| Keratoconus is an autosomal recessive inheritant disease, charactered by cornea distension. The center part of cornea extends anteriorly to form a conus, which deforms the cornea. Cornea edema, thickening and scar happen in serious patients, and cause reduced bilateral visual acuity. In the final phrase it can only be treated by cornea transplantation. In 1748, Mauchart was the first to describe the disease in details. In 1933,Zongxian Luo also reported such disease. Typical keratoconus happens in teenages, and gradually progressed. Its onset can be found in any age, with very few cases are congenital. Recently there are many hypothesis about the etiology of keratoconus such as collage, metabolism and developmental disorder, inheritance, pithelial themry and allergic themry. though there are so many hypothesis, its actual etiology is still unknown. The researches show that the substrate plays an important role in the development of keratoconus. Cornea substrate' s agenesis leads to the reduced solidity, which is possibly related to kearatoconus. There is still a lot to be researched on etilogy and early diagnosis of keratoconus.The typical triad syndrom of keratoconus histopathological changes are the thinning of corneal stroma, breakage of Bowman' s membrane, and iron deposit in the epithelial basement membrane. In the early stage, the main change is the breakage of Bowman' smembrane. The Descemet membrane and endothelial layer may also break, which result in corneal edema. Acid mucopolysaccharide is found to decrease in every layer of cornea. Iron deposit can be found in epithelial cells, basement membrane and Bowman membrane of keratoconus. In ultrastructural study, Bowman layer' s change is most obvious. It has focal deletion, with fibrous cells and epithelial basement membrane inserted into the broken area. Organells in the stroma cells have obvious changes. These changes will affect collagen translation and synthesis in stromal cells, so further research on corneal ultrastructure will help us know more of the etilology of keratoconus.Different collagen with different function distributes in layers of cornea. Different types of collagens interacts, their proportion may affect the aggregation of fiber, which may cause the instable of stroma. The reduced collagen or abnormal arrangement will cause the decreased mechanical resistance. The key to solve the problem is to research on collagen abnormal conformation' s gene.Researches show that P ig-h3, a protein inducible by transforming growth factor- f3 is related to many corneal diseases, especially in corneal degeneration and inherent diseases. P ig-h3 promote corneal cells' s binding to substrate in cellular adhesion and immigration during corneal fibrous substrate growth and development. When its qual ity and quant ity changes, that will affect corneal cells binding to stromal collagen, then lead to the reduced corneal stability. In the process of keratoconus, corneal mechanical resistance reduces. The function of 3 ig~h3 is going to be found out.With the widespread of corneal refractive surgery, early diagnosis of keratoconus is very important. Using corneal topography to screen subclinical keratoconus may avoid incorrectrefractive surgery. Using corneal topography to analyse the form of cornea can direct design of contact lens and localization of the bottom of cone to determine the graft' s position and size. Corneal topography is important to improve clinical therapeutic results and postoperational follow-up.To investigate the pathogenesis and early diagnosis of keratoconus, we study the disease from four aspects.Part I The study of Pathology , ultrastructure , iron and acid mucopolysaccharide in keratoconusObjective: To observe Pathology, ultrastructure, iron and acid mucopolysaccharide changes in keratoconus.Material and methods: 18 cases of keratoconus and 7 cases of normal cornea was stained by haematine-eosin, iron stain, alcian blue stain method and observed by transmit electron microscope and scanni...
|
PDF Full Text Request