Horizontal
strabismus –
A review
Chantal Boisvert OD, MD, FAAO, FAAP
Pediatric Ophthalmologist
The University of New Mexico Health Sciences Center
Ocular alignment in infancy
 Ocular deviations during the first month of life do not
necessarily indicate an abnormality;
 Adequate assessment of the eye alignment is usually not made
until the patient is ~ 3 months of age;
 Infants are rarely born with their eyes aligned
 Nixon et al1 observed 1,219 alert infants in newborn nursery :
 40% had straight eyes
 33% had exotropia (XT)
 3% had esotropia (ET)
 7% were not sufficiently alert to permit classification
1 Nixon RB, Helveston EM, Miller K, et al. Incidence of strabismus in neonates. Am J Ophthalmol 1985;100:798-
801.
ESOTROPIA
Definition
 Convergent misalignment of the visual axis
 Pseudoesotropia
 Infantile esotropia
 Accommodative esotropia
 6th nerve palsy
Epidemiology
 Occurs in 2% of American children 1-3 years old;
 3% of school-age children, adolescents and young adults
13 to 24 years old;
 No gender difference;
 Most common strabismus of childhood (60%);
 Amblyopia is commonly associated with esotropia.
Pseudoesotropia
 One of the most common reasons that an ophthalmologist
is asked to evaluate an infant;
 Patient is orthophoric but has an appearance of esotropia
 Flat, broad nasal bridge
 Prominent medial epicanthal folds
 Narrow interpupillary distance
 Negative angle kappa (the eye deviates nasally to pick up
fixation as the fovea is displaced toward the optic nerve, the
line of sight is not parallel with the corneal pupillary axis)
Pseudoesotropia
 Costenbader1 found that, of 753 patients suspected by their
parents to have esotropia, 47% actually had
pseudoesotropia;
 Can be differentiated from a true manifest deviation by use
of the corneal light reflex and the cover-uncover test;
 When pseudostrabismus has been confirmed, parents can be
reassured that the child will outgrow the appearance of
esotropia.
1 Costenbader FD. Infantile esotropia. Trans Am Ophthalmol Soc 1961;59:397-419.
Look at the corneal light reflex!
http://www.aapos.org/terms_faqs/faq_list/pseudostrabismus
Infantile (or congenital) esotropia
 1-2% of all strabismus;
 Equal sex distribution;
 Present by 6 months of age;
 Family history of strabismus is common;
 Incidence is higher in patients with a history of prematurity,
cerebral palsy, hydrocephalus, and other neurological disorders;
 Maternal cigarette smoking and low birthrate have also been
linked to the development of esotropia1.
1 Chew E, Remaley NA, Tamboli A, et al. Risk factors for esotropia and exotropia. Arch Ophthalmol
1994;112:1349-1355.
Infantile (or congenital) esotropia
 Physical examination:
 High incidence of amblyopia (40-72%);
 Often cross-fixation (viewing targets in the right field of gaze with the left
eye and vice versa) with equal visual acuity in each eye;
 Apparent abduction deficit (pseudoparesis);
 Large angle of esodeviation (usually ≥ 30 prism diopters);
 Generally unaffected by accommodation;
 Cycloplegic refractions similar to those of normal children of
the same age (low hyperopia).
Infantile (or congenital) esotropia
 Associated Findings:
 Dissociated vertical deviation (DVD):
 Intermittent slow deviation of nonfixing eye consisting of
upward excursion, excyclotorsion
 Incidence: 46-92% (mean: 70%)
 Inferior oblique overaction (IOOA):
 Results in elevation of the involved eye as it moves nasally
 Incidence: 78%
 Nystagmus:
 Latent nystagmus: becomes manifest when one eye is occluded
Infantile (or congenital) esotropia
 Treatment:
 Nonsurgical:
 Correct amblyopia before surgery (patching, atropine eye
drops)
 Cross-fixation suggests equal visual acuity of both eyes
 Glasses (rarely necessary)
 Surgical:
 Aim for alignment within 10 prism diopters of orthophoria
 Surgical alignment earlier than age 2 is associated with better
sensory binocular fusion potential
Look at the corneal light reflex!
