We performed morphologic and tissue culture studies on scleral tissues obtained from a nanophthalmic patient. Seen by light and electron microscopy, collagens in these unusually thick scleral tissues were arranged in irregularly interlacing bundles. The size of the collagen fibers was more variable than that observed in the controls. These abnormal fibers appeared twisted and, in some areas, were more closely packed. In tissue culture, scleral cells derived from the nanophthalmic patient synthesized proteins and collagen at a rate similar to that of normal control cells. The level of glycosaminoglycan produced, however, was markedly reduced. The modified glycosaminoglycan metabolism in scleral cells may be related to the abnormal packing of collagen bundles, which may in turn contribute to the thickening of sclera and the formation of nanophthalmos.