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Hintergrund: Die Excimer Laser PRK zur Korrektur der geringen bis moderaten Myopie wird als präzises Verfahren der refraktiven Chirurgie angesehen und weltweit angewandt. Die Genauigkeit der PRK nimmt jedoch mit steigender Korrektur ab. Das Ziel dieser Untersuchung bestand darin, den Einfluß unterschiedlicher Laserstrahlapplikations- und -formungssysteme auf die korneale Oberflächenstruktur, das Hornhautprofil und die Zielrefraktion zu untersuchen. Materialien und Methoden: Es wurden mit dem Meditec Mel 60 und dem Schwind Keratom, zwei Excimer Laser der Wellenlänge 193 nm, an jeweils 10 enukleierten Schweinehornhäuten eine PRK mit einer Zielkorrektur von -3, -6, -9 D mit einem Ablationsdurchmesser von 6 mm (5 mm - 9D) durchgeführt, ein Silikonabdruck von der Hornhautoberfläche angefertigt und mit einem dynamisch fokussierenden Topometrie System UBM Microfocus vermessen. Hornhautradius, Brechkraft der stromalen Oberfläche, Profilabweichungen von der idealen sphärischen Form sowie Rauheitsparameter der verschiedenen Zonen wurden ermittelt. Ergebnisse: Epithelfreie Hornhäute besitzen ein sphärisches Profil. Der Meditec Mel60 Laser erzielte nach PRK von -3, -6 und -9 D sphärische Profile mit einer durchschnittlichen Refraktionsänderung von -3.4, -6.7 und -8.7 D. Das Schwind Keratom erzeugte eine mittlere Refraktionsänderung von -3.5, -5.8 und 8.4 D, wobei das korneale Ablationsprofil in allen Korrekturgruppen erhebliche Profilabweichungen in Form von zentralen Profilkuppen aufwies. Die durchschnittliche Höhe der zentralen Profilkuppen betrug nach der -3 D PRK 7.39 (±0.34) µm und stieg auf 16.31 (±1.06) µm bzw. 15.06 (±0.96) µm in der -6 und in der -9 D Serie. Die Relation zwischen der Profilkuppenhöhe und der Abtragtiefe lag zwischen 21 - 25% und konnte durch eine Anti-Central-Island Programm (ACI 100%) nur um 4% auf 18-20 % der Abtragtiefe reduziert werden. Die stromale Oberfläche der unbehandelten, epithelfreien Kontrollgruppe hat eine glatte, homogene Struktur. Die Rauheit der stromalen Oberfläche nach Ablation mit dem Meditec Laser war um 50 % stärker ausgeprägt als beim Schwind Keratom. Diskussion: Die Beschaffenheit der stromalen Oberfläche nach der Excimer Laser PRK zur Korrektur der Myopie, wird durch die Rauheitsparameter quantitativ beschrieben und ermöglicht den direkten Vergleich zwischen den Lasersystemen. Die Rauheit ist positiv mit der Ablationstiefe und dem Ablationsdurchmesser korreliert. Je höher eine myope Korrektur angestrebt wird, desto rauher ist die stromale Oberfläche und damit das Risiko, dass sich eine epitheliale Hyperplasie und subepitheliale Trübungen entwickeln, die ursächlich mit den klinisch beobachteten Phänomenen der myopen Regression, der Abnahme der Kontrastsehschärfe, dem Verlust der bestkorrigierten Sehschärfe und monokularer Doppelbilder in Zusammenhang stehen. Ob der Unterschied der Rauheit von durchschnittlich 50% sich in der Inzidenz der klinischen Komplikationen widerspiegelt, können nur vergleichende Studien belegen. Sicher ist, das die Vorhersagbarkeit des refraktiven Ergebnisses durch die Ablation mit dem Aesculap Meditec MEL 60 Laser besser einzuschätzen ist, als das mit zentralen Profilkuppen komplizierte Ablationsprofil des Schwind Keratoms. / Purpose: To evaluate the predictability of refractive outcome, sphericitiy of corneal profiles and surface roughness parameters after myopic PRK with different, commercially available excimer laser beam delivery and beam shaping systems. Materials and Methods: Myopic Excimer Laser PRK of -3, -6 and -9 D in 6mm ablation zone (5 mm in -9 D) on performed on porcine eyes was performed with the Aesculap Meditec Mel 60, a slit scanning Laser and the Schwind Keratom I, a broad area laser with band mask beam shaping. A silicone replica was obtained to conserve the corneal profile and measured with a dynamic focusing topometry system (UBM Microfocus) to obtain radius, corrected corneal refraction and corneal surface roughness parameters. Results: Untreated corneas of the control group displayed spherical profiles. PRK of intended -3, -6 and -9 D correction with the slit scanning Aesculap Meditec Mel60 excimer laser achieved a refractive change of an average -3.4, -6.7 and -8.7 D respectively without major profile deviations. PRK with the Schwind Keratom, a broad area beam excimer laser resulted a refractive change of -3.5, -5.8 and -8.4 D respectively. The Ablation created considerable central profile deviations representing central islands of 7.39 (±0.34) µm after -3 D, 16.31 (±1.06) µm and 15.06 (±0.96) µm height after - 6 and -9 D PRK, respectively. Mean central island height was 21 - 25% of ablation depth and was reduced by anti-central-island-program to 18-20 % of ablation depth. Stromal surface roughness increased with ablation depth and was significantly rougher after scanning beam ablation compared to broad area ablation. Conclusions: Profile deviations increase with higher corrections and lessen the predictability of the refractive results. The Aesculap Meditec MEL60 Slit scanning system creates predictable spherical corneal profiles. The Schwind Keratom broad area laser create with band mask beam shaping central islands increasing with higher corrections. The application of an Anti-Central-Island Program does not eliminate the central profile elevations sufficiently. Stromal surface was rougher after scanning beam compared to broad area beam ablation.

