Ophthalmology Clinic, Department of Medicine and Aging Sciences, University "G. D'Annunzio" of Chieti-Pescara, Chieti, Italy.
Cornea, Cataract and Refractive Surgery Unit, Vissum (Miranza Group), Alicante, Spain.
Invest Ophthalmol Vis Sci. 2024 Aug 1;65(10):9. doi: 10.1167/iovs.65.10.9.
The purpose of this study was to explore the optimal shape of customized lenticules for stromal lenticule addition keratoplasty (SLAK) for off-centered ectasia.
Two different methods to create ex vivo models of eccentric-keratoconus were investigated. Twelve human corneas were used to create model 1 by a hyperopic photorefractive keratectomy (PRK), and model 2 by masked phototherapeutic keratectomy (PTK) on the anterior corneal surface, whereas both types received myopic ablation of the posterior surface. Keratoconus models underwent a modified femtosecond laser (FSL) flap-cut to create stromal pockets. Sixteen human corneas underwent FSL dissection to obtain four lenticule types: type I (planar) and type II (negative) lenticules were used without modifications, whereas type III (customized-planar), and type IV (customized-negative) lenticules underwent further masked-PRK to obtain an asymmetric bow-tie shape. Topographic, aberrometric analysis, and anterior segment optical coherence tomography (AS-OCT) were performed in all recipient corneas before and after lenticule implantation.
Keratoconus model was successfully reproduced. Tomographic analysis showed a significant inferiorly decentered corneal steepening with coherent stromal thinning. Model 2 reproduced better the curvature of real keratoconus. Lenticules type I implantation induced a homogeneous corneal thickening, type III produced higher thickening in the inferior half of the cornea. Type II determined a maximal peripheral pachymetric increase, with a gradual reduction toward the center, and type IV presented an asymmetric peripheral thickening. Topographic assessment showed a cone apex flattening in all cases, but it was significantly higher in types II and IV. Customized lenticules improved significantly corneal surface regularity regarding types I and II.
The approach of customizing lenticules by increasing their asymmetry and tailoring the re-shaping effects, may improve SLAK outcomes in eccentric keratoconus.
本研究旨在探讨用于偏心性扩张性角膜病变的基质透镜加法角膜成形术（SLAK）的定制透镜的最佳形状。
研究了两种不同的方法来创建偏心性圆锥角膜的体外模型。使用 12 个人角膜通过远视光性屈光性角膜切削术（PRK）创建模型 1，在前角膜表面通过掩蔽光热角膜切除术（PTK）创建模型 2，而两种类型的后表面均接受近视消融。圆锥角膜模型进行了改良的飞秒激光（FSL）瓣切割以创建基质口袋。16 个人角膜进行 FSL 解剖以获得四种透镜类型：类型 I（平面）和类型 II（负）透镜未经修改使用，而类型 III（定制平面）和类型 IV（定制负）透镜则进一步接受掩蔽 PRK 以获得不对称的蝴蝶结形状。在所有受体角膜中进行了术前和术后的地形图、像差分析和眼前节光学相干断层扫描（AS-OCT）。
成功地复制了圆锥角膜模型。断层分析显示角膜明显向下偏心性变陡，伴有相干基质变薄。模型 2更好地复制了真实圆锥角膜的曲率。透镜类型 I 植入导致角膜均匀增厚，类型 III 导致下角膜一半的增厚增加。类型 II 导致最大的周边角膜增厚，向中心逐渐减少，而类型 IV 则呈现不对称的周边增厚。地形评估显示所有病例的圆锥顶点变平，但类型 II 和 IV 明显更高。与类型 I 和 II 相比，定制透镜显著提高了角膜表面规则性。
通过增加不对称性和定制重塑效果来定制透镜的方法，可能会改善偏心性圆锥角膜的 SLAK 结果。
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