The purpose of this study was to evaluate elasticity and viscoelasticity in the anterior and deeper stromal regions of the cornea after cross linking with three different protocols using atomic force microscopy (AFM) through indentation. A total of 40 porcine corneas were used in this study and were divided into 4 groups (10 corneas per group): control (no treatment), Dresden (corneal epithelial debridement, riboflavin pretreatment for 30 minutes and a 3mw/cm2 for 30 minutes UVA irradiation), accelerated (corneal epithelial debridement, riboflavin pretreatment for 30 minutes and a 30mw/cm2 for 3 minutes UVA irradiation), and genipin (corneal epithelial debridement and submersion of anterior surface in a 1% genipin solution for 4 hours). Elasticity and viscoelasticity were quantified using AFM through indentation for all corneas, for the anterior stroma and at a depth of 200μm. For the control, Dresden, accelerated, and Genipin groups, respectively, the average Young’s modulus for the anterior stromal region was 0.60±0.58MPa, 1.58 ±1.04MPa, 0.86±0.46MPa, and 1.71±0.51MPa; the average for the 200μm stromal depth was 0.08±0.06MPa, 0.08±0.04MPa, 0.08±0.04MPa, and 0.06±0.01MPa. Corneas crosslinked with the Dresden protocol and genipin were significantly stiffer than controls (p<0.05) in the anterior region only. For the control, Dresden, Accelerated, and Genipin groups, respectively, the average calculated apparent viscosity for the anterior stroma was 88.2±43.7kPa-s, 8.3±7.1kPa-s, 8.1±2.3kPa-s, and 9.5±3.8kPa-s; the average for the 200μm stromal depth was 35.0±3.7kPa-s, 49.6±35.1kPa-s, 42.4±17.6kPa-s, and 41.8±37.6kPa-s. All crosslinking protocols resulted in a decrease in viscosity in the anterior region only (p<0.05). The effects of cross-linking seem to be limited to the anterior corneal stroma and do not extend to the deeper stromal region. Additionally, the Dresden and genipin protocols seem to produce a stiffer anterior corneal stroma when compared to the accelerated protocol.
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机译：这项研究的目的是通过原子力显微镜（AFM）通过压痕与三种不同的方案交叉链接后，评估角膜前部和深层基质区域的弹性和粘弹性。这项研究总共使用了40个猪角膜，分为4组（每组10个角膜）：对照组（不治疗），德累斯顿（角膜上皮清创术，核黄素预处理30分钟和3mw / cm sup 2） 进行30分钟的UVA照射），加速（角膜上皮清创，核黄素预处理30分钟和30mw / cm 2 进行3分钟的UVA照射）和genipin（角膜上皮的清创术和浸没）在1％的Genipin溶液中浸泡4小时）。使用AFM通过压痕量化所有角膜，前基质和200μm深度的弹性和粘弹性。对于对照组，德累斯顿组，加速组和Genipin组，前间质区域的平均杨氏模量分别为0.60±0.58MPa，1.58±1.04MPa，0.86±0.46MPa和1.71±0.51MPa。 200μm基质深度的平均值为0.08±0.06MPa，0.08±0.04MPa，0.08±0.04MPa和0.06±0.01MPa。仅使用前部区域，通过Dresden方案和Genipin交联的角膜明显比对照组硬（p <0.05）。对于对照组，德累斯顿，加速和基尼平组，前基质的平均计算表观粘度分别为88.2±43.7kPa-s，8.3±7.1kPa-s，8.1±2.3kPa-s和9.5±3.8kPa -s; 200μm基质深度的平均值为35.0±3.7kPa-s，49.6±35.1kPa-s，42.4±17.6kPa-s和41.8±37.6kPa-s。所有交联规程仅导致前部区域的粘度降低（p <0.05）。交联的作用似乎仅限于角膜前基质，而没有扩展到更深的基质区域。另外，与加速方案相比，德累斯顿方案和genipin方案似乎产生更硬的角膜前基质。
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