Infantile Esotropia
Disease Entity
Strabismus/Eye misalignment
Disease
Infantile esotropia is a form of ocular motility disorder in which there is an inward turning of one or both eyes, commonly referred to as "crossed eyes".[1]
Infantile esotropia is esotropia that occurs during the first 6 months of life in an otherwise neurologically normal child. The term "congenital esotropia" has been used synonymously but the condition is rarely present at birth. The angle of deviation is constant and large (>30 PD). It may be accompanied by dissociated vertical deviation (DVD) 50%-90%, inferior oblique muscle overaction 70%, latent nystagmus 40%, and optokinetic asymmetry.
Transient misalignment of the eyes is common up to the age of 3 months and this should not be confused with infantile esotropia.
Etiology
The etiology of infantile esotropia is unknown. Many theories have been postulated regarding the pathogenesis of the disease. Worth[2] theory suggests that there is an irreparable congenital defect in the infant's visual system and that surgery can be carried out at leisure mostly for cosmetic purposes. On the other hand, Chavasse[3] suggested a primary motor dysfunction, where the associated poor fusion and lack of high-grade stereopsis is probably a sensory adaptation to abnormal visual stimulation during early binocular development caused by the motor misalignment. Thus, surgical correction should be performed early during infancy. This second view was largely accepted afterwards by Costenbader and Parks. There can be a hereditary component with other family members having history of strabismus.
Diagnosis
History
Detailed history taking regarding birth weight, complications of birth, the health of the child and developmental milestones may help in the management of the case. History of first presentation aided by photographs of the child in the first few months of life can assist in documenting the onset, detecting the stability of the condition and confirming the diagnosis. Family history may elicit the presence of a genetic factor/ familial inheritance.
Physical examination
Appropriate diagnosis and management requires full ophthalmologic evaluation with cycloplegia and dilation to examine for other causes of esotropia in young children, including media opacities, refractive error, cranial nerve palsy etc.
Detailed examination of motility and alignment is needed and can be challenging in the young child. The exam should be quick and performed in a fun atmosphere. Try to maintain the child’s attention at all times. This can be done by engaging the patient through the use of colorful toys, whistling and making noises. Corneal light reflex tests (Hirshberg and Krismky) can be helpful estimating angle of deviation, but cover testing should be employed when possible.
Signs
Size of the deviation
As mentioned previously, the angle of deviation is usually larger than 30 PD, and it is constant.
Visual acuity
Amblyopia occurs in approximately 40% - 50% of children with congenital esotropia.[4] This can be determined by observing the child for a fixation preference for one eye.
Many infants may freely alternate their fixation. Others may cross fixate using alternate eyes in the opposite field of gaze, (i.e. looking to the left with the right eye and looking to the right with the left) and do not develop amblyopia.
Refractive errors
Infantile esotropia with hypermetropia more than +2.50 diopters need to be differentiated from accommodative esotropia, which can also occur as early as 6 months of age. Accommodative esotropia manifests as eye inturning secondary to the increased work of focusing through significant hypermetropia.
Ocular rotation
Some infants may show some limitation of abduction upon initial examination of eye movements as a result of cross fixation. However, doll’s head maneuver, in which gentle spinning of the child stimulates a vestibular movement to the opposite direction of the spin and a refixation saccade in the same direction, full abduction can be elicited.
Associated conditions
Dissociated vertical deviation (DVD) occurs in approximately 75% of patients with infantile esotropia. DVD is elevation of the non-fixing eye when covered or with visual inattention.
Inferior oblique overaction occurs in approximately 70% of patients with infantile esotropia. This is seen as over-elevation of the eye in supra-adduction.
Latent nystagmus occurs in approximately 40% of patients with infantile esotropia. It is a predominantly horizontal jerk nystagmus elicited by occluding either eye. The slow phase is toward the side of the occluded eye.[5]
Diagnostic procedures
Visual evaluation
Understanding visual milestones and anatomic development is mandatory for precise visual assessment of the child. On average, by 2 months of age, the optic nerve completes myelinization. At 3 to 4 months, the fovea develops, and by 6 months iris pigmentation is approximately 90% complete. Methods to evaluate vision in infants include observing fixation and following visual behaviors, Visual evoked potential (VEP) testing, optokinetic response, preferential looking and optotype visual acuity depending on the child’s age and level of cooperation.[6]
Motor evaluation
Cover/uncover testing is used to detect and quantify eye misalignment. It is necessary to test the function of each extraocular muscle (ductions and versions) and the patient’s control over the deviation. Additional tests may include prism adaptation and diagnostic occlusion.[7]
Sensory evaluation
Complete sensory evaluation in a preverbal child is difficult. Some signs may give a clue about the sensory development and the prognosis of the condition. Detection of fixation preference for one eye can be performed by the use of vertical prism test (10-prism diopter test)[8]. Optokinetic response to detect smooth pursuit and saccade eye movements will aid in the diagnosis of amblyopia.
Differential diagnosis
- Pseudoesotropia
- Sensory esotropia
- Congenital sixth nerve palsy
- Nystagmus blockage syndrome
- Type I Duane’s syndrome
- Ciancia syndrome
- Congenital fibrosis syndrome
- Mobius syndrome
- Infantile Myasthenia Gravis
- Esotropia associated with neurologic diseases e.g. cerebral palsy, periventricular encephlomalasia
Management
Evaluation for an underlying disease process should be made when symptoms and signs lead in that direction. Most cases of infantile esotropia will require surgical intervention.[9] Children with esotropia that present after 6-9 months of age and those who show limited abduction may require imaging.