Introdução: A ceratectornia fotorrefrativa (PRK) é uma das técnicas de cirurgia refrativa mais empregadas no mundo. A despeito de sua efetividade e segurança no tratamento de miopia, hipermetropia e astigmatismo, a dor permanece ainda como um dos grandes desafios no período pós-operatório da PRK. Embora a associação dos fármacos codeína (opióide oral) e paracetamol (analgésico) seja amplamente empregada no período pós-cirúrgico de várias especialidades médicas. a eficácia e segurança dessa associação não foi avaliada no manejo da dor no pós-PRK. Objetivo: O objetivo da presente tese foi testar a combinação codeína + paracetamol no manejo da dor pós-PRK. Métodos: Trata-se de um ensaio clínico controlado por placebo, randomizado, paralelo e duplo-cego. O subdelineamento é do tipo \"add-on \", isto é. o grupo da intervenção recebeu a terapia padrão + a intervenção. enquanto o grupo controle recebeu a terapia padrão + placebo. A amostra foi composta por 41 participantes (82 olhos) - por meio do delineamento \"olhos pareados\" (paired-eye design), ou seja, o olho foi a unidade de análise. As cirurgias foram realizadas com duas semanas de intervalo. Um olho recebeu codeína (30 mg) + paracetamol (500 mg) 4x1dia por quatro dias (período A), enquanto o outro olho recebeu placebo 4x/dia por quatro dias (período B). Tanto a alocação (intervenção ou placebo) quanto a ordem (A-B ou B-A) foram aleatorizadas. A dor foi avaliada por meio de três escalas: questionário de dor McGill (MPQ). Inventário Resumido da Dor (I3PI) e escala visual análoga (EVA) nos períodos I, 24, 48 e 72 horas após a cirurgia. O período de seguimento total foi de quatro meses. Resultados: A idade média dos pacientes foi de 30 anos (rnin-máx: 22-52), dos quais 67% foram mulheres. Dos 82 olhos inicialmente arrolados no estudo, 80 completaram os quatro meses de seguimento (40 na intervenção e 40 no placebo). Os escores medianos de dor mensurados pela EVA foram significativamente mais baixos no grupo da intervenção comparado com o grupo placebo - durante todo o período do pós- cirúrgico imediato (1-48 horas). Os eventos adversos foram brandos e de fácil manejo clínico; os mais comuns foram sonolência, náusea e constipação. Após um seguimento de quatro meses, não foi observado nenhum retardo na resposta de cicatrização da córnea ou haze. Conclusões: A combinação de codeína (30mg) e paracetamol (500mg) via oral (4x/dia) é segura e significativamente superior ao placebo para o controle da dor após a PRK / Introduction: Photorefractive keratectomy (PRK) is one of most widely performed types of refractive surgery in the world. In spite of its effectiveness and safety for the treatment of myopia, hypermetropia and astigmatism, pain remains one of the biggest clinical challenges during the early postoperative period after PRK. Although the combination of codeine (an oral opioid) plus acetaminophcn (an analgesic) has been widely used during the postoperative period in many medical specialties, both its efficacy and safety have not been formally investigated for pain control after PRK. Objective: To carry out a randomized, controlled c1inical trial, specifically dcsigned to test whether the combination of codeine + acetaminophen is efficacious and safe for pain control after PRK. Methods: Double-blind (patients and outcome assessors), randomized, parallel, placebo-controlled trial. An add-on design was adopted. tl.at is, the intervention group received the standard of care therapy + codeine/acetaminophen, whereas the control group received the standard o[ care therapy + placebo. The sample encompassed 41 participants (82 eyes) through the \"paired-eye design\". In other words, the eye was the unity of analysis. Surgeries were performed two weeks ap311. One eye received codeine (30mg) + acetaminophen (500mg) 4x/day for four days (period A), whereas the fellow (control) eye received placebo 4x/day for four days (period B). Both treatrnents (intervention or placebo) and treatment order (A-B or B-A) were randomly chosen. Pain was asscsscd at 1, 24, 48 and 72h postopcrativcly by three scales: visual analogue scale (VAS), McGill Pain Questionnaire (MQP) and Brief Pain Inventory (BPI). The total follow-up period was 4 months. Results: The mean age of patients was 30 years (rnin-max: 22-52) and 67% (27/40) were female. Ofthe initial 82 eyes, 80 completed the trial (40 in the intervention 31m, 40 in the placebo arm). Median pain scores as measured by the VAS were significantly lower during treatment with codeine/acetaminophen compared to the placebo throughout the early postoperative period (1-48h). Virtually identical results were obtained by the MQP and BPI scales, suggesting that the intervention can have a positive impact not only on the pain intensity, but also on the multidimensional aspects of pain, such as interference on activities of daily living as well as emotional status. Adverse events (AEs) were usually mild and easily managed. The most common AEs were drowsiness, nausea and constipation. After a follow- up period of four months, no case of delayed epithelial healing or haze was observed in both treatment arms. Conclusions: When added to the standard of care therapy, the oral combination of codeine (30mg) and acetaminophen (500mg) given 4x/day was safe and significantly superior to placebo for pain control after PRK

