A retrospective chart review performed from January 2009 to October 2013 assessed 1009 cases that underwent LASEK treatment using 20% alcohol and 120 mm eye spatula for epithelium mobilization; the STAR S4 IR^TM Excimer Laser was used to treat the eye. Evaluation of intraoperative flap events was conducted to assess the efficacy behind this minimal technique posed by surgeon, Dr. Samir Melki. Out of 1009 cases, 72.35% operative eyes showed complete flap preservation, 17.65% flap tears, and 10.01% flaps discarded, demonstrating the viability in applying this technique. All patients considered were required to have a pre-operative consultation to identify any possibly risk factors before surgery. For the purposes of this study, we investigated if age played a significant role in the intraoperative success of mechanically mobilizing the epithelium after 40-second alcohol exposure. We found that patients 50 years and older were statistically different from their younger counterparts (e.g. 20 to 29, 30 to 39, 40 to 49). They were more at risk for less epithelial preservation (e.g. flap equal to or less than 180 degrees) and overall flap removal (p < 0.001). There were no statistically significant differences between the age group 20 to 29 and 30 to 39; however, there was a relatively significant disparity in successful flap events for patients in their 20s versus those in their 40s (p < 0.001) suggesting that as one ages, the likelihood of flap tear increases.

Thesis (M.S.)--University of Adelaide, Dept. of Surgery, 2004. / "December 2003" Bibliography: leaves 82-99.

Purpose: To improve the predictability, accuracy and stability of laser in-situ keratomileusis (LASIK), by evaluating the clinical, procedural and tissue response factors that affect refractive outcomes. Methods: Myopic LASIK surgeries (n=5,978) were carried out using the Technolas planoscan and Nidek EC-5000 excimer lasers. Clinical variables associated with a refractive outcome of within ??0.50 D of the target were identified using regression analysis. Possible procedural variations such as the timing of the procedure and accuracy of both the chosen keratome and excimer laser were evaluated. The predictability and accuracy of the ablation was assessed by measuring changes in corneal thickness during and after the procedure. Factors influencing the stability of refractive outcome were assessed. Results: Clinical factors associated with a refractive outcome of within ??0.50 D of the target included; corrections less than 5.00 DS (OR 0.21x, 95% CI 0.11-0.40x compared with corrections over -5.00 DS[referent]), patients younger than 40 years (patients over 50 OR 8.27x, 95% CI 3.41-20.03x, patients 40 to 50 years OR 1.93x, 95% CI 0.96-3.90x, compared with patients under 40[referent]) and average pre-operative curvatures between 43.50 and 45.50D (OR 0.39x, 95% CI 0.18-0.83 compared with curvatures of less than 43.50D [referent]). Refractive stability was improved using optic zone sizes between 5.5-6.0 mm, reduced myopic corrections, flatter pre-operative corneal curvatures and thicker corneal flaps (R??=25%, p&lt0.001). Procedural factors associated with poorer outcomes included: thinner measured flap thickness, deeper ablations and the use of the automated corneal shaper (ACS) microkeratome with a novice surgical team (R??=34%, p &lt 0.001). Delaying the ablation from 20 to 90 seconds (s) after flap lift was associated with a more stable refractive outcome at three months (p=0.017). In the 90 s following flap lift, the cornea thinned by 5??3%. The ablation rate per scan varied between procedures, however, the effect on refractive outcome was small (r=0.15, p=0.267). Changes in central corneal thickness indicated refractive stability (p=0.039). Conclusions: Applying the optimal clinical and procedural factors as described afforded a refractive outcome in a further 8% of cases, resulting in 94% to 96% of cases within ??0.50 DS of target. Refractive predictability was limited due to the inability of the keratome to produce a consistent corneal flap thickness and unexpected changes in corneal thickness. The accuracy of refractive outcome will decrease with larger ablations. The degree of refractive inaccuracy with high refractive corrections (&gt -10.00 D) can be over 1.00 D.

