Age-related distance esotropia (ARDE) is thought to be caused by sagging eye syndrome. Sagging of the lateral rectus derives from the naturally occurring aging process and induces excyclotorsion of the eye. To date, no study has compared the cyclodeviation in ARDE with that in the age-matched individuals without strabismus. This study aimed to measure the objective cyclotorsion on fundus photographs of ARDE patients and compare the findings with those for normal age-matched individuals. Objective cyclotorsion was measured by determining the disc-to-fovea angle (DFA) on fundus photographs, which were obtained from two groups: 38 consecutive patients with ARDE (age, 74.1 ± 7.9 years), 76 normal age-matched controls (age, 73.9 ± 8.1 years). DFA in ARDE patients was not different from that in the control group (Welch's t-test: ARDE vs Control, right eye; 7.7° ± 2.9° vs 6.8° ± 3.9°, p = .18. Left eye; 10.0° ± 4.5° vs 9.4° ± 3.6°, p = .54. Sum of both eyes; 17.6° ± 5.8° vs 16.2° ± 4.7°, p = .21). These findings suggest sagging of the lateral rectus is not the sole cause of ARDE. Another aging-related factor, such as decreased phoria adaptation, might also be responsible for ARDE.
Keywords: Age-related distance esotropia; objective cyclotorsion; phoria adaptation; sagging eye syndrome.