Ординатура / Офтальмология / Английские материалы / Pediatric Ophthalmology for Primary Care 3rd edition_Wright, Farzavandi_2008
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Figure 4 5.
Six-year-old with intermittent exotropia. A, Patient in the phoric phase with straight eyes and high-grade stereopsis. B, Patient in the tropic phase with large right exotropia. Patient is suppressing right eye and does not have diplopia.
exotropia (after 5 or 6 years of age) will experience diplopia. Significant amblyopia is rare in patients with intermittent exotropia.
Treatment of Intermittent Exotropia
In contrast to esotropia, which requires urgent intervention, the treatment of intermittent exotropia is elective. These children have binocular fusion and are well aligned most of the time. Eye muscle surgery is the treatment of choice for most forms of intermittent exotropia. Indications for surgery include increasing exotropia, exotropia present more than 50% of the
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time, and poor fusion control of the exotropia. Nonsurgical treatments include part time occlusion of the dominant eye, prescribing myopic cor rection, and eye exercises. These interventions act as temporary treatments at best, except for patients with a special type of exotropia termed conver gence insufficiency.
Convergence Insufficiency
The type of intermittent exotropia where there is an exotropia at near but straight eyes with distance fixation is called convergence insufficiency (Figure 4 6). There is a lack of appropriate near convergence. Convergence insufficiency is the one form of strabismus that is best treated with eye exer cises instead of surgery. Convergence insufficiency is a common cause of reading fatigue in older children and adults.
Figure 4 6.
Adult patient with convergence insufficiency. Note the left eye is fixing on the fixation target and the right eye is exotropic. The patient had no significant deviation for the distance. Convergence insufficiency is best treated with convergence exercises.
Incomitant Strabismus
Fourth Nerve Palsy
The superior oblique muscle is a depressor and intortor (twists the eye nasally). A weak superior oblique muscle (fourth nerve palsy) will cause strabismus consisting of hypertropia (vertical strabismus) and extorsion
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(temporal twisting of the eye). The hypertropia is worse when the patient’s head tilts to the side of the weak superior oblique muscle (Figure 4 7). Thus, patients with a superior oblique paresis usually present with a com pensatory head tilt to the opposite side of the paresis to help keep their eyes aligned. The most common types of superior oblique palsies are con genital and traumatic.
Figure 4 7.
Right superior oblique muscle paresis. Note the right hypertropia when the patient’s head is tilted to his right shoulder. This patient maintained a compensatory head tilt to the left to keep his eyes aligned.
Congenital Superior Oblique Palsy—common
Congenital superior oblique muscle palsy is the most common cause for a vertical strabismus in childhood. The etiology of congenital superior oblique palsies is unknown. The child will invariably present with a compensatory head tilt, often misdiagnosed as a musculoskeletal problem of the neck (Figure 4 8). Examine the family photo album to document the onset of the head tilt.
A patient with a congenital superior oblique palsy tilts his or her head to the opposite side of the palsy to keep the eyes aligned. Patients with con genital superior oblique paresis typically have good stereopsis and manifest the hyperdeviation intermittently when fatigued. Most have the ability to suppress so they do not experience diplopia when the deviation is manifest. A subtle finding in most children with a congenital superior oblique palsy is facial asymmetry. The dependent side of the face is more shallow (Figure 4 8). This is possibly due to the effects of gravity on facial development.
Even though the paresis is present at birth, symptoms may present in late childhood or even adulthood. Over time, the fusional control weakens and results in a vertical deviation; in these cases, strabismus surgery is indicated.
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Figure 4 8.
Right congenital superior oblique muscle paresis with compensatory head tilt to the left to keep the eyes aligned. Note the facial asymmetry with left side of the face smaller than the right.
Other Causes of Superior Oblique Paresis
Closed head trauma is a common cause of acquired superior oblique pare sis. Traumatic palsies tend to be bilateral, and patients present with vertical and torsional diplopia. In many cases, the palsy will spontaneously resolve; however, if diplopia persists after 6 months, strabismus surgery is indicated. Other causes of acquired superior oblique paresis include vascular disease with brain stem lacunar infarcts, multiple sclerosis, intracranial neoplasm, herpes zoster ophthalmicus, and diabetes with an associated mononeuropa thy. These disorders, however, usually occur in adults and not children.
Sixth Nerve Palsy—uncommon
Sixth nerve palsy results in limited abduction and an esotropia that is worse on the side of the palsy (Figure 4 9). Neonates can have a transient sixth nerve palsy often associated with a facial palsy that resolves spontaneously
Figure 4 9.
Right sixth nerve palsy. Patient demonstrates an inability to abduct the right eye. Note the esotropia in primary position and that it increases in right gaze because the right eye cannot abduct. In left gaze, the eyes are straight.
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by 4 to 8 weeks. One of the more common causes of an acquired sixth nerve palsy in childhood is post viral or post immunization neuropathy, usually occurring between 2 and 6 years of age. Most of the patients in this group show resolution of the palsy within 8 to 10 weeks. If there is no sign of improvement or if there are other neurologic signs, a full neurologic evalua tion is indicated. Head trauma is another cause of a sixth nerve palsy. About half of the traumatic sixth nerve palsies show resolution over a 6 month observational period. Other causes include intracranial tumors, meningitis, mastoiditis (Gradenigo syndrome), post lumbar puncture, hydrocephalus, or migraine.
