Nada Ossama, Marian Anca, Tran-Khanh Nicolas, Buschmann Michael, Podtetenev Michel, Vidal François, Costantino Santiago, Brunette Isabelle
Maisonneuve-Rosemont Hospital Research Center, Montreal, Québec, Canada; Ain Shams University, Cairo, Egypt.
Maisonneuve-Rosemont Hospital Research Center, Montreal, Québec, Canada.
PLoS One. 2014 Jun 9;9(6):e98852. doi: 10.1371/journal.pone.0098852. eCollection 2014.
The goal of this study was to assess the effect of corneal hydration on the quality of the femtosecond laser (FSL) anterior lamellar cut. The Visumax FSL was used to dissect an 8-mm-diameter corneal flap in 22 eye bank corneas showing various levels of hydration. The intended ablation depth was 220 µm in all eyes, which corresponded to the maximal depth available with this laser. After the cut, the achieved ablation depth was measured using optical coherence tomography images, flap separability was assessed by measuring the mean force generated to detach the flap, and stromal bed roughness was assessed by measuring the Haralick contrast level on the 1000× scanning electron microscopy images of the ablated surfaces. The preoperative central corneal thickness ranged from 547 to 1104 µm (mean ± SEM: 833 ± 30 µm). A negative correlation was found between the level of corneal hydration and the ablation depth measured in the mid-peripheral cornea (r = -0.626, p = 0.003), the ablation being more superficial in more edematous corneas. The Haralick contrast also tended to increase as a function of corneal hydration (r = 0.416, p = 0.061), suggesting that laser ablation in edematous corneas results in rougher stromal surfaces. These results support the hypothesis that the quality of the FSL lamellar cut decreases as the level of corneal hydration increases. Although FSL is still considered in the field as the tool of the future for corneal dissection, a better understanding of the limits of this tool will be needed before it can replace manual or automated stromal dissection techniques in hydrated corneas.
本研究的目的是评估角膜水化对飞秒激光（FSL）前弹力层切割质量的影响。使用Visumax FSL在22只呈现不同水化程度的眼库角膜中制作直径8毫米的角膜瓣。所有眼睛的预期消融深度均为220微米，这与该激光可达到的最大深度相对应。切割后，使用光学相干断层扫描图像测量实际消融深度，通过测量分离角膜瓣产生的平均力来评估角膜瓣的可分离性，并通过测量消融表面1000倍扫描电子显微镜图像上的哈拉里克对比度水平来评估基质床粗糙度。术前中央角膜厚度范围为547至1104微米（平均值±标准误：833±30微米）。发现角膜水化程度与周边角膜中部测量的消融深度之间呈负相关（r = -0.626，p = 0.003），角膜水肿越严重，消融越浅。哈拉里克对比度也倾向于随着角膜水化程度的增加而升高（r = 0.416，p = 0.061），这表明水肿角膜中的激光消融会导致基质表面更粗糙。这些结果支持了随着角膜水化程度增加，FSL板层切割质量下降的假设。尽管在该领域FSL仍被视为未来角膜切割的工具，但在其能够取代水化角膜中的手动或自动基质切割技术之前，需要更好地了解该工具的局限性。
