- 1.
What is an esodeviation?
A convergent deviation, noted by crossing or in-turning of the eyes, is designated by the prefix eso .
- 2.
What are the different types of esodeviations?
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Esophoria is a latent tendency for the eyes to cross. This latent deviation is normally controlled by fusional mechanisms that provide binocular vision or avoid diplopia. The eye deviates only under certain conditions, such as fatigue, illness, stress, or tests that interfere with the maintenance of normal fusional abilities (e.g., covering one eye).
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Esotropia is a manifest misalignment of the eyes. The condition may be alternating or unilateral, depending on the vision. In alternating strabismus, either eye may be used for fixation while the fellow eye deviates. In cases of unilateral esotropia, the deviating eye is noted in the description of the misalignment (left esotropia).
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- 3.
How common is strabismus in infants?
Infants are rarely born with straight eyes. Alignment may vary intermittently from esotropia to orthotropia to exotropia during the first few months of life. Forty percent of newborn infants seem to have straight eyes, 33% may display exotropia, and approximately 3% may be esotropic. Many infants have variable alignment and cannot easily be classified in any single category. Few patients with an esotropia of 40 or more prism diopters that is constant at 10 weeks of age will demonstrate spontaneous resolution of their deviation.
- 4.
What is pseudoesotropia?
Pseudoesotropia is the false appearance of esotropia when the visual axes are actually aligned. A flat, broad nasal bridge, prominent epicanthal folds, or a narrow interpupillary distance causes the observer to see less sclera nasally than expected. This creates the impression that the eye is turned in toward the nose.
- 5.
What is congenital or infantile esotropia?
Congenital or infantile esotropia is a convergent strabismus, with no identifiable cause, that develops in a child before the age of 6 months. Although the two terms are often used interchangeably, there is an important difference between them. A child with true congenital esotropia is born with strabismus, whereas a child with infantile esotropia will develop it during the first few months of life. The period of time during early infancy in which the eyes are straight may play an important role in the development of binocular vision after the eyes are aligned.
- 6.
What are the characteristics of congenital esotropia?
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Large deviation: The characteristic angle of congenital esotropia is considerably larger than angles of esotropia acquired later in life ( Fig. 25-1 ). In most series reported in the literature, average deviations are between 40 and 60 prism diopters. The diagnosis of congenital esotropia should be reconsidered in a child with a relatively small deviation.
Figure 25-1
A child with congenital esotropia. Note the characteristic large angle of crossing.
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Normal refractive error: Children with congenital esotropia tend to have cycloplegic refractions similar to those of normal children of the same age.
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- 7.
What is cross-fixation?
Children with equal vision and a large esotropia have no need to abduct either eye. They use the adducted, or crossed, eye to look to the opposite field of gaze. This is called cross-fixation.
- 8.
Why do some children with congenital esotropia appear to have an abduction deficit?
In children with good vision in both eyes and who demonstrate cross-fixation, neither eye will appear to abduct. If amblyopia is present, only the eye that sees better will cross-fixate, making the amblyopic eye appear to have an abduction weakness.
- 9.
How can a pseudoabduction deficit be distinguished from a true abduction deficit?
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By rotating the infant’s head, either with the infant sitting upright in a moveable chair or by using a doll’s head maneuver
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By patching one eye for a short period. The child will eventually move the unpatched eye
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- 10.
What is the differential diagnosis of an infant with esotropia?
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Pseudoesotropia
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Congenital sixth nerve palsy
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Duane’s retraction syndrome
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Early-onset accommodative esotropia
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Möbius syndrome
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Sensory esotropia
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Nystagmus blockage syndrome
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Esotropia in the neurologically impaired
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- 11.
How is vision evaluated in a child with congenital esotropia?
The following observations can be made to look for equal vision in a child with a large-angle esotropia:
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Spontaneously alternates fixation
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Holds fixation with either eye when one eye is covered and then uncovered
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Cross-fixation present in both eyes
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- 12.
How common is amblyopia in congenital esotropia?
Amblyopia may occur in as many as 19% to 72% of infants with congenital esotropia.
- 13.
What are the goals in the treatment of congenital esotropia?
