No description available.

Despite the effort to optimize soft contact lens performance, almost half of the 140 million contact lens wearers worldwide experience symptoms of ocular dryness and discomfort, especially towards the end of the day. These symptoms are attributed to reduced compatibility between the contact lens and the ocular surface and are the main reason for contact lens discontinuation. As the interactions of the contact lens-eye interface are dynamic, the surface properties play a key role in improving ocular compatibility, comfort and overall performance of contact lenses. One promising method to reduce adverse interfacial interactions between the contact lens and the ocular surface is to modify the contact lens surface with a biomimetic layer inspired by the ocular surface and the tear film. Hyaluronic acid (HA) is a non-sulfated glycosaminoglycan naturally found in the ocular environment providing ocular hydration and lubrication. Proteoglycan 4 (PRG4), a mucin-like glycoprotein naturally produced at the ocular surface contributes to natural lubrication during blinking and to tear film stability. Surface modification with HA or PRG4 has been shown to result in improved wetting, lubricating and antifouling properties. Moreover, HA and PRG4 have been previously found to interact and synergistically reduce friction further. In the current work, novel HA and PRG4-grafted soft contact lens surfaces were prepared, and the impact of the surface tethered layer on important contact lens properties was assessed. Furthermore, the potential synergistic effect between HA and rhPRG4 on the examined properties was evaluated. Surface immobilization of HA on model conventional (pHEMA) and silicone (pHEMA-co-TRIS) hydrogel contact lenses was achieved by thiol-ene “click” chemistry, while full-length recombinant human PRG4 (rhPRG4) was surface grafted via carbonyldiimidazole (CDI) linking chemistry respectively. The chemical structure after each modification step was determined by attenuated total reflectance FTIR (FTIR-ATR) and X-ray photoelectron spectroscopy (XPS) analyses. HA-grafted model soft contact lenses were characterized by improved surface wettability, antifouling and water retentive properties, while a decreasing trend in boundary friction was observed but only for the HA-grafted pHEMA-co-TRIS materials. Surface-tethering of rhPRG4 was found to effectively enhance the surface wettability and boundary lubricating properties of pHEMA-co-TRIS hydrogels only, whereas both rhPRG4-grafted pHEMA and pHEMA-co-TRIS materials exhibited lower protein sorption and dehydration rate. Overall, the surface immobilization processes followed herein did not alter the optical transparency of the model soft contact lenses or their in vitro compatibility with human corneal epithelial cells. Finally, there was evidence that HA and rhPRG4 synergistically interacted, further improving the contact lens properties. However, the degree of HA/rhPRG4 synergy was found to be dependent on the configuration of the formed HA/rhPRG4 complex as well as the composition of the substrate hydrogel material, with the noted improvement being more significant for the model silicone hydrogels. This is the first study to examine surface grafted full-length rhPRG4 and the effect of this modification on contact lens properties. Moreover, the study is the first to investigate the interactions between covalently tethered rhPRG4 and solutions containing HA. The results of this thesis demonstrate that HA and rhPRG4 are good candidates for the development of novel biomimetic surfaces, especially for silicone hydrogel contact lenses. The potential for using these compounds in synergy was also demonstrated, with wetting solutions of HA showing promise for modifying rhPRG4 modified materials to improve symptoms of discomfort. These naturally occurring ocular agents have the potential to improve the management of ocular dryness and discomfort, thus optimizing the overall soft contact lens performance. / Thesis / Doctor of Philosophy (PhD)

An efficient delivery system and patient compliance are two of the most important factors for any drug delivery system design to be successful. The current standard, particularly to the ocular anterior segment, are topical applications including eye drops. However, due to ocular physical barriers including blinking, the varying tear film layers, and the structure of the corneal epithelium, less that 5% of drug reach the target tissue from a single eye drop dose. While most treatment regiments combat this with increased frequency of dosage and higher than needed concentrations, the need for a more efficient and controlled system has been recognized to reduce the risk of possible side effects. Contact lenses (CL) have been a widely discussed potential drug delivery device given their accepted use in the population, their ability to hold drug, as well as their placement on the ocular surface. The current work focuses on testing a novel delivery system using CLs with the incorporation of drug specific oligonucleotide chains known as aptamers on the surface of the lenses. This application of contact lenses is aimed at capitalizing on the strong affinity of aptamers to hold drug on the surface of the lenses until they are applied to the eyes. The aptamers were covalently attached to the surface via the activation of the hydroxyl groups on pHEMA as a model lens material using 1’1-carbonyldiimidazone CDI chemistry and subsequent reaction with the amine group on the 5' end of the aptamer. The presence of aptamers was confirmed using 6-carbofluorescein (6-FAM) fluorescence detection and x-ray photoelectron spectroscopy (XPS). The release of kanamycin B in comparison to regular pHEMA gels using a soaking uptake method was assessed. In this work, aptamers were confirmed through fluorescence to have been successfully reacted onto the surface, however XPS was not able to confirm a consistent reading. This may have been due to low initial amounts of aptamer or uneven distributions along the surface. The efficiency of the aptamer reaction was not tested and would need to be further investigated. The contact angle had a significant change with increased hydrophilicity at 60.7 ± 1.55° compared to 66.6 ± 0.67°, however physically it should not affect wettability. The lower aptamer amounts resulted in no significant difference during drug release. Kanamycin B was detected using liquid chromatography mass spectroscopy (LCMS) with a reverse phase method using a C18 column however quite a few errors in the methodology led to the conclusion that this method of drug release requires further investigation. It is recommended an aptamer-surface reaction efficiency be determined with the use of a much larger starting aptamer amount, as well as a follow up drug release. / Thesis / Master of Applied Science (MASc)

The aim of the present study was to determine adaptive gait changes in long-term wearers of monovision correction contact lenses by comparing gait parameters when wearing monovision correction to those observed when wearing binocular distance correction contact lenses. Methods: Gait and toe clearance parameters were measