Medial rectus insertion site in cases of acute acquired comitant esotropia associated with excessive digital device usage.

Purpose: To compare the distance of the medial rectus muscle insertion to the limbus (DMIL) between patients with acute acquired comitant esotropia (AACE) associated with excessive digital device usage (EDDU) and exotropic patients.

Study design: Retrospective study.

Methods: The medical records of 72 eyes of 44 patients with EDDU were retrospectively analyzed. The DMIL was measured from the anterior part at the midpoint of the medial rectus muscle insertion into the anterior limbus using a caliper after dissecting the medial rectus muscle with two control sutures at 12 o'clock and 6 o'clock. The DMIL in the non-fixation eye was compared between 44 patients with AACE and 23 patients with exotropia.

Results: The mean daily EDDU was 6.5 ± 3.1 h. The mean cycloplegic refractive errors (spherical equivalent: SE) were - 3.18 ± 2.52 diopters (D) OD and - 3.03 ± 2.42 D OS. The mean DMIL in the 72 eyes of 44 patients with AACE associated with EDDU was 4.30 ± 0.66 mm. The difference in DMIL of non-fixation eyes between 44 AACE patients and 23 exotropic patients was significant (4.28 ± 0.65 mm vs. 5.28 ± 0.50 mm, p < 0.0001). However, the SE in 44 non-dominant eyes of AACE was - 3.08 ± 2.56 D, significantly stronger than - 1.22 ± 1.93 D in the 23 exotropic eyes (p = 0.008).

Conclusion: DMIL in patients with AACE associated with EDDU was significantly shorter. This anatomical anomaly may be an etiology of AACE associated with EDDU.