Introdução: A ceratectornia fotorrefrativa (PRK) é uma das técnicas de cirurgia refrativa mais empregadas no mundo. A despeito de sua efetividade e segurança no tratamento de miopia, hipermetropia e astigmatismo, a dor permanece ainda como um dos grandes desafios no período pós-operatório da PRK. Embora a associação dos fármacos codeína (opióide oral) e paracetamol (analgésico) seja amplamente empregada no período pós-cirúrgico de várias especialidades médicas. a eficácia e segurança dessa associação não foi avaliada no manejo da dor no pós-PRK. Objetivo: O objetivo da presente tese foi testar a combinação codeína + paracetamol no manejo da dor pós-PRK. Métodos: Trata-se de um ensaio clínico controlado por placebo, randomizado, paralelo e duplo-cego. O subdelineamento é do tipo \"add-on \", isto é. o grupo da intervenção recebeu a terapia padrão + a intervenção. enquanto o grupo controle recebeu a terapia padrão + placebo. A amostra foi composta por 41 participantes (82 olhos) - por meio do delineamento \"olhos pareados\" (paired-eye design), ou seja, o olho foi a unidade de análise. As cirurgias foram realizadas com duas semanas de intervalo. Um olho recebeu codeína (30 mg) + paracetamol (500 mg) 4x1dia por quatro dias (período A), enquanto o outro olho recebeu placebo 4x/dia por quatro dias (período B). Tanto a alocação (intervenção ou placebo) quanto a ordem (A-B ou B-A) foram aleatorizadas. A dor foi avaliada por meio de três escalas: questionário de dor McGill (MPQ). Inventário Resumido da Dor (I3PI) e escala visual análoga (EVA) nos períodos I, 24, 48 e 72 horas após a cirurgia. O período de seguimento total foi de quatro meses. Resultados: A idade média dos pacientes foi de 30 anos (rnin-máx: 22-52), dos quais 67% foram mulheres. Dos 82 olhos inicialmente arrolados no estudo, 80 completaram os quatro meses de seguimento (40 na intervenção e 40 no placebo). Os escores medianos de dor mensurados pela EVA foram significativamente mais baixos no grupo da intervenção comparado com o grupo placebo - durante todo o período do pós- cirúrgico imediato (1-48 horas). Os eventos adversos foram brandos e de fácil manejo clínico; os mais comuns foram sonolência, náusea e constipação. Após um seguimento de quatro meses, não foi observado nenhum retardo na resposta de cicatrização da córnea ou haze. Conclusões: A combinação de codeína (30mg) e paracetamol (500mg) via oral (4x/dia) é segura e significativamente superior ao placebo para o controle da dor após a PRK / Introduction: Photorefractive keratectomy (PRK) is one of most widely performed types of refractive surgery in the world. In spite of its effectiveness and safety for the treatment of myopia, hypermetropia and astigmatism, pain remains one of the biggest clinical challenges during the early postoperative period after PRK. Although the combination of codeine (an oral opioid) plus acetaminophcn (an analgesic) has been widely used during the postoperative period in many medical specialties, both its efficacy and safety have not been formally investigated for pain control after PRK. Objective: To carry out a randomized, controlled c1inical trial, specifically dcsigned to test whether the combination of codeine + acetaminophen is efficacious and safe for pain control after PRK. Methods: Double-blind (patients and outcome assessors), randomized, parallel, placebo-controlled trial. An add-on design was adopted. tl.at is, the intervention group received the standard of care therapy + codeine/acetaminophen, whereas the control group received the standard o[ care therapy + placebo. The sample encompassed 41 participants (82 eyes) through the \"paired-eye design\". In other words, the eye was the unity of analysis. Surgeries were performed two weeks ap311. One eye received codeine (30mg) + acetaminophen (500mg) 4x/day for four days (period A), whereas the fellow (control) eye received placebo 4x/day for four days (period B). Both treatrnents (intervention or placebo) and treatment order (A-B or B-A) were randomly chosen. Pain was asscsscd at 1, 24, 48 and 72h postopcrativcly by three scales: visual analogue scale (VAS), McGill Pain Questionnaire (MQP) and Brief Pain Inventory (BPI). The total follow-up period was 4 months. Results: The mean age of patients was 30 years (rnin-max: 22-52) and 67% (27/40) were female. Ofthe initial 82 eyes, 80 completed the trial (40 in the intervention 31m, 40 in the placebo arm). Median pain scores as measured by the VAS were significantly lower during treatment with codeine/acetaminophen compared to the placebo throughout the early postoperative period (1-48h). Virtually identical results were obtained by the MQP and BPI scales, suggesting that the intervention can have a positive impact not only on the pain intensity, but also on the multidimensional aspects of pain, such as interference on activities of daily living as well as emotional status. Adverse events (AEs) were usually mild and easily managed. The most common AEs were drowsiness, nausea and constipation. After a follow- up period of four months, no case of delayed epithelial healing or haze was observed in both treatment arms. Conclusions: When added to the standard of care therapy, the oral combination of codeine (30mg) and acetaminophen (500mg) given 4x/day was safe and significantly superior to placebo for pain control after PRK

