Factors affecting epithelial hyperplasia after photorefractive keratectomy

Gauthier, Charline; Holden, Brien A.; Epstein, David; Tengroth, Björn; Fagerholm, Per; Hamberg‐Nyström, Heléne

doi:10.1016/s0886-3350(97)80078-8

Cited by 74 publications

(36 citation statements)

References 23 publications

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“…[42][43][44][45][46] An important aspect for consideration in postoperative refractive outcomes is the epithelial masking that will finish the smoothing process after the corneal ablation. 47,48 An optimum topography of the stroma facilitates re-epithelialisation.…”

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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“…Amm e col. ao estudar córneas de coelhos operados por PRK e LASIK, detectaram hiperplasia epitelial através de microscopia fluorescente (1) . Gauthier e col. estudando 136 míopes operados através de PRK concluíram que a HEC é mais comum em olhos com zonas de ablação pequenas e profundas e com grandes alterações dióptricas em suas margens (6) . Estas evidências destacam a HEC dos outros mecanismos de regressão citados anteriormente e instigam a realização de trabalhos visando descobrir sua verdadeira interferência na refração final após o LASIK.…”

Section: Discussionunclassified

“…Isto se deve a algumas vantagens desta técnica sobre as demais como: mínimo desconforto pós-operatório, estabilidade precoce com pouca regressão, menor índice de "haze", possibilidade de corrigir ametropias mais altas (1)(2) . A regressão do efeito obtido com as cirurgias refrativas, tem sido descrita na maioria dos procedimentos (3)(4)(5)(6) . A hidratação corneana, a síntese do colágeno estromal e a hiperplasia epitelial compensatória estão entre as causas mais freqüentes desta regressão (3) .…”

Section: Introductionunclassified

Paquimetria esperada X obtida após LASIK para miopia

Paranhos¹,

Netto²,

Nassaralla³

2001

Arq. Bras. Oftalmol.

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Objetivo: Comparar a paquimetria corneana encontrada (PEn) com a esperada (PEs) 3 meses após a cirurgia de LASIK para correção de miopia. Métodos: 77 olhos de 39 pacientes míopes foram incluídos neste estudo. A cirurgia foi realizada utilizando-se o excimer laser Technolas 217 e o microcerátomo automático da Chiron. Paquimetria foi realizada em todos os olhos antes e 3 meses após o LASIK. PEs foi obtida subtraindo-se a profundidade de ablação realizada pelo laser, da paquimetria pré-operatória. Os pacientes foram divididos em 3 grupos: grupo A (55 olhos) com miopia variando de -1,00D a -5,75D; grupo B (14 olhos), de -6,00D a -10,00D e grupo C (8 olhos) acima de -10,00D. Resultados: Houve uma diminuição da média do equivalente esférico de -2,71D para 0,00 no grupo A, -8,18D para 0,00 no grupo B e de -11,4D para -1,06D no grupo C. As médias das PEs foram 468 µm, 370 µm e 382 µm para os grupos A,B e C, respectivamente. As médias das PEn foram de 491 µm, 431 µm e 427 µm nos grupos A, B e C, respectivamente. Em 70 olhos (90,9 %) a PEn foi superior a PEs, sendo esta diferença estatisticamente significativa (p=0,001). Conclusão: Apesar dos resultados mostrarem que a córnea encontrava-se mais espessa do que o esperado após a cirurgia de LASIK, não foi observada hipocorreção significativa. Após 3 meses a refração da maioria dos pacientes estava próxima da emetropia. Achieved X expected pachymetry after LASIK for myopia INTRODUÇÃOA cirurgia de ceratomileusis in situ a laser (LASIK/ laser in situ keratomileusis) é considerada atualmente a técnica de eleição para correção de ametropias. Isto se deve a algumas vantagens desta técnica sobre as demais como: mínimo desconforto pós-operatório, estabilidade precoce com pouca regressão, menor índice de "haze", possibilidade de corrigir ametropias mais altas (1)(2) . A regressão do efeito obtido com as cirurgias refrativas, tem sido descrita na maioria dos procedimentos (3)(4)(5)(6) . A hidratação corneana, a síntese do colágeno estromal e a hiperplasia epitelial compensatória estão entre as causas mais freqüentes desta regressão (3) . Todas elas podem alterar a paquimetria corneana após a cirurgia de LASIK.Este estudo tem como objetivo comparar a paquimetria esperada com a obtida 3 meses após LASIK em pacientes míopes, relacionando-as aos resultados refracionais alcançados.