Purpose: To improve the predictability, accuracy and stability of laser in-situ keratomileusis (LASIK), by evaluating the clinical, procedural and tissue response factors that affect refractive outcomes. Methods: Myopic LASIK surgeries (n=5,978) were carried out using the Technolas planoscan and Nidek EC-5000 excimer lasers. Clinical variables associated with a refractive outcome of within ??0.50 D of the target were identified using regression analysis. Possible procedural variations such as the timing of the procedure and accuracy of both the chosen keratome and excimer laser were evaluated. The predictability and accuracy of the ablation was assessed by measuring changes in corneal thickness during and after the procedure. Factors influencing the stability of refractive outcome were assessed. Results: Clinical factors associated with a refractive outcome of within ??0.50 D of the target included; corrections less than 5.00 DS (OR 0.21x, 95% CI 0.11-0.40x compared with corrections over -5.00 DS[referent]), patients younger than 40 years (patients over 50 OR 8.27x, 95% CI 3.41-20.03x, patients 40 to 50 years OR 1.93x, 95% CI 0.96-3.90x, compared with patients under 40[referent]) and average pre-operative curvatures between 43.50 and 45.50D (OR 0.39x, 95% CI 0.18-0.83 compared with curvatures of less than 43.50D [referent]). Refractive stability was improved using optic zone sizes between 5.5-6.0 mm, reduced myopic corrections, flatter pre-operative corneal curvatures and thicker corneal flaps (R??=25%, p&lt0.001). Procedural factors associated with poorer outcomes included: thinner measured flap thickness, deeper ablations and the use of the automated corneal shaper (ACS) microkeratome with a novice surgical team (R??=34%, p &lt 0.001). Delaying the ablation from 20 to 90 seconds (s) after flap lift was associated with a more stable refractive outcome at three months (p=0.017). In the 90 s following flap lift, the cornea thinned by 5??3%. The ablation rate per scan varied between procedures, however, the effect on refractive outcome was small (r=0.15, p=0.267). Changes in central corneal thickness indicated refractive stability (p=0.039). Conclusions: Applying the optimal clinical and procedural factors as described afforded a refractive outcome in a further 8% of cases, resulting in 94% to 96% of cases within ??0.50 DS of target. Refractive predictability was limited due to the inability of the keratome to produce a consistent corneal flap thickness and unexpected changes in corneal thickness. The accuracy of refractive outcome will decrease with larger ablations. The degree of refractive inaccuracy with high refractive corrections (&gt -10.00 D) can be over 1.00 D.

Purpose: To improve the predictability, accuracy and stability of laser in-situ keratomileusis (LASIK), by evaluating the clinical, procedural and tissue response factors that affect refractive outcomes. Methods: Myopic LASIK surgeries (n=5,978) were carried out using the Technolas planoscan and Nidek EC-5000 excimer lasers. Clinical variables associated with a refractive outcome of within ??0.50 D of the target were identified using regression analysis. Possible procedural variations such as the timing of the procedure and accuracy of both the chosen keratome and excimer laser were evaluated. The predictability and accuracy of the ablation was assessed by measuring changes in corneal thickness during and after the procedure. Factors influencing the stability of refractive outcome were assessed. Results: Clinical factors associated with a refractive outcome of within ??0.50 D of the target included; corrections less than 5.00 DS (OR 0.21x, 95% CI 0.11-0.40x compared with corrections over -5.00 DS[referent]), patients younger than 40 years (patients over 50 OR 8.27x, 95% CI 3.41-20.03x, patients 40 to 50 years OR 1.93x, 95% CI 0.96-3.90x, compared with patients under 40[referent]) and average pre-operative curvatures between 43.50 and 45.50D (OR 0.39x, 95% CI 0.18-0.83 compared with curvatures of less than 43.50D [referent]). Refractive stability was improved using optic zone sizes between 5.5-6.0 mm, reduced myopic corrections, flatter pre-operative corneal curvatures and thicker corneal flaps (R??=25%, p&lt0.001). Procedural factors associated with poorer outcomes included: thinner measured flap thickness, deeper ablations and the use of the automated corneal shaper (ACS) microkeratome with a novice surgical team (R??=34%, p &lt 0.001). Delaying the ablation from 20 to 90 seconds (s) after flap lift was associated with a more stable refractive outcome at three months (p=0.017). In the 90 s following flap lift, the cornea thinned by 5??3%. The ablation rate per scan varied between procedures, however, the effect on refractive outcome was small (r=0.15, p=0.267). Changes in central corneal thickness indicated refractive stability (p=0.039). Conclusions: Applying the optimal clinical and procedural factors as described afforded a refractive outcome in a further 8% of cases, resulting in 94% to 96% of cases within ??0.50 DS of target. Refractive predictability was limited due to the inability of the keratome to produce a consistent corneal flap thickness and unexpected changes in corneal thickness. The accuracy of refractive outcome will decrease with larger ablations. The degree of refractive inaccuracy with high refractive corrections (&gt -10.00 D) can be over 1.00 D.