The control of cell adhesion to synthetic polymers is a key factor in tissue engineering, resting on the ability to direct specific cell types to adhere and proliferate in order to stimulate tissue reconstruction. But often the surface properties are compromised for the sake of the bulk properties, leading to surfaces that do not support sufficiently the level of bioactivity required and accordingly the polymeric biomaterial will fail clinically. Laser treatment offers a unique means of enhancing the osteoblast cell response of the surface of a polymeric biomaterial, whilst keeping the already sufficient bulk properties intact. To this end, infra-red (IR) and ultraviolet (UV) lasers have been employed to modify the wettability characteristics of nylon 6,6, as wetting is often the primary factor dictating the adhesion and bonding potential of materials, as a route to enhancing the surface in terms of osteoblast cell response. What is more, modifying wettability characteristics in this way is a highly attractive means of estimating the biofunctionality of a polymer. IR (CO2) and UV (F2 and KrF excimer) lasers were employed to carry out two different processes: laser whole area irradiative processing and laser-induced patterning. With both CO2 and the excimer lasers changes in the wettability characteristics could be effected with subsequent enhancement of osteoblast cell response. This was also the case with both laser-induced patterning and laser whole area irradiative processing. Essentially, an approach has been established whereby the osteoblast cell response on the surfaces of laser treated nylon 6,6 can be predicted through the laser-induced wettability characteristics modification, particularly for the laser whole area irradiative processed nylon 6,6. This ultimately allows one to determine the osteoblast cell response of the laser surface treated nylon 6,6 surfaces directly from the laser operating parameters. In concurrence with established wetting theory the laser whole area irradiative processing of the nylon 6,6 surfaces caused increased surface roughness, increased surface oxygen content, increased polar component, γP , and increased total surface energy, γT ; thereby generating surfaces displaying reduced contact angle, θ, making the nylon 6,6 surfaces more hydrophilic. The laser-induced patterned samples differed from current theory insofar as the nylon 6,6 surfaces became less hydrophilic due to an increase in θ despite an increase in surface roughness, an increase in surface oxygen content, an increase in γP and an increase in γT . This phenomena can be explained by the transition in wetting regimes from a Wenzel regime to a mixed-state wetting regime. Nevertheless, collation of the wettability characteristics results revealed that θ was a strong correlative decreasing function of both γP and γT , indicating that surface energy played a large role in determining the wetting nature of the nylon 6,6. It was found that for all laser whole area irradiative processed nylon 6,6 surfaces the osteoblast cell response was an increasing correlative and therefore predictive function of θ and was a decreasing function of γP . To an extent, the surface oxygen content and surface roughness could be used indirectly to foretell the osteoblast cell response of the nylon 6,6 surfaces. This is on account of the CO2 and KrF excimer laser whole area irradiative processing bringing about increased surface toxicity, which above a certain level hindered the osteoblast cell response. For the laser-induced patterned nylon 6,6 samples there did not appear to be any particular correlative trend between the modified surface parameters and osteoblast cell response. This can be accounted for by the transition in wetting regimes. Another important factor is that cell morphologies were modulated over all samples which suggests that varying surface parameters on account of laser surface treatment gave rise to variations in cell signaling. It was determined that θ, γP and γT all had very strong correlative relationships with the cytotoxicity. The cytotoxicity reduced upon an increase in θ until a minimum constant was achieved, whereas the cytotoxicity remained constant at low γP and γT until a point at which the cytotoxicity began to increase. These results are noteworthy as they allow one to deduce that, with constant cytotoxicity levels, the osteoblast cell response appeared to be modulated by the wettability characteristics. But once the cytotoxicity increased, the toxicity began to dominate and so negated the identified positive wettability characteristic correlations with osteoblast cell response. Practically, the surface roughness and surface oxygen content could be implemented indirectly to estimate the cytotoxicity. Increase in cytotoxicity was the result of the laser processing with higher fluences generating excessive melting. As a result of this, it is possible to deduce that there was a maximum threshold fluence, beyond which the toxicity of the nylon 6,6 began to dominate, giving rise to a less enhanced osteoblast cell response. On account of the correlative trends which have been identified between the laser surface treatment, wettability characteristics and osteoblast cell response of nylon 6,6 it is likely for one to have the ability to estimate the osteoblast cell response in vitro. This is significant as it indicates that laser surface modification of polymeric materials could have tremendous potential for application within the field of regenerative medicine.

