Influence of Orbit Size and Interorbital Distance on Development and Outcome of Surgery for Intermittent Exotropia

ABSTRACT

PURPOSE: To evaluate the influence of orbital size and interorbital distance on the development and recurrence of intermittent exotropia. METHODS: We selected 55 intermittent exotropes(group A), 30 esotropes (group B), and 30 normal children(group C). Width and height of orbit, inner interorbital distance (IIOD), and outer interorbital distance (OIOD) in both orbits were measured with skull A-P(Anterior-Posterior) roentgenogram, and orbital index (IIOD/OIOD X 100) was calculated. The cephalometric results of the 6 recurrent exotropes and the 6 consecutive esotropes in group A were analyzed too. RESULTS: There is no significant difference in orbital height and orbital length among 3 groups. The IIOD was 25.0+/-3.86 mm in group A, 21.9+/-3.95 mm in group B, and 22.7+/-4.34 mm in group C. Mean OIOD was 100.3+/-9.75 mm in group A, 97.0+/-8.96 mm in group B, and 98.4+/-5.61 mm in group C. Orbital index was not different with the increase of age (p=0.23). It was greater in group A (25.0+/-2.79) than that in group B (22.9+/-2.66) and group C (23.1+/-2.79) (p<0.05). Orbital index of the orthophoric children after strabismus surgery in group A was 24.7+/-2.99. It was greatest in the 6 recurrent extropes (25.2+/-2.00) and was smallest in 6 the consecutive esotropes (23.5+/-1.69) CONCLUSIONS: Intermittent exotropia is more prevalenat in subjects with longer IIOD and greater OI, and esotropia is more prevalent in subjects with shorter IIOD and lower OI. The possibility of recurrence after surgery was high in patients with greater OI, and the possiibility of consecutive esotropia was high in patients with low orbital index.