Purpose: To improve the predictability, accuracy and stability of laser in-situ keratomileusis (LASIK), by evaluating the clinical, procedural and tissue response factors that affect refractive outcomes. Methods: Myopic LASIK surgeries (n=5,978) were carried out using the Technolas planoscan and Nidek EC-5000 excimer lasers. Clinical variables associated with a refractive outcome of within ??0.50 D of the target were identified using regression analysis. Possible procedural variations such as the timing of the procedure and accuracy of both the chosen keratome and excimer laser were evaluated. The predictability and accuracy of the ablation was assessed by measuring changes in corneal thickness during and after the procedure. Factors influencing the stability of refractive outcome were assessed. Results: Clinical factors associated with a refractive outcome of within ??0.50 D of the target included; corrections less than 5.00 DS (OR 0.21x, 95% CI 0.11-0.40x compared with corrections over -5.00 DS[referent]), patients younger than 40 years (patients over 50 OR 8.27x, 95% CI 3.41-20.03x, patients 40 to 50 years OR 1.93x, 95% CI 0.96-3.90x, compared with patients under 40[referent]) and average pre-operative curvatures between 43.50 and 45.50D (OR 0.39x, 95% CI 0.18-0.83 compared with curvatures of less than 43.50D [referent]). Refractive stability was improved using optic zone sizes between 5.5-6.0 mm, reduced myopic corrections, flatter pre-operative corneal curvatures and thicker corneal flaps (R??=25%, p&lt0.001). Procedural factors associated with poorer outcomes included: thinner measured flap thickness, deeper ablations and the use of the automated corneal shaper (ACS) microkeratome with a novice surgical team (R??=34%, p &lt 0.001). Delaying the ablation from 20 to 90 seconds (s) after flap lift was associated with a more stable refractive outcome at three months (p=0.017). In the 90 s following flap lift, the cornea thinned by 5??3%. The ablation rate per scan varied between procedures, however, the effect on refractive outcome was small (r=0.15, p=0.267). Changes in central corneal thickness indicated refractive stability (p=0.039). Conclusions: Applying the optimal clinical and procedural factors as described afforded a refractive outcome in a further 8% of cases, resulting in 94% to 96% of cases within ??0.50 DS of target. Refractive predictability was limited due to the inability of the keratome to produce a consistent corneal flap thickness and unexpected changes in corneal thickness. The accuracy of refractive outcome will decrease with larger ablations. The degree of refractive inaccuracy with high refractive corrections (&gt -10.00 D) can be over 1.00 D.

