Physical problems of excimer laser cornea ablation

Bor, Zsolt; Hopp, B.; Rácz, B.; Szabó, Gábor; Márton, Zsuzsanna; Ratkay, Imola; Sueveges, Ildiko; Fuest, Agnes

doi:10.1117/12.145357

Cited by 15 publications

(14 citation statements)

References 1 publication

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“…8) suggests that it might be < 50 mJ/cm 2 . When the radiant exposure was below 200 mJ/cm 2 , the ablation rates of 213 nm and 193 nm were similar [5,[21][22][23]25]. For example, at 120 mJ/cm 2 , the ablation rates of 213 nm and 193 nm were both in the range of 0.12-0.17 m per pulse.…”

Section: Discussionmentioning

confidence: 98%

“…For example, at 120 mJ/cm 2 , the ablation rates of 213 nm and 193 nm were both in the range of 0.12-0.17 m per pulse. However, the ablation rate of 213 nm increased gradually faster as radiant exposure increased when compared with the 193 nm excimer laser [5,18,19,[21][22][23][24][25]. When the radiant exposure was increased over 250 mJ/cm 2 , the ablation rate for 213 nm was between 1.2 and 2.2 times faster than the ablation rate for 193 nm (Fig.…”

Section: Discussionmentioning

confidence: 98%

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Ablation rate of PMMA and human cornea with a frequency-quintupled Nd:YAG laser (213 nm)

et al. 1997

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Section: Discussionmentioning

confidence: 98%

Section: Discussionmentioning

confidence: 98%

Ablation rate of PMMA and human cornea with a frequency-quintupled Nd:YAG laser (213 nm)

et al. 1997

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“…The complex amplitude of a monochromatic component of the total wave field from an amplitude diffraction grating at the point of observation r is the sum of the wave fields of slits, equation (12) and, with account of equation (11) and equation (13), it is…”

Section: Spectral Composition Of the Diffraction Patternmentioning

confidence: 99%

Diffraction of a pulsed plane wave from an amplitude diffraction grating

Sereda

Ferrari

Bertolotti

1997

Journal of Modern Optics

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A study of diffraction of a time Gaussian-shaped pulse from an amplitude diffraction grating is presented. T h e changes of the spectral composition, time intensity and energy of the diffraction pattern are considered. The measurement of the spectral composition of the primary pulse with the help of a diffraction grating based on the measurement of the spatial distribution of energy of the diffraction pattern is discussed. IntroductionWhat happens to the spectrum and time intensity of a single ultrashort pulse interacting with a diffraction grating? Several studies are available considering diffraction gratings in general, diffraction of pulses on gratings and their applications (see for example [l-141). Nevertheless, the complete answer to the above question has not been given until now. In order to find it out, we developed a unified spectral theory of light propagation, considering, from the same point of view, both stationary and nonstationary light sources and their wave fields.Considering a time Gaussian-shaped plane wave diffracted by a single slit [15-171 or its intereference from two very narrow slits [18], we showed that in both cases the changes of the spectral composition and evolution of the time intensity as functions of the observation angle are the same. T h e reason for the appearance of the spectral changes, known in the theory of stationary light radiation as the Wolf effect, lies in the spatial coherence of the incident plane wave [19, 201. As the spatial coherence of the incident wave decreases, the changes of the spectral composition and time intensity of the wave field become less evident and, when the incident wave is spatially incoherent, the normalized spectral composition, time intensity and energy of the far zone pulsed wave field do not change at all [21]. The dependence of the energy of a pulsed wave field on the spatial coherence of its source gives a method of measurement of the spatial coherence of a pulsed source through the measurement of the energy of its wave field at the on-axis points [21].In the present paper we gather the above results in the study of an amplitude diffraction grating consisting of equidistant slits, illuminated by a time Gaussianshaped pulsed plane wave, in scalar approximation. We consider the changes of the spectrum and time intensity of the diffraction pattern at the off-axis points of observation and discuss the influence of finite slit width on these features. We

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“…Although we recognize that the measured thermal radiation originates from not only the corneal surface but also from ablation plume/fragmentation, the thermal radiation originating from ablation plume/fragmentation would be only a small percentage of total thermal radiation (estimated to be about 12%) since thermal radiation is correlated with density of the material and the density of plume/fragmentation was estimated from the distance between the corneal surface and the propagated plume/ fragmentation a few microseconds after irradiation of the excimer laser pulse to be only 1/150 of that of the cornea [6]. However, the thermal distribution of the ablation plume/fragmentation, which was not obtained, seemed to make the measured temperature low.…”

Section: Measurement Of Corneal Surface Temperature With 15-nanoseconmentioning

confidence: 99%

“…However, to reproduce reliable corneal shape processing, a parameter directly related to the ablation process needs to be monitored. In ArF excimer laser ablation of the cornea, the generated heat plays an important role in ablation kinetics [5,6]. If excess heat is produced from an extra-energy other than the energy consumed in the ablation, it may damage tissue surrounding the ablated area.…”

Section: Introductionmentioning

confidence: 99%

Measurement of the surface temperature of the cornea during ArF excimer laser ablation by thermal radiometry with a 15‐nanosecond time response

et al. 2002

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Background and Objective: The purpose of this work was to develop a temperature measurement system with a nanosecond time response to monitor the transient temperature of the corneal surface during laser refractive surgery. Materials and Methods: Thermal radiation from the surface of the porcine cornea during ArF excimer laser irradiation was measured using a photovoltaic HgCdTe detector with a response bandwidth of 150 MHz. Results: Maximum thermal radiation occurred at 31 AE 4 nanoseconds, which was longer than the time response of the measurement system. The temperature derived from the detected signal reached over 1008C at a¯uence of 80 mJ/cm 2 , which was the ablation threshold, and reached 2408C at a¯uence of 180 mJ/cm 2 . Conclusion: The present system of temperature measurement with a time response of 15.7 nanoseconds revealed that the transient surface temperature of the cornea during ablation is much higher than that previously reported.

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Physical problems of excimer laser cornea ablation

Cited by 15 publications

References 1 publication

Ablation rate of PMMA and human cornea with a frequency-quintupled Nd:YAG laser (213 nm)

Ablation rate of PMMA and human cornea with a frequency-quintupled Nd:YAG laser (213 nm)

Diffraction of a pulsed plane wave from an amplitude diffraction grating

Measurement of the surface temperature of the cornea during ArF excimer laser ablation by thermal radiometry with a 15‐nanosecond time response

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