Abstract
Purpose: :
The lid wiper is a structure at the inner eye lid border for the distribution of the thin preocular tear film. It can develop characteristic alterations (lid wiper epitheliopathy, LWE) in dry eye disease and contact lens wear. The exact morphology of the lid wiper that enables it to perform the proposed function is insufficiently known.
Methods: :
Conjunctival whole-mount specimens including the lid margin from ten body donors were embedded in paraffin. Serial sections were stained by H&E as well as by histochemical stains for goblet cells (PAS and Alcian blue) and by immunohistochemistry for the secreted goblet cell mucin MUC5AC.
Results: :
The lid wiper represented a thickened epithelium of typically 100µm thickness and 8-12 cell layers that formed a lip-like elevation at the inner lid border. It started at the crest of the lid border and was hence directly apposed to the globe. It was located proximal from the line of Marx that represents the surface of the muco-cutaneous junction.The lid wiper had a conjunctival structure and regularly contained goblet cells. These were identified in routine H&E histology by their roundish shape, faint staining and basal flat nucleus. These goblet cells contained neutral mucins as identified by the PAS reaction and also acidic mucins as identified by the Alcian blue stain. In immunohistochemistry the goblet cell stained positive for the secreted mucin MUC5AC which occasionally also stained a surface layer. A subpopulation of the goblet cells in the lid wiper were negative for MUC5AC. Goblet cells did not only occur at the surface but also in the depth of the epithelium. In serial sections it could be observed that such goblet cells were arranged along cryptal infoldings of the surface epithelium.
Conclusions: :
The lid wiper a the inner border of the human eye lid margin regularly contains goblet cells. This may constitute a novel built-in lubrication system that is necessary to in order reduce friction and prevent wounding of the lid wiper and cornea during its frequent gliding over the bulbar surface in the eye blink.
Keywords: cornea: tears/tear film/dry eye • microscopy: light/fluorescence/immunohistochemistry • anatomy