Dans un contexte d’augmentation du nombre d’amétropes dans la population mondiale, et en conséquence, de l’accroissement du recours aux techniques de corrections chirurgicales, la compréhension et l’amélioration de celles-ci sont un enjeu crucial. Nous avons cherché à améliorer la prédictibilité de certains résultats postopératoires dans le cas d’un LASIK (Laser-Assisted In-Situ Keratomileusis), d’une PKR (Photorefractive Keratectomy) ou d'une chirurgie de la cataracte, et ainsi formuler des recommandations pratiques qui contribueraient au développement de stratégies de traitement davantage personnalisés. Pour cela, nous avons utilisé prospectivement des méthodologies de « contrôle de qualité » des chirurgies sur de larges échantillons de patients. Dans un premier temps, nous avons étudié la dynamique pupillaire dans le cadre de chirurgies au LASIK et notamment le rôle du centre pupillaire, point de référence important dans les stratégies de centrage. Nous avons également évalué la dynamique du diamètre pupillaire et les modifications du segment antérieur sur des yeux subissant une chirurgie de la cataracte. La seconde partie du travail s’est focalisée sur le rôle de l’épithélium dans la topographique cornéenne. Nous avons comparé les topographies spéculaires de l'épithélium et de la couche de Bowman sur des cornées saines et des cornées kératoconiques, présentant une myopie faible à modérée corrigée par PKR. Enfin, dans la dernière partie de notre recherche, nous nous sommes intéressés aux changements de paramètres anatomiques de l'oeil, des performances visuelles et de la qualité de vision subjective survenant dans un échantillon d’yeux myopes après un LASIK réalisé avec le laser WaveLight® Refractive Suite (Alcon® Laboratories Inc., USA). / While the number of ametropic eyes in the world’s population and consequently the use of surgical correction techniques is increasing, understanding and improving these techniques is a crucial issue. We sought to improve the predictability of certain postoperative results in the case of LASIK (Laser-Assisted In-Situ Keratomileusis), PRK (Photorefractive Keratectomy) and cataract surgery, and thus to formulate practical recommendations that would contribute to the development of more personalized treatment strategies. To achieve this objective, we have prospectively used "quality control" methodologies to assess surgeries performed on large samples of patients. First, we studied the pupillary dynamics in LASIK surgery and in particular the role of the pupillary centre, an important point of reference in the centration strategies. We also assessed the dynamics of pupillary diameter and anterior segment changes on eyes undergoing cataract surgery. The second part of the work focused on the role of the epithelium in the corneal topography. We compared specular topographies of the epithelium and Bowman's layer in healthy and keratoconus corneas with mild to moderate myopia corrected by PRK. Finally, in the last part of our research, we were interested in the changes in anatomical parameters of the eye, visual performance and subjective quality of vision occurring in a sample of myopic eyes after LASIK performed with the WaveLight® Refractive Suite (Alcon® Laboratories Inc., USA).

Syfte: Studiens syfte var att undersöka hur refraktiv kirurgi ser ut i Sverige idag, vilka komplikationer som finns och vilka metoder som används genom att göra en kort redovisning av de vanligaste teknikerna FS-lasik, LASEK, TransPRK och RLE som finns inom refraktiv kirurgi och med hjälp av en enkät ta reda på de olika komplikationerna mellan olika åldersgrupper.  Metod: En enkätstudie inom refraktiv kirurgi i Sverige genomfördes. Enkäten var webbaserad och skapad i Google Docs (http://docs.google.com). Enkäten innehöll totalt 11 frågor som handlade om patientens tidiga refraktion, operationsmetod och ögonhälsa efter operationen. Enkäten spreds via sociala medier som Facebook, Instagram, Twitter, olika forumsiter, samt mail. En del av enkäten var även fördelad på två olika ögonkliniker i Lund. Resultat: Resultaten av enkäten visar att det finns inte någon skillnad i komplikationsgraden mellan de olika åldersgrupperna och komplikationerna efter kirurgin beror på typen av metod och patientens synfel och brytningsfel.  Slutsats: Vid de olika metoderna förekommer olika komplikationer och ju mer närsynt patienten är desto större är risken för komplikationer i samband med operationen. / Refractive surgery is an effective method for correcting visual refractive errors. The method has evolved quickly over the past decade. The aim of this study was to examine what refractive surgery is in Sweden today. What complications exist and which methods are used, are described by making a presentation of the refractive surgery techniques FS-LASIK, LASEK, TransPRK and RLE. This was done by a survey to find out the various complications between different age groups. A web-based survey was disseminated trough social media like Facebook, different forum sites and e-mail. The survey was also submitted to various eye clinics. The respondents were asked questions about their age, gender, the surgical method used and the complications after surgery. The results of the survey showed that there is no difference in the complication rate between the different age groups. Complications only depend on the type of method used and the patient’s refractive errors.

