Optical side-effects of fs-laser treatment in refractive surgery investigated by means of a model eye

Ackermann, Roland; Kammel, Robert; Merker, Marina; Kamm, Andreas; Tünnermann, Andreas; Nolte, Stefan

doi:10.1364/boe.4.000220

Cited by 20 publications

(29 citation statements)

References 36 publications

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“…18 All such nonlinear side effects are detrimental because the increased breakdown length reduces the quality of surgical cuts or even harms tissue outside the focal spot, while extended cut patterns of enlarged, persistent disruptions decrease the visual quality of the eye. 19 Additionally, retinal safety limits may be affected due to the strong broadband SC generation.…”

Section: Introductionmentioning

confidence: 99%

Enhancing precision in fs-laser material processing by simultaneous spatial and temporal focusing

et al. 2014

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In recent years, femtosecond (fs)-lasers have evolved into a versatile tool for high precision micromachining of transparent materials because nonlinear absorption in the focus can result in refractive index modifications or material disruptions. However, when high pulse energies or low numerical apertures are required, nonlinear side effects such as self-focusing, filamentation or white light generation can decrease the modification quality. In this paper, we apply simultaneous spatial and temporal focusing (SSTF) to overcome these limitations. The main advantage of SSTF is that the ultrashort pulse is only formed at the focal plane, thereby confining the intensity distribution strongly to the focal volume and suppressing detrimental nonlinear side effects. Thus, we investigate the optical breakdown within a water cell by pump-probe shadowgraphy, comparing conventional focusing and SSTF under equivalent focusing conditions. The plasma formation is well confined for low pulse energies ,2 mJ, but higher pulse energies lead to the filamentation and break-up of the disruptions for conventional focusing, thereby decreasing the modification quality. In contrast, plasma induced by SSTF stays well confined to the focal plane, even for high pulse energies up to 8 mJ, preventing extended filaments, side branches or break-up of the disruptions. Furthermore, while conventional focusing leads to broadband supercontinuum generation, only marginal spectral broadening is observed using SSTF. These experimental findings are in excellent agreement with numerical simulations of the nonlinear pulse propagation and interaction processes. Therefore, SSTF appears to be a powerful tool to control the processing of transparent materials, e.g., for precise ophthalmic fs-surgery.

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Section: Introductionmentioning

confidence: 99%

Enhancing precision in fs-laser material processing by simultaneous spatial and temporal focusing

et al. 2014

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“…Similar RG effects have been observed after FS irradiation of test gels and contact lenses 3,9. A more comprehensive study that investigated the optical side effects of different FS flap creation patterns (raster, spiral, and random) on model corneas showed that only a random pattern was capable of entirely preventing the occurrence of RG 10. Current FS laser systems are not capable of producing a randomized beam pattern for flap creation.…”

Section: Clinical Presentation and Etiologymentioning

confidence: 54%

“…Irrespective of whether this finding is a result of a true decline in incidence or decreased reporting, it is important to recognize that a spiral pattern still has the necessary spot periodicity to produce RG 10. Thus, the apparent decline in RG when using a spiral pattern should not be attributed to the change in pattern from raster to spiral, but rather to better quality optics that reduce the formation of a roughly grated flap surface.…”

Section: Clinical Presentation and Etiologymentioning

confidence: 99%

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Rainbow glare after laser-assisted in situ keratomileusis: a review of literature

Moshirfar

Desautels

Quist

et al. 2016

OPTH

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This article reviews the current literature pertaining to rainbow glare (RG), including incidence rate, clinical presentation, etiology, prognosis, and management. RG is a rare optical complication of femtosecond laser-assisted in situ keratomileusis that results in patients seeing an array of spectral bands surrounding point sources of light under mesopic and scotopic conditions. The mechanism is thought to be a consequence of the formation of a transmissive diffraction grating on the posterior surface of the corneal flap created by the FS laser. RG has a good prognosis and is usually self-limiting. Persistent RG with concomitant residual refractive error may warrant lifting the flap and photoablating the posterior surface of the flap. Patients with persistent RG and no residual refractive error should be considered candidates for phototherapeutic keratectomy on the posterior flap surface.

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“…In fact, the increased breakdown length due to the nonlinear side effects reduces the quality of surgical cuts and harms tissue outside the focal spot, while extended disrupted cut patterns decrease the visual quality of the eye 41 . Moreover, retinal safety limits may be affected due to the broadband SCG 39 .…”

Section: Introductionmentioning

confidence: 99%

A simple technique to overcome self-focusing, filamentation, supercontinuum generation, aberrations, depth dependence and waveguide interface roughness using fs laser processing

Lapointe

Kashyap

2017

Sci Rep

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Several detrimental effects limit the use of ultrafast lasers in multi-photon processing and the direct manufacture of integrated photonics devices, not least, dispersion, aberrations, depth dependence, undesirable ablation at a surface, limited depth of writing, nonlinear optical effects such as supercontinuum generation and filamentation due to Kerr self-focusing. We show that all these effects can be significantly reduced if not eliminated using two coherent, ultrafast laser-beams through a single lens - which we call the Dual-Beam technique. Simulations and experimental measurements at the focus are used to understand how the Dual-Beam technique can mitigate these problems. The high peak laser intensity is only formed at the aberration-free tightly localised focal spot, simultaneously, suppressing unwanted nonlinear side effects for any intensity or processing depth. Therefore, we believe this simple and innovative technique makes the fs laser capable of much more at even higher intensities than previously possible, allowing applications in multi-photon processing, bio-medical imaging, laser surgery of cells, tissue and in ophthalmology, along with laser writing of waveguides.

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Optical side-effects of fs-laser treatment in refractive surgery investigated by means of a model eye

Cited by 20 publications

References 36 publications

Enhancing precision in fs-laser material processing by simultaneous spatial and temporal focusing

Enhancing precision in fs-laser material processing by simultaneous spatial and temporal focusing

Rainbow glare after laser-assisted in situ keratomileusis: a review of literature

A simple technique to overcome self-focusing, filamentation, supercontinuum generation, aberrations, depth dependence and waveguide interface roughness using fs laser processing

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