The Institute of Optics, University of Rochester, Rochester, New York, USA.
Invest Ophthalmol Vis Sci. 2011 Oct 17;52(11):8148-55. doi: 10.1167/iovs.11-7323.
To test the feasibility of intratissue refractive index shaping (IRIS) in living corneas by using 400-nm femtosecond (fs) laser pulses (blue-IRIS). To test the hypothesis that the intrinsic two-photon absorption of the cornea allows blue-IRIS to be performed with greater efficacy than when using 800-nm femtosecond laser pulses.
Fresh cat corneas were obtained postmortem and cut into six wedges. Blue laser pulses at 400 nm, with 100-fs pulse duration at 80 MHz were used to micromachine phase gratings into each corneal wedge at scanning speeds from 1 to 15 mm/s. Grating lines were 1 μm wide, 5 μm apart, and 150 μm below the anterior corneal surface. Refractive index (RI) changes in micromachined regions were measured immediately by recording the diffraction efficiency of inscribed gratings. Six hours later, the corneas were processed for histology, and TUNEL staining was performed to assess whether blue-IRIS causes cell death.
Scanning at 1 and 2 mm/s caused overt corneal damage in the form of bubbles and burns. At faster scanning speeds (5, 10, and 15 mm/s), phase gratings were created in the corneal stroma, which were shown to be pure RI changes ranging from 0.037 to 0.021 in magnitude. The magnitude of RI change was inversely related to scanning speed. TUNEL staining showed cell death only around bubbles and burns.
Blue-IRIS can be performed safely and effectively in living cornea. Compared with near-infrared laser pulses, blue-IRIS enhances both achievable RI change and scanning speed without the need to dope the tissue with two-photon sensitizers, increasing the clinical applicability of this technique.
通过使用 400nm 飞秒（fs）激光脉冲（蓝 IRIS）测试活体角膜内组织折射率整形（IRIS）的可行性。验证假设，角膜固有双光子吸收允许使用比 800nm 飞秒激光脉冲更高的效率进行蓝 IRIS。
死后获取新鲜猫角膜并切成六块楔形。使用 400nm 的蓝激光脉冲，100fs 脉冲持续时间，80MHz，以 1 至 15mm/s 的扫描速度在每个角膜楔形物中微加工相位光栅。光栅线宽为 1μm，间隔 5μm，在前角膜表面以下 150μm。通过记录写入光栅的衍射效率，立即测量微加工区域中的折射率（RI）变化。六小时后，对角膜进行组织学处理，并进行 TUNEL 染色以评估蓝 IRIS 是否导致细胞死亡。
以 1 和 2mm/s 的速度扫描会导致明显的角膜损伤，形成气泡和灼伤。在更快的扫描速度（5、10 和 15mm/s）下，在角膜基质中创建了相位光栅，结果表明这些光栅是纯 RI 变化，幅度从 0.037 到 0.021。RI 变化的幅度与扫描速度成反比。TUNEL 染色仅显示气泡和灼伤周围的细胞死亡。
蓝 IRIS 可以在活体角膜中安全有效地进行。与近红外激光脉冲相比，蓝 IRIS 增强了可实现的 RI 变化和扫描速度，而无需用双光子敏化剂掺杂组织，增加了该技术的临床适用性。
