Morphometry of extraocular muscles and investigation of their relationship with axial length of eye

Purpose: The extraocular muscles (EOM) within the orbit provide ocular motility. Knowing the morphometric properties of these muscles is of clinical importance because various pathologies can affect the orbit and its structures. This study aims to compare normative EOM thickness values across gender and age groups and to investigate the potential relationship between refractive errors caused by the eye's axial length (AL). Methods: A retrospective study was conducted on 120 males and 125 females over 20 years of age who underwent orbital magnetic resonance imaging (MRI) in the Department of Radiology. Interzygomatic line length (IZL) in 245 individuals, axial length in 490 eyes, and long-short diameters of the EOM in coronal sections were measured, and variations were investigated. Results: Three of the 11 EOM measurements were significantly larger on the left and one was significantly larger on the right (p < 0.05). AL was not significantly different between the sides (p˃0.05). AL, IZL, and 8 of the 11 EOM lengths were significantly larger in men (p < 0.05). Among the individuals divided into 20-year age groups, the EOM short diameters were smaller in individuals aged 20–39 compared to those in older age groups (p < 0.05). Conclusion: While normative EOM lengths may vary depending on gender, side of eyelid, and age, they have been shown to be unchanged in axial myopia or hyperopia. The information obtained may contribute to the diagnosis and treatment of orbital pathologies.