Purpose: To examine the composition of scleral sulfated proteoglycans in three nanophthalmic eyes by electron microscopic histochemistry.
Methods: Scleral tissues from three cases of nanophthalmos were collected from the Niigata University Hospital for transmission electron microscopic examination. Sulfated proteoglycans were studied using the cuprolinic blue (CB) dye binding method in conjunction with enzymatic digestion.
Results: Compared with the controls, the nanophthalmic sclerae were much thicker, and the collagen fibrils showed a less orderly arrangement. Twisting or fraying of collagen fibrils was noted in some areas, and fine fibrous materials surrounded the abnormal fibrils. CB-positive proteoglycan filaments were found around the collagen fibrils and in the fine fibrous materials in the nanophthalmic specimens. The number of proteoglycan filaments was smaller than that in the normal specimens. After enzymatic digestion, the CB-positive filaments were identified as dermatan/chondroitin sulfate proteoglycans. Although the number of dermatan sulfate filaments in nanophthalmos sclerae was similar to that in the controls, there were many fewer chondroitin sulfate filaments.
Conclusion: A loss of chondroitin sulfate proteoglycan was observed in nanophthalmic sclerae. The alteration may be related to the abnormal organization of collagen fibrils and the onset of uveal effusion.