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Added 1 bitstream(s) on 2015-08-11T03:25:36Z : No. of bitstreams: 4 Publico-026a.pdf: 72550 bytes, checksum: afe0787528f227bc8c799cf1cd67fcc7 (MD5) Publico-026b.pdf: 2073659 bytes, checksum: b85cc4a971ac414e9e8aa01daa4ad8ed (MD5) Publico-026c.pdf: 2083167 bytes, checksum: 806646b87026c136bf8b329233fe315b (MD5) Publico-026d.pdf: 895113 bytes, checksum: 37de279e78fead2b9aa3c17fd44ab0f0 (MD5) / Objetivos: Comparar os resultados de acuidade visual, refração estática, aberrometria e sensibilidade ao contraste em olhos com miopia moderada submetidos à ceratectomia fotorrefrativa (PRK) com mitomicina C (MMC) ou à ceratomileuse assistida por excimer laser in situ (LASIK) em cirurgias guiadas por frente de onda durante acompanhamento de um ano. Avaliar o aspecto biomicroscópico nos dois grupos durante seguimento. Avaliar subjetivamente percepção de dor, queixas visuais e satisfação com resultado cirúrgico nos dois grupos durante acompanhamento. Analisar índices de microscopia especular nos dois grupos antes e seis meses após cirurgia. Comparar propriedades biomecânicas da córnea nos dois grupos um ano após o procedimento cirúrgico. Métodos: Quarenta e quatro pacientes (88 olhos) com miopia moderada e cálculo de consumo corneano maior que 50 μm na plataforma LADARWave 4000 (Alcon) em ambos os olhos foram selecionados para receber aleatoriamente LASIK em um olho e PRK com aplicação de MMC 0,002% durante um minuto no olho contralateral em cirurgias guiadas por frente de onda. Topografia corneana (EyeSys 2000, EyeSys e Orbscan II, Orbtek/Bausch & Lomb), acuidade visual sem correção (AVSC, tabela Early Treatment Diabetic Retinopaty Study), refração estática, acuidade visual com correção (AVCC), aberrometria (LADARWave 4000), paquimetria ultrassônica corneana central (Sonogage) e exame oftalmológico completo foram realizados no pré-operatório e no seguimento de um, três, seis e doze meses pós-operatório. Sensibilidade ao contraste fotópica e mesópica (Optec 6500, F.A.C.T.; Stereo Optical) com correção foram realizadas nos dois olhos antes da cirurgia e três, seis e doze meses após. Questionário subjetivo de dor foi aplicado no pós-operatório recente, e questionário de sintomas visuais e satisfação com o procedimento em cada olho foi aplicado nas visitas de acompanhamento com um, três, seis e doze meses de pós-operatório. Biomicroscopia de segmento anterior foi realizada no período pós-operatório recente e nas visitas de acompanhamento sempre como último exame do dia (examinador mascarado para procedimento cirúrgico). Microscopia especular (Topcon SP 2000p) foi realizada antes e seis meses após cirurgia. Avaliação biomecânica da córnea (ORA, Reichert) foi realizada um ano após o procedimento cirúrgico. Os testes ANOVA para medidas repetidas e t de student foram utilizados para análise estatística. Resultados: A média de idade dos pacientes do estudo foi de 31,7 anos (variou entre 21 e 54 anos). Não houve diferença significativa entre os grupos antes da cirurgia quanto a AVSC, AVCC, aberrometria, sensibilidade ao contraste ou microscopia especular. O equivalente esférico (EE) médio programado nos olhos que receberam LASIK foi de - 3,99±1,20 dioptrias (D) e de - 3,85±1,12 D nos olhos que receberam PRK com MMC (p>0,05). A profundidade de ablação média foi de 73,09±14,55 μm e 70,70±14,07 μm, no grupo LASIK e no grupo PRK com MMC, respectivamente (p>0,05). Quarenta e dois pacientes (95,5%) completaram um ano de acompanhamento. Os olhos que receberam PRK com MMC apresentaram média de AVSC significativamente superior aos olhos que receberam LASIK com três, seis e doze meses de pós-operatório. A média de AVCC também foi estatisticamente superior no grupo PRK com MMC na visita de um ano de pós-operatório (p<0,05). Não houve diferença estatística entre os grupos quanto ao EE ao longo do acompanhamento. Todos os olhos que receberam PRK com MMC completaram a reepitelização corneana em até cinco