OBJETIVOS: Determinar la técnica de LASIK (convencional o personalizada) que consigue una mayor calidad visual en los pacientes intervenidos de cirugía refractiva (en términos de agudeza visual, sensibilidad al contraste y sensación subjetiva), así como comparar su efectividad, eficacia, predictibilidad, seguridad, estabilidad y su repercusión en las aberraciones corneales provocadas tras la cirugía.MATERIAL Y METODOS:En una muestra de 27 pacientes con las mismas características en los dos ojos se analiza la calidad visual del paciente, así como las aberraciones pre y postoperatorias tras la aplicación de cirugía refractiva corneal con láser Excímer, realizando un tratamiento convencional en un ojo del paciente y un tratamiento personalizado en el otro ojo. Se realizan controles postoperatorios al día siguiente de la cirugía, a la semana, al mes, a los tres, seis y doce meses.La calidad visual del paciente se analiza en términos de agudeza visual, sensación subjetiva y sensibilidad al contraste con el test CSV-1000. Las aberraciones se han medido con un aberrómetro basado en el método de Hartmann-Shack. El láser se ha aplicado con el Technolas 217z, que posee la capacidad de realizar un tratamiento LASIK estándar o personalizado.RESULTADOS:El tratamiento personalizado consigue una calidad visual levemente superior a la técnica convencional en términos de agudeza visual (sobre todo en ganancia de líneas de visión) y sensibilidad al contraste, pero sin significación estadística a los 12 meses de la intervención.La predictibilidad, eficacia, seguridad y estabilidad de ambos tipos de técnicas son similares. En cuanto a las aberraciones, el tratamiento personalizado ha conseguido reducir o inducir en menor grado aberraciones de tercer y cuarto orden, pero las de quinto orden han empeorado más en los ojos intervenidos con el tratamiento personalizado.DISCUSIÓN:Al comparar el tratamiento LASIK convencional de la miopía con el personalizado se puede llegar a afirmar que sólo se encuentran sutiles diferencias entre ellos (como la mayor ganancia de líneas de visión en el tratamiento personalizado) pero sin significación estadística. Esto podría ser debido a que las aberraciones de la población seleccionada no son muy elevadas. Por ello se puede considerar que la ablación personalizada puede lograr una mayor calidad visual tras cirugía refractiva si los pacientes tienen altos valores elevados de las aberraciones de alto orden.