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Development of normal sight in each eye
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Reduction of distant and near deviation as close to orthotropia (straight eyes) as possible
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Development of at least a rudimentary form of binocular vision
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- 14.
What level of binocular vision can develop in children with congenital esotropia?
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Classically, it has been taught that patients with congenital esotropia do not develop bifoveal fixation (perfect binocular vision) regardless of their age at treatment.
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Alignment within 10 prism diopters of orthotropia early in life is often associated with the attainment of some degree of binocular vision and stereopsis.
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Some surgeons have suggested that surgery performed on a patient at a very early age can lead to the development of bifoveal fixation.
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- 15.
When is congenital esotropia treated?
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Most surgeons attempt to operate on children with congenital esotropia between 6 and 12 months of age, usually with bilateral medial rectus recessions.
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Some surgeons operate on patients who are younger than 6 months of age in hopes of providing higher levels of binocular vision.
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- 16.
Why is it important to treat amblyopia before surgical correction of congenital esotropia?
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Detecting reduced vision in an infant is easier in the presence of a large esotropia.
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Judgment about fixation preference is difficult in a preverbal child with straight eyes.
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Occlusion therapy in children at a young age generally requires only a small amount of time to equalize vision.
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If the vision is not equal after surgery, the chance of developing binocular vision and maintaining ocular alignment is lowered.
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Parental incentive to comply with the often arduous task of occlusion therapy is greatly diminished once the child’s eyes are straight.
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- 17.
What other motility disorders are often associated with congenital esotropia?
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Inferior oblique overaction: Elevation of the eye during adduction ( Fig. 25-2 ); occurs in 78% of cases; most common in second or third year of life; may require surgery
Figure 25-2
Inferior oblique overaction. As the eye adducts (moves toward the nose), it elevates.
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Dissociated vertical deviation: Slow upward deviation; occurs in 46% to 90% of cases; onset greatest in second year of life; may require surgery
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Nystagmus: Latent or rotary possible; occurs in 50% of cases; usually diminishes with time
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- 18.
What is accommodative esotropia?
Accommodative esotropia is a convergent deviation of the eyes associated with activation of the accommodative reflex ( Fig. 25-3 ).
Figure 25-3
Accommodative esotropia. As the child attempts to accommodate (focus), the eyes cross (left). With glasses that eliminate the need to accommodate, the eyes are straight (right).
- 19.
At what age does accommodative esotropia develop?
Accommodative esotropia usually occurs in a child between 2 and 3 years of age. Occasionally, children who are 1 year of age or younger present with all of the clinical features of accommodative esotropia.
- 20.
What are the three types of accommodative esotropia?
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Refractive
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Nonrefractive
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Partial or decompensated
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- 21.
What three factors influence the development of refractive accommodative esotropia?
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Uncorrected hyperopia
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Accommodative convergence
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Insufficient fusional divergence
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- 22.
How do the aforementioned three factors lead to accommodative esotropia?
A hyperopic person must exert excessive accommodation to clear a blurred retinal image. This, in turn, stimulates excessive convergence. If the amplitude of fusional divergence is sufficient to correct the excessive convergence, no esotropia results. However, if the fusional divergence amplitudes are inadequate, or if motor fusion is altered by some sensory obstacle, esotropia results.
- 23.
What is the AC:A ratio?
The accommodative convergence:accommodation (AC:A) ratio describes how many prism diopters a person’s eyes converge for each diopter that he or she accommodates. The normal AC:A ratio is approximately 3 to 5 prism diopters of convergence per diopter of accommodation.
- 24.
How can the AC:A ratio be measured?
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The heterophoria method: A strabismic deviation is recorded in prism diopters for a distance at 6 meters ( D ) and a near at ⅓ meter ( N ). After the patient’s interpupillary distance is measured in centimeters (PD), the AC:A ratio can then be calculated as follows:
<SPAN role=presentation tabIndex=0 id=MathJax-Element-1-Frame class=MathJax style="POSITION: relative" data-mathml='AC:A=(PD)+N−DNearmeasurementdistance(indiopters)’>AC:A=(PD)+?−?Nearmeasurementdistance(indiopters)AC:A=(PD)+N−DNearmeasurementdistance(indiopters)
AC : A = ( PD ) + N − D Near measurement distance ( in diopters )
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Esodeviations
