Horizontal Extraocular Muscle Insertion Site in Relation to Axial Length Using Swept-Source Anterior Segment OCT

Dina El-Fayoumi; Nermeen Bahgat; Mohamed Khafagy; Ragai Hatata; Dalia Sabry; Ghada Allam; Manal Ali Kasem; Sherin Sadek

doi:10.2147/OPTH.S262916

Horizontal Extraocular Muscle Insertion Site in Relation to Axial Length Using Swept-Source Anterior Segment OCT

Clin Ophthalmol. 2020 Oct 29:14:3583-3589. doi: 10.2147/OPTH.S262916. eCollection 2020.

Authors

Dina El-Fayoumi¹, Nermeen Bahgat¹, Mohamed Khafagy¹, Ragai Hatata², Dalia Sabry³, Ghada Allam³, Manal Ali Kasem³, Sherin Sadek²

Affiliations

¹ Ophthalmology Department, Faculty of Medicine, Cairo University, Cairo, Egypt.
² Ophthalmology Department, Faculty of Medicine, Fayoum University, Fayoum, Egypt.
³ Mansoura Ophthalmic Centre, Faculty of Medicine, Mansoura University, Mansoura, Egypt.

Abstract

Purpose: The purpose of this study was to correlate between the axial length of the globe and the insertion site of horizontal extraocular muscles using swept-source anterior segment optical coherence tomography (SS-ASOCT), with posing an equation to calculate the muscle insertion site from the axial length.

Methods: The study design was observational and cross-sectional. It was performed on 157 eyes of 157 healthy subjects. The distance of the medial rectus (MR) and the lateral rectus (LR) insertion sites from the limbus were measured using SS-ASOCT. The insertion sites' distances were correlated to the axial length (hypermetropes < 22.5 mm, myopes > 24.5). Correlation between numerical variables was done by Pearson's correlation coefficient and confirmed by linear regression analysis and scatter diagrams.

Results: The mean MR insertion site was 5.47 ± 0.19 mm in hypermetropes versus 5.68 ± 0.23 mm in myopes, whereas the mean LR insertion site was 6.81± 0.23 mm in hyperopes versus 7.08 ± 0.16 mm in myopes. The axial length showed a moderate positive, but significant, correlation to the insertional position for the medial and lateral rectus muscles (MR: r=0.417, p<0.001; LR: r=0.410, p<0.001).

Conclusion: Comparing the horizontal extraocular muscle insertion site to axial length using SS-ASOCT showed a significant positive correlation. The model equation for MR insertion: MR (mm) = 4.522 + 0.045 (AXL in mm) with an R = 0.437, R²= 0.191, F=12.071, P<0.001. The model equation for LR insertion: LR (mm) = 5.72 + 0.048 (AXL in mm) with an R = 0.438, R²= 0.192, F=12.116, P<0.001.

Keywords: AS-OCT; axial length; extraocular muscle insertion site; swept-source OCT.