Blinking and upper eyelid morphology

To explore blinking patterns and sagittal eyelid misalignment in the East Asian eye.

Forty-four participants (22 females; age 26 ± 5 years; 52% of East Asian ethnicity) were enrolled in this pilot study and subdivided, based on upper eyelid crease presence and extent, into single (n = 10), partial (n = 11) or double (n = 23) eyelid crease groups. Blinking was filmed surreptitiously with high-speed video simultaneously from an inferior temporal and frontal view. Spontaneous blink rate and type (incomplete, almost complete, or complete) were assessed over a 30 s period. Sagittal misalignment of the lids on closure was graded during complete spontaneous blinks, voluntary lid closure and voluntary maximal lid contraction (squeezing). A 0.15 µL drop of lissamine green was placed on the central lower lid margin and the number and type of blinks required to eliminate the drop informed complete palpebral apposition during blinking.

Mean ± SD blink rates averaged 16.9 ± 10.5 blinks/minute. The proportion of incomplete blinks was 83 ± 22% in single, 58 ± 35% in partial and 59 ± 30% in double eyelid crease groups. The sagittal misalignment of the lid margins during blinking was limited to approximately one-third of the lid margin width; this was similar for all lid morphologies and blink types. The lissamine green drop was eliminated only by voluntary maximal lid contraction, and was similar in all groups (p = 0.97).

Incomplete blinking and sagittal lid misalignment of the central eyelid margin predominate in habitual blinking, irrespective of lid morphology.