dias após o procedimento, e nenhum olho apresentou haze maior que grau 1 (escala de Fantes). Os olhos que receberam LASIK apresentaram valores de aberrações de baixa e alta ordem estatisticamente superiores aos olhos que receberam PRK com MMC durante todo o acompanhamento (p<0.05). Os olhos que receberam PRK com MMC obtiveram desempenho superior no teste de sensibilidade ao contraste em condições fotópicas e mesópicas quando comparados ao grupo LASIK durante seguimento (p<0,05). Até o quinto dia de pós-operatório, o grupo PRK com MMC apresentou índices de dor superiores ao grupo LASIK. O grupo PRK com MMC foi melhor avaliado no questionário subjetivo de queixas visuais e satisfação cirúrgica. Não houve diferença estatística entre os grupos quanto à microscopia especular (p>0,05). Na avaliação biomecânica da córnea, o grupo LASIK apresentou valores de fator de resistência corneana (CRF) e histerese (CH) significativamente superiores ao grupo PRK com MMC (p<0,05). Conclusões: Os olhos que receberam PRK com MMC apresentaram melhores valores de AVSC e AVCC, melhor correção de aberrações de baixa ordem e menores valores de aberrações de alta ordem em relação aos olhos que receberam LASIK. O grupo PRK com MMC também apresentou valores superiores de sensibilidade ao contraste e foi melhor avaliado em questionário subjetivo de satisfação cirúrgica. Não houve presença de haze clinicamente significativo no grupo PRK com MMC. O grupo PRK com MMC apresentou maiores índices de dor no período pósoperatório recente. Não houve diferença entre os índices de microscopia especular nos dois grupos. O grupo LASIK apresentou índices superiores de CRF e CH. / Purpose: To compare visual acuity results, cycloplegic refraction, aberrometry and contrast sensitivity in eyes that underwent photorefractive keratectomy (PRK) with mitomycin C (MMC) or laser in situ keratomileusis (LASIK) for wavefront-guided myopic corrections during one year follow-up. To evaluate slit-lamp microscopy in both groups during follow-up. To evaluate subjective pain, visual complains and satisfaction with visual results in the two groups during follow-up. To analyse specular microscopy values before and six months after surgeries in both groups. To compare biomechanical properties of the cornea in the two groups one year after surgeries. Methods: Forty-four patients (88 eyes) with moderate myopia and an estimated ablation depth greater than 50 μm using the LADARWave 4000 (Alcon Laboratories) platform in both eyes were randomized to receive LASIK in one eye and PRK with application of MMC 0.002% for one minute in the fellow eye in wavefront-guided surgeries. Corneal topography (EyeSys 2000, EyeSys and Orbscan II, Orbtek/Bausch & Lomb), uncorrected visual acuity (UCVA, Early Treatment Diabetic Retinopaty Study table), cycloplegic refraction, best spectacle-corrected visual acuity (BSCVA), aberrometry (LADARWave 4000), central ultrasound corneal pachymetry (Sonogage Inc) and a comprehensive ophthalmologic examination were performed before surgeries and at one, three, six and twelve months postoperative visits. Photopic and mesopic contrast sensitivity (Optec 6500, F.A.C.T.; Stereo Optical Co) with BSCVA was performed in both eyes before surgeries and at three, six and 12 months follow-up. A subjective pain questionnaire was applied at early postoperative visits and another visual complain and satisfaction questionnaire with surgery in each eye was applied one, three, six and twelve months after surgical procedures. Slit-lamp anterior segment microscopy was performed at early postoperative visits and at follow-up visits always as the last examination (blind examiner for surgical procedure). Specular microscopy (Topcon SP 2000p, Topcon) was performed before and six months after surgeries. Biomechanical properties of the cornea (ORA, Reichert) were evaluated one year after surgeries. The tests ANOVA for repeated measures and the student’s t test were used for statistical