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首页> 美国卫生研究院文献>Biomedical Optics Express >Lowered threshold energy for femtosecond laser induced optical breakdown in a water based eye model by aberration correction with adaptive optics
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Lowered threshold energy for femtosecond laser induced optical breakdown in a water based eye model by aberration correction with adaptive optics

机译：通过自适应光学像差校正可降低水眼模型中飞秒激光引起的光学击穿的阈值能量

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摘要

In femtosecond laser ophthalmic surgery tissue dissection is achieved by photodisruption based on laser induced optical breakdown. In order to minimize collateral damage to the eye laser surgery systems should be optimized towards the lowest possible energy threshold for photodisruption. However, optical aberrations of the eye and the laser system distort the irradiance distribution from an ideal profile which causes a rise in breakdown threshold energy even if great care is taken to minimize the aberrations of the system during design and alignment. In this study we used a water chamber with an achromatic focusing lens and a scattering sample as eye model and determined breakdown threshold in single pulse plasma transmission loss measurements. Due to aberrations, the precise lower limit for breakdown threshold irradiance in water is still unknown. Here we show that the threshold energy can be substantially reduced when using adaptive optics to improve the irradiance distribution by spatial beam shaping. We found that for initial aberrations with a root-mean-square wave front error of only one third of the wavelength the threshold energy can still be reduced by a factor of three if the aberrations are corrected to the diffraction limit by adaptive optics. The transmitted pulse energy is reduced by 17% at twice the threshold. Furthermore, the gas bubble motions after breakdown for pulse trains at 5 kilohertz repetition rate show a more transverse direction in the corrected case compared to the more spherical distribution without correction. Our results demonstrate how both applied and transmitted pulse energy could be reduced during ophthalmic surgery when correcting for aberrations. As a consequence, the risk of retinal damage by transmitted energy and the extent of collateral damage to the focal volume could be minimized accordingly when using adaptive optics in fs-laser surgery.
机译：在飞秒激光眼科手术中，组织剥离是通过基于激光诱导的光学击穿的光致破裂实现的。为了最大程度地减少对眼睛的附带损害，应优化激光手术系统，使其朝着尽可能最低的光破裂能量阈值发展。然而，即使在设计和对准期间非常注意最小化系统的像差，眼睛和激光系统的光学像差也会使辐照度分布偏离理想轮廓，这会导致击穿阈值能量的增加。在这项研究中，我们使用了带有消色差聚焦透镜和散射样品的水室作为眼睛模型，并确定了单脉冲等离子体传输损耗测量中的击穿阈值。由于像差，水中分解阈值辐照度的精确下限仍然未知。在这里我们表明，当使用自适应光学器件通过空间光束整形来改善辐照度分布时，可以大大降低阈值能量。我们发现，对于均方根波前误差仅为波长三分之一的初始像差，如果通过自适应光学将像差校正到衍射极限，则阈值能量仍可降低三倍。发射的脉冲能量在阈值的两倍处降低了17％。此外，与未经校正的球形分布相比，在经过校正的情况下，脉冲序列在5 kHz重复频率下击穿后的气泡运动显示出更大的横向方向。我们的结果表明，在矫正像差时，在眼科手术中如何同时减少施加和传输的脉冲能量。因此，在fs激光手术中使用自适应光学器件时，可以将因传输能量造成的视网膜损害的风险以及对局灶体积的附带损害的程度降至最低。

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