Zhang Zhen-Yong, Chu Ren-Yuan, Zhou Xing-Tao, Dai Jin-Hui, Sun Xing-Huai, Hoffman Matthew R, Zhang Xing-Ru
Eye and ENT Hospital, Shanghai Medical College, Fudan University, Shanghai, China.
Invest Ophthalmol Vis Sci. 2009 May;50(5):2147-53. doi: 10.1167/iovs.08-2400. Epub 2009 Jan 10.
To observe morphologic and histopathologic changes in the midperiphery of the rabbit cornea produced by femtosecond laser-assisted multilayer intrastromal ablation, determine whether this method may be used to correct myopia, and study how the cornea heals when the epithelium is not injured.
The right eyes of 10 New Zealand White rabbits were used for the experiments. A 60-kHz femtosecond laser delivery system was used, and three lamellar layers of laser pulses were focused starting at a corneal depth of 180 microm and ending at 90 microm from the surface, with each successive layer placed 45 microm anterior to the previous layer. In the interface of the applanation contact lens cone, a 6-mm diameter aluminum circle was placed at the center to block the laser, and ablation was limited to the midperiphery of the cornea. The laser settings were spot/line separation, 10 microm; diameter, 8.5 mm; energy for ablating the stroma, 1.3 microJ. Topography examination was used to document changes in corneal power. Light microscopy, transmission electron microscopy (TEM), and confocal microscopy in vivo were applied to observe changes in the cornea.
There was significant change in mean corneal power between baseline and postoperative month 3 (n = 8; P = 0.0001), with a decrease from 46.82 D to 44.42 D. There was no haze formation or refractive regression throughout the follow-up. There were no corneal structural abnormalities under light microscopy. Activated keratocytes and necrotic debris were visible under confocal microscopy. Fibroblasts were observed, and no myofibroblasts appeared under TEM.
Multilayer intrastromal ablation by the femtosecond laser with intact epithelium in the midperiphery of the corneal stroma can flatten the cornea without causing haze formation or refractive regression. This procedure allows the cornea to heal differently than when traditional corneal refractive surgery is performed and the epithelium is damaged.
观察飞秒激光辅助角膜基质层多层消融术对兔角膜中周边部造成的形态学和组织病理学变化，确定该方法是否可用于矫正近视，并研究上皮未受损时角膜的愈合情况。
选取10只新西兰白兔的右眼进行实验。使用60kHz飞秒激光传输系统，从角膜深度180微米处开始聚焦三层激光脉冲，至距角膜表面90微米处结束，每层依次向前一层前移45微米。在压平接触镜锥体的界面中心放置一个直径6毫米的铝圈以阻挡激光，消融仅限于角膜中周边部。激光设置为光斑/线间距10微米；直径8.5毫米；消融基质的能量1.3微焦。使用地形图检查记录角膜屈光力的变化。应用光学显微镜、透射电子显微镜（TEM）和活体共聚焦显微镜观察角膜变化。
基线与术后3个月之间平均角膜屈光力有显著变化（n = 8；P = 0.0001），从46.82 D降至44.42 D。随访期间无 haze形成或屈光回退。光学显微镜下未见角膜结构异常。共聚焦显微镜下可见活化的角膜细胞和坏死碎片。观察到成纤维细胞，TEM下未见肌成纤维细胞。
飞秒激光在角膜基质中周边部进行多层基质内消融，上皮完整，可使角膜变平，不引起 haze形成或屈光回退。该手术使角膜的愈合方式与传统角膜屈光手术且上皮受损时不同。
