Abnormal Biorbital Angle in Children with Infantile Exotropia
Makiko Tsukui, MD; Teiji Yagasaki, MD; Yoshimi Yokoyama, MD
Department of Ophthalmology, Japan Community Health Care Organization Chukyo Hospital
1-1-10, Sanjyo, Minami-ku, Nagoya, Aichi, Japan
Introduction: Causative factors of the rare motility disorder, infantile exotropia, have yet to be determined. The purpose of this study was to investigate the relationship between abnormal findings of the orbit and causative factors of infantile exotropia.
Methods: Axial magnetic resonance imaging or computed tomography of the orbit in the transverse plane of the horizontal extraocular muscles was obtained in consecutive 26 infantile exotropic children without neurological disorder or
developmental delay. The opening angle between both lateral walls of the orbit was defined as the biorbital angle.
Results: The 106.0°±6.1°(SD) mean biorbital angle was significantly larger than the 94.2°±5.1° angle found in 129 normal infants (p<0.001; t-test). There were 19 (73.1%) out of 26 cases that were outside of the 95% confidence interval calculated for the 129 normal infants. Cases were divided into the intermittent (14 cases) and constant (12 cases) groups. There was no significant difference between the two groups for the mean biorbital angles (105.3°±6.1° vs. 102.5°±5.7°).
Discussion: The relationship between the morphology of the orbit and the presence of strabismus has yet to be definitively established. Exotropia is the major type of complicated strabismus found in 39-90.9% of craniosynostosis patients. When craniofacial surgery is performed without any strabismic procedure, exotropia will change to orthophoria or esotropia. This suggests that the larger biorbital angle may be one of the causative factors of infantile exotropia.
Conclusion: Children with infantile exotropia have a larger biorbital angle, with this anatomical abnormality potentially one of the causative factors responsible for exodeviation.
References: Morax S :Change in eye position after cranio-facial surgery. J Maxillofac Surg. 12:47-55,1984.