Experimental and clinical investigation of efficiency and ablation profiles of new solid-state deep-ultraviolet laser for vision correction

Roszkowska, Anna M.; Korn, G.; Lenzner, M.; Kirsch, M.; Kittelmann, O.; Zatonski, R.; Ferreri, Paolo; Ferreri, Giuseppe

doi:10.1016/j.jcrs.2004.04.071

Cited by 22 publications

(28 citation statements)

References 5 publications

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“…8,11,[37][38][39] However, it has not been until recently that plastic models have been used to study in detail the changes in the shape of the flat or spherical surfaces, after refractive surgery. 40,41 Ablating plastic model corneas not affected by biomechanical or other biological effects with clinical lasers allows to directly measure the actual ablation pattern provided by the laser, avoiding the approximations and assumptions used in theoretical models.…”

Section: Discussionmentioning

confidence: 99%

Optimum Laser Beam Characteristics for Achieving Smoother Ablations in Laser Vision Correction

Verma

Hesser

Arba-Mosquera

2017

Invest. Ophthalmol. Vis. Sci.

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PURPOSE. Controversial opinions exist regarding optimum laser beam characteristics for achieving smoother ablations in laser-based vision correction. The purpose of the study was to outline a rigorous simulation model for simulating shot-by-shot ablation process. The impact of laser beam characteristics like super Gaussian order, truncation radius, spot geometry, spot overlap, and lattice geometry were tested on ablation smoothness. METHODS.Given the super Gaussian order, the theoretical beam profile was determined following Lambert-Beer model. The intensity beam profile originating from an excimer laser was measured with a beam profiler camera. For both, the measured and theoretical beam profiles, two spot geometries (round and square spots) were considered, and two types of lattices (reticular and triangular) were simulated with varying spot overlaps and ablated material (cornea or polymethylmethacrylate [PMMA]). The roughness in ablation was determined by the root-mean-square per square root of layer depth. RESULTS.Truncating the beam profile increases the roughness in ablation, Gaussian profiles theoretically result in smoother ablations, round spot geometries produce lower roughness in ablation compared to square geometry, triangular lattices theoretically produce lower roughness in ablation compared to the reticular lattice, theoretically modeled beam profiles show lower roughness in ablation compared to the measured beam profile, and the simulated roughness in ablation on PMMA tends to be lower than on human cornea. For given input parameters, proper optimum parameters for minimizing the roughness have been found. CONCLUSIONS.Theoretically, the proposed model can be used for achieving smoothness with laser systems used for ablation processes at relatively low cost. This model may improve the quality of results and could be directly applied for improving postoperative surface quality.

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Section: Discussionmentioning

confidence: 99%

Optimum Laser Beam Characteristics for Achieving Smoother Ablations in Laser Vision Correction

Verma

Hesser

Arba-Mosquera

2017

Invest. Ophthalmol. Vis. Sci.

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“…[1][2][3][4] In recent times, solid state refractive laser platform has been developed, [5][6] providing an alternative to excimer lasers with certain added advantages. The newer solid state laser is a quintupled Nd: Yag laser with a 213nm wavelength, small spot size 0.6mm.…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…[6][7] Photo ablation of the stromal tissue within the wavelength ranging from 190nm to 220nm is with high degree of accuracy and minimal collateral damage. [4][5] This laser has higher pulse to pulse energy stability.There is no need of using toxic gas and it has least noise levels in the operation theatre, less maintenance costs and the greatest advantage is its ready to use option anytime unlike with excimer laser. The repetition rate of solid state laser is 300hz, much higher than in the excimer laser.…”

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confidence: 99%

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Laser Assisted Sub Epithelial Keratectomy for Hyperopia Using 213 Nm Wavelength Solid State Laser, 3 Year Follow Up Study of Refractive and Visual Outcomes

Yenugandula¹,

Goud²,

J³

2015

jemds

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PURPOSE:To evaluate the visual and refractive outcomes, using 213 nm solid lasers for the correction of broad range of hyperopia, covering pediatric age group to presbyopic age group. MATERIALS AND METHODS:The Present study is a prospective case series in a private practice setup, analysed series of eyes, with low to high hyperopia, who underwent conventional LASEK. Long term (3 year) visual and refractive outcomes and overall patient satisfaction studied. RESULTS: This cohort study of 37 eyes included broad range of hyperopia between +1.5 D to +7.5 D. For 70.27% of eyes, there was no change in CDVA post operatively and there was a significant Gain of one line in 21.62% of eyes and the paediatric eyes (4) CONCLUSION:The conventional LASEK can be performed using solid laser, safely and effectively for hyperopia covering broad age groups and it can achieve effective visual outcomes with excellent overall patient satisfaction. KEYWORDS: LASEK, CDVA, UDVA, logMAR and PRK. INTRODUCTION:Corneal photo ablation has been performed over the years using refractive excimer laser 193nm wavelength safely and effectively. [1][2][3][4] In recent times, solid state refractive laser platform has been developed, [5][6] providing an alternative to excimer lasers with certain added advantages. The newer solid state laser is a quintupled Nd: Yag laser with a 213nm wavelength, small spot size 0.6mm. Experimental studies indeed found that solid lasers (213nm wavelength) don't induce thermal damage or collateral damage in deep corneal layers. [6][7] Photo ablation of the stromal tissue within the wavelength ranging from 190nm to 220nm is with high degree of accuracy and minimal collateral damage. [4][5] This laser has higher pulse to pulse energy stability.There is no need of using toxic gas and it has least noise levels in the operation theatre, less maintenance costs and the greatest advantage is its ready to use option anytime unlike with excimer laser. The repetition rate of solid state laser is 300hz, much higher than in the excimer laser. This laser provides true Gaussian profile of the beam. The 213 nm wavelength is less sensitive to corneal hydration than 193 nm, due to its better transmissibility in hydrated cornea. [8] The hydrated cornea has bearing on corrections. The over hydrated cornea results in frequent under corrections, dry stromal bed (under hydrated) results in over corrections. [9] The solid state lasers are more complex to manufacture and needs frequent and meticulous maintenance of the machine.

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“…Ablation of PMMA flat surfaces has been used before [16][17][18], with the aim of assessing the roughness created by the current ablation patterns. However none of these studied the changes in asphericity induced by the ablation patterns.…”

Section: Introductionmentioning

confidence: 99%

Experiments on PMMA models to predict the impact of corneal refractive surgery on corneal shape

et al. 2006

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Flat and spherical PMMA surfaces were ablated with a standard refractive surgery laser system. The ratio of profiles on flat to spherical PMMA surfaces was used to estimate experimentally the radial change in ablation efficiency for PMMA and cornea. Changes in ablation efficiency accounted for most of the asphericity increase found clinically, using the same laser system. This protocol is useful to obtain a correction factor for any ablation algorithm and laser system, and to estimate the contribution of biomechanics to the increase of corneal asphericity in myopic refractive surgery.

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Experimental and clinical investigation of efficiency and ablation profiles of new solid-state deep-ultraviolet laser for vision correction

Abstract: The efficacy of the ablation was good, with the profile meter results confirmed by the topographic measurements.

Cited by 22 publications

References 5 publications

Optimum Laser Beam Characteristics for Achieving Smoother Ablations in Laser Vision Correction

Optimum Laser Beam Characteristics for Achieving Smoother Ablations in Laser Vision Correction

Laser Assisted Sub Epithelial Keratectomy for Hyperopia Using 213 Nm Wavelength Solid State Laser, 3 Year Follow Up Study of Refractive and Visual Outcomes

Experiments on PMMA models to predict the impact of corneal refractive surgery on corneal shape

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