General treatment
Medical therapy
Occasionally infants with small angle esotropia <30 PD may be corrected with hypermetropic spectacle correction.
The timing of amblyopia treatment in relation to eye muscle realignment surgery is debatable. Some surgeons treat amblyopia before performing surgery to create a stronger visual drive for straight eyes and thus better outcomes. Amblyopia occlusion treatment after the eyes are aligned can interfere with the exercise of binocularity. However, some surgeons may opt to surgically realign the eyes prior to amblyopia therapy if strabismic amblyopia is suspected. Early re-alignment has been shown to lead to improved sensory outcomes. [10]
Stability of the esotropia angle is assessed prior to surgical intervention.
Surgery
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Some studies have shown early strabismus surgery provides more potential for development of binocular function.[11] [12]However, the surgery is more technically challenging earlier in infancy because of the small size of an infant’s eye and orbit, in addition to the lack of stability of the deviation and difficulties in measuring the alignment.[9] Parents should be aware that the goal of treatment is to get the eyes aligned and encourage the best sensory development possible, which might take more than one surgical procedure. The standard approach for treatment is bilateral medial rectus recessions which weakens the medial recti (the muscles pulling the eyes inward). Alternately, a medial rectus recession with an ipsilateral lateral rectus resection can achieve the same effect. Botulinum toxin injection into the medial recti to weaken them has also been used, but studies have shown mixed sensorimotor outcomes when compared to traditional incisional surgery. If signs of inferior oblique overaction are noted, surgical weakening of the inferior oblique muscles is performed simultaneously. The other associated conditions of DVD and latent nystagmus usually appear later in life and may be addressed surgically at that point.
Surgical follow up
After surgical realignment, patients are usually advised to return with a few weeks following surgery to assess eye alignment and the ocular healing process. Intraocular infection is rare following strabismus surgery Patients should be followed closely for amblyopia, even if they achieve good motor alignment. Close follow up is required especially in cross fixating children as amblyopia in one eye can present after surgical alignment.[13][7]
Complications
Undercorrection (persistent crossing) and overcorrection (wandering of an eye) are the most commonly noted complications of surgery. Many of these are transient. Other less common complications include perforation of the sclera, lost or slipped muscles, infection, anterior segment ischemia, postoperative diplopia, conjunctival granulomas and cysts.
Prognosis
Untreated, children with infantile esotropia can develop good vision in each eye, but bifoveal fixation with full binocular function will not be achieved. Therefore, they will have poor depth perception and atypical appearance. Poor visual acuity will occur in the face of amblyopia. When infants undergo early surgical intervention, they have a chance of better alignment and stereopsis outcomes. Multiple surgeries may be needed to correct large angle esotropia. The number of children requiring a second operation varies between 15-30%.[13] Amblyopia, residual esotropia or consecutive persistent exotropia may develop and should be addressed early to get the best possible visual and fusion potential.
Additional Resources
References
- ↑ Costenbader FD. Infantile esotropia. Trans Am Ophthalmol Soc 1961;59:397-429.
- ↑ Worth C. squint, its causes and treatment. London: Bailliere, Tindall, and Cox, 1903.
- ↑ Chavasse FB. Worth’s squint on the binocular reflexes and the treatment of strabismus, 7th ed. Philadelphia: P.Blakiston’s Son & Co, 1939.
- ↑ Wright KW. Esotropia. In: Wright KW. Pediatric ophthalmology and strabismus. St. Louis, MO: CV Mosby;1995.p.179-94.
- ↑ Hiles DA, Watson A, Biglan AW. Characteristics of infantile esotropia following early bimedial rectus recession. Arch ophthalmol 1980;98:697-703.
- ↑ Robbins SL et al, Vision testing in the pediatric population, Ophthalmol Clin N Am 16 (2003) 253-267.
- ↑ 7.0 7.1 Raab EL. Comitant esotropia. In: Wilson ME, Saunders RA, Trivedi RH. Pediatric ophthalmology: current thoughts and practicle guide. Leipzig. Springer;2009. p. 85-112.
- ↑ Wright KW, Walonker F, Edelman PM, , 10-diopter fixation test for amblyopia. Arch Ophthalmol 1981;99:1242-6.
- ↑ 9.0 9.1 Pediatric Eye Disease Investigator Group. Spontaneous resolution of early-onset esotropia: experience of the Congenital Esotropia Observational Study. Am J Ophthalmol 2002;133:109-18.
- ↑ Birch EE, Stager DR, Berry P, and Everett ME. Prospective assessment of acuity and stereopsis in amblyopic infantile esotropes following early surgery. Inv Ophthalmol and Vis Sci, 1990; 31:758-65.
- ↑ Ing M, Costenbader FD, Parks MM, et al. Early surgery for congenital esotropia. Am J Ophthalmol 1966;62:1419-1427.
- ↑ Taylor DM. How early is early surgery in the management of strabismus? Arch Ophthalmol 1963;70:752-6.
- ↑ 13.0 13.1 Elston J. Concomitant strabismus. In: Taylor D. Pediatric ophthalmology. 2nd ed. London: Blackwell science; 1997. p. 925-36.
