Using an automatic image analysis technique, we studied the characteristics of the collagenous fibers of the corneal stroma of keratoconus at different stages of development. The clear portions of keratoconus specimens were studied at three different levels: anterior, middle, and posterior. The parameters obtained were compared with those of a normal adult cornea with the purpose of determining which ultrastructural alterations were caused by the appearance and progression of keratoconus.