OBJETIVO: Avaliar a eficácia, estabilidade, previsibilidade e segurança da ceratectomia fotorrefrativa (PRK) guiada pelas frentes de onda corneana para o tratamento da hipermetropia secundária à ceratotomia radial (CR). MÉTODOS: Foram avaliados prospectivamente 61 olhos de 39 pacientes consecutivos, submetidos a PRK personalizado com o laser Esiris-Schwind. A técnica constou de desepitelização mecânica, fotoablação, e utilização de mitomicina C (MMC) 0,02% por 20 ou 40 segundos. A MMC foi aplicada por 40 segundos em 17 olhos (27,9%) que haviam sido submetidos a ablações mais profundas do que 100 ?m ou apresentavam córneas previamente suturadas. As avaliações pós-operatórias foram realizadas após sete dias, um, seis, 12 e 24 meses. Todos os olhos foram avaliados após um ano e dois anos. RESULTADOS: O intervalo médio entre a CR e o PRK foi de 18,8 anos ± 3,8 (DP); o equivalente esférico (EE) médio antes da ceratotomia radial era -4,10 dioptrias (D) ± 1,44. As medidas prévias ao PRK mostraram EE médio de +4,17 D ± 1,97; astigmatismo médio de -1,39 D ± 1,04; AV com correção (AVcc) média de 0,161 ± 0,137 (logMAR); e curvatura corneana média de 35,85 ± 3,60 D. Os resultados encontrados dois anos após a cirurgia foram: EE médio de 0,14 ± 0,99 D (p < 0,001); astigmatismo médio de -1,19 ± 1,02 D (p = 0,627); AV sem correção (AVsc) média de 0,265 ± 0,196 (p < 0,001); AVcc média de 0,072 ± 0,094 (p < 0,001); e curvatura corneana média de 39,01 ± 3,18 D (p < 0,001). AVsc igual ou melhor a 20/25 foi observada em 38% dos olhos e igual ou melhor a 20/40 em 69%. A AVcc melhorou em 62,3% dos olhos, sendo que 21 olhos (34,4%) melhoraram uma linha e outros 17 olhos (27,9%), duas ou mais linhas. Um olho (1,6%) perdeu duas linhas devido ao astigmatismo irregular ocasionado por opacificação corneana periférica. Outro olho perdeu três linhas pelo desenvolvimento de ectasia corneana entre seis e 24 meses, devido ao alargamento progressivo de uma incisão radial inferior, e foi posteriormente submetido à sutura da incisão. Houve 30 olhos (49,2%) entre ± 0,50 D do EE planejado e 45 (73,8%) entre ± 1,00 D. Entre seis e 24 meses, a regressão média do EE foi de +0,39 D (p < 0,05) e cinco olhos (8,3%) sofreram desvio hipermetrópico > 1,00 D. Ocorreu redução estatisticamente significante do coma (p = 0,001), trefoil (p = 0,008), aberração esférica (p < 0,001), astigmatismo secundário (p = 0,001) e quatrefoil (p < 0,001). Não houve mudança estatisticamente significativa da contagem endotelial (p = 0,161). Dois olhos (3,3%) desenvolveram opacificação corneana periférica grau 2 e um, grau 3. CONCLUSÃO: O PRK personalizado pelas frentes de onda corneana coadjuvado pela MMC foi eficaz, previsível e seguro pelo período de dois anos para a redução da hipermetropia após a CR. No pós-operatório observou-se melhora significativa da AVsc, AVcc e das aberrações corneanas. Constatou-se, entretanto, que a hipermetropia consecutiva à CR continua a progredir após o tratamento com o excimer laser. / PURPOSE: To assess the efficacy, stability, predictability and safety of corneal wavefront-guided photorefractive keratectomy (PRK) for correcting hyperopia after radial keratotomy (RK). METHODS: In a prospective study, 61 eyes of 39 consecutive patients were treated with PRK using an Esiris-Schwind excimer laser. Corneal epithelium was mechanically removed, followed by photoablation and use of 0.02% mitomycin C (MMC) for 20 or 40 seconds. MMC was used for 40 seconds in 18 eyes (27.9%) which underwent ablations deeper than 100 micron or had previous corneal sutures. Postoperative evaluations were performed after seven days, six, 12 and 24 months. All patients were followed up for two years. RESULTS: The mean time between RK and PRK was 18.8 years ± 3.8 (SD); mean spherical equivalent (SE) before RK was -4.10 diopters (D) ± 1.44. Before PRK, the mean SE was +4.17 D ± 1.97, mean astigmatism was -1.39 D ± 1.04, the mean best-corrected visual acuity (BCVA) was 0.161 ± 0.137 (logMAR) and the mean corneal curvature was 35.85 ± 3.60 D. At 24 months, mean SE was 0.14 ± 0.99 D (p < 0.001), mean astigmatism was -1.19 ± 1.02 D (p = 0.627), mean UCVA was 0.265 ± 0.196 (p < 0.001), mean BSCVA was 0.072 ± 0.094 (p < 0.001) and the mean corneal curvature was 39.01 ± 3.18 D (p < 0.001). UCVA was 20/25 or better in 38% of eyes and 20/40 or better in 69%. BCVA improved in 62.3% of eyes, with 21 (34.4%) gaining one line and 17 (27.9%), two or more lines. One eye (1.6%) lost two lines due to irregular astigmatism and peripheral haze. Another eye lost three lines due to keratectasia occurring between six and 24 months resulting from widening of an inferior radial incision that was later sutured. Thirty eyes (49.2%) were within ± 0.50 D of intended SE and 45 (73.8%) were within ± 1.00 D. From six to 24 months, the mean SE regression was +0.39 D (p < 0.05) and five eyes (8.3%) had a hyperopic shift > 1.00 D. A significant decrease in coma (p = 0.001), trefoil (p = 0.008), spherical aberration (p < 0.001), secondary astigmatism (p = 0.001) and quatrefoil (p < 0.001) was observed. Endothelial cell counts did not show a statistically significant decrease (p = 0.161). Two eyes (3.3%) developed peripheral haze grade 2 and one, grade 3. CONCLUSION: Corneal wavefront-guided PRK with MMC was effective, predictable and safe after two years for the treatment of hyperopia after RK. A significant improvement in UCVA, BSCVA and corneal aberrations was obtained. However, hyperopic shift after RK continued to progress after excimer laser surgery.

