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This study investigated the anatomy of human eyelashes through analysis of root depth, angle, and spatial relationship. Four eyelids from Caucasian donors were obtained from fresh donors and four eyelids from Indian donors were obtained from eye bank calls. The Declaration of Helsinki was followed. For macroscopic analysis, eyelids were frozen. A vertical incision was made 4mm from the lid margin and dissection exposed the entire root of the eyelash to calculate the distance between the most inferior part of the eyelash and the follicle exiting the skin surface, using Image J software. For histological examination, the central third of the eyelids was cut out and fixed in 4% paraformaldehyde, paraffin, and stained with Azan stain. Image J software measured the angle between the epithelium of the skin and the lash root. Scanning electron microscopy was performed on eyelids fixed in 4% formalin, 2.5% tannic acid and 2% OsO4, subsequently dehydrated with ethanol, and dried. The specimens were coated with gold and examined with a Jeol scanning electron microscope. Statistical analysis was carried out using GraphPad Prism 9. Wilcoxon sum rank test was used to compare groups. Ninety upper eyelid eyelashes and 76 lower eyelid lashes were analysed. The mean depth of eyelash roots in the Indian upper eyelids was 2.3 ±0.38mm (1.6–3.04mm), and in the Indian lower eyelids was 1.9 ±0.2mm (1.4–2.2mm). The mean depth of eyelash roots in the Caucasian upper eyelids was 1.9 ±0.26mm (1.7–2.7mm), and in the Caucasian lower eyelids was 1.8 ±0.1mm (1.07–2.1mm), with a significant difference between the ethnic groups (p=0.007). The mean angle between the lash follicle root and skin epithelium was 75 ±11°, with no significant difference between the upper and lower eyelids, nor ethnic groups. Scanning electron microscopy revealed the mean difference between adjacent eyelashes was 493 ±78μm in Indians and 510 ±83μm in Caucasians (p=0.03). Differences in eyelash anatomy between Caucasians and Indians is evident. More study is required to reveal differences across a greater population, and between sex and more ethnicities.

New insights into the anatomy of the eyelashes with regard to ethnic differences against a clinical background.
Singh S, Hammer CM, Paulsen F.
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Lucy Osborne

The University of Manchester; Royal Preston Hospital, UK.

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