Congenital Exotropia

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Background

Exotropia is a disorder of eye alignment with one or both eyes deviated outwards relative to their normal relative position causing visual impairment. Congenital exotropia, also known as infantile exotropia, is a rare manifestation of this disease presenting in patients less than 6 months of age.[13]

Congenital exotropia could arguably be subdivided in exotropia in an otherwise healthy patient or found in a patient with other systemic diseases. Constant congenital exotropia may occur with systemic disease in as many as 60% of patients. Patients with craniofacial syndromes, ocular albinism, midline defects, cerebral palsy, and genetic syndromes may present with congenital exotropia. A recent study has shown that earlier age of onset has been associated with a worse visual acuity prognosis.[14]

Pathophysiology

The pathophysiology of congenital exotropia is unknown currently. Exotropia occurs due to a difference in muscular tone between antagonistic ocular muscles with the tone of the lateral muscle overpowering the tone of the medial muscle.

The development of congenital exotropia may be due to aberrant development of the muscle fibers themselves, creating fibrosis and weakness in the muscle to create proper alignment.[15]  The outward alignment could also result from a deficit in proper fusion and irregularity of the horizontal gaze centers.

Strabismus has been known to occur in families, suggesting a multifactorial autosomal dominant pattern with incomplete penetrance. Genetically, the disease is passed down to each generation but does not produce symptoms in every individual who receives the set of aberrant genes. Additionally, environmental factors also influence development of exotropia.

A good review of risk factors and genetics in common comitant strabismus can be found here.[3, 12]

Epidemiology

Frequency

United States

Congenital exotropia is extremely rare in the United States. A 10 year retrospective study from Minnesota suggest occurs in less than 4 per 100,000 patients under 19 years old for a group of exotropia disorders including congenital exotropia.[16]

International

Exotropia of any kind had a worldwide prevalence of 1.23%. Congenital exotropia is a more rare form of exotropia with even lower prevalence.[17]

Mortality/Morbidity

There is a higher incidence of amblyopia in congenital exotropia than in other forms of exotropia. If uncorrected, persistent exotropia may lead to patients experiencing teasing and low self-esteem.

Race

No racial predispositions for congenital exotropia exist. Recent studies suggest a higher burden of the milder exotropia in Asian populations.[18]

Sex

No known sexual predilection exists.

Age

Congenital exotropia presents in infants younger than 6 months. Children who are born premature are at higher risk of developing strabismus; however, congenital exotropia is not known to occur at a higher rate in premature children.

History

By definition, children present when they are younger than 6 months with outward deviation of the eyes.

Physical

Unlike other neurologic forms of exotropia, there should be no pupillary nor eyelid asymmetry. Although craniofacial syndromes can be seen with congenital exotropia, there should be no ptosis or pupillary mydriasis (see Oculomotor Nerve Palsy).

The eyes should appear diverging with no limitation of adduction.

Over time, a preference may occur with one eye used consistently for fixation; then, the other eye will develop amblyopia.

As many as 60% of patients may develop oblique muscle dysfunction, dissociated vertical deviation, and amblyopia. Nystagmus is rare.

Causes

There is a familial predisposition suggestive of an autosomal dominant pattern with incomplete penetrance.

Imaging Studies

Radiographic imaging is indicated if neurologic signs and/or craniofacial anomalies are present.

High-resolution MR imaging enables direct imaging of the ocular motor nerves. In a cohort of 247 consecutive patients with strabismus, Kim et al demonstrated ocular motor nerve abnormalities by high resolution MRI in 98/112 (88%) of patients with congenital or developmental neuropathic strabismus.[4]

Other Tests

Chromosomal studies may be performed if any other facial or systemic anomalies are present.

Medical Care

Generally, nonsurgical measures are attempted first followed by surgical measures. Conservative therapies often include patching or penalizing the fixating eye or the use of refractive lenses. Additionally, congenital exotropia may be accompanied with neurological and craniofacial impairments that warrant testing and treatment to uncover. 

