the medial canthi. It is typical of Asians and is present to some degree in most children of all races. The skinfold is often large enough to cover part of the nasal sclera and cause "pseudo- esotropia." The eye appears to be crossed when the medial aspect of the sclera is not visible. The most frequent type is epicanthus tarsalis, in which the superior lid fold is continuous medially with the epicanthal fold. In epicanthus inversus, the skinfold blends into the lower lid. Other types are less common. Epicanthal skinfolds may also be acquired after surgery or trauma to the medial eyelid and nose. The cause of epicanthus is vertical shortening of the skin between the canthus and the nose. Surgical correction is directed at vertical lengthening and horizontal shortening. Epicanthal folds in normal children, however, diminish gradually by puberty and seldom require surgery.
TELECANTHUS
The normal distance between the medial canthus of each eye-the intercanthal distance-is equal to the length of each palpebral fissure (approximately 30 mm in adults). A wide intercanthal distance may be the result of traumatic disinsertion or congenital cra-niofacial dysgenesis. Minor degrees of telecanthus (eg, blepharophimosis syndrome) can be corrected with skin and soft tissue surgery. Major craniofacial reconstruction, however, is required when the orbits are widely separated, as in Crouzon's disease (see Chapter 17).
BLEPHAROCHALASIS
Blepharochalasis (Figure 4-6) is a rare condition of unknown cause, sometimes familial, which resembles angioneurotic edema. Repeated attacks begin near puberty, diminish during adulthood, and cause atrophy of periorbital structures. Eyelid skin appears thin, wrinkled, and redundant and is described as resembling cigarette paper. A sunken appearance is the result of fat atrophy. Involvement of the levator aponeurosis produces moderate to severe ptosis. Medical management is limited to symptomatic treatment of edema. Surgical repair of levator dehiscence and excision of redundant skin is most likely to be successful after attacks have abated.
DERMATOCHALASIS
Dermatochalasis (Figure 4-7) is eyelid skin redundancy and loss of elasticity, usually as a result of aging. In the upper lid, the preseptal skin and orbicularis muscle, which normally forms a crease near the upper tarsal border in Caucasians, hangs over the pretarsal portion of the lid. When dermatochalasis is severe, the superior visual field is obstructed. Weakness of the orbital septum causes the medial and preaponeurotic fat pads to bulge. "Bags" in the preseptal region of the lower lid represent herniated orbital fat.
Blepharoplasty may be indicated for visual or cosmetic reasons. In the upper lid, superfluous eyelid skin is removed as well as muscle and fat for optimum aesthetics. Lower lid blepharoplasty is considered cosmetic surgery unless extreme redundancy contributes to ectropion of the lid margin. Pulsed CO2 and erbium lasers have been found effective in tightening periocular skin but must be used with caution on the delicate skin of the lids.
BLEPHAROSPASM
Benign essential blepharospasm is an uncommon type of involuntary muscle contraction characterized by persistent or repetitive spasm of the orbicularis oculi muscle. It is almost always bilateral and is most common in the elderly. The spasms tend to progress in force and frequency, resulting in a grimacing expression and involuntary closure of the eyes. Patients may be incapacitated-able to experience only brief intervals of vision between spasms. When the entire face and neck are involved, the condition is known as Meigs' syndrome.
The cause is not known, but the dysfunction is believed to originate in the basal ganglia. Emotional stress and fatigue sometimes make the condition worse, leading to speculation that this is a psychogenic affliction. Psychotherapy and psychoactive drugs, however, have had very limited success.
It is important to differentiate benign essential blepharospasm from hemifacial spasm. The latter condition tends to be unilateral and to involve the upper and lower face. Hemifacial spasm is thought to be related to compression of the facial nerve by an artery or posterior fossa tumor. Jenetta's neurosurgical decompression is the definitive mode of treatment; however, temporary neuromuscular blockade (see below) is less invasive and more frequently employed.
Other types of involuntary facial movements include tardive dyskinesia, which results from prolonged phenothiazine therapy and seldom affects the orbicularis muscle selectively; and facial tics, common in children, which are thought to be psychogenic.
Treatment of blepharospasm begins with an attempt to identify the unusual instances of psychoneurotic behavior. Psychotherapy, neuroleptic drug treatment, biofeedback training, and hypnosis can be useful in this subset. Most patients, however, require repeated injections of botulinum toxin type A to produce temporary neuromuscular paralysis. If intolerance or unresponsiveness to the toxin develops, selective surgical ablation of the facial nerve or selective extirpation of the orbicularis muscles can be performed.
BLEPHAROPTOSIS
The upper lid normally rests approximately midway between the superior limbus and the pupillary margin. Considerable variation may exist as long as symmetry is maintained. Blepharoptosis, or "ptosis" as it is more commonly called, is the condition in which one or both upper eyelids assume an abnormally low position. Blepharoptosis may be congenital or acquired and can be hereditary in either case.
Classification
Classification is important for proper treatment. Beard's revised scheme (Table 4-1) attempts to classify ptosis by etiology.
A. Levator Maldevelopment:
Ptosis from levator maldevelopment-formerly classified as true congenital ptosis-is the result of an isolated dystrophy of the levator muscle affecting both contraction and relaxation of the fibers. Ptosis is present in the primary position of gaze, and there is reduced movement of the lid in upgaze and impaired closure on downgaze. Lid lag on downgaze is an important clue to diagnosis of levator maldevelopment. Other ocular abnormalities such as strabismus are sometimes associated with this form of congenital ptosis. In 25% of cases, the superior rectus muscle shares the same dystrophic changes as the levator, resulting in weakness of upgaze. It is important to identify this finding. Successful surgical outcome in the presence of superior rectus weakness requires the resection of an additional length of levator.
