Background
The term congenital exotropia is typically reserved for patients presenting in the first year of life with a large, constant angle.
However, as Hunter et al (2001) state, no published study provides a rationale for this restrictive definition. [1] In their study, they 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]
True congenital exotropia (with a fixed exotropia) is an extremely rare form of strabismus and may occur with systemic disease in as many as 60% of patients. Patients with craniofacial syndromes, ocular albinism, midline defects, and cerebral palsy may present with congenital exotropia.
See related CME at Highlights of the American Association for Pediatric Ophthalmology and Strabismus Annual Meeting.
Pathophysiology
The pathophysiology is unknown, although strabismus does occur in families, suggesting a multifactorial autosomal dominant pattern with incomplete penetrance.
A good recent 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.
International
The worldwide incidence of congenital exotropia is unknown.
Mortality/Morbidity
There is a higher incidence of amblyopia in congenital exotropia than in other forms of exotropia.
Race
No known racial predisposition to congenital exotropia exists.
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 does not occur at a higher rate in premature children.
