Primary infantile esotropia develops in the first few weeks to
months of life, most often prior to 6 months of age. Previously,
this condition had been incorrectly termed congenital esotropia. There
is often a family history of strabismus, with esotropia observed
in as many as 10% to 20% of first-degree relatives.4 Classic
infantile esotropia is constant and involves a large amount of misalignment,
often 25 to 35 degrees (40 to 60 prism diopters) at both distance
and near viewing (Fig. 586-1). Infantile
esotropia rarely can resolve spontaneously over time, with the magnitude
of deviation being inversely proportional to the probability of
resolution. Multiple studies have confirmed that a constant large
esotropia that is still present at age 2 to 4 months is unlikely
to resolve without treatment, and the angle of strabismus may increase
with continued observation.5
Normal amounts of farsightedness are present in most of these
patients. Glasses are therefore not generally required or helpful,
as the esotropia is unrelated to the refractive error. Significant
nearsighted or astigmatic refractive error, if present, may require
correction, not to improve the alignment but to maximize vision.
Managing primary infantile esotropia generally involves eye muscle
surgery, which is successful approximately 80% of the time
after a single operation. Surgical treatment of infantile esotropia generally
involves recession (weakening) of the medial rectus muscles on both
eyes. Most clinical experience suggests that very useful, sometimes
near-normal sensory and oculomotor functions can be developed or
restored if successful ocular alignment is achieved within the first
2 years of life.6,7 The optimum timing for eye
muscle surgery for primary infantile esotropia is the subject of
much research, with some suggesting intervention as young as 6 months
of age in an effort to maximize binocular visual potential. Even
surgery as early as 13 weeks has been advocated by some ophthalmologists.8 Botulinum
toxin injection into the medial rectus has been investigated as
an alternative to traditional surgery. While some authors have noted
success with smaller deviations, the efficacy when compared to incisional
surgery has not always been convincing.9
Careful longitudinal follow-up of these patients is necessary,
since an accommodative esotropia (see below) requiring glasses can
develop at a later date. Even with successful surgical ocular realignment,
patients with infantile esotropia are more likely to exhibit latent
nystagmus, vertical misalignment, and monocular smooth pursuit abnormalities.
These features may persist throughout the patient’s life.
When we focus on objects near us, the ciliary muscle of the eye
contracts, resulting in relaxation of the lens (a process called accommodation),
and the eyes converge. Children have particularly large abilities
to accommodate. We lose this ability in later adulthood and thus
the reason for needing reading glasses or bifocals. If a child is
farsighted, they need to accommodate even more than usual to focus,
and they are able to do so without any sense of stress or discomfort.
In fact, most children are farsighted in the first decade of life,
and very few need glasses. But in some children, this excess accommodative
need results in overconvergence of the eyes, called accommodative
Children with accommodative esotropia generally present between
the ages of 18 and 48 months of age, with an average age of onset
of 2.5 years. The esotropia is often intermittent in the beginning
and becomes constant without intervention. The amount of esotropia
is generally less than is present in patients with primary infantile
esotropia and may be more prominent at near fixation. These children
have larger than average amounts of hyperopia, averaging about +4
diopters, with some patients exhibiting as much as +8 to
10 diopters. Over 30% of children with +4 diopters
or more of hyperopia will develop esotropia by 3 years of age. Amblyopia
may also develop, even bilaterally, in children whose hyperopia
is excessively high. Some experts contend that children with accommodative
esotropia more frequently have amblyopia at presentation than children
with infantile esotropia.
Managing accommodative esotropia usually involves spectacle correction
for the farsightedness to eliminate the need to accommodate and
overconverge. Bifocals may be required if there is excessive accommodative
convergence at near fixation. With the glasses on, the patient has
straight eyes. When the glasses are removed, the patient again starts
to accommodate in order to see clearly and the eyes are esotropic
(Fig. 586-2). The child may actually see
as clearly without the glasses as with them, but the glasses are
there to keep the eyes straight.
Accommodative esotropia. Child has left esotropia (note
abnormal Hirschberg light reflex) with glasses off (A)
but straight eyes with glasses on (B).
A second form of accommodative esotropia does
not involve farsightedness. Children with this subtype of esotropia
often have straight eyes, or nearly so, when looking at an object
in the distance, but their eyes cross excessively only when fixating
on near objects. This is due to an abnormal relationship between
accommodation and convergence. These children are most often treated
with reading glasses (if correction is needed only for near work)
or bifocals (if they also need correction to see clearly at a distance,
such as with astigmatism).
A miotic agent such as phospholine iodide, a cholinesterase inhibitor,
is sometimes effective in realigning the eyes of patients with accommodative
esotropia where compliance with wearing glasses is poor but potential
ocular and systemic side effects limit their long-term usage.
It is normal for children to demonstrate increasing amounts of
hyperopia until 6 to 8 years of age, when the amount of hyperopia
naturally begins to decrease in most children. In patients with
accommodative esotropia, a gradual reduction (“weaning”)
of the spectacle strength may be possible over time, while maintaining good
vision and alignment. If glasses are worn faithfully and good fusional
patterns are established, many patients with refractive esotropia can
be weaned from their glasses by the time they are teenagers. The
same is true for bifocals. When beneficial, bifocal correction can often
be weakened after 4 to 7 years of age and even eventually eliminated
in over half of cases, usually by the midteens. A few eye surgeons recommend
eye muscle surgery for children who cannot be weaned out of bifocals
by 15 to 16 years of age. This allows the patient to discontinue
bifocal wear and simply wear single-vision glasses or contact lenses.
Some patients will always need glasses (or contact lenses) to
keep their eyes straight. Significant delay, as little as 3 to 4
months, in initiating spectacle treatment following the onset of
accommodative esotropia increases the possibility that a portion
of the esotropia will not resolve with spectacle correction alone.
This mixed form of strabismus (partially accommodative esotropia)
often requires surgery for the nonaccommodative component.
Esotropia that develops after infancy and is not accommodative
is termed basic acquired esotropia. Organic pathologies,
often in the retina or vitreous of the eye (eg, traumatic injury,
cataract, Toxoplasma infection), have been diagnosed
in a significant percentage of these patients, emphasizing the importance
of an ophthalmologist performing a complete eye examination (with
pupil dilation) in any patient presenting with strabismus. Underlying
central nervous system lesions in otherwise healthy children must
also be considered and ruled out by neuroimaging or pediatric neurological
consultation if no ocular pathology is found. Underlying refractive
error or amblyopia should also be treated in an appropriate manner.
After ruling out other specific ocular or neurological pathology,
management of acquired esotropia generally requires strabismus surgery.
This usually involves bilateral medical rectus recession (weakening) or
unilateral surgery with medial rectus recession and lateral rectus
The infant often has a wide, flat nasal bridge with prominent
epicanthal folds. The child may appear esotropic even when the eyes
are straight, because there is less white sclera visible medially
compared to laterally, especially if the child is looking slightly
to one side or looking up close. This optical illusion causes the
child to appear cross-eyed (Fig. 586-3).
The Hirschberg light reflex test is normal. While no treatment is
necessary for pseudoesotropia, as this appearance will disappear
spontaneously as the infant grows older, these children should be
reevaluated every 6 to 12 months, since some of these patients may
develop accommodative or acquired esotropia at a later age.
Pseudoesotropia. Note that the Hirschberg light reflex
is symmetric in the pupil of both eyes. Even though the eyes look
grossly esotropic, they are actually aligned.