Comparison of orbital structures between age-related distance esotropia and acute acquired concomitant esotropia using magnetic resonance imaging

Abstract This study aimed to compare orbital Magnetic Resonance Imaging (MRI) findings of age-related distance esotropia (ARDE) against age-matched healthy controls and acute acquired concomitant esotropia (AACE) patients. In this retrospective study, we analyzed the coronal MRI images of 9 ARDE patients, 8 AACE patients, 13 elderly controls, and 12 young controls. We measured the (1) displacement angles of the lateral rectus (LR) and medial rectus (MR), (2) LR tilting angle, (3) ratio of the MR to LR cross-sectional area, and (4) superior rectus downward displacement ratio (SDR). ARDE patients showed significant LR sagging compared to elderly controls by 5.1° (p = 0.048), with no significant LR displacement in AACE versus young controls. ARDE patients also had marked LR tilting compared to all groups. Additionally, the ARDE and AACE groups exhibited a greater MR/LR area ratio than their controls by 26% (p = 0.002) and 27% (p = 0.001), indicating a horizontal rectus muscle imbalance. Additionally, SDR values were higher in ARDE and elderly controls, suggesting a proximity of superior rectus muscle to the globe as an age-related alteration. The findings demonstrate that ARDE is characterized by unique orbital changes, particularly in the LR, distinguishing it from AACE. The observed increase in the MR/LR area ratio among the esotropia groups points to a horizontal rectus imbalance. These MRI-based insights advance our understanding of the distinct pathophysiological mechanisms underlying these conditions.