Change of the angle of strabismus during extreme lateral gaze: MRI study

Abstract

Purpose : To investigate how extreme lateral gaze affects the angle of deviation in comitant strabismus using 3D MRI.

Methods : 40 patients with comitant strabismus (exotropia, n=27; esotropia, n=13) was enrolled in this study. Participants had undergone orbital MRI (high resolution T2-weighted) in axial planes. Imaging was performed in central, right, and left gaze using the fixation target located at an angle of 40 degrees. MRI images were processed to analyze the angle of deviation using self-produced software based on Visual C++, which enabled 3D reconstruction.

Results : The mean angles of deviation were 21.1±12.3° and 20.8±11.7° (P=0.799) at central and lateral gaze in exotropia, respectively and 14.2±8.3° and 4.7±7.9° (P<0.001) in esotropia. When comparing the deviation angle in right and left gaze, seventeen patients (43.6%) showed an angle difference of more than 5 degrees, although the mean values were not statistically significant(P=0.645).

Conclusions : The angle of strabismus could be measured in central gaze as well as in extreme lateral gaze using MRI, and we found that the angles of strabismus were changed during lateral gaze. We expect that this angle difference can be useful in identifying the etiology of eye movement disorder and help surgeons plan a strabismus surgery.