Do rectus muscle parameters vary between emmetropes and myopes?

Area of Science:

• Ophthalmology
• Ocular anatomy
• Myopia research

Background:

• Myopia is a prevalent refractive error with complex etiologies.
• Understanding ocular muscle characteristics may offer insights into myopia development.

Purpose of the Study:

• To investigate differences in thickness, area, and insertion site of medial (MR) and lateral (LR) rectus muscles between emmetropes and myopes.
• To explore potential associations between ocular muscle parameters and myopia.

Main Methods:

• Swept-source optical coherence tomography (OCT) was used to image MR and LR muscles in 80 participants (14 emmetropes, 66 myopes).
• Custom software analyzed muscle thickness, area, and insertion distance from the limbus.
• Measurements included muscle thickness at 1-3 mm periphery and muscle area from the insertion site.

Main Results:

• The medial rectus (MR) muscle was significantly thinner and occupied less area than the lateral rectus (LR) muscle in all participants.
• MR muscle thickness increased gradually from the insertion site to peripheral locations.
• Myopic individuals exhibited significantly thinner MR muscles compared to emmetropes; no significant difference was observed in LR muscles.
• Muscle area and insertion distance did not differ significantly between emmetropes and myopes for either horizontal rectus muscle.

Conclusions:

• Medial rectus (MR) muscle parameters, specifically reduced thickness and area, are significantly associated with myopia.
• These findings suggest a potential role for MR characteristics in myopia, warranting further investigation into their clinical relevance and impact on myopiagenesis and progression.