Surgical Care

Early surgical intervention often is required to treat congenital exotropia and limit long-term complications such as amblyopia. Surgical intervention involves repositioning the ocular muscles to reduce the exotropia by a calculated distance.[19]

There are multiple surgical options, with several studies reporting no clear advantage of one procedure over the other[20] :

Resection is a procedure that shortens and strengthens the muscle, creating a stronger pull on the eye when reattached. Recession is a procedure that reduces tension on a muscle by repositioning its insertion on the eye.

Hunter et al (2001) evaluated differences between infants, aged younger than 1 year, with constant exotropia versus intermittent exotropia at presentation.[1] They found that "half of infantile exotropia patients may present with intermittent exotropia, with similar clinical outcomes regardless of presentation."[1] In their study, surgical intervention resulted in successful alignment in most cases.[1] More than half the patients developed measurable stereopsis, but none achieved bifixation.[1]

In a 2008 study of 12 patients with intermittent exotropia treated with bilateral lateral rectus recession, stereoacuity, as seen in the late follow-up period, measured at 40 arcsec in 2 patients, 100 arcsec in 3 patients, 140-400 arcsec in 2 patients, and none in 5 patients.[2]

Consultations

Consultations include the following:

Further Outpatient Care

A child with any form of strabismus is at risk of losing vision due to amblyopia. Since these children present at a nonverbal age, it is imperative that a pediatric ophthalmologist screen and follow the visual status during the critical years of visual development.

Deterrence/Prevention

Prevention measures include the following:

Complications

Complications include the following:

Prognosis

The following factors influence prognosis:

Patient Education

Patient education includes the following:

Author

Adam J Cantor, MD, Assistant Professor of Ophthalmology, Department of Pediatric Ophthalmology and Adult Strabismus, Baylor College of Medicine; Attending Physician, Texas Children’s Hospital

Disclosure: Nothing to disclose.

Coauthor(s)

Taimur Siddiqui, BSA, BBA, MD Candidate, Baylor College of Medicine

Disclosure: Nothing to disclose.

Specialty Editors

Francisco Talavera, PharmD, PhD, Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Received salary from Medscape for employment. for: Medscape.

J James Rowsey, MD, Former Director of Corneal Services, St Luke's Cataract and Laser Institute

Disclosure: Nothing to disclose.

Chief Editor

Edsel B Ing, MD, PhD, MBA, MEd, MPH, MA, FRCSC, Professor, Department of Ophthalmology and Vision Sciences, Sunnybrook Hospital, University of Toronto Faculty of Medicine; Incoming Chair of Ophthalmology, University of Alberta Faculty of Medicine and Dentistry, Canada

Disclosure: Nothing to disclose.

Additional Contributors

C Corina Gerontis, MD, Consulting Staff, Departments of Pediatrics and Ophthalmology, Schneider Children's Hospital/Long Island Jewish Medical Center

Disclosure: Nothing to disclose.

Gerhard W Cibis, MD, † Clinical Professor, Director of Pediatric Ophthalmology Service, Department of Ophthalmology, University of Kansas School of Medicine

Disclosure: Nothing to disclose.

Mounir Bashour, MD, PhD, CM, FRCSC, FACS, Assistant Professor of Ophthalmology, McGill University Faculty of Medicine; Clinical Assistant Professor of Ophthalmology, Sherbrooke University; Medical Director, Cornea Laser and Lasik MD

Disclosure: Nothing to disclose.