http://www.aapos.org/terms_faqs/esotropia
Accommodative esotropia
 Convergent deviation of the eyes associated with activation
of the accommodation reflex;
 Onset 6 months to 7 years (usually between ages 2 and 3);
 Often, positive family history;
 May be intermittent at onset;
 Associated with amblyopia (generally from anisometropia);
 May be precipitated by trauma or illness;
 High hyperopia (range +3.00 to +10.00; average: +4.00D).
Accommodative esotropia
 Treatment:
 Full hyperopic correction
 Treat amblyopia (patching, atropine eye drops)
 If residual strabismus > 10 prism diopters: SURGERY
Look at the corneal light reflex!
http://www.aapos.org/faq_list/accommodative_estropia
6th nerve palsy
 Incomitant esotropia (esotropia varies in different fields of gaze);
 Congenital 6th nerve palsy is uncommon:
 Usually resolves spontaneously within 6 weeks;
 Thought to be caused by increased ICP associated with the birth
process;
 Occurs much more frequently in childhood than in infancy;
 Trauma and neoplastic disorders are the most common cause;
 ~ 1/3 of the cases are associated with intracranial lesions;
 Spontaneous benign lesions usually resolve over several months.
6th nerve palsy
 Neurologic evaluation and CT or MRI recommended;
 Surgery is indicated when spontaneous resolution does
not take place after 6 months or more of follow-up and
after exclusion of intracranial lesions.
http://www.nature.com/eye/journal/v20/n12/fig_tab/6702272f1.html
EXOTROPIA
Definition
 Divergent misalignment of the visual axis
 Pseudoexotropia
 Congenital exotropia
 Intermittent exotropia
 Sensory exotropia
 Consecutive exotropia
Epidemiology
 Less common than esotropia;
 Account for 25% of strabismus in children;
 Exact etiology unknown;
 Most common form is intermittent exotropia.
Pseudoexotropia
 Appearance of exodeviation when the eyes are in fact the
eyes are properly aligned;
 May result from the following:
 Positive angle kappa (the corneal light reflection is slightly
nasal to the center of the cornea)
 Macular dragging in Retinopathy of Prematurity (ROP)
 Wide interpupillary distance (hypertelorism)
Pseudoesotropia
http://www.peds.ufl.edu/divisions/genetics/teaching/facial_dysmorphology.htm
Pseudoexotropia
(Hypertelorism)
Congenital exotropia
 Presents before age 6 months;
 Large-angle constant exotropia (>35 prism diopters);
 Often associated with neurologic impairment or craniofacial
disorders;
 Amblyopia uncommon
 These children usually alternate fixation;
 The refractive error is similar to that of the general
population;
 Treatment: Surgery early in life.
http://www.nature.com/eye/journal/v23/n6/fig_tab/eye2008183f1.html
Intermittent exotropia
 The most common divergent strabismus in childhood;
 Onset usually before age 5;
 Deviation becomes manifest during times of visual
inattention, fatigue, or stress;
 Exposure to bright light often causes a reflex closure of
one eye;
 Amblyopia is uncommon.
Intermittent exotropia
 Nonsurgical treatment:
 Corrective lenses are prescribed for significant refractive
errors
 Myopia, astigmatism, and hyperopia >+4.00D;
 Additional minus lens power (overminus spectacles) to
stimulate accomodative convergence to help control;
 Alternate daily patching;
 Active orthoptic treatment to improve fusional convergence
amplitudes (if convergence insufficiency);
 Base-in prisms.
Intermittent exotropia
 Surgical treatment:
 Surgery for increased tropic phase, poor recovery of fusion
once tropic, increasing ease of dissociation;
 Bilateral lateral rectus recession;
 3 or 4 muscle surgeries for large deviation.
