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

Shen, Jin; Joos, Karen M.; Manns, Fabrice; Ren, Qiushi; Fankhauser, Franz; Denham, David B.; Söderberg, Per G.; Parel, Jean Marie

doi:10.1002/(sici)1096-9101(1997)21:2<179::aid-lsm9>3.0.co;2-n

Cited by 16 publications

(7 citation statements)

References 30 publications

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“…Nonetheless, it was choose to ensure proper ablation effect in PMMA and ex-vivo rabbit cornea since the absorption coefficient in PMMA and rabbit cornea is relatively lower at 266 nm than that at 193 nm. Despite the fact that the absorption coefficient at 266 nm is lower than 193 nm, the obtained ablation threshold using PMMA was approximately 328 mJ/cm 2 and the obtained ablation rate was comparable to that obtained by other UV wavelengths [ 39 ]. The threshold fluence was 328 mJ/cm 2 for the 100-pulses experiment which is slightly higher than that at 249 nm and lower than that at 308 nm as reported by Krueger et al [ 40 ].…”

Section: Resultssupporting

confidence: 57%

Nd:YAG fourth harmonic (266-nm) generation for corneal reshaping procedure: An ex-vivo experimental study

et al. 2021

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Corneal reshaping is a common medical procedure utilized for the correction of different vision disorders relying on the ablation effect of the UV pulsed lasers, especially excimer lasers (ArF) at 193 nm. This wavelength is preferred in such medical procedures since laser radiation at 193 nm exhibits an optimum absorption by corneal tissue. However, it is also significantly absorbed by the water content of the cornea resulting in an unpredictability in the clinical results, as well as the high service and operation cost of the commercial ArF excimer laser device. Consequently, other types of solid-state UV pulsed lasers have been introduced. The present work investigates the ablation effect of solid-state laser at 266 nm in order to be utilized in corneal reshaping procedures. Different number of pulses has been applied to Polymethyl Methacrylate (PMMA) and ex-vivo rabbit cornea to evaluate the ablation effect of the produced laser radiation. PMMA target experienced ellipse-like ablated areas with a conical shape in the depth. The results revealed an almost constant ablation area regardless the number of laser pulses, which indicates the stability of the produced laser beam, whereas the ablation depth increases only with increasing the number of laser pulses. Examination of the ex-vivo cornea showed a significant tissue undulation, minimal thermal damage, and relatively smooth ablation surfaces. Accordingly, the obtained 266-nm laser specifications provide promising alternative to the traditional 193-nm excimer laser in corneal reshaping procedure.

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Section: Resultssupporting

confidence: 57%

Nd:YAG fourth harmonic (266-nm) generation for corneal reshaping procedure: An ex-vivo experimental study

et al. 2021

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“…25 The rate of our solid-state laser was comparable to that of the argon-fluoride excimer laser. The smoothness of the edges of the ablated porcine corneas was comparable to that reported for the 193 nm excimer laser and the 213 nm UV solid-state laser.…”

Section: Discussionmentioning

confidence: 99%

Corneal ablation with new 193 nm solid-state laser

Nakagawa

Maeda

Çekıç

et al. 2008

Journal of Cataract and Refractive Surgery

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“… 4 , 7 , 8 The main difference is the two- to threefold higher absorption coefficient at 193 nm and, as a consequence, the lower threshold fluence for ablation. 9 – 11 Corneal ablation experiments were also performed with KrCl and KrF excimer lasers at 222 and 248 nm, respectively, but the severe thermal effects on the surrounding tissue 12 made these lasers unsuitable for refractive surgery.…”

Section: Contextmentioning

confidence: 99%

Corneal absorption spectra in the deep UV range

et al. 2022

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. Significance: Refractive surgery in ophthalmology uses pulsed lasers at 193, 210, or 213 nm. The reason is that most molecular constituents of cornea absorb strongly in this wavelength range. Precise refractive surgery via ablation requires an accurate knowledge of the absorption coefficient at the relevant wavelengths. Yet, the absorption coefficients of corneal tissue reported in literature vary by almost an order of magnitude; moreover, they were measured mostly at the wavelengths mentioned earlier. Aim: By measuring the corneal absorption coefficient of intact eyeballs stored at different environmental conditions, prepared by following different procedures, and as a function of postmortem time, we determine the absorption coefficient for the entire wavelength range between 185 and 250 nm for as close as possible to in-vivo conditions. Approach: We use a specially designed UV ellipsometer to measure refractive index and absorption coefficient. Specifically, we investigate the temporal evolution of refractive index and absorption coefficient after enucleation of the eyeballs under different environmental conditions and preparation procedures. Results: Our measurements provide accurate values for refractive index as well as absorption coefficient of cornea in the wavelength range between 185 and 250 nm. We find that the absorption coefficient decreases with time and that neither storage conditions nor preparation procedures but a continuous degeneration of the cornea is responsible for the observed time evolution. We use the measured time evolution to extrapolate refractive index and absorption coefficient to in-vivo conditions. Conclusion: Our measurements of the close to in-vivo absorption coefficient of cornea between 185 and 250 nm allow for a better understanding and modeling of refractive cornea surgery, also at other than the three commonly used wavelengths. In the future, this may be relevant when new pulsed laser sources with other wavelengths become available.

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

Cited by 16 publications

References 30 publications

Nd:YAG fourth harmonic (266-nm) generation for corneal reshaping procedure: An ex-vivo experimental study

Nd:YAG fourth harmonic (266-nm) generation for corneal reshaping procedure: An ex-vivo experimental study

Corneal ablation with new 193 nm solid-state laser

Corneal absorption spectra in the deep UV range

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