Collagen fibrils of the vertebrate corneal stroma.

The collagen fibrils in adult corneal stromal lamellae from (a) bony fish and (b) cartilaginous fish, amphibians, reptiles, birds, and mammals have been shown to have diameters of about 170 and 240–250 A, respectively. The only observed exception was for a young sea lion which had a mean collagen fibril diameter of about 170 A. Also, the mean diameters of the collagen fibrils in the corneas of six animas (snake, magpic, chick, rat, guinea pig, and human) were studied as a function of their location within the stroma. Contrary to some reports it was shown that the size of the collagen fibrils was, within experimental error, constant across the width of the stroma. On some occasions, however, smaller-diameter fibrils were observed in close proximity to descemet's membrane. An age study of rat, guinea pig, and human cornea has shown that the mean collagen fibril diameter is about 170 A during fetal development and 240 A during the remainder of life.