Even though lenticular and retinal abnormalities seem to dominate the ophthalmologic picture in Marfan's syndrome, the cornea shows significant abnormalities consisting of a striking flattening and corneal astigmatism. The use of conjunctival biopsies followed by histochemical and electron-microscopic evaluation shows low morbidity but an excellent yield of diagnostic information on storage diseases, and an ectopic collagen may be the basis of at least one type of keratoconus. Much more work has to be done on defining the collagens of the human eye in embryologic, fetal, and postnatal stages under normal and pathologic conditions. The yield of such studies may be high for an understanding of such diseases as myopia, retinal detachment, and keratoconus.