Purposes: To use optical coherence tomography (OCT) to image and quantify the effect of various corneal conditions, in terms of corneal, stromal and epithelial thickness, and light backscatter. To assess the changes caused by overnight orthokeratology (Corneal Refractive Therapy; CRT^TM) lens wear, keratoconus and laser in-situ keratomileusis (LASIK) refractive surgery, each of which may lead to topographical alterations in corneal thickness either by temporary moulding, degeneration, or permanent laser ablation, respectively. <br /><br /> Methods: Topographical thickness of the cornea was measured using OCT in all studies. The CRT^TM studies investigated myopic and hyperopic treatment, throughout the day. The myopic studies followed lens wear over a 4 week period, which was extended to 12 months, and investigated the thickness changes produced by two lenses of different oxygen transmissibility. CRT^TM for hyperopia (CRTH^TM) was evaluated after a single night of lens wear. <br /><br /> In the investigation of keratoconus, OCT corneal thickness values were compared to those obtained from Orbscan II (ORB) and ultrasound pachymetry (UP). A new fixation device was constructed to aid in the measurement of topographical corneal and epithelial thickness along 8 directions of gaze. Pachymetry maps were produced for the normal non-lens wearing cornea, and compared with the rigid gas permeable (RGP) lens wearing cornea and the keratoconic cornea. <br /><br /> Thickness changes prior to, and following LASIK were measured and monitored throughout six months. Myopic and hyperopic correction was investigated individually, as the laser ablation profiles differ for each type of procedure. The LASIK flap interface was also evaluated by using light backscatter data to monitor healing. <br /><br /> Results: Following immediate lens removal after myopic CRT^TM, the central cornea swelled less than the periphery, with corneal swelling recovering to baseline levels within 3 hours. The central epithelium decreased and mid-peripheral epithelium increased in thickness, with a more gradual recovery throughout the day. There also seemed to be an adaptation effect on the cornea and epithelium, showing a reduced amount of change by the end of the 4 week study period. The thickness changes did not alter dramatically during the 12 month extended study. In comparing the two lens materials used for myopic CRT^TM (Dk/t 91 vs. 47), there were differences in stromal swelling, but no differences in the central epithelial thinning caused by lens wear. There was a statistically insignificant asymmetry in mid-peripheral epithelial thickening between eyes, with the lens of lower Dk causing the greater amount of thickening. Hyperopic CRT^TM produced a greater increase in central stromal and central epithelial thickness than the mid-periphery. Once again, the stroma recovered faster than the epithelium, which remained significantly thicker centrally for at least six hours following lens removal. <br /><br /> Global pachymetry measurements of the normal cornea and epithelium found the periphery to be thicker than the centre. The superior cornea and epithelium was thicker than the inferior. In the measurement of the keratoconic cornea, OCT and ORB correlated well in corneal thickness values. UP measured greater values of corneal thickness. The keratoconic epithelium was thinner than normal, and more so over the apex of the cone than at the centre. The location of the cone was most commonly found in the inferior temporal region. Central epithelial thickness was thinner in keratoconics than in RGP lens wearers, which in turn was thinner than in non-lens wearers. <br /><br /> Following LASIK surgery for both myopia and hyperopia, the topographical OCT thickness profiles showed stromal thinning in the areas of ablation. The central myopic cornea showed slight regression at 6 months. During early recovery, epithelial thickness increased centrally in hyperopes and mid-peripherally in myopes. By the end of the 6 month study, mid-peripheral epithelial thickness was greater than the centre in both groups of subjects. The light backscatter profiles after LASIK showed a greater increase in backscatter on the anterior side of the flap interface (nearer the epithelium), than the posterior side (in the mid-stroma) during healing. The flap interface was difficult to locate in the OCT images at 6 months. <br /><br /> Conclusion: All the CRT^TM lenses used in this project produced more corneal swelling than that seen normally overnight without lens wear. In order for these lenses to be worn safely for long periods of time without affecting the health of the cornea, they need to be manufactured from the highest oxygen transmissible material available. The long-term effect of thinning on the epithelium's barrier properties needs to be monitored closely. <br /><br /> Global topographical thickness of the cornea and epithelium was measured using OCT in normal, RGP lens wearing and keratoconic eyes. Corneal and epithelial thickness was not symmetrical across meridians. The epithelium of RGP lens wearers was slightly thinner than normal, but not as thin as in keratoconics, suggesting that the epithelial change seen in keratoconus is mainly due to the condition. <br /><br /> Post-LASIK corneal and epithelial thickness profiles were not the same for myopic and hyperopic subjects, since the ablation patterns vary. Epithelial thickening in the mid-periphery had not recovered by six months in myopes or hyperopes, possibly indicating epithelial hyperplasia. Light backscatter profiles were used to monitor the recovery of the LASIK flap interface, showing the band of light backscatter around the flap interface to decrease as the cornea healed.

