Comparison of Bilateral Lateral Rectus Muscle Insertion in Patients Who Have Intermittent Exotropia with Non-Dominant Eye
Seung Ah Chung, MD; Jong Bok Lee, MD
Department of Ophthalmology, Ajou University School of Medicine
Suwon, South Korea
Introduction: Two third of patients with concomitant intermittent exotropia (IXT) have a non-dominant eye. We aimed to investigate whether the lateral rectus muscle insertion would make any difference between two eyes in patients who have IXT with a non-dominant eye.
Methods: One hundred nine patients who underwent bilateral lateral rectus recession for the basic type of IXT were included: 81 with a non-dominant eye and 28 with equal dominance. The distance between the corneal limbus and the midpoint of lateral rectus muscle insertion was measured intraoperatively using calipers. The arc of contact was calculated as the difference in distances between the measured insertion and the estimated equator based on axial length and cornea diameter. The distances in each eye were compared according to the dominancy.
Results: Mean limbus-insertion distance of lateral rectus muscle was 6.12 ± 0.74 mm, and estimated arc of contact was 5.71 ± 1.04 mm. There was no difference in the limbus-insertion distance according to the dominancy. Forty six of 81 patients with a non-dominant eye (56.8%) had the longer estimated arc of contact by 0.5 mm or more in the non-dominant eye (28.6% in patient with equal dominance, P=0.046).
Discussion: The arc of contact of lateral rectus muscle in the non-dominant eye was more frequently longer than that in the fixating eye. This suggests that the dominancy may be determined by structural difference in both eyes as well as sensory function.
Conclusion: We should be aware of this difference when planning surgery for IXT in patients with a non-dominant eye.
References: 1. Lee JY, Lee EJ, Park KA, Oh SY. Correlation between the limbus-insertion distance of the lateral rectus muscle and lateral rectus recession surgery in intermittent exotropia. PLoS One 2016;11:e0160263.
2. Kim SH, Choi YJ. Effects of unilateral lateral rectus recession according to the tendon width in intermittent exotropia. Eye (Lond) 2006;20:785-8.
3. Cho YA, Kim SH. Role of the equator in the early overcorrection of intermittent exotropia. J Pediatr Ophthalmol Strabismus 2009;46:30-4.