Abstract
Purpose: :
The anatomy of the marginal lid conjunctiva has received increased attention because it contains the so called lid-wiper. The lid-wiper serves to spread the pre-ocular tear film and epitheliopathy of the lid-wiper appears as a sensitive early indicator of a dry eye syndrome. In order to more specifically localize the lid-wiper, we defined the morphological subdivisions of this region.
Methods: :
Conjunctival whole-mount specimens including the lid margin from ten human body donors were analysed in serial histological sections and compared to in-vivo confocal microscopy of four eyes with a Heidelberg retina tomograph (HRT II) and attached Rostock cornea module.
Results: :
Several zones of different morphology occur at the inner border of the upper and lower lid. At the meibomian gland orifices the stratified squamous keratinized epithelium becomes para-keratinized with pyknotic nuclei in the superficial layers. This zone stains intensively with Masson-Goldners stain and increasingly dissolves into separate para-keratinized cells towards the conjunctival side. It represents the muco-cutaneous junction and also meets the historical description of Marx. In HRT, this zone occurs as a distinct line. Proximally from there on the epithelium increases in thickness (ca. 8-12 layers) forming a cushion-like structure of about 50-100µm thickness as measured in optical HT sections. Dermal papillae occur at the beginning of this zone but are gradually lost and the basement membrane level becomes flat. This zone continues for about 1-2mm and transforms into the epithelium of the subtarsal fold which has less cell layers (6-8) and cuboidal to columnar morphology until it is replaced by the usual 2-3 layered cuboidal tarsal conjunctival epithelium.
Conclusions: :
At the marginal conjunctiva the epidermis transforms via a para-keratinized muco-cutaneous junction (MCJ), that corresponds to the line of Marx, into the multi-layered epithelial cushion-like structure of the lid-wiper . The lid-wiper occurs not only at the upper but also at the lower lid and is, at the inner lid border, directly apposed to the cornea.
Keywords: cornea: tears/tear film/dry eye • anatomy • conjunctiva