Histopathologic and electron-microscopic features of corneal and scleral collagen fibers in osteogenesis imperfecta type III

Abstract

Background: This report describes the histopathologic and electron-microscopic features of an eye from a patient with osteogenesis imperfecta type III. In particular, the diameters of corneal stromal and scleral collagen fibers were determined.

Methods: The eyes of an 18-year-old white male with osteogenesis imperfecta type III were examined by light and electron microscopy and the pathological features were compared with an age-matched control eye.

Results: The cornea was clear. The sclera had a blue color and was moderately thinned, especially at the equator. Light microscopy revealed absence of Bowman's layer. Transmission electron microscopy confirmed complete absence of Bowman's layer without evidence of scarring or inflammation. The collagen fibers of the corneal stromal lamellae were about 25% narrower than in the control, but the cornea was otherwise unremarkable ultrastructurally. The collagen fibers of the sclera were approximately 50% narrower than in the control and were much more uniform in size. Prominent portions of elastic fibers, which are usually only present in a small number in the inner portion of the sclera, were present throughout the sclera.

Conclusion: We propose that it is the uniformity of the scleral collagen fibers which gives the sclera translucence, producing the blue color often observed clinically in osteogenesis imperfecta. Absence of Bowman's layer of the cornea did not interfere with the stability of the cornea in this case. This appears to be the first published pathological examination of the eye in osteogenesis imperfecta type III.