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H Bissen-Miyajima, M Miyake-Kashima, Y Taira, K Minami, M Nakamura; Stage I and II Diffuse Lamellar Keratitis: Its Histopathological Changes in Endotoxin-treated Rabbit Eyes . Invest. Ophthalmol. Vis. Sci. 2002;43(13):2102.
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Purpose:To understand the pathophysiology of diffuse lamellar keratitis (DLK) following laser in situ keratomileusis (LASIK), we investigated the histopathological changes of mild DLK using endotoxin in rabbit eyes. Methods:Thirty-eight eyes of 22 pigmented rabbits were used in this study. After making corneal flap, 6 eyes of control group received balanced salt solution on the corneal bed, and 32 eyes of endotoxin group received Pseudomonas aeruginosa endotoxin with 4 different concentrations (10pg/ml, 1ng/ml, 100ng/ml, 10µg/ml). Seven days postoperatively, all the eyes were examined with slit-lamp microscope and classified DLK according to the staging reported by Linebarger. Then the eyes were enucleated and the histological specimens were stained with Hematoxylin-Eosin and Toluidine Blue. Results:The appearance of DLK-like changes in the interface of corneal flaps were precisely examined and classified. In control group, 1 eye (17%) showed stage I DLK. In endotoxin groups, 10 eyes (31%) showed stage I and 2 eyes (6%) showed stage II DLK. The occurrence and the stage of DLK were not dependent on the endotoxin's concentration. Most pathological changes were found in stromal flap area. Activated keratocytes were observed in 5 eyes (83%) in control group and 20 eyes (63%) in endotoxin groups. Disorganized collagen fibers were also found in 5 eyes (83%) in control group and 18 eyes (56%) in endotoxin groups. These changes were affected by neither existence of DLK nor treatment of endotoxin. On the other hand, the changes of epithelial cell layers were relatively small. Two eyes showed the thick and 2 eyes showed the thin layers, and others kept original layers. Significant inflammatory reactions were not found even in the eyes with stage I and II DLK. Conclusion:These results suggested that mild DLK (stage I and II) might not induce the obvious histological changes at the interface of corneal flaps, such as invasion of inflammatory cells and accumulation of activated keratocytes. These changes seem to be a general healing process after corneal incision. Further investigations are needed to understand the histopathology of mild DLK.
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