Straight eyes
http://www.aapos.org/terms_faqs/faq_list/exotropia
Exotropic
Sensory exotropia
 Due to vision loss or long-standing poor vision in one eye;
 Children younger than 5 with unilateral vision loss may
develop ET or XT; adults and older children usually develop
XT;
 Angle of deviation may be variable and usually increases
with time.
Consecutive exotropia
 Exotropia that follows previous strabismus surgery for
esotropia;
 Surgery depends on many factors:
 Size of deviation;
 Type and amount of surgery that preceded its development;
 Presence of duction limitation;
 Lateral incomitance;
 Level of visual acuity in each eye.
SPECIAL FORMS OF
STRABISMUS
 Duane’s retraction syndrome
 Möbius syndrome
 Congenital fibrosis syndrome
Duane’s retraction syndrome
 Usually sporadic, may be inherited (5-10% AD);
 Co-contraction of medial and lateral rectus muscles causes
retraction of the globe with secondary narrowing of the
palpebral fissure in adduction;
 Characteristic upshoot and downshoot (leash phenomenon);
 Bilateral in 15 to 20%;
 Higher prevalence in females;
 Predilection for the left eye;
 Head turn common for fusion.
Duane’s retraction syndrome
 Etiology:
 Abnormal innervation of lateral rectus by a branch of CN 3;
 EMG shows decreased firing of lateral rectus during
abduction and paradoxical innervation of the lateral rectus
during adduction;
 Exact etiology unclear
 Proposed mechanisms include hypoplasia of 6th nerve nucleus,
midbrain pathology, fibrosis of lateral rectus.
Duane’s retraction syndrome
 3 types:
 Type 1 (most common; 50-80%):
 Limitation of abduction
 Appears esotropic (ET)
 Type 2:
 Limitation of adduction
 Appears exotropic (XT)
 Type 3:
 Limitation of abduction and adductio
 ET, XT, no primary position deviation
Duane’s retraction syndrome
 Associations:
 Deafness;
 Crocodile tears;
 Syndromes (Goldenhar, Klippel-Feil, Wildervanck, cat-eye,
fetal alcohol syndrome, thalidomine toxicity).
 Treatment:
 Correction of refractive error;
 Amblyopia treatment;
 Surgery.
http://duanes.org/
Möbius syndrome
 Association of both 6th and 7th nerve palsies;
 Etiology unknown (current evidence points to brainstem defects
secondary to a vascular insult in utero);
 Esotropia is the most common form of strabismus seen;
 Exposure keratitis from poor lid closure;
 Frequently associated with paresis of other muscles supplied by
the cranial nerves;
 Various skeletal and muscle defects are common, including
absence or hypoplasia of pectoral muscles (Poland syndrome),
syndactyly, club feet, and congenital limb amputations.
http://factoidz.com/moebius-syndrome-a-rare-disease-that-can-break-parents-hearts/
Congenital fibrosis syndrome
 Rare group of congenital disorders characterized by
varying amount of restriction of the extraocular muscles
and replacement of the muscles by fibrous tissue;
 Etiology unknown;
 Nonprogressive.
Congenital fibrosis syndrome
 Types:
 General fibrosis is the more severe form (usually AD, may be AR),




involving all the extraocular muscles of both eyes, including levator
palpebrae superioris, with ptosis;
Congenital unilateral fibrosis with enophthalmos and ptosis is
nonfamilial;
Congenital fibrosis of the inferior rectus is sporadic or familial,
levator may be involved;
Strabismus fixus involves the horizontal recti with severe esotropia;
Vertical retraction syndrome involves the superior rectus muscle,
with inability to depress the eye;
Congenital fibrosis syndrome
 Surgery is difficult and requires release of the restricted
muscles;
 A good surgical result aligns the eyes in primary position,
but full ocular rotations cannot be restored and the
outcome is unpredictable.
http://www.sarawakeyecare.com/Atlasofophthalmology/paediatric/paediatricophthalmologytpicture41congentialfibrosissyndrome.htm