The distinction between levator maldevelopment and other forms of ptosis is an important one that cannot always be made by the history. Neurologic and other myogenic ptosis may be present at birth. Application of the surgical principles intended for levator maldevelopment to these types of ptosis patients would result in a gross overcorrection.
B. Other Types of Myogenic Ptosis:
Blepharophimosis accounts for 5% of cases of congenital ptosis. Poor levator function and severe ptosis are accompanied by telecanthus, epicanthal folds, and cicatricial ectropion of the lower lids. The condition is familial.
Chronic progressive external ophthalmoplegia is a slowly progressive hereditary neuromuscular disease that begins in mid life. All extraocular muscles including the levator and the muscles of facial expression gradually become affected. Other neurodegenerative disorders may be present. In the form known as oculopharyngeal dystrophy, myopathy of the laryngeal muscles produces dysphagia. In Kearns-Sayre syndrome, ophthalmoplegia is associated with retinitis pigmentosa and heart block.
Ptosis and facial weakness may also be found in myotonic dystrophy. Other findings include cataract, pupillary abnormalities, frontal baldness, testicular atrophy, and diabetes.
Ptosis associated with the rare and sometimes familial congenital fibrosis of the extraocular muscles may be unilateral.
Ptosis and diplopia are often the initial manifestations of myasthenia gravis. The orbicularis oculi muscles are also frequently involved. Cogan's lid twitch is sometimes present-on rapid movements of the eyes from downgaze to the primary position, the upper lid twitches upward. Demonstration of lid fatigue, however, is more consistent. The diagnosis can be confirmed by intravenous administration of edrophonium, which temporarily reverses the weakness. Another useful test is the detection of circulating anti-acetylcholine receptor autoantibodies.
Medical management is usually effective initially, but ptosis surgery often becomes necessary. Thymectomy may be helpful in refractory cases. When lid closure and Bell's phenomenon have been impaired, difficult problems with exposure keratitis may complicate ptosis surgery.
C. Aponeurotic Ptosis:
A common form of myogenic ptosis occurs late in life and results from partial disinsertion or dehiscence of the levator aponeurosis from the tarsal plate. Typically, there are sufficient residual attachments to the tarsus to maintain full excursion of the lid with upgaze. Retention of the attachment of the retracted levator aponeurosis to the skin and orbicularis muscle creates an unusually high lid fold. Thinning of the lid may also occur, and on occasion the image of the iris may be seen through the skin of the upper lid. Trauma is often a precipitating cause of disinsertion of the levator. Ptosis following cataract surgery is thought to be due to this mechanism. A hereditary variant is known as "late-developing hereditary ptosis." The mechanism of ptosis associated with ocular surgery, blepharochalasis, pregnancy, and Graves' disease is usually damage to the aponeurosis.
D. Neurogenic Ptosis:
In Marcus Gunn syndrome (jaw-winking phenomenon), the eye opens when the mandible is opened or is deviated to the opposite side. The ptotic levator muscle is innervated by motor branches of the trigeminal nerve as well as the oculomotor nerve.
Partial or complete oculomotor palsy due to trauma is often complicated by aberrant regeneration, resulting in bizarre movements of the globe, eyelid, and pupil. Congenital oculomotor nerve paralysis, however, is not associated with aberrant regeneration. If the lid is completely closed, deprivational amblyopia will develop unless the ptosis is corrected. Visually immature children with oculomotor nerve paralysis, even after successful ptosis repair, are almost certain to develop strabismic amblyopia without vigorous and early treatment.
Paralysis of Müller's muscle is almost always associated with Horner's syndrome and is usually acquired. Rarely is there more than 2 mm of ptosis, and amblyopia is never a threat.
E. Mechanical Ptosis:
The upper lid may be prevented from opening completely because of the mass effect of a neoplasm or the tethering effect of scar formation. Excessive horizontal shortening of the upper lid is a common cause of mechanical ptosis. Another form is that seen following enucleation, when absence of support to the levator by the globe permits the lid to drop.
F. Apparent Ptosis:
Hypotropia may give the appearance of ptosis. When the eye looks down, the upper lid drops more than the lower lid. The narrowed palpebral fissure and the ptotic upper lid are much more apparent than the hypotropic globe. Occlusion of the opposite eye, however, reveals the true condition. In severe dermatochalasis, a fold of pretarsal orbicularis and skin may conceal the lid margin and give the appearance of blepharoptosis.
Treatment (
Figure 4-8)
With the exception of myasthenia gravis, all types of ptosis are treated surgically. In children, surgery can be performed when accurate evaluation can be obtained and the child is able to cooperate postoperatively. Astigmatism and myopia may be associated with childhood ptosis. Early surgery might be helpful in preventing anisometropic amblyopia, but this has not been proved. Deprivational amblyopia probably occurs only with complete ptosis, as in oculomotor nerve palsy.
Symmetry is the goal of surgery, and symmetry in all positions of gaze is possible only if levator function is unimpaired. In most cases, the best result that can be achieved is to balance the lids in the primary position. With unilateral ptosis, achievement of symmetry in other positions of gaze is proportionate to levator function.
Most ptosis operations involve resection of the le-vator aponeurosis or superior tarsal muscle (or both). The superior portion of the tarsus is often resected for additional elevation. Many approaches, from both skin and conjunctiva, are currently in use. In recent years, emphasis has been placed on the advantages of confining the operation to advancement and resection of the levator aponeurosis, especially in acquired ptosis.
Patients with little or no levator function require an alternative elevating source. Suspension of the lids to the brow allows the patient to elevate the lids with the natural movement of the frontalis muscle. Autogenous fascia lata is usually considered the best means of suspension.
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10.1036/1535-8860.ch4