Magnetic resonance imaging analysis of age-related distance esotropia in geriatric Indian subjects

Abstract

Purpose : Cross-sectional assessment of extraocular muscles (EOM) and adnexa by high-resolution surface coil orbital magnetic resonance imaging {(MRI), 1.5T Seimens Symphony} was performed in symptomatic Indian geriatric subjects with small-angle horizontal diplopia at distance, diagnosed as having age-related distance esotropia (ARDE). These MRI parameters was compared with similar image derivations in age matched asymptomatic and younger subjects.

Methods : 9 ARDE subjects (18 orbits) of average age 77.2±3.6 years (8 males) were imaged fixating at a central target. 2mm thick contiguous quasi-coronal image planes perpendicular to the orbital axis were analysed for EOM pulley locations, EOM cross sections and LR-SR band length while quasi-sagittal and axial planes were used to measure rectus EOM length, all by Image J software as per published norms. A comprehensive ophthalmic and neurological evaluation was performed in all subjects. The comparative control groups comprised 10 age matched asymptomatic subjects (20 orbits) of average age 67±4.7 years (7 males)–Group 1; 13 middle-aged subjects (26 orbits) of average age 48±4.7 years (7 males)–Group 2 and 12 young subjects (24 orbits) of average age 26±7.8 years (6 males)–Group 3.

Results : The average LR-SR band length in Group 1, 2 and 3 respectively were 12.8±3.2mm, 10.3±1.7mm and 8.7±1.8mm as compared to 14.4±2.8mm in the ARDE group (p=0.06, ≤0.0001, ≤0.00001). The angulation of the long axis of the lateral rectus (LR) muscle to the globe vertical axis was 23±7.4^o (Group 1), 7.5±8.8^o (Group 2) and 1.2±7.9^o (Group 3) as compared to 22.4±11.3^o in the ARDE group (p=0.8, ≤0.0001, ≤0.00001). The rectus EOM length was similar in all groups. Unilateral LR-SR band rupture was observed in one ARDE subject (Figure 1A-E).

Conclusions : The significant rectus EOM elongation and characteristic LR-SR band rupture observed in 2/3^rd cases of ARDE patients in the Caucasian population was not observed in a similar symptomatic geriatric Indian cohort. However, age-related progressive LR-SR band lengthening and increased angulation of the LR muscle to the globe probably accounted for the loss of LR functioning as an abductor at distance and consequent ARDE (Figure 2A-E).

This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.

 

Figure 1A-E: MRI montage demonstrating unilateral left LR-SR band rupture in an ARDE subject

 

Figure 2A-E: MRI montage demonstrating marked bilateral angulation of the LR muscle to the globe in an ARDE subject