Mechanical analysis of eyelid morphology

Area of Science:

• Biomechanical Engineering
• Dermatology
• Morphogenesis

Background:

• Double eyelids are characterized by a visible crease, distinguishing them from single eyelids.
• The formation of eyelid morphology is not fully understood from a mechanical perspective.

Purpose of the Study:

• To investigate the mechanical principles governing the formation of double eyelids.
• To identify critical factors influencing double-folded eyelid structures using computational modeling.

Main Methods:

• Utilized a modeling and simulation framework to study mechanical instabilities.
• Employed a minimalist model to analyze the wrinkle-to-fold transition.
• Developed refined models incorporating anatomical features of the eyelid.

Main Results:

• Identified three critical factors for double-folded eyelid formation: a weak crease line, specific skin thickness/width above the crease, and sufficient stiffness below the crease.
• Demonstrated that double-folded structures emerge when the eye opens beyond approximately 40% of the initial wrinkle wavelength.
• The mechanical model explains various eyelid morphologies.

Conclusions:

• The formation of double eyelids is a result of mechanical instability and specific geometric/material properties.
• Insights gained are applicable to cosmetic surgery, eyelid reconstruction, and understanding developmental processes.
• The study provides a mechanistic basis for eyelid folding relevant to both biological and artificial systems.