Diagnosis: Infantile Esotropia
This is a case of strabismus, specifically infantile esotropia, given that onset was before 6 months of age.
Strabismus, or ocular misalignment of the eye, is a common pediatric condition. It arises when the eye muscles do not work together to produce a single image. When eye deviation occurs, the brain will try to compensate by ignoring the visual input from the deviated eye. This can lead to amblyopia, which refers to poor development of visual acuity from causes such as ocular misalignment, significant refractive error, or structural abnormalities. With strabismic amblyopia, the eye can be structurally normal but will not achieve 20/20 vision because brain is suppressing the image received from the eye due to ocular misalignment.
Why is amblyopia important? Amblyopia can be reversible if the underlying cause is corrected while the patient is young (<13 years of age). Once the patient reaches visual maturity (>13 years old), the visual pathways are less adaptable and the brain suppression of the eye may become permanent. If infantile esotropia and associated amblyopia, prompt correction of the misalignment can lead to reversal the amblyopia. Once the eyes are realigned, the brain no will longer suppresses the eye and vision can continue to develop. However if the esotropia is addressed at an older age, correcting the strabismus may not improve the amblyopia because the visual pathway has matured, resulting in permanent decreased vision.
Strabismus can be classified by the direction of the deviation: hypertropia, hypotropia, exotropia, or esotropia. In this case, the patient has right esotropia, or inward deviation of the right eye. Of note, strabismus should be distinguished from pseudostrabismus. In pseudostrabismus, the eyes may appear falsely misaligned due to large epicanthal folds or a wide nasal bridge. In pseudostrabismus the corneal light reflex, cover, and alternating cover tests are normal. Furthermore, normal newborns can have physiologic intermittent strabismus. This can be present as early as birth but will typically resolve by 2 months. Any child with intermittent crossing after two months of age, or persistent crossing at any age should be referred immediately to a pediatric ophthalmologist. (Upper left image credit: CC BY-SA 4.0).
Risk factors for strabismus include family history, preterm birth or premature weight, history of ocular conditions that obstruct the visual axis (i.e ptosis, cataracts, retinoblastoma), developmental abnormalities (Down’s syndrome, hydrocephalus) and neuromuscular conditions (Graves disease or cerebral palsy).
Strabismus is a clinical diagnosis and thus a thorough history and physical exam are warranted. The physical exam should include tests such as the corneal light reflex test, cover test and alternate-cover test. Cycloplegic refraction should also be done, especially in patients with suspected esotropias as patients tend to have hyperopic refractive error. Esotropia with hyperopia typically arises from increased accommodation leading to excessive convergence. Cycloplegic refraction allows for the full refractive error to be measured without be confounded by accommodation. Further work-up should be conducted if there is concern that the strabismus is secondarily caused (e.g. retinoblastoma).
Treatment for strabismus includes correction of the underlying cause of the misalignment in order to restore binocular vision. Strategies include prescription glasses to correct refractive error, occlusion therapy (covering the normal eye), pharmacologic therapy (i.e. atropine to impair sight of the normal eye), and surgery to realign the eyes. Surgical techniques for horizontal ocular deviations commonly include recessions or resections of the eye muscles to achieve ocular alignment.
References and Additional Resources:
1. Boyd K.“Strabismus in Children.” Lipsky SN, Turbert D. (Eds). Eye Health A-Z. December 2020 .Available at: https://www.aao.org/eye-health/diseases/strabismus-in-children.
2. Leuder G. “Chapter 9. Strabismus in Infants.” Pediatric Ophthalmology. St. Louis, McGraw-Hill Medical, 2011.
3. Mestre C, Otera C, Diaz-Douton F et al. “An automated and objective cover test to measure heterophoria.” PloS One. 2018;13(11)e0206674.
4. Coats D, Payasse EA, Olitsky SE, Armsby C. “Evaluation and management of strabismus in children.” Olitsky SE, Armsby C. (Eds). UptoDate. Available at: https://www-uptodate-com.eresources.mssm.edu/contents/evaluation-and-management-of-strabismus-in-children?search=stabismus&source=search_result&selectedTitle=1~150&usage_type=default&display_rank=1#H3.
5. Ferris J. “Amblyopia: Atropine” Clinical Education: Basic Skills Video. October 2015. Available at: https://www.aao.org/basic-skills/amblyopia-atropine.
6. Helveston EM. “Understanding, detecting, and managing strabismus.” Community Eye Health. 2010;23(72):12-14.
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