Refractive surgery is designed to minimize the need for glasses and/or contact lenses and is often used for convenience, cosmetic or occupational purposes. The two most common types of laser eye surgery are LASIK and LASEK. During LASIK, the first step is the creation of the corneal flap using either a femtosecond laser or a mechanical microkeratome. The femtosecond laser has been seen to create more uniform flaps that reduce the risk of intraoperative and postoperative flap complications compared to the mechanical microkeratome. The purpose of this study was to investigate the effect on visual outcomes of second surgery LASEK on patients following aborted LASIK surgeries due to Femtosecond laser flap complications. LASIK was performed as planned and the corneal flap was created by the femtosecond laser but could not be lifted when a surgical cut was made. The procedure was aborted and LASEK was performed within a few weeks to attain the desired vision correction. A total of 14 patients were identified over a 6-year period ranging from 2009-2015. Most patients underwent surface ablation within two weeks of the initial aborted procedure. 12 of the 14 patients had a UCVA of 20/20, while the remaining 2 patients had a UCVA of 20/25 at their last postoperative visit. None of the patients required surgical enhancements despite the flap complications and no major postoperative complications were noted in any of the patients. Provided the corneal flap was well centered and there was no evidence of microstriae or epithelial ingrowth, surface ablation LASEK can be performed within a week of the aborted LASIK procedure to minimize discomfort and trauma to the patient. LASEK is associated with a slightly longer healing time but no evidence of corneal or retinal issues were noted in these patients. None of the patients experienced any significant changes in refraction between surgeries and was thus a reliable indicator of refractive stability following the flap complication. No significant differences were noted with delaying the second surgery LASEK as several patients attained 20/20 vision when it was performed within a week. The most common flap complication was the formation of an incomplete flap that could not be lifted. The cause could not be identified.

No description available.

This thesis sets up the problem of sight in a visual society, with the aim to answer how the visual makes itself known. The conversation starts on visuality, and where there are gaps in understanding. The first of two case studies examines the absence of sight, or blindness, both literal and figurative. Through a study of blind photographers and their work, this chapter examines the nature of perception, and how biological blindness may influence and inform our understanding of figurative blindness. The second case study examines what the improvement of damaged sight has to say about the rhetorical nature of images. This chapter examines various means of improving sight, using literal improvements to sight to understand figurative improvements in vision and perception. The fourth and final chapter seeks to sum up what has been discovered about the rhetorical nature of sight through the ends of the spectrum of sight.

Purpose: To compare and analyze the differences in visual outcomes between Visx iDesign Advanced WaveScan Studio (TM) System, Alcon Wavelight Allegro Topolyzer and Nidek EC-5000 using Final Fit (TM) Custom Ablation Treatment Software from the submitted summary of safety and effectiveness of the US Food and Drug Administration (FDA) data. Methods: In this retrospective comparative study, 334 eyes from Visx iDesign, 212 eyes from Alcon Contour, and 135 eyes from Nidek CATz platforms were analyzed for primary and secondary visual outcomes. These outcomes were compared via side-by-side graphical and tabular representation of the FDA data. Statistical significance was calculated when appropriate to assess differences. A P-value <0.05 was considered statistically significant. Results: The mean postoperative uncorrected distance visual acuity (UDVA) at 12 months was 20/19.25 +/- 8.76, 20/16.59 +/- 5.94, and 20/19.17 +/- 4.46 for Visx iDesign, Alcon Contoura, and Nidek CATz, respectively. In at least 90% of treated eyes at 3 months and 12 months, all three lasers showed either no change or a gain of corrected distance visual acuity (CDVA). Mesopic contrast sensitivity at 6 months showed a clinically significant increase of 41.3%, 25.1%, and 10.6% for eyes using Visx iDesign, Alcon Contoura, and Nidek CATz, respectively. Photopic contrast sensitivity at 6 months showed a clinically significant increase of 19.2%, 31.9%, and 10.6% for eyes using Visx iDesign, Alcon Contoura, and Nidek CATz, respectively. Conclusion: FDA data for the three platforms shows all three were excellent with respect to efficacy, safety, accuracy, and stability. However, there are some differences between the platforms with certain outcome measurements. Overall, patients using all three lasers showed significant improvements in primary and secondary visual outcomes after LASIK surgery.

