HISTOPATHOLOGIC AND ELECTRON-MICROSCOPIC FEATURES OF CORNEAL AND SCLERAL COLLAGEN-FIBERS IN OSTEOGENESIS IMPERFECTA TYPE-III

Background: This report describes the histopathologic and electron-mic roscopic features of an eye from a patient with osteogenesis imperfect a type ITT, Tn particular, the diameters of corneal stromal and sclera l collagen fibers were determined. Methods: The eyes of an 18-year-old white male with osteogenesis imperfecta type III were examined by lig ht and electron microscopy and the pathological features were compared with an age-matched control eye. Results: The cornea was clear. The s clera had a blue color and was moderately thinned, especially at the e quator. Light microscopy revealed absence of Bowman's laver. Transmiss ion electron microscopy confirmed complete absence of Bowman's layer w ithout evidence of scarring or inflammation. The collagen fibers of th e corneal stromal lamellae were about 25% narrower than in the control , but the cornea was otherwise unremarkable ultrastructurally. The col lagen fibers of the sclera were approximately 50% narrower than in the control and were much more uniform in size. Prominent portions of ela stic fibers, which are usually only present in a small number in the i nner portion of the sclera, were present throughout the sclera. Conclu sion: We propose that it is the uniformity of the scleral collagen fib ers which gives the sclera translucence, producing the blue color ofte n 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 exa mination of the eye in osteogenesis imperfecta type III.