Biobased materials made from renewable resources, such as wood, play an important role in the sustainable development of society. One main challenge of biobased building materials is their inherent moisture sensitivity, a major cause for fungal decay, mold growth and dimensional instability, resulting in decreased service life as well as costly maintenance. A new building material known as wood-plastic composites (WPCs) has emerged. WPCs are a combination of a thermoplastic matrix and a wood component, the former is usually recycled polyethylene or polypropylene, and the latter a wood processing residual, e.g. sawdust and wood shavings. The objective of this thesis was to gain more insight about characteristics of WPCs containing a modified wood component. The hypothesis was that a modified wood component in WPCs would increase the moisture resistance and durability in outdoor applications. The study comprises both injection molded and extruded WPC samples made with an unmodified, acetylated, thermally modified or furfurylated wood component in a polypropylene (PP), high density polyethylene (HDPE), cellulose ester (CAP, a cellulose ester containing both acetate and propionate substituents) or polylactate (PLA) matrix. The WPCs were prepared with 50-70 weight-% wood. The emphasis was on studying the moisture sorption, fungal resistance and micromorphological features of these new types of composites. Water sorption in both liquid and vapor phases was studied, and the biological performance was studied both in laboratory and in long term outdoor field tests. Micromorphological features were assessed by analyzing of the wood component prior to and after processing, and by studying the composite microstructure by means of a new sample preparation technique based on UV excimer laser ablation combined with scanning electron microscopy (SEM). Results showed that the WPCs with a modified wood component had a distinctly lower hygroscopicity than the WPCs with unmodified wood, which resulted in less wood-plastic interfacial cracks when subjected to a moisture soaking-drying cycle. Durability assessments in field and marine tests showed that WPCs with PP or CAP as a matrix and 70 weight-% unmodified wood degraded severely within a few years, whereas the corresponding WPCs with a modified wood component were sound after 7 years in field tests and 6 years in marine tests. Accelerated durability tests of WPCs with PLA as a matrix showed only low mass losses due to decay. However, strength losses due to moisture sorption suggest that the compatibility between the PLA and the different wood components must be improved. The micromorphological studies showed that WPC processing distinctly reduces the size and changes the shape of the wood component. The change was most pronounced in the thermally modified wood component which became significantly reduced in size. The disintegration of the modified wood components during processing also creates a more homogeneous micromorphology of the WPCs, which may be beneficial from a mechanical performance perspective. Future studies are suggested to include analyses of the surface composition, the surface energy and the surface energy heterogeneity of both wood and polymer components in order to tailor new compatible wood-polymer combinations in WPCs and biocomposites. / <p>QC 20121119</p>

Η εξέλιξη που γνώρισε το laser κατά τα χρόνια που πέρασαν μέχρι σήμερα είναι ραγδαία και θεαματική. Οι καταπληκτικές ιδιότητες του γοήτεψαν τόσο τους ερευνητές όσο και τους εκπροσώπους της βιομηχανίας και της τεχνολογίας. Τα laser αερίου ενεργού μέσου αποτελούν την πλειοψηφία των βιομηχανικών laser. Ένας τύπος αυτών είναι τα excimer laser τα οποία αποτελούν τα πιο ισχυρά laser στην υπεριώδη UV φασματική περιοχή. Το excimer (ή ακριβεστερα exciplex) laser XeCl αποτελεί αντικείμενο της παρούσας διπλωματικής εργασίας και περιλαμβάνει τα εξής μέρη: a. Συνοπτική παρουσίαση των βασικών αρχών λειτουργίας ενός laser b. Γενική παρουσίαση των Excimer laser αλλά και του laser XeCl c. Γενικές παρατηρήσεις στη μοντελοποίηση ενός excimer d. Παρουσίαση ενός απλού θεωρητικού μοντέλου για το laser XeCl e. Παρουσίαση και αξιολόγηση της υπολογιστικής μεθόδου και των αποτελεσμάτων της. Για τη μηδενικής διάστασης αριθμητική προσέγγιση αναπτύσσεται μία υπολογιστική μέθοδος επίλυσης. Η ίδια η μέθοδος στηρίζεται σε εξομοίωση που πραγματοποιήθηκε με χρήση του πακέτου λογισμικού Matlab 7.0. Τέλος, γίνεται έλεγχος της εξάρτησης της ισχύος και σύγκριση των αποτελεσμάτων, όπου αυτό είναι δυνατό. / -

