Differences Between Single and Double Eyelid Anatomy in Asians Using Ultrasound Biomicroscopy.

PURPOSE The aim of this study was to clarify the differences between single and double eyelid structures quantitatively using an ultrasound biomicroscopy. DESIGN A single-center observational study. METHODS Upper eyelids of Asian volunteers were evaluated with a 50-MHz ultrasound biomicroscopy. The skin-orbicularis oculi complex (SOOC), levator aponeurosis, Mueller muscle-conjunctival complex, and tarsus were imaged at the eyelid crease in the double eyelid group and 7 mm above the eyelid margin in the single eyelid group. The SOOC was also measured 2 mm above the eyelid margin and 5 mm above the eyelid crease. RESULTS Forty-two upper eyelids of 42 subjects were studied. Mean SOOC thickness at the eyelid crease was 0.62 ± 0.12 mm in single eyelids and 0.57 ± 0.08 mm in double eyelids (P = 0.03). Mean SOOC thickness at 2 mm above the eyelid margin and 5 mm above the crease was not significantly different between single and double eyelids (P = 0.004 and P = 0.62, respectively). The levator aponeurosis, Mueller muscle-conjunctival complex, and tarsus measured 0.38 ± 0.12 mm, 0.86 ± 0.28 mm, and 10.84 ± 1.10 mm in single eyelids and 0.39 ± 0.14 mm, 0.88 ± 0.34 mm, and 10.61 ± 1.36 mm in double eyelids (P = 0.75, P = 0.81, and P = 0.54, respectively). CONCLUSIONS Single eyelids showed slightly thicker SOOC in the pre-tarsal area and at the eyelid crease but not 5 mm above the eyelid crease. The levator aponeurosis, Mueller muscle-conjunctival complex, and tarsus showed no differences in thickness.