analyses. Results: The mean age was 31.7 years (range, 21-54 years). There was no statistically significant between-group difference in UCVA, BSCVA, aberrometry, contrast sensitivity or specular microscopy before surgeries. The mean attempted spherical equivalent (SE) was - 3.99±1.20 diopters (D) in LASIK eyes and - 3.85±1.12 D in PRK with MMC eyes (p>0.05). The mean ablation depth was 73.09±14.55 μm and 70.70±14.07 μm in LASIK and PRK with MMC eyes, respectively (p>0.05). Forty-two patients (95.5%) completed one year follow-up. The PRK with MMC eyes presented statistically significant better mean UCVA values than LASIK eyes at three, six and 12 months visits. The mean BSCVA was also statistically significant better in PRK with MMC eyes than in LASIK eyes one year after surgeries (p<0.05). There was no between-groups statistical difference in SE during one year follow-up. All PRK with MMC eyes reepithelialized within five days after surgical procedure and no eye presented more than grade 1 haze (Fantes scale). The LASIK eyes presented statistically significant higher lower and higher order aberrations values than PRK with MMC eyes during follow-up (p<0.05). The PRK with MMC group showed better results in photopic and mesopic contrast sensitivity than LASIK eyes during one year follow-up (p<0.05). Until the fifth postoperative day, PRK with MMC eyes presented higher pain scores than LASIK eyes. PRK with MMC eyes were better rated in terms of subjective visual symptoms and visual satisfaction. There were no statistical differences between the groups in specular microscopy (p>0.05). LASIK eyes showed statistically significant higher corneal resistance factor (CRF) and corneal hysteresis (CH) values than PRK with MMC eyes (p<0.05). Conclusions: The PRK with MMC eyes presented better UCVA, BSCVA, better correction of lower order aberrations and lower higher order aberration values than LASIK eyes. It also showed better contrast sensitivity results and was better rated in terms of visual satisfaction. There was no clinically significant haze in PRK with MMC eyes. The PRK with MMC eyes presented higher pain scores at early postoperative visits. There was no between groups differences in specular microscopy. LASIK eyes presented higher CRF and CH values one year after surgeries. / TEDE / BV UNIFESP: Teses e dissertações

Objetivo: Investigar as alterações biomecânicas da córnea de suínos induzidas pela confecção de lamelas pediculadas de diferentes espessuras pelo laser de femtossegundo. Métodos: Para a formação dos dois grupos, 12 olhos de porcos foram usados: lamelas pediculadas de 100 e de 300 micrômetros confeccionadas pelo laser de femtossegundo. Cada olho foi submetido aos seguintes exames, antes da criação das lamelas: topografia por rasterstereography, Ocular Response Analyzer (ORA), tomografia do segmento anterior por coerência óptica para a avaliação paquimétrica corneal e das lamelas criadas e sistema de velocidade de onda (SVO), que mede a velocidade de propagação de ondas acústicas entre dois transdutores posicionados na superfície corneal antes e imediatamente, após a feitura da lamela. O primerio passo foi desenhado para o estudo das diferenças em relação à histerese corneal, fator de resistência corneal, mudanças na curvatura e velocidade de propagação de onda acústica entre córneas com lamelas finas e espessas. Posteriormente, as lamelas foram amputadas, e as medidas do sistema de velocidade de onda foram repetidas. Resultados: A média de espessura das lamelas ± desviopadrão (DP) foi de 108,5±6,9 (8,5% da espessura total) e 307,8±11,5 m (22,9% da espessura total), para os grupos de lamelas finas e espessas, respectivamente (p< 0,001). Histerese corneal e o fator de resistência corneal não apresentaram diferença estatística, após a criação de lamelas finas (p = 0,81 e p = 0,62, respectivamente). Histerese corneal foi significantemente mais baixa, depois da confecção de lamelas mais espessas (8,0±1,0 para 5,1±1,5 