Actualmente uno de los principales objetivos en cirugía refractiva no es sólo la emetropía, sino obtener una alta calidad de visión, parámetro de difícil cuantificación al estar involucrada la subjetividad del paciente. Para obtener un buen resultado postoperatorio es necesario que la zona óptica del procedimiento a realizar sea amplia. Por otro lado, a medida que aumenta el defecto refractivo a corregir esta zona óptica debe ser disminuida por razones de seguridad. Es por ello que han hecho su aparición los procedimientos combinados, generalmente uno corneal y otro intraocular; al utilizarse la zona óptica más grande posible en ambos se mejora por una parte, la calidad de visión en condiciones de baja iluminación y por otra, disminuyen quejas frecuentes como el deslumbramiento y los halos en pacientes con miopías altas.En el presente estudio prospectivo, longitudinal y aleatorizado se muestra una serie de casos de pacientes afectos de miopía alta con equivalentes esféricos superiores a -15.50 D. En un grupo de estos pacientes se empleó una técnica combinada, una corneal (LASIK) y otra intraocular (implante de lente fáquica de Artisan®) para mantener una zona óptica de tratamiento de 6 mm. Este grupo de pacientes se comparó con otro de iguales características en los que se empleó una sola técnica, el implante de lente fáquica de Artisan®, con una zona óptica de 5 mm. Se valoró la respuesta clínica objetiva mediante la medición de la agudeza visual sin y con corrección, refracción manifiesta y sensibilidad al contraste, la respuesta clínica subjetiva medida a través de cuestionarios subjetivos, la predictibilidad, seguridad y estabilidad de ambos métodos.La respuesta clínica objetiva y subjetiva, así como la predictibilidad del método combinado (implantación de LIO Artisan" más LASIK) fue mejor que la del método único (implantación de LIO Artisan"), por lo que se concluye que el método combinado es más eficaz y predecible que el método único. Todo esto nos hace inferir que la zona óptica de 6 mm es muy importante y determinante en las diferencias presentadas entre los dos grupos. Indudablemente, otros factores también influyen los resultados como, por ejemplo, el buen centramiento de la lente, factor que depende de la habilidad del cirujano en el caso de la lente Artisan".No se observaron diferencias estadísticamente significativas entre ambos métodos tomando en cuenta los criterios de seguridad y estabilidad ya establecidos en cirugía refractiva, durante el primer año de postoperatorio.El concepto de satisfacción del paciente es un punto muy importante que también debe examinarse en aquellos pacientes sometidos a cualquier tipo de cirugía refractiva. Las principales fuentes de insatisfacción son los halos, deslumbramiento y alteraciones en la visión nocturna, especialmente cuando se efectúa cirugía refractiva con zona óptica pequeña. En este sentido, la agudeza visual y la refracción postoperatoria no son parámetros suficientes para juzgar los resultados obtenidos. La auto-evaluación por parte del paciente así como pruebas funcionales del tipo de sensibilidad al contraste o medición de las aberraciones ópticas son también necesarias para la valoración integral de nuestros pacientes. / Currently one of the main objectives in refractive surgery it is not emetropia but high quality of vision, which is difficult to evaluate because of the patients subjectivity.It is necessary to use a wide optical zone in order to obtain a high-quality postoperative result. On the other hand, when the refractive error increases, the optical zone must be reduced for safety reasons. For this rationale, combined procedures have emerged, usually one corneal and other intraocular, to improve the quality of vision in dim illumination conditions and diminish frequent complaints such as glare and halos in high myopic patients, when the widest optical zone is used in both procedures. The current prospective, longitudinal and randomized study shows a series of cases of high myopic patients with spherical equivalents higher than -15.50 diopters. In one group of these patients a combined technique was used, one corneal, LASIK, and other intraocular, phakic Artisan® intraocular lens (IOL)implantation, in order to maintain a 6 mm optical zone. This group of patients was matched up to another group with equal characteristics submitted to 5 mm phakic Artisan® IOL implantation. The assessment included the objective response evaluated by visual acuity with/without correction, manifest refraction, and contrast sensitivity while subjective response was evaluated by questionnaires. Moreover, predictability, safety and stability of both methods were measured and compared. The objective and subjective responses as well as the predictability of the combined method (Artisan® lens implantation plus LASIK) were better than those in the unique method (Artisan® lens implantation), consequently the combined method is more efficient and predictable than the unique method. All of this rationale let us infer that the 6 mm optical zone is very important and determinant in the differences between the two groups. Nevertheless, other factors such as a well-centred IOL, influence the final result, issue that depends on surgeon's skill.There were no statistically significant differences between both groups considering safety and stability criteria, already established in refractive surgery, during the first postoperative year.Patient's satisfaction concept is a very important subject that must be check up in those patients submitted to any refractive surgery. The main source of unsatisfied patients are halos, glare and night vision alterations, especially in those cases submitted to procedures with small optical zone. Therefore, postoperative visual acuity and refraction are not the only parameters to take into account in results assessment. Patient's self-evaluation and functional tests such as contrast sensitivity or optical aberration measurement are necessary to achieve a complete evaluation.

