A Comparative study of retinal effects from continuous wave and femtosecond mode‐locked lasers

“…1 The titanium sapphire laser, a type of femtosecond pulse laser, has a wavelength in the near infrared level (range 780-1000 nm) and can be frequency doubled or frequency tripled to access wavelengths in the visible and ultraviolet spectral regions. 2 In refractive surgery, the femtosecond pulse laser is beneficial because it causes less bubble formation generated from shock waves than nanosecond or picosecond pulse lasers. 3 The femtosecond infrared titanium sapphire laser has been applied to enhance an in vivo gene delivery procedure.…”

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confidence: 99%

Application of femtosecond ultrashort pulse laser to photodynamic therapy mediated by indocyanine green

Sawa

2004

British Journal of Ophthalmology

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Backgrounds/aims: To evaluate treatment with high peak power pulse energy by femtosecond ultrashort pulse laser (titanium sapphire laser) delivered at an 800 nm wavelength for corneal neovascularisation using photodynamic therapy (PDT) mediated by indocyanine green (ICG). Methods: Using a gelatin solid as an in vitro corneal model, the safety of laser power was studied to determine if it degenerated gelatin with or without ICG. The authors then induced corneal neovascularisation in rabbit eyes by an intracorneal suturing technique. Fluorescein angiography was used to evaluate occlusion before PDT and 0, 1, 3, and 10 days after PDT. The authors performed light microscopy with haematoxylin eosin staining and transmission electron microscopy to determine thrombosis formation in the neovascular regions. Results: The threshold of peak laser power density ranged from 39 to 53 W/cm 2 . Laser irradiation was started 30 seconds after a 10 mg/kg ICG injection, and all irradiated segments were occluded at 0, 1, 3, and 10 days at 3.8 J/cm 2 . Light and electron microscopy documented thrombosis formation in the neovascular region. Conclusion: Femtosecond pulse laser enhanced by ICG can be used for PDT. Because of effective closure of corneal neovascularisation at a low energy level, the high peak power pulse energy of the femtosecond pulse laser might be more efficacious than continuous wave laser for use with PDT.

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“…Respective the com parability of the retina damage thresholds in the CW and fs regime it is found in literature, that there is a good correlation in ophthalmoscopic and angio graphic CW and fs thresholds for in vivo threshold determinations on rhesus monkeys, at a wavelength from 800 nm a repetition rate of 76 MHz and 130 fs pulses [13]. These studies are a conduction to our former results [14,15].…”

Section: Introductionmentioning

confidence: 62%

“…Studies have been shown, that changing the time interval between short laser pulses in a multiple pulse envelope could have an effect on limiting the area of thermal laser effect [18]. By delivering moderate energy per laser pulse with a pause interval between pulses that is greater than the thermal relaxation time of the target tissue, than the additive thermal effect is inexistent [13,19].…”

Section: Discussionmentioning

confidence: 98%

“…Concerning the comparability of the retinal thresh old potentials between CW and fs regime for in vivo threshold data on rhesus monkeys, a good correlation of the ophthalmoscopic and angiographic thresholds is quoted with a wavelength of 800 nm, a pulse rate of 120 fs and a repetition rate of 76 MHz [13]. Here they found the laser dosage thresholds and 95% confidence intervals for minimal visible damage at 24 h postexpo sure to be 5.9 mJ (5.23-6.60 mJ) and 5.84 mJ (5.23-6.58 mJ) for mode locked and CW exposures, respec tively.…”

Section: Discussionmentioning

confidence: 99%

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Comparison of retina damage thresholds simulating the femtosecond-laser in situ keratomileusis (fs-LASIK) process with two laser systems in the CW- and fs-regime

Sander¹,

Minet

Zabaryło

et al. 2012

Laser Phys.

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The femtosecond laser in situ keratomileusis procedure affords the opportunity to correct ametropia by cutting transparent corneal tissue with ultra short laser pulses. Thereby the tissue cut is gener ated by a laser induced optical breakdown in the cornea with ultra short laser pulses in the near infrared range. Compared to standard procedures such as photorefractive keratectomy and laser in situ keratomileusis with the excimer laser, where the risk potential for the eye is low due to the complete absorption of ultraviolet irradiation from corneal tissue, only a certain amount of the pulse energy is deposited in the cornea during the fs LASIK process. The remaining energy propagates through the eye and interacts with the retina and the strong absorbing tissue layers behind. The objective of the presented study was to determine and compare the retina damage thresholds during the fs LASIK process simulated with two various laser systems in the CW and fs regime.

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A Comparative study of retinal effects from continuous wave and femtosecond mode‐locked lasers

Abstract: Results are compared with published studies conducted at similar exposures. These nearly identical damage thresholds indicate a primarily thermal tissue damage mechanism. Comparative histopathology of acute and chronic lesions of both exposure types is also presented.

Cited by 16 publications

References 22 publications

Near-Infrared Ultrashort Pulse Laser Bioeffects Studies

Near-Infrared Ultrashort Pulse Laser Bioeffects Studies

Application of femtosecond ultrashort pulse laser to photodynamic therapy mediated by indocyanine green

Comparison of retina damage thresholds simulating the femtosecond-laser in situ keratomileusis (fs-LASIK) process with two laser systems in the CW- and fs-regime

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