Femto-LASIK. Pulsewidth: Ultrashort-pulse micro- machining can make sub- wavelength holes. micromachining

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1 All-laser laser LASIK (Femto( Femto-LASIK) Femto-LASIK 台 大 眼 科 王 一 中 IntraLase 2/1 Perfect Vision Ziemer (DaVinci) Carl Zeiss Meditec Pulsewidth: Femtosecond laser (Nd:Glass)) 153 nm (near infrared) Each pulse of focused laser light lasts approximately 1-13 seconds (1 femtoseconds) Ultrashort-pulse micro- machining can make sub- wavelength holes. Because high-order nonlinear-optical processes are responsible for cutting, there is effectively a threshold for cutting. This means that careful control of the intensity can yield a very small hole. Beam profile Size of hole Threshold for cutting Beam focused to l/2 x Long- vs. short-pulse micromachining Long pulse Short pulse Holes as small as ~1 nm have been created. Clark-MXR web site 1

2 A Femtosecond-Pulse Drilled Hole Sub-micron holes in stainless steel 54 nm Eric Mazur, Harvard University Eric Mazur, Harvard University Ultrafast machining set up Traditional al LASIK - Microkeratom rokeratome Not much to it! Eric Mazur, Harvard University FEMTO-LASIK 2

3 In this oblique dissection line, circles mark three areas of differing morphology in the layers between the epithelium on top to the endothelium at bottom. Bubbles resulting from a single shot from a femtosecond laser are shown. Bubbles are merged from overlapping shots. Notice the disruption in the bubble from the merged bubbles. Cavity resulting from multiple femtosecond laser shots. 3

4 Complication of Microkeratome Buttonhole Flap tear Epithelial defect Incidence of Mechanical Microkeratome Complications Buttonhole Flaps.1% (lowest) Incomplete/Partial Flaps.1-.5%.5% Epithelial Defects 1-5% 1 Epithelial Ingrowth 2% DLK 1-4% 1 Femtosecond Pros: Safety Complications Nordan/Slade Christenbury Will Femtosecond Pros: Precision Aberrations Number or Cases Free Cap Buttonhole Flap Incomplete/ Partial Flap 4

5 Microkeratomes: : Meniscus Flap Mechanical vs IntraLase Flaps Flap thickness Mechanical al vs. Intralase Flap Stromal Thickness Mikrokeratom LASIK Flap FEMTO-LASIK Flap, Intralase Images provided by Dr. Richard Foulkes IntraLASIK Thickness Profile *demonstrates better interface morphology Microkeratome Flap Thickness 5

6 Comparison of Mechanical and IntraLase FS Flap Thickness Femtosecond Pros Precision-Flap Thickness IntraLase vs Hansatome Flap Flap thickness is more predictable than with mechanical microkeratomes: Mean closer to predicted Smaller S.D. Smaller Range Microkeratome Flap Diameter Intralase Flap Diameter 6

7 Intralase Hinge Angle Femtosecond Pros Precision -Edge Configuration Corneal Sensitivity IntraLase vs. Hansatome: Randomized Prospective Study Dan Durrie,, MD Randomized prospective contralateral study 51 patients, 12 eyes Alcon CustomCornea OU One eye Hansatome,, one eye IntraLase, superior hinge OU Baseline data analyzed and verified as a statistically matched population Independent observer for post-op op exams Uncorrected Vision: Hansatome Uncorrected Vision: IntraLase 7

8 Post-op op UCVA vs. Pre-op BCVA: Hansatome Post-op op UCVA vs. Pre-op BCVA: IntraLase Post-op op UCVA vs. Pre-op BCVA: IntraLase 3 mo Predictability: Hansatome Predictability: IntraLase Intralase creates Fewer Aberrations HOA Preop to 3 months 8

9 Flap Induced Hyperopia (Manifest Refraction) Results: 1 Week Post Flap Lower Order Aberrations Results: 1 Week Post Flap Higher Order Aberrations In Conclusion, Customized IntraLASIK is the ultimate customized procedure.. IntraLASIK Histology (Rabbit).but, it s s not Perfect! Takes longer to perform more inflammation more expensive Nevertheless, its now more than 25% of US practice! 9

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11 Complications of Femtosecond Laser 藕 斷 絲 連 Unliftable flap Non-dissceted islands Suction loss Interference by gas bubbles Transient light sensitivity Keratitis (DLK) Transient Light Syndrome (Good Good Acuity Photophobia Syndrome) 原 因 不 明, 可 能 是 keratocyte 被 activate 造 成 iritis,scleritis scleritis,neuritis 沒 有 任 何 manifestation 類 固 醇 可 以 在 一 星 期 內 減 緩 症 狀 不 治 療 在 2-6 星 期 也 可 以 自 行 resolve Sun glasses during this period 1 KHz 15 KHz 3 KHz 6 KHz (95 s) (57 s) (3 s) (2 s) TLS at 3 KHz or 6 KHz Opaque Bubble Layers Interference by gas bubble In the anterior chamber From peripheral cornea Trabecular meshwork AC Bubble in the center during excimer laser ablation obscuring pupil margin Inability to fixation and tracking Wait for hours till absorption Opaque Bubble Layers Interference by gas bubble In the cornea Disappear after lifting no problem Deep opaque bubble layers (in the superficial layer of stromal bed) not released after flap lifting resolve 3-45 minutes Depends on pupil tracking and iris registration 11

12 Button Hole Thin flap during lift Wait for months recut with 4-5 μm m deeper Suction Loss During the propagation of the lamellar interface Reapply suction ring with the same settings During the side cut Reapply the suction ring and decrease the diameter of the side cut by 1 mm Unliftable flap 藕 斷 絲 連, 常 常 是 兩 眼 都 會 發 生, 原 因 不 明 Forcefully open Torn flap and irregular surface Forcefully open keratocyte activation Interface haze Interface haze steroid sensitive resolved within 3-4 months no effect on vision 真 的 分 不 開 蓋 回 去 等 一 個 月 用 blade micrkeratome 重 切 ( 更 深 5μm) Non-dissected islands Opaque bubble layer 跑 到 flap 裡 面, 甚 至 在 cornea 和 applanation plate 間 bubble 會 跑 得 比 laser 快, 而 影 響 雷 射 的 進 行 和 對 焦 造 成 雷 射 切 割 不 能 完 成 如 果 florcefully dissect 造 成 central island-like like effect 大 部 分 原 因 是 因 為 thin flap 或 原 先 cornea 有 傷 口, 例 如 RK,PKP,corneal scar,ck 以 前 的 LASIK 傷 口 也 會 造 成 同 樣 的 結 果,bubble, 跑 到 以 前 LASIK 的 interface 蓋 回 去 等 6 個 星 期 用 blade micrkeratome 重 切 ( 更 深 5mm) Keratitis Intracorneal lens with femtosecond laser for hyperopia treatment Localized around the edge of the flap 2-77 days after flap creation Photophobia 像 DLK,inflammation 在 flap edge 內 但 是 治 療 和 結 果 和 DLK 是 一 樣 的 12