Introducción: Se ha realizado un estudio comparativo entre el tratamiento LASIK estándar, y el tratamiento personalizado de la miopía basado en la aberrometría. La diferencia principal entre los dos tratamientos es el patrón de ablación, siendo en el tratamiento personalizado un patrón asférico. Con éste se pretende conseguir una mejor calidad visual postoperatoria en los pacientes operados de cirugía refractiva. Material y métodos: Se ha dividido la población en dos grupos homogéneos en cuanto a miopía, edad, sexo, y aberraciones preoperatorias. A cada grupo se le ha tratado con un laser diferente, y se les ha comparado en términos de predictibilidad, eficacia, seguridad y estabilidad. Además se les ha realizado un seguimiento postoperatorio de la evolución de las aberraciones para determinar las diferencias en la corrección de éstas entre los dos laseres. Se ha utilizado un aberrómetro basado en el método de Hartmann-Shack, y un topógrafo de elevación. Junto a esto se ha determinado el cambio inducido en la sensibilidad al contraste debido a la cirugía mediante la caja de Ginsburg. Por ultimo hemos comparado los dos láseres en términos de paquimetría y cantidad de ablación, y zona óptica. La aplicación del laser se ha realizado con un Technolas 217Z, que incorpora la posibilidad de tratamiento LASIK estándar, o personalizado, con las novedades del haz de 1mm y con perfil gausiano truncado.Resultados: La predictibilidad, eficacia, seguridad y estabilidad han sido similares en ambos laseres aunque el tratamiento personalizado consigue mejores resultados en cuanto a seguridad, ya que algunos pacientes pueden llegar a ganar hasta 2 líneas de visión, lo que no hemos podido apreciar con el tratamiento estándar. En cuanto a las aberraciones, el tratamiento personalizado ha conseguido reducir, o en algunos casos inducir en menor grado aberraciones de tercer y cuarto orden. En lo que se refiere a la sensibilidad al contraste, con el tratamiento personalizado se consigue conservar ésta en las altas frecuencias. Otro resultado interesante ha sido que el tratamiento personalizado de la miopía ablaciona un 30% menos de tejido de media, debido al patrón de ablación asférico que le permite reducir la zona de transición, razón por la cual las zonas ópticas del tratamiento personalizado son menores.Conclusiones: Los resultados obtenidos son esperanzadores, ya que el tratamiento personalizado ha demostrado ventajas respecto al tratamiento estándar, y nos animan a seguir la investigación en esta dirección. Debemos tener en cuenta que estamos en los albores de esta nueva tecnología y que nos falta mucho por descubrir para poder poner a la práctica todo lo que ésta nos puede aportar. / Introduction: We have compared standard LASIK treatment with customized ablation based on aberrometry. The main difference between these two treatments is the ablation pattern, as in customized ablation this pattern is aspheric. This way, we aim to a better postoperatively visual quality in patients who have undergone corneal refractive surgery.Materials and methods: We have split the population into two homogeneous groups in terms of myopia, age, sex and preoperative aberrations. Each group was treated with a different laser and were compared in terms of predictability, efficacy, security and stability. Moreover we carried on a postoperative follow-up of the aberrations evolution so as to define the difference between the two lasers. We used an aberrometer based on Hartmann-Shack technology, and elevation topography. We also determined the change in contrast sensitivity induced by the surgery with the Ginsburg box. Finally, we compared the two lasers in terms of paquimetry and depth of ablation, and optical zone. Laser delivery has been done with a Technolas 217Z, which can ablate in a standard or a customized way, as it introduces new technology as the 1mm spot or the truncated gausian beam.Results: Predictability, efficacy, security and stability were similar in both lasers,although the customized treatment achieves better results in terms of security, as some patients can gain two lines of vision, contrary to the results obtains with standard LASIK. About the performance in the correction of aberrations, customized ablation has reduced or induced in a smaller way, third and fourth order aberrations. About contrast sensitivity, customized ablation allows not to lose contrast sensitivity in higher frequencies. Another interesting result is that customized ablation ablates 30% less tissue due to its aspheric ablation pattern which allows a reduction in the transition zone, reason why the optical zone in customized ablations are smaller than in standard treatments.Conclusions: Results obtained are encouraging, as customized ablations has shown advantages with respect to standard LASIK and this gives us reasons to going on investigating in this new and promising technology. We have to bear in mind that we are in the very beginning of this new technology and we have a long way to go in order to put into practice all this technology can offer to us.