References

  1. Hunter DG, Kelly JB, Buffenn AN, et al. Long-term outcome of uncomplicated infantile exotropia. J AAPOS. 2001 Dec. 5(6):352-6. [View Abstract]
  2. Saunders RA, Trivedi RH. Sensory results after lateral rectus muscle recession for intermittent exotropia operated before two years of age. J AAPOS. 2008 Apr. 12(2):132-5. [View Abstract]
  3. Maconachie GD, Gottlob I, McLean RJ. Risk factors and genetics in common comitant strabismus: a systematic review of the literature. JAMA Ophthalmol. 2013 Sep. 131 (9):1179-86. [View Abstract]
  4. Kim E, Kim JH, Hwang JM, Choi BS, Jung C. MR Imaging of Congenital or Developmental Neuropathic Strabismus: Common and Uncommon Findings. AJNR Am J Neuroradiol. 2012 May 17. [View Abstract]
  5. Biglan AW, Davis JS, Cheng KP, et al. Infantile exotropia. J Pediatr Ophthalmol Strabismus. 1996 Mar-Apr. 33(2):79-84. [View Abstract]
  6. Brodsky MC, Baker RS, Hamed LM. Pediatric Neuro-ophthalmology. 1996.
  7. Hunter DG, Ellis FJ. Prevalence of systemic and ocular disease in infantile exotropia: comparison with infantile esotropia. Ophthalmology. 1999 Oct. 106(10):1951-6. [View Abstract]
  8. Matsuo T, Yamane T, Ohtsuki H. Heredity versus abnormalities in pregnancy and delivery as risk factors for different types of comitant strabismus. J Pediatr Ophthalmol Strabismus. 2001 Mar-Apr. 38(2):78-82. [View Abstract]
  9. Mohney BG, Huffaker RK. Common forms of childhood exotropia. Ophthalmology. 2003 Nov. 110(11):2093-6. [View Abstract]
  10. von Noorden GK. Binocular Vision and Binocular Motility: Theory and Management of Strabismus. 1996.
  11. Wright KW, Buckley EG, Del Monte MA. Pediatric Ophthalmology and Strabismus. 1995.
  12. Kruger JM, Mansouri B, Cestari DM. An update on the genetics of comitant strabismus. Semin Ophthalmol. 2013 Sep-Nov. 28 (5-6):438-41. [View Abstract]
  13. Green-Simms AE, Mohney BG. Epidemiology of Pediatric Strabismus. Lorenz B, Brodsky MC, eds. Pediatric Ophthalmology, Neuro-Ophthalmology, Genetics. 3rd ed. Heidelberg, Germany: Springer Berlin; 2010. 1-9.
  14. Na KH, Kim SH. Different surgical outcomes in infantile exotropia according to onset time. J AAPOS. 2019 Dec. 23 (6):317.e1-317.e6. [View Abstract]
  15. Kaur K, Gurnani B. Exotropia. StatPearls. Available at https://www.statpearls.com/point-of-care/142913. 2023 Jan; Accessed: January 7, 2024.
  16. Govindan M, Mohney BG, Diehl NN, Burke JP. Incidence and types of childhood exotropia: a population-based study. Ophthalmology. 2005 Jan. 112 (1):104-8. [View Abstract]
  17. Hashemi H, Pakzad R, Heydarian S, Yekta A, Aghamirsalim M, Shokrollahzadeh F, et al. Global and regional prevalence of strabismus: a comprehensive systematic review and meta-analysis. Strabismus. 2019 Jun. 27 (2):54-65. [View Abstract]
  18. Pan CW, Zhu H, Yu JJ, Ding H, Bai J, Chen J, et al. Epidemiology of Intermittent Exotropia in Preschool Children in China. Optom Vis Sci. 2016 Jan. 93 (1):57-62. [View Abstract]
  19. Marcotty A, Utz V. Management of Exotropia in Childhood. Traboulsi E, Utz V, eds. Practical Management of Pediatric Ocular Disorders and Strabismus. New York, NY: Springer; 2016. 535-46.
  20. Kim DH, Yang HK, Hwang JM. Long term surgical outcomes of unilateral recession-resection versus bilateral lateral rectus recession in basic-type intermittent exotropia in children. Sci Rep. 2021 Sep 29. 11 (1):19383. [View Abstract]
  21. Na KH, Kim SH. Early versus late surgery for infantile exotropia. J AAPOS. 2018 Feb. 22 (1):3-6. [View Abstract]