Relationships between tilt angles of rectus muscles and positions of rectus muscle pulleys in patients with sagging eye syndrome

Purpose To examine the relationship between the rectus muscle (RM) angle and RM pulley displacement in patients with sagging eye syndrome (SES) without myopia.
Study design Retrospective cross-sectional case series.
Methods High-resolution quasi-coronal magnetic resonance imaging (MRI) data from 20 orbits of ten Japanese patients with SES but without high myopia were analyzed. The patients had no abduction deficiency. The RM angles were measured between the major axes of the horizontal and vertical RMs relative to the vertical and horizontal planes, respectively. The positions of the RM pulleys relative to the center of the globe were analyzed as previously described.
Results The mean age of the patients was 75.8 ± 4.5 years (standard deviation). The average axial length was 23.6 ± 0.6 mm. The lateral rectus (LR) muscle angle (22 ± 6°) had moderate negative correlations with the inferior displacement of the inferior rectus (IR), superior rectus (SR), and LR pulleys (r =– 0.63,– 0.45, and– 0.45, respectively); however, no change was observed in the medial rectus (MR) pulley (r =– 0.41). No correlations were found between the angles of the SR (4 ± 8°), IR (– 13 ± 8°), and MR (– 1 ± 6°) muscles and the positions of the RM pulleys.
Conclusion Given the correlation between increased LR muscle angle and inferior displacement of adjacent RM pulleys in SES, the LR muscle angle may serve as a diagnostic clue, even when inferior displacement is not identifiable on MRI. Further confirmation in larger studies is warranted.