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“…Despite the fact that the transmission of radiation into the surrounding tissue is minimal during femtoLASIK surgery, considering the principle of tissue removal, the energy level is manifold higher than in ReLEx SMILE surgery. Therefore, stimulation of the healing process is significantly higher 5,6 . A change in corneal curvature may also occur during pregnancy and lactation.…”

Section: Principle Of Dioptric Error Regressionmentioning

confidence: 99%

“…If the width of the ablation zone is below 6 mm, it leads to development of the halo phenomenon (round phosphine around lights), glare effect and a higher probability of regression due to larger epithelial hyperplasia. The wider ablation zone includes a larger optical zone, which leads to improved quality of vision and offers a more stable basis for refraction 5,10 .…”

Section: Principle Of Dioptric Error Regressionmentioning

confidence: 99%

Comparison of the efficiency of femtoLASIK and ReLEx SMILE in terms of dioptric error reduction

Pavkova¹,

Kacerovská²,

Kacerovsky³

2018

Biomed Pap Med Fac Univ Palacky Olomouc Czech Repub

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Background and Aims. Refractive eye surgery is a rapidly expanding field of ophthalmology and corneal surgery is undergoing constant development leading to less invasive technologies. The goal of this study was to compare the most common femtoLASIK surgery with the newer ReLEx SMILE surgery which is gentler to the cornea. The comparison was made in terms of dioptric error reduction. Methods. The studied cohort of patients consisted of two major groups: 30 patients who underwent femtoLASIK surgery and 30 who underwent ReLEx SMILE surgery. -30 patients, 60 eyes. All patients were aged 18-45 years with moderate myopia or astigmatism ranging from -3.25 to -6.0 spherical diopters and from 0 to -1.0 cylindrical diopters. In all, the best corrected visual acuity measured prior to surgery was 1.0. Pachymetry was not comparable because each surgical method was performed at a different time point and the introduction of an innovative method into practice led to a change in selection criteria. Results. During postsurgical check-ups, the ReLEx SMILE method (0.74) led to lower values of non-corrected visual acuity compared to the femtoLASIK method (0.88), (P<0.001). However, the results changed at the one-year post-surgery check-up, when ReLEX SMILE patients achieved non-corrected visual acuity of 0.97 compared to femtoLASIK patients, who scored 0.83, (P=0.007). Based on data analysis from the automatic refractometer, the average spherical diopters of the femtoLASIK (-0.32 D) were higher than those of the ReLEx SMILE (-0.07 D), (P<0.001). The results for the cylindrical diopters were also significant, (P=0.021). When we compared the spherical equivalent one year after surgery, the difference between methods was significant. The FemtoLASIK method resulted in an average SE -0.55 D compared to -0.09 D for the ReLEx SMILE method, (P<0.001). Conclusion. This study showed that there was a significant difference in results between the two surgical methods of treatment of moderate myopia and astigmatism, in terms of regression of dioptric error, as well as in achievement and maintenance of visual acuity during the observed period. The ReLEx SMILE had better results.

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Factors affecting epithelial hyperplasia after photorefractive keratectomy

Abstract: The factors associated with an increase in epithelial thickness were small ablation zones, greater attempted corrections, and deeper ablations. Larger, smoother ablation profiles may result in less epithelial hyperplasia.

Cited by 74 publications

References 23 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

Paquimetria esperada X obtida após LASIK para miopia

Comparison of the efficiency of femtoLASIK and ReLEx SMILE in terms of dioptric error reduction

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