OBJETIVO: Avaliar a eficácia, estabilidade, previsibilidade e segurança da ceratectomia fotorrefrativa (PRK) guiada pelas frentes de onda corneana para o tratamento da hipermetropia secundária à ceratotomia radial (CR). MÉTODOS: Foram avaliados prospectivamente 61 olhos de 39 pacientes consecutivos, submetidos a PRK personalizado com o laser Esiris-Schwind. A técnica constou de desepitelização mecânica, fotoablação, e utilização de mitomicina C (MMC) 0,02% por 20 ou 40 segundos. A MMC foi aplicada por 40 segundos em 17 olhos (27,9%) que haviam sido submetidos a ablações mais profundas do que 100 ?m ou apresentavam córneas previamente suturadas. As avaliações pós-operatórias foram realizadas após sete dias, um, seis, 12 e 24 meses. Todos os olhos foram avaliados após um ano e dois anos. RESULTADOS: O intervalo médio entre a CR e o PRK foi de 18,8 anos ± 3,8 (DP); o equivalente esférico (EE) médio antes da ceratotomia radial era -4,10 dioptrias (D) ± 1,44. As medidas prévias ao PRK mostraram EE médio de +4,17 D ± 1,97; astigmatismo médio de -1,39 D ± 1,04; AV com correção (AVcc) média de 0,161 ± 0,137 (logMAR); e curvatura corneana média de 35,85 ± 3,60 D. Os resultados encontrados dois anos após a cirurgia foram: EE médio de 0,14 ± 0,99 D (p < 0,001); astigmatismo médio de -1,19 ± 1,02 D (p = 0,627); AV sem correção (AVsc) média de 0,265 ± 0,196 (p < 0,001); AVcc média de 0,072 ± 0,094 (p < 0,001); e curvatura corneana média de 39,01 ± 3,18 D (p < 0,001). AVsc igual ou melhor a 20/25 foi observada em 38% dos olhos e igual ou melhor a 20/40 em 69%. A AVcc melhorou em 62,3% dos olhos, sendo que 21 olhos (34,4%) melhoraram uma linha e outros 17 olhos (27,9%), duas ou mais linhas. Um olho (1,6%) perdeu duas linhas devido ao astigmatismo irregular ocasionado por opacificação corneana periférica. Outro olho perdeu três linhas pelo desenvolvimento de ectasia corneana entre seis e 24 meses, devido ao alargamento progressivo de uma incisão radial inferior, e foi posteriormente submetido à sutura da incisão. Houve 30 olhos (49,2%) entre ± 0,50 D do EE planejado e 45 (73,8%) entre ± 1,00 D. Entre seis e 24 meses, a regressão média do EE foi de +0,39 D (p < 0,05) e cinco olhos (8,3%) sofreram desvio hipermetrópico > 1,00 D. Ocorreu redução estatisticamente significante do coma (p = 0,001), trefoil (p = 0,008), aberração esférica (p < 0,001), astigmatismo secundário (p = 0,001) e quatrefoil (p < 0,001). Não houve mudança estatisticamente significativa da contagem endotelial (p = 0,161). Dois olhos (3,3%) desenvolveram opacificação corneana periférica grau 2 e um, grau 3. CONCLUSÃO: O PRK personalizado pelas frentes de onda corneana coadjuvado pela MMC foi eficaz, previsível e seguro pelo período de dois anos para a redução da hipermetropia após a CR. No pós-operatório observou-se melhora significativa da AVsc, AVcc e das aberrações corneanas. Constatou-se, entretanto, que a hipermetropia consecutiva à CR continua a progredir após o tratamento com o excimer laser. / PURPOSE: To assess the efficacy, stability, predictability and safety of corneal wavefront-guided photorefractive keratectomy (PRK) for correcting hyperopia after radial keratotomy (RK). METHODS: In a prospective study, 61 eyes of 39 consecutive patients were treated with PRK using an Esiris-Schwind excimer laser. Corneal epithelium was mechanically removed, followed by photoablation and use of 0.02% mitomycin C (MMC) for 20 or 40 seconds. MMC was used for 40 seconds in 18 eyes (27.9%) which underwent ablations deeper than 100 micron or had previous corneal sutures. Postoperative evaluations were performed after seven days, six, 12 and 24 months. All patients were followed up for two years. RESULTS: The mean time between RK and PRK was 18.8 years ± 3.8 (SD); mean spherical equivalent (SE) before RK was -4.10 diopters (D) ± 1.44. Before PRK, the mean SE was +4.17 D ± 1.97, mean astigmatism was -1.39 D ± 1.04, the mean best-corrected visual acuity (BCVA) was 0.161 ± 0.137 (logMAR) and the mean corneal curvature was 35.85 ± 3.60 D. At 24 months, mean SE was 0.14 ± 0.99 D (p < 0.001), mean astigmatism was -1.19 ± 1.02 D (p = 0.627), mean UCVA was 0.265 ± 0.196 (p < 0.001), mean BSCVA was 0.072 ± 0.094 (p < 0.001) and the mean corneal curvature was 39.01 ± 3.18 D (p < 0.001). UCVA was 20/25 or better in 38% of eyes and 20/40 or better in 69%. BCVA improved in 62.3% of eyes, with 21 (34.4%) gaining one line and 17 (27.9%), two or more lines. One eye (1.6%) lost two lines due to irregular astigmatism and peripheral haze. Another eye lost three lines due to keratectasia occurring between six and 24 months resulting from widening