Structural Changes in Rabbit Iris Following Excimer Laser Treatment

Refractive surgery has evolved with the advent of the excimer laser, which is capable of removing an accurate quantity of corneal tissue through photoablation. Many complications of excimer laser treatment including uveitis and relative papillary mydriasis are reported. So we aimed in this study to investigate the possible pathological effects of excimer laser on the iris tissue. This study included thirteen albino rabbits that were used and divided into 3 groups (1, 2, 3). Group 1 used as control group and groups 2, 3 were subjected to photorefractive Keratotomy (PRK) using the excimer laser unit, then decapitated after 24 h and four weeks, respectively. At the end of each experiment histopathological investigations were carried out and the iris tissue specimens were cut into semi-thin sections stained and were examined by both light and transmission electron microscopy. Many findings were demonstrated in groups 2 and 3 including the main layers of the iris which are the anterior stromal border, loose connective tissue blood vessels and the posterior epithelial cells. Mild changes occurred after 24 h which were aggravated after 4 weeks including degenerative changes in iris tissue, rupture of membrane of posterior epithelial cells, reduction of stromal cells and thickening of blood vessels. These changes were confirmed by electron transmission microscope in which the stromal cells were destroyed, fibroblasts were degenerated, disorganized melanocytes with the appearance of phagocytic and apoptotic cells. In conclusion these histopathological findings correlate with the clinical findings affecting the iris and pupil including mydriasis and uveitis.