mmHg para medidas pré e pós-operatórias, respectivamente, p = 0,003, diminuição de 36,25%) e fator de resistência corneal também mostrou significante diminuição nesse grupo, após o procedimento cirúrgico; valores médios pré e pós-operatórios de 8,2±1,6 e 4,1±2,5 mmHg respectivamente (p= 0,007), diminuição de 50%. A ceratometria média simulada apresentou maiores valores, após a confecção das lamelas mais espessas em relação ao pré-operatório (ceratometria pré e pós-operatória de 39,5±1 D e 45,9±1,2 D, respectivamente, p= 0,003). Para o grupo de lamelas finas, não houve diferença estatisticamente significante (ceratometria pré e pós-operatória de 40,6±0,6 D e 41,4±1,0 D, respectivamente, p=0,55). Em relação ao Sistema de Velocidade de Onda, após a criação das lamelas e sua amputação, houve diminuição da velocidade de propagação acústica, embora na maior parte das posições não fosse estatisticamente significante. Conclusão: Nas condições experimentais estabelecidas por este estudo, a criação de lamelas de maior espessura pareceu exercer efeito mais relevante sobre a biomecânica da córnea de suínos / Purpose: To study the impact of programmed flaps at two different thicknesses on the biomechanical properties of the swine corneas. Methods: Twelve pig eyes were enrolled in this study and were formed two groups: 100m and 300 m flaps performed with the femtosecond laser. Each eye had the following procedure before the flap creation: raster photograph topographic maps, Ocular Response Analyzer (ORA), Optical Coherence Tomography to measure the pachymetry and flap thickness and Surface Wave Velocity system which is a prototype system that measures sonic wave propagation time between two transducers positioned on the corneal surface before and after flap creation. This first step was designed to investigate the differences in respect to corneal hysteresis, corneal resistance factor, curvature change and ultrasonic wave propagation between the groups with thinner and thicker flaps. After this initial procedure, flap amputation was performed and new measurements with the surface wave velocity system were taken again. Results: Measured flap thicknesses averaged 108.5±6.9 (8.5% of the total cornea) and 307.8±11.5 m (22.9% of the total cornea) for thin and thick flap groups, respectively (p< 0.001). Hysteresis and corneal resistance factor did not change significantly after flap creation in the thin flap group (p = 0.81 and p = 0.62, respectively). With thicker flaps, both parameters decreased significantly from 8.0±1.0 to 5.1±1.5 mmHg (p=0.003, reduction of 36.25%) and from 8.2±1.6 to 4.1±2.5 mmHg, respectively (p = 0.007), reduction of 50%. Simulated keratometry values increased in the thick flap group (from 39.5±1 D to 45.9±1.2 D, p=0.003) after flap creation and not in the thin flap group (from 40.6±0.6D to 41.4±1.0D, p= 0.55). Regarding surface wave velocity analysis, the surgical procedures induced lower values in some positions although most of them did not present statistically different results. Conclusion: In this experimental model, thicker flaps seemed to have a greater effect on the biomechanics of the swinish cornea

Objetivo: Investigar as alterações biomecânicas da córnea de suínos induzidas pela confecção de lamelas pediculadas de diferentes espessuras pelo laser de femtossegundo. Métodos: Para a formação dos dois grupos, 12 olhos de porcos foram usados: lamelas pediculadas de 100 e de 300 micrômetros confeccionadas pelo laser de femtossegundo. Cada olho foi submetido aos seguintes exames, antes da criação das lamelas: topografia por rasterstereography, Ocular Response Analyzer (ORA), tomografia do segmento anterior por coerência óptica para a avaliação paquimétrica corneal e das lamelas criadas e sistema de velocidade de onda (SVO), que mede a velocidade de propagação de ondas acústicas entre dois transdutores posicionados na superfície corneal antes e imediatamente, após a feitura da lamela. O primerio passo foi