of an inferior radial incision that was later sutured. Thirty eyes (49.2%) were within ± 0.50 D of intended SE and 45 (73.8%) were within ± 1.00 D. From six to 24 months, the mean SE regression was +0.39 D (p < 0.05) and five eyes (8.3%) had a hyperopic shift > 1.00 D. A significant decrease in coma (p = 0.001), trefoil (p = 0.008), spherical aberration (p < 0.001), secondary astigmatism (p = 0.001) and quatrefoil (p < 0.001) was observed. Endothelial cell counts did not show a statistically significant decrease (p = 0.161). Two eyes (3.3%) developed peripheral haze grade 2 and one, grade 3. CONCLUSION: Corneal wavefront-guided PRK with MMC was effective, predictable and safe after two years for the treatment of hyperopia after RK. A significant improvement in UCVA, BSCVA and corneal aberrations was obtained. However, hyperopic shift after RK continued to progress after excimer laser surgery.

In the present research, a novel method, namely sol-gel/laser-induced technique (SGLIT), has been developed to generate nano-structured TiO2-based films. The TiO2 films based on unloaded (pure) TiO2, Ce-TiO2, W-TiO2 and Ag-TiO2, have been investigated in attempt to stabilise the formation of anatase and consequently of enhancing photo-catalytic and anti-bacterial activities. The TiO2 precursor loaded with Ce2+, W6+ and Ag2+ ions (Ce-TiO2, W-TiO2 and Ag-TiO2) were separately prepared by sol-gel method and spin-coated on microscopic glass slides. A pulsed KrF excimer laser with a wavelength of 248 nm and pulse width of 13-20 ns was employed to irradiate on the sol-gel prepared films at various operating parameters, in terms of laser fluence, number of laser pulses and repetition rate. The work has been focussed on microstructural characterisation of various films prepared by both SGLIT and furnace, in the consideration of crystallographic structure, phase transformation, crystallite sizes, surface morphology, film thickness and optical properties, by means of Raman spectroscopy, XRD, FEG-SEM/EDX, TEM/HR-TEM/EDX, AFM and UV-Vis spectroscopy etc. The results showed that nano-crystallisation of the films after laser irradiation has been achieved, with controllable amount of anatase formation. These coatings presented a unique feature of surface morphology with meso-porosity and much enlarged surface areas, compared with the films prepared by furnace sintering technique. The addition of Ce and Ag, stabilized the anatase structure during the laser irradiations, whereas the addition of W destabilized the anatase structure. The Ce-TiO2 films prepared by SGLIT exhibited anatase structure which was stable up to 500 laser pulses at 35 mJ cm-2 fluence. The anatase was formed after 10 laser pulses only at 65-75 mJ cm-2 fluence in the W-TiO2 films. When a higher number of laser pulses, fluence or higher W6+ loading were chosen, rutile structure started to form. On the other hand, the Ag-TiO2 nano-composite films prepared by SGLIT presented the anatase up to 200 laser pulses at 85 mJ cm-2 fluence. On average, anatase crystallite size of about 38 nm was achieved from both the W-TiO2 and Ag-TiO2 films prepared by SGLIT. In contrast, the furnace-sintered W-TiO2 and Ag-TiO2 films produced anatase crystallite size of 49.4 nm and 29.8 nm respectively. Another achievement of the present research is the development of a single-step laser irradiation technique to generate an Ag-TiO2 nano-composite film on the glass substrate. A pulsed laser beam produced hexagonal Ag nanoparticles along with the crystallization of anatase-based nano-structured TiO2 film which was accomplished in 1 µs only. The films prepared by SGLIT displayed a higher photo-absorption compared to their furnace-sintered counterparts due to the unique surface features with a higher surface roughness. Overall, an enhanced bactericidal activity against E. coli cells was demonstrated under UV light by each of the W-TiO2 films compared to furnace-sintered films except the 1W-TiO2. The E. coli cells did not survive on the W-TiO2 films prepared by SGLIT, after 80 minutes under UV (365 nm) light. In contrast, E. coli cells still survived on the surface of furnace-sintered W-TiO2 films under the same conditions. Ag-TiO2 nano-composite films prepared by SGLIT, demonstrated an enhanced anti-bacterial activity against E. coli compared to the conventionally- made Ag-TiO2 films. No bacteria survived on the Ag-TiO2 films prepared by 50 laser pulses at 85 mJ cm-2 fluence, whereas E. coli colonies always survived on the furnace-sintered Ag-TiO2 films under the UV, natural light and the dark room conditions.