DEMONSTRATION OF THE MUCOUS LAYER OF THE TEAR FILM BY ELECTRON-MICROSCOPY

  • 1 January 1985
    • journal article
    • research article
    • Vol. 26  (4) , 464-473
Abstract
The mucous layer on the ocular surface maintains the stability, spread, and coherence of the tear film and is essential for normal vision. In spite of its importance, the precise thickness and localization of mucus on the surface of the eye are not known because it is not preserved in conventional EM preparations. Two different methods to show mucus on the guinea pig cornea and conjunctiva. Mucous glycoproteins was precipitated by adding a quaternary ammonium compound, either cetylpyridinium chloride or hexadecyltrimethylammonium bromide, to aldehyde fixatives. This procedure stabilized the mucus over the goblet cells and adjacent epithelium, although the mucous layer was not preserved uniformly in other areas. Tannic acid intensely stained mucus precipitated by these methods and showed it to be 0.8 .mu.m thick on the cornea and 1.4 .mu.m thick on the conjunctiva. Specimens of cornea and conjunctiva were prepared by freeze substitution. This technique preserved the mucus in a smooth, uninterrupted layer. The thickness of the mucus was somewhat variable; it measured 1.0 .mu.m over the cornea and varied from 2.0 to 7.0 .mu.m over the conjunctiva because of the greater irregularity of the tissue. Apparently, mucus constitutes a considerable part of the precorneal tear film and its thicker than was recognized formerly.

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