The relationship between morphology and transparency in the nonswelling corneal stroma of the shark.

The ultrastructure of the corneal stroma of the spiny dogfish, Squalus acanthias, was studied in order to determine whether there was a morphologic basis for the alleged inability of the elasmobranch cornea to swell, and for the possibly related maintenance of corneal transparency when it is immersed in distilled water. The most apparent morphologic explanation for the nonswelling properties was the presence of "sutural fibers" which seemingly bound the anterior and posterior limits of the corneal stroma. The filamentous strands connecting collagen fibers within the lamellae were more pronounced than those seen in the corneal stroma of other species. Bowman's layer ivas found to comprise 15 per cent of the total stromal thickness, yet the structural organization of its collagen fibers was incompatible with the "lattice theory" for corneal transparency proposed by Maurice. Densitometric studies of a slit-lamp photograph of dogfish stroma showed that Bowman's layer scatters less light than the underlying tissue. Measurements of collagen fiber size and density were made at different depths within the corneal stroma in order to provide a basis for future physiologic studies, and to determine whether there might be an explanation for transparency consistent with the collagenous idtrastructure of both Bowman's layer and the more organized corneal stroma.