Purposes: To use optical coherence tomography (OCT) to image and quantify the effect of various corneal conditions, in terms of corneal, stromal and epithelial thickness, and light backscatter. To assess the changes caused by overnight orthokeratology (Corneal Refractive Therapy; CRT^TM) lens wear, keratoconus and laser in-situ keratomileusis (LASIK) refractive surgery, each of which may lead to topographical alterations in corneal thickness either by temporary moulding, degeneration, or permanent laser ablation, respectively. <br /><br /> Methods: Topographical thickness of the cornea was measured using OCT in all studies. The CRT^TM studies investigated myopic and hyperopic treatment, throughout the day. The myopic studies followed lens wear over a 4 week period, which was extended to 12 months, and investigated the thickness changes produced by two lenses of different oxygen transmissibility. CRT^TM for hyperopia (CRTH^TM) was evaluated after a single night of lens wear. <br /><br /> In the investigation of keratoconus, OCT corneal thickness values were compared to those obtained from Orbscan II (ORB) and ultrasound pachymetry (UP). A new fixation device was constructed to aid in the measurement of topographical corneal and epithelial thickness along 8 directions of gaze. Pachymetry maps were produced for the normal non-lens wearing cornea, and compared with the rigid gas permeable (RGP) lens wearing cornea and the keratoconic cornea. <br /><br /> Thickness changes prior to, and following LASIK were measured and monitored throughout six months. Myopic and hyperopic correction was investigated individually, as the laser ablation profiles differ for each type of procedure. The LASIK flap interface was also evaluated by using light backscatter data to monitor healing. <br /><br /> Results: Following immediate lens removal after myopic CRT^TM, the central cornea swelled less than the periphery, with corneal swelling recovering to baseline levels within 3 hours. The central epithelium decreased and mid-peripheral epithelium increased in thickness, with a more gradual recovery throughout the day. There also seemed to be an adaptation effect on the cornea and epithelium, showing a reduced amount of change by the end of the 4 week study period. The thickness changes did not alter dramatically during the 12 month extended study. In comparing the two lens materials used for myopic CRT^TM (Dk/t 91 vs. 47), there were differences in stromal swelling, but no differences in the central epithelial thinning caused by lens wear. There was a statistically insignificant asymmetry in mid-peripheral epithelial thickening between eyes, with the lens of lower Dk causing the greater amount of thickening. Hyperopic CRT^TM produced a greater increase in central stromal and central epithelial thickness than the mid-periphery. Once again, the stroma recovered faster than the epithelium, which remained significantly thicker centrally for at least six hours following lens removal. <br /><br /> Global pachymetry measurements of the normal cornea and epithelium found the periphery to be thicker than the centre. The superior cornea and epithelium was thicker than the inferior. In the measurement of the keratoconic cornea, OCT and ORB correlated well in corneal thickness values. UP measured greater values of corneal thickness. The keratoconic epithelium was thinner than normal, and more so over the apex of the cone than at the centre. The location of the cone was most commonly found in the inferior temporal region. Central epithelial thickness was thinner in keratoconics than in RGP lens wearers, which in turn was thinner than in non-lens wearers. <br /><br /> Following LASIK surgery for both myopia and hyperopia, the topographical OCT thickness profiles showed stromal thinning in the areas of ablation. The central myopic cornea showed slight regression at 6 months. During early recovery, epithelial thickness increased centrally in hyperopes and mid-peripherally in myopes. By the end of the 6 month study, mid-peripheral epithelial thickness was greater than the centre in both groups of subjects. The light backscatter profiles after LASIK showed a greater increase in backscatter on the anterior side of the flap interface (nearer the epithelium), than the posterior side (in the mid-stroma) during healing. The flap interface was difficult to locate in the OCT images at 6 months. <br /><br /> Conclusion: All the CRT^TM lenses used in this project produced more corneal swelling than that seen normally overnight without lens wear. In order for these lenses to be worn safely for long periods of time without affecting the health of the cornea, they need to be manufactured from the highest oxygen transmissible material available. The long-term effect of thinning on the epithelium's barrier properties needs to be monitored closely. <br /><br /> Global topographical thickness of the cornea and epithelium was measured using OCT in normal, RGP lens wearing and keratoconic eyes. Corneal and epithelial thickness was not symmetrical across meridians. The epithelium of RGP lens wearers was slightly thinner than normal, but not as thin as in keratoconics, suggesting that the epithelial change seen in keratoconus is mainly due to the condition. <br /><br /> Post-LASIK corneal and epithelial thickness profiles were not the same for myopic and hyperopic subjects, since the ablation patterns vary. Epithelial thickening in the mid-periphery had not recovered by six months in myopes or hyperopes, possibly indicating epithelial hyperplasia. Light backscatter profiles were used to monitor the recovery of the LASIK flap interface, showing the band of light backscatter around the flap interface to decrease as the cornea healed.

