Non-linear Optical Collagen Cross-linking (NLO CXL) for Treatment of Keratoconus.

描述（由申请人提供）：本提案的主要目的是测试假设，通过非线性光学（NLO），利用飞秒激光（FS）光的双光子过程（TP）光激活核黄素，诱导完整的活兔子眼睛的空间分解（X-Y-Z）胶原交联（CXL）和机械硬化。最近的研究表明，370nm光（UVA）对核黄素的光激活可导致自由基诱导的胶原CXL的产生和角膜硬化，这对圆锥角膜患者有显著的治疗效果。虽然UVA和核黄素本身是无毒的，但UVA准直光路中自由基的产生会导致影响角膜内皮和晶状体的细胞损伤，导致大疱性角膜病变和潜在的白内障。为了避免这一并发症，已经滴定了UVA CXL的治疗给药，以限制前角膜自由基的产生，从而降低了CXL的疗效，并将治疗范围限制在角膜厚度大于400um的患者。我们建议用近红外FS激光代替准直的UVA光，在由聚焦透镜确定的空间分辨焦体积内诱导NLO CXL，将大大提高CXL的安全性和有效性。与常规UVA CXL相比，NLO CXL的主要优点包括：1)扩大了角膜CXL的应用范围，可用于治疗LASIK术后扩张患者等较薄的膨胀性角膜（<400 um），以及目前建议用于常规UVA CXL的其他角膜疾病，包括大疱性角膜病变、角膜溃疡和微生物感染；2)除前间质外的额外治疗区域，包括中、后、全层角膜间质；3)扩大使用由低紫外线（UVB和UVC）和可见光（400至780 nm）激活的替代光敏剂，这些光敏剂使用单光子方法对视网膜具有光毒性。为了验证这一假设，我们提出以下具体目标：1)适应当前活兔角膜NLO CXL FS交付系统,2)确定不同TP震源体积的影响,FS激光功率和扫描速度NLO CXL角膜加劲,3)确定的短期影响(1和3天)NLO CXL角膜CAF, 3 d角膜弹性模量,和细胞损伤和UVA CXL相比,4)确定的长期影响(1和6个月)NLO CXL角膜CAF, 3 d角膜弹性模量,比UVA CXL细胞修复。

DESCRIPTION (provided by applicant): The major objective of this proposal is to test the hypothesis that photoactivation of riboflavin by non- linear optical (NLO), two photon processes (TP) using femtosecond laser (FS) light induces spatially resolved (X-Y-Z) collagen cross-linking (CXL) and mechanical stiffening of intact, live rabbit eyes. Recent studies have established that photoactivation of riboflavin by 370 nm light (UVA) leads to the generation of free radical-induced collagen CXL and corneal stiffening that shows significant therapeutic benefits for patients suffering from Keratoconus. While UVA and riboflavin are themselves non-toxic, the generation of free radicals within the UVA collimated light path can lead to cellular damage affecting the corneal endothelium and crystallin lens, resulting in bullous keratopathy and potentially cataract. To avoid this complication, therapeutic administration of UVA CXL has been titrated to limit free radical generation to the anterior cornea, thus reducing the efficacy o CXL and limiting the therapeutic range to patients with affected corneas thicker than 400 um. We propose that replacement of collimated UVA light with near-infrared FS laser light to induce NLO CXL within a spatially resolved focal volume determined by the focusing lenses would greatly improve the safety and efficacy of CXL. Major benefits of NLO CXL compared to conventional UVA CXL would included: 1) expanded application of corneal CXL to the treatment of thinner ectatic corneas (<400 um) including post LASIK ectasia patients and other corneal disorders currently proposed for conventional UVA CXL including, bullous keratopathy, corneal ulceration and microbial infection; 2) additional treatment areas beyond that of the anterior stroma, including middle, posterior and full thickness corneal stroma; and 3) expanded use of alternative photosensitizers activated by low ultraviolet (UVB and UVC) and visible light (400 to 780 nm) that would be phototoxic to the retina using a single photon approach. To test this hypothesis we propose the following Specific Aims: 1) Adapt the current FS delivery system for live rabbit corneal NLO CXL, 2) Determine the effect of varying TP focal volume, FS laser power and scanning speed on NLO CXL corneal stiffening, 3) Determine the short-term affect (1 and 3 days) of NLO CXL on corneal CAF, 3D corneal elastic modulus, and cell damage compared to UVA CXL, 4) Determine the long-term affects (1 and 6 months) of NLO CXL on corneal CAF, 3D corneal elastic modulus, and cell repair compared to UVA CXL.