Wavefront-guided (WFG) laser in situ keratomileusis (LASIK) differs from conventional surgery by applying a refined algorithm for tissue removal, based on information from preoperative wavefront aberration data. Since the introduction of this technology, there have been few investigations comprehensively reporting outcomes, particularly for hyperopic treatments. This thesis aimed to determine the impact of myopic and hyperopic WFG LASIK on visual acuity, contrast sensitivity, higher order aberrations and subjective ratings, as well as determine the relationship between these outcome measures. Bilateral WFG LASIK was performed on 324 myopic eyes (162 subjects) and 62 hyperopic eyes (31 subjects). High contrast (HC) and low contrast (LC) best-corrected visual acuity (BCVA) and contrast sensitivity were assessed using ETDRS charts and vertical sinusoidal gratings, respectively. Higher order ocular aberrations were measured using a Shack-Hartmann wavefront sensor and analyzed across a 5.0 mm pupil. Subjective ratings were assessed using a closed-ended categorical questionnaire. Assessments were conducted prior to surgery and at three and six months postoperatively. WFG LASIK had minimal impact on BCVA and contrast sensitivity; however there was an impact on the magnitude and profile of higher order aberrations, which differed between the myopic and hyperopic groups. There was a greater increase in higher order aberrations for the hyperopic group, who also had a tendency to have lower visual outcomes and worse subjective ratings. Despite these results, there were no associations between subjective ratings and higher order aberrations, LC BCVA or contrast sensitivity for both groups and a clear understanding of the relationship between these outcome measures was not apparent. Factor analysis revealed a variety of factors that contributed to the outcome measures for this data set, with the three main factors being: subjective ratings, vision and optical quality. In conclusion, WFG LASIK had excellent outcomes in terms of visual acuity, contrast sensitivity, and subjective ratings, despite an increase in higher order aberrations compared with those found prior to surgery. Hyperopic outcomes were slightly worse than myopic outcomes. Further investigation is required to determine the impact of higher order aberrations on visual acuity, contrast sensitivity and subjective ratings, as well as the relationship between these measures.

Wavefront-guided (WFG) laser in situ keratomileusis (LASIK) differs from conventional surgery by applying a refined algorithm for tissue removal, based on information from preoperative wavefront aberration data. Since the introduction of this technology, there have been few investigations comprehensively reporting outcomes, particularly for hyperopic treatments. This thesis aimed to determine the impact of myopic and hyperopic WFG LASIK on visual acuity, contrast sensitivity, higher order aberrations and subjective ratings, as well as determine the relationship between these outcome measures. Bilateral WFG LASIK was performed on 324 myopic eyes (162 subjects) and 62 hyperopic eyes (31 subjects). High contrast (HC) and low contrast (LC) best-corrected visual acuity (BCVA) and contrast sensitivity were assessed using ETDRS charts and vertical sinusoidal gratings, respectively. Higher order ocular aberrations were measured using a Shack-Hartmann wavefront sensor and analyzed across a 5.0 mm pupil. Subjective ratings were assessed using a closed-ended categorical questionnaire. Assessments were conducted prior to surgery and at three and six months postoperatively. WFG LASIK had minimal impact on BCVA and contrast sensitivity; however there was an impact on the magnitude and profile of higher order aberrations, which differed between the myopic and hyperopic groups. There was a greater increase in higher order aberrations for the hyperopic group, who also had a tendency to have lower visual outcomes and worse subjective ratings. Despite these results, there were no associations between subjective ratings and higher order aberrations, LC BCVA or contrast sensitivity for both groups and a clear understanding of the relationship between these outcome measures was not apparent. Factor analysis revealed a variety of factors that contributed to the outcome measures for this data set, with the three main factors being: subjective ratings, vision and optical quality. In conclusion, WFG LASIK had excellent outcomes in terms of visual acuity, contrast sensitivity, and subjective ratings, despite an increase in higher order aberrations compared with those found prior to surgery. Hyperopic outcomes were slightly worse than myopic outcomes. Further investigation is required to determine the impact of higher order aberrations on visual acuity, contrast sensitivity and subjective ratings, as well as the relationship between these measures.

Thesis (M. Med. Sc.)--University of Hong Kong, 2002. / Includes bibliographical references (46-49).

Thesis (M.Med.Sc.)--University of Hong Kong, 2002. / Includes bibliographical references (46-49). Also available in print.