published_or_final_version / Medical Sciences / Master / Master of Medical Sciences

INTRODUCTION/PURPOSE: Billions of people world wide suffer from refractive errors requiring glasses, contact lenses, or other means of correction to enable them to see better. Many people seeking permanent means to correct their vision consider undergoing corneal refractive laser surgeries (CRLS), photorefractive keratectomy (PRK), laser-assisted subepithelial keratectomy (LASEK), or laser in situ keratomileusis (LASIK). These surgeries have been shown to improve vision, but are not without risks for complications intra-operatively and postoperatively. Few studies have looked at the long-term incidence of postoperative complications such as dry eyes and visual aberrations and the associated preoperative risk factors. It is the aim of this study to examine the long-term incidence of dry eyes and visual aberrations (starbursts, halos, glare) after CRLS, and assess for preoperative risk factors associated with the persistence of these symptoms after surgery. METHODS: This study consisted of 319 patients identified for undergoing PRK, LASEK, or LASIK, at Boston Laser between December 2009 and January 2014. The participants in this study completed a novel online questionnaire consisting of questions to assess dry eye and visual aberration symptoms, and included questions adapted from the Ocular Surface Disease Index (OSDI). Postoperative dry eye symptoms were measured based on the OSDI score and a new dry eye measurement score created for this study's questionnaire. Presence or absence of visual aberration symptoms postoperatively were measured based on a score created for this study and derived from the calculation of the OSDI score. Additionally, a retrospective chart review was conducted of the 319 participants' medical charts to gather and assess for preoperative risk factors related to the long-term incidence of both dry eye and visual aberration symptoms. RESULTS: Our data found a significant association (p < 0.05) that suggests a relationship between development of long-term dry eye symptoms and the following preoperative variables: pupil size, flap thickness, and dry eye risk assessment (including: Zone Quick test values ≤ 9.0mm, contact lens use, and dry eyes with and without contact lenses). No significant association (p > 0.05) was found between the novel dry eye score and the preoperative factors, but it did approach significance with two variables, necessitating further investigation: gender and actual ablation. No significance (p >0.05) was found in the association between the preoperative dry eye risk assessment and severity of postoperative symptoms as gathered using the OSDI score. Our data found a significant association (p < 0.05) that suggests an increased risk for development of long-term visual aberrations symptoms postoperatively with the following preoperative variables: cylindrical manifest refraction, flat K, and greater actual flap thickness. As well as identifying two other possible variables that approached significance requiring further investigation: steep K and preoperative visual aberrations risk (including: spherical manifest refraction &#8805; -6.00, astigmatic manifest refraction ≥ -2.00, and pupil diameter ≥ 7.0). The data showed a significant association (p < 0.05) between postoperative symptom presence and the aforementioned preoperative visual aberrations risk. Our data showed no significance (p > 0.05) when comparing the difference between mean OSDI, dry eye, and visual aberration scores between participants grouped by years since surgery. DISCUSSION/CONCLUSION: Our data found a significant relationship between long-term dry eye risk after CRLS and preoperative pupil size, flap thickness, and dry eye risk assessment. Similarly the data also displayed a significant association between long-term visual aberration risk after CRLS and greater preoperative cylindrical manifest refraction, flat K, and flap thickness. These findings contribute to the risk factors identified in similar short-term follow-up studies, and support the need for increased research into the risk factors and long-term incidence of dry eyes and visual aberrations after CRLS. While the data showed no significance between participants grouped by years since surgery and reported postoperative symptoms, the OSDI mean scores did approach significance (p = 0.088), suggesting that further research with a greater survey population is required.

