Zonal differentiation of the epithelium including the lid wiper at the human lid margin

Abstract

Abstract Purpose The lid margin represent the “other end” of the tear film and appear critically important for ocular surface integrity, in addition to the glandular structures that produce the tears. It guarantees the thin expansion of the tear film with every blink and prevents the leakage of tears over the lid border. However, the differentiation of the lid margin zones is insufficiently known as yet. Methods The upper and lower lid margin in human whole‐mount specimens from ten body donors was investigated in serial section histology and compared to the image by in‐vivo confocal microscopy in four eyes with a Heidelberg retina tomograph and Rostock cornea module (RLSM). Results At the inner lid border, following the keratinised epidermis of the free lid margin, a narrow zone (100‐150µm) of para‐keratinised squamous epithelium represented the muco‐cutaneous junction (MCJ) corresponding to the line of Marx. This was followed by a much broader zone of epithelial thickening (50‐100µm) that formed a kind of cushion, reclined sharply at the inner lid border and represented the so called lid wiper which extended for about 1mm and finally transformed into the epithelium of the sub‐tarsal fold. MCJ and lid wiper extended all along the lid margin from nasal to temporal in upper and lower lid. Details of the epithelial structure as well as the underlying dermal papillae in these zones were also detectable by RLSM. Conclusion Due to its location and structure, the lid wiper appears as the structure that actually spreads the tear film and is distinct from the MCJ/line of Marx. Better knowledge of the lid margin structure and its different zones appears important for the understanding of ocular surface disease, in particular the dry eye disease.