Everyday Exotropia: Learning from the Littlest.

Background and purpose: Early onset exodeviations in systemically and ocularly healthy young children, diagnosed at less than 1 year of age, may be of the constant, "infantile XT" type, or early X(T) type. The onset of common childhood X(T) is not clearly known. The purpose of this lecture is to discuss theories and characteristics of early onset exodeviations, and report on our observations of infantile XT and early X(T) at Children's Eye Care in Michigan.

Patients and methods: A retrospective review of 470 cases of childhood exodeviations (ages 6 months to 15 years) were reviewed and met inclusion criteria of no prior surgical treatment, no ocular, CNS or craniofacial disease, and no significant prematurity. Thirty-nine cases were diagnosed at less than 1 year of age: thirty-five patients with early X(T) and four patients with infantile XT, based upon a motility evaluation at 6 m and 1/3 m fixation using dissociative methods. The clinical characteristics and outcomes of these two groups were described and compared.

Results: Comparing infantile XT and early X(T) groups, reported onset by caregivers was significantly younger in the infantile XT group (3 months vs. 6 months), and size of the deviation at both distance and near fixation ranges was significantly larger in the infantile XT group (XT-43/XT'-48^Δ vs. X(T)-25/X(T)'-23^Δ). Three of 4 infantile XT patients received surgery, one spontaneously resolved, and all resulted in small, residual XT, and DVD without measurable stereoacuity. Many patients with early X(T) demonstrated good/excellent control at near range and fair/poor control at distance range. Four early X(T) patients who did not receive surgical correction either resolved, remained the same, or decompensated. Surgical correction for X(T) resulted in a 50% success rate for one procedure with a minimum of 2 years postoperative follow-up. Stereoacuity outcomes did not appear to correlate with quality of control.

Conclusions: Most healthy children with X(T) are diagnosed by age 5 years, although many have a reported onset by caregivers of less than 1 year of age. Good control of X(T) at near range may preclude early examinations. Motility evaluation by dissociative methods at near and far-range fixation may facilitate early diagnosis. Infantile XT is less common than early X(T), by a ratio of 1:10. Characteristics of infantile XT and early X(T) have significant differences in report onset, deviation size, and outcomes with and without surgical intervention. Patients with either infantile XT or early X(T) may spontaneously resolve over time.