BACKGROUND: The human eye is an incredible organ, capable of focusing and detecting light that passes through its specialized structures. These organs are responsible for the sensation of vision and are crucial to the ability to function and operate during daily life. Loss of the sense of vision can result in serious deficits that greatly reduce the quality of a person’s life. One of the most prevalent causes of vision impairment in the world is refractive error. Although this is a common and relatively simple problem to fix with modern technology, ophthalmologists are continuously searching for new methods of treating people’s eyes to correct refractive errors and improve vision. There are several popular methods for correcting refractive errors, including traditional glasses, contact lenses, and laser vision correction. Laser vision correction is the most modern method for improving visual acuity deficits caused by refractive errors. The two most favored techniques for laser vision correction are laser assisted in site keratomileusis (LASIK) and photorefractive keratectomy (PRK). The performance of these procedures requires a laser treatment input to be calculated based on the patient’s refractive error. These laser treatment inputs are often determined using a nomogram. Nomograms are mathematical functions utilizing a graphical display to calculate a given value based on a set of parameters. Nomograms are crucial for safe and effective LASIK and PRK procedures and there is much interest in enhancing these algorithms to improve the refractive and visual acuity outcomes. OBJECTIVES: The objective of the study was to determine if a newer, more complex laser vision correction nomogram could generate laser treatment inputs better than another more traditional nomogram in terms of refractive and visual acuity outcomes. METHODS: The study included 109 eyes belonging to 59 patients. Fifty-one eyes belonging to 28 patients were operated on using the Wellington nomogram and 58 eyes belonging to 31 patients were operated on using the Internet-based refractive analysis (IBRA) nomogram. Visual acuity and refractive outcomes were recorded at a six-week follow-up evaluation. Data were analyzed using statistical tests to determine significant values. RESULTS: No statistically significant difference was found between the recorded visual acuity and refractive outcomes of eyes operated on using the Wellington and IBRA nomograms. CONCLUSIONS: The two nomograms were found to perform at equal efficacy and to reach the established standards for safety. Although no significant difference was found between the two nomogram outcomes it is possible that there were variables limiting the external validity of the statistical analysis. With extra time, additional cases, and better sample matching the study could be expanded and developed to provide a more reliable and more representative dataset to elucidate conclusions with greater impact. / 2022-06-07T00:00:00Z

INTRODUCTION: There are two main procedures responsible for correcting refractive error: laser-assisted in situ keratomileusis (LASIK) and photorefractive keratectomy (PRK). The most common postoperative complication of all laser vision correction (LVC) surgeries is keratoconjunctivitis sicca, or dry eye. In addition to physical irritation, dry eye can cause poor visual acuity and reduced quality of life. There are inconsistencies in the literature about which procedure results in higher rates of dry eye thus we explored the likelihood of a dry eye intervention within the first year after surgery. METHODS: Performing a retrospective chart review of all patients who underwent LVC procedures between 2009-2019 at a private Boston ophthalmology clinic, we were able to quantify the proportion of patients that required postoperative dry eye interventions within the 12 months following surgery. At this clinic, a dry eye intervention was defined as one of two treatments: punctal plug insertion or prescription medication (Restasis or Xiidra) use. RESULTS: A total of 11,175 LASIK eyes from 5,920 individuals, 1,549 LASEK eyes from 880 individuals, and 2,006 PRK eyes from 1,165 individuals were included in the analysis. Comparing the proportion of LASIK dry eye interventions to the proportion of PRK/LASEK dry eye interventions via a 2-sample z-test at an alpha level of significance of 0.05, yielded a z-value= 5.7 and a p-value= <0.0001 at a 95% CI (0.0102 - 0.0208). CONCLUSION: Our results suggest a greater incidence of postoperative dry eye interventions for PRK/LASEK patients compared to LASIK patients in the 12 months following LVC surgery. This study was limited in regards to both objective and subjective indicators of dryness; therefore future studies should attempt to be more comprehensive in evaluating postoperative dry eye. However, this study should help surgeons in the decision making process of which refractive eye surgery to recommend in order to reduce postoperative dry eye incidence and improve overall patient quality of life and satisfaction. / 2022-06-08T00:00:00Z

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