Duane Syndrome—uncommon
•Congenital absence of sixth nerve nucleus with aberrant innervation of the lateral rectus muscle by part of the medial rectus nerve
•Contralateral face turn to align eyes
•Limited abduction (rarely bilateral)
•Lid fissure narrowing on adduction and lid fissure widening on abduction
Duane syndrome is caused by a congenital absence of the sixth nerve
nucleus with misdirection of the medial rectus nerve, innervating both the medial rectus and the lateral rectus muscles (Figure 4 10). Because the medial and lateral rectus muscles are innervated by the nerve to the medial rectus muscle, both muscles fire and contract simultaneously on attempted adduction. This co contraction of the medial and lateral rectus muscles causes globe retraction and lid fissure narrowing on attempted adduction
(Figure 4 11). Most children with Duane syn drome adopt a compensatory face turn to keep their eyes straight (Figure 4 12). Strabismus sur gery is very effective for correcting the face turn and improving abduction slightly, but does not provide full abduction capabilities (Figure 4 12C).
Figure 4 10.
Diagrammatic representation of misdirection of nerve fibers in Duane syndrome. The aberrant nerve pathway is shown in red, and the dotted lines represent hypoplasia or
agenesis. (Modified from Wilcox LM, Gittinger JW, Breinin GM. Congenital adduction palsy and synergistic divergence.
Am J Ophthalmol. 1981;91:1–7)
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Figure 4 11.
Duane retraction syndrome in the left eye. A, Left eye shows limited abduction and widening of palpebral fissures on attempted abduction. B, On adduction, there is narrowing of palpebral fissures, left eye.
Duane syndrome may be associated with a variety of systemic diseases including Goldenhar syndrome and prenatal exposure to the teratogen thalidomide. Duane syndrome, however, is most often isolated, sporadic, and of unknown cause.
Möbius Syndrome—rare
Möbius syndrome is characterized by a combination of facial palsy, sixth nerve palsy often with a partial third nerve palsy, and distal limb abnormali ties such as syndactyly or even amputation defects. Craniofacial anomalies can occur and include micrognathia, tongue abnormalities, and facial or oral clefts. Ocular motility typically shows limited abduction that has the appear ance of a sixth nerve palsy. The facial palsy usually spares the lower face,
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Figure 4 12.
Left Duane syndrome. A, Compensatory face turn to the left and eyes in right gaze to place eyes where they are aligned. B, Limited abduction left eye and large esotropia as patient looks to his left. On right gaze, the left eye fully adducts, eyes are aligned, but note the lid fissure narrowing left side. C, One day postoperative after a left medial rectus recession. Note the head turn has resolved and eyes are well aligned.
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although orbicularis function is weak. Skeletal abnormalities also include pectoralis muscle deficits. The inheritance pattern is variable and may be familial, but most cases are sporadic.
Third Nerve Palsy—uncommon
Third nerve palsy involves all the extraocular muscles (ie, medial rectus, superior rectus, inferior rectus, inferior oblique muscles) except the lateral rectus (sixth cranial nerve) and the superior oblique (fourth cranial nerve). Since both major vertical muscles are weak, the eye does not move up or down and is exotropic because of the weak medial rectus muscle. The leva tor muscle of the upper eyelid is also innervated by the third cranial nerve and ptosis is usually present (Figure 4 13) in a third nerve palsy. The pupil is large and nonreactive in complete third nerve palsy. Causes of third nerve palsy include congenital (unknown etiology), traumatic, or migraine related. Other rare causes include intracranial tumor, viral illness, posterior commu nicating artery aneurysm, and post immunization.
Figure 4 13.
Left third nerve palsy. Patient with a left third nerve palsy illustrating inability to adduct, elevate, or depress the left eye. Note complete ptosis and dilated pupil on the left.
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Brown Syndrome—uncommon
Brown syndrome consists of an inability to elevate an eye when the eye is in adduction (Figure 4 14). The most common cause is a congenitally tight superior oblique muscle tendon complex, termed true congenital Brown syndrome. Clinical findings include limited elevation in adduction, an exo deviation in attempted up gaze, and an ipsilateral hypotropia that increases in up gaze. Most patients with Brown syndrome have good binocular vision with a compensatory chin elevation and slight face turn away from the Brown eye.
Figure 4 14.
Patient with Brown syndrome in the right eye. A, Composite preoperative photographs show defective elevation in adduction. B, Postoperative photographs showing normal eye movements after Wright superior oblique silicone tendon expander insertion.
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The management of true congenital Brown syndrome is conservative unless there is a significant vertical deviation in primary position. In most cases, it is better to wait until the child is visually mature before performing surgery because an induced strabismus after surgery is not uncommon and can lead to the loss of binocular vision. If surgery is indicated, the procedure of choice is superior oblique tenotomy with insertion of a segment of sili cone (Wright silicone tendon expander procedure, invented by this author)
(Figure 4 15).
Figure 4 15.
Wright superior oblique silicone tendon expander: A segment of a retinal 240 band is sown between the cut ends of the superior oblique tendon. The procedure lengthens the tendon in a graded fashion, separating the tendon ends by a specific amount. The silicone keeps the ends from growing back together.