desenhado para o estudo das diferenças em relação à histerese corneal, fator de resistência corneal, mudanças na curvatura e velocidade de propagação de onda acústica entre córneas com lamelas finas e espessas. Posteriormente, as lamelas foram amputadas, e as medidas do sistema de velocidade de onda foram repetidas. Resultados: A média de espessura das lamelas ± desviopadrão (DP) foi de 108,5±6,9 (8,5% da espessura total) e 307,8±11,5 m (22,9% da espessura total), para os grupos de lamelas finas e espessas, respectivamente (p< 0,001). Histerese corneal e o fator de resistência corneal não apresentaram diferença estatística, após a criação de lamelas finas (p = 0,81 e p = 0,62, respectivamente). Histerese corneal foi significantemente mais baixa, depois da confecção de lamelas mais espessas (8,0±1,0 para 5,1±1,5 mmHg para medidas pré e pós-operatórias, respectivamente, p = 0,003, diminuição de 36,25%) e fator de resistência corneal também mostrou significante diminuição nesse grupo, após o procedimento cirúrgico; valores médios pré e pós-operatórios de 8,2±1,6 e 4,1±2,5 mmHg respectivamente (p= 0,007), diminuição de 50%. A ceratometria média simulada apresentou maiores valores, após a confecção das lamelas mais espessas em relação ao pré-operatório (ceratometria pré e pós-operatória de 39,5±1 D e 45,9±1,2 D, respectivamente, p= 0,003). Para o grupo de lamelas finas, não houve diferença estatisticamente significante (ceratometria pré e pós-operatória de 40,6±0,6 D e 41,4±1,0 D, respectivamente, p=0,55). Em relação ao Sistema de Velocidade de Onda, após a criação das lamelas e sua amputação, houve diminuição da velocidade de propagação acústica, embora na maior parte das posições não fosse estatisticamente significante. Conclusão: Nas condições experimentais estabelecidas por este estudo, a criação de lamelas de maior espessura pareceu exercer efeito mais relevante sobre a biomecânica da córnea de suínos / Purpose: To study the impact of programmed flaps at two different thicknesses on the biomechanical properties of the swine corneas. Methods: Twelve pig eyes were enrolled in this study and were formed two groups: 100m and 300 m flaps performed with the femtosecond laser. Each eye had the following procedure before the flap creation: raster photograph topographic maps, Ocular Response Analyzer (ORA), Optical Coherence Tomography to measure the pachymetry and flap thickness and Surface Wave Velocity system which is a prototype system that measures sonic wave propagation time between two transducers positioned on the corneal surface before and after flap creation. This first step was designed to investigate the differences in respect to corneal hysteresis, corneal resistance factor, curvature change and ultrasonic wave propagation between the groups with thinner and thicker flaps. After this initial procedure, flap amputation was performed and new measurements with the surface wave velocity system were taken again. Results: Measured flap thicknesses averaged 108.5±6.9 (8.5% of the total cornea) and 307.8±11.5 m (22.9% of the total cornea) for thin and thick flap groups, respectively (p< 0.001). Hysteresis and corneal resistance factor did not change significantly after flap creation in the thin flap group (p = 0.81 and p = 0.62, respectively). With thicker flaps, both parameters decreased significantly from 8.0±1.0 to 5.1±1.5 mmHg (p=0.003, reduction of 36.25%) and from 8.2±1.6 to 4.1±2.5 mmHg, respectively (p = 0.007), reduction of 50%. Simulated keratometry values increased in the thick flap group (from 39.5±1 D to 45.9±1.2 D, p=0.003) after flap creation and not in the thin flap group (from 40.6±0.6D to 41.4±1.0D, p= 0.55). Regarding surface wave velocity analysis, the surgical procedures induced lower values in some positions although most of them did not present statistically different results. Conclusion: In this experimental model, thicker flaps seemed to have a greater effect on the biomechanics of the swinish cornea