Anatomic Studies of "A" and "V" Strabismus as Assessed by Magnetic Resonance Imaging

Abstract

Abstract: : Purpose:To evaluate vertical displacement of the horizontal rectus muscles in patients with "A" and "V" strabismus as well as in normal subjects with no strabismus,using magnetic resonance imaging (MRI).. Methods:A total of 103 subjects who underwent MRI scans were enrolled. The study group comprised 46 patients with "A" and "V" strabismus( V–XT:22, A–XT:18, A–ET: 6) and 57 normal subjects. The presence or absence of vertical displacement of the horizontal muscles was assessed by measuring the difference in the horizontal plane between the lower margins of the muscles, using a scale placed on the imaging film of coronal sections as reference. Results:Vertical displacement consistent with the theory of "A" and "V" strabismus was present in 27 (58.7 %) of the 46 patients with "A" and "V" strabismus. Vertical displacement of the horizontal rectus muscles was found in 17 (29.8%) of the 57 normal subjects. The difference was significant (p<0.001). Conclusions:Our results suggest that vertical displacement of the horizontal rectus muscles has important role in the development of "A" and "V" strabismus.

Keywords: strabismus: etiology • anatomy • extraocular muscles: structure