Histopathological changes in iridocorneal angle of inherited glaucoma in rabbits

Background: We examined morphologically the angular region of eyes affected by inherited glaucoma in rabbits genetically developed by crossbreeding in order to investigate the etiologic changes in the iridocorneal angle and to establish whether this strain of rabbit is a suitable animal model of goniodysgenetic glaucoma in humans. Methods: The angular regions of both normal and glaucomatous eyes from four rabbits having unilateral inherited glaucoma were observed with light and electron microscopy. Results: In the glaucomatous eyes angular region, the aqueous plexus corresponding to Schlemm's canal in humans was open and located far peripherally to the peripheral margin of the anterior chamber angler although the plexus of one glaucomatous eye was poorly developed with a small lumen. In the angular mesh work, which corresponds to the trabecular meshwork in humans, a thick abnormal tissue with round cells embedded in the extracellular matrix was located just beneath the plexus. A large amount of extracellular matrix of basal lamina-like material was observed in the thick tissue. In the normal eyes, the angular region consisted of well-developed trabecular sheets with neither a thick tissue nor accumulations of extracellular matrix in the angular meshwork. Conclusion: The findings observed in the glaucomatous eyes are much the same as those observed in goniodysgenetic glaucoma in humans, suggesting that this strain of inherited glaucoma rabbits is a suitable animal model of goniodysgenetic glaucoma in humans. The present study also supports the hypothesis that the presence of a thick subcanalicular tissue due to maldevelopment of the iridocorneal angle is one of the main causes of this type of glaucoma.