紫外线激发的角膜胶原交联术的动态安全

The new protocol and dynamic safety of UV-light activated corneal collagen cross-linking

目的 探讨紫外线引发角膜交联光动力学的关键问题,并以实验数据确认紫外线在核黄素内的吸收动力学理论.方法 耦合动力学方程的数值求解和分析公式推导出3个重要的参数：安全深度（z＊）,安全剂量（E＊）和交联时间（T＊）.经由对时间函数的核黄素吸收系数实验测量,核黄素的动态频谱显示光敏剂随时间的耗竭.角膜交联光动力是由7个关键参数决定：核黄素（B2）的消光系数,浓度,光敏剂穿透深度,紫外线的强度和剂量,照射时间以及角膜厚度.结果 核黄素浓度范围为0.1％-0.2％,穿透深度范围为0.02～0.04 cm,安全剂量范围为2.3～8.2 J/cm2.我们的数学模式显示,较高的紫外线强度和消光系数导致较短的表面交联时间,而角膜厚度大的交联时间也增加.安全深度为消光系数和光敏剂浓度的反比函数.结论 基于我们的新的发现,角膜胶原交联术的动态安全参数包括安全深度,安全剂量,交联时间,和安全光敏剂浓度,我们提出一个新的交联临床规范.

Objective To discuss the critical issues of the dynamics of UV-light-photoinitiated cross-linking in corneal collagen （CXL） and to confirm the dynamics of riboflavin （vitamin-B2） absorption under UV light.Methods Coupled dynamic equations are numerically solved and analytic formulas are derived for three critical parameters：the safe depth （z＊）,the safe dose （E＊） and the cross-linking time （t＊）.Time-dependent absorption of UV light due to the depletion of the initiator is measured and shown by a dynamic spectrum of riboflavin.The critical issues of CXL are explored by seven parameters：the extinction coefficient,concentration,the penetration depth of the riboflavin,the UV light intensity and dose,irradiation duration,and corneal thickness.Results The safe dose （E＊） has a wide range from 2.3 to 8.2 （J/cm2） for riboflavin concentrations of 0.1% to 0.2% and penetration depths of 0.02 to 0.04 cm.It is shown by mathematical modeling that a higher light intensity and extinction coefficient lead to shorter t＊ for a given cross-linking depth,while t＊ increases with corneal thickness （z＊）.The safety depth decreases as a function of the extinction coefficient and initiator concentration.Conclusion A new cross-linking protocol is suggested based on new findings,which include the safe depth （z＊）,the safe dose （E＊）,the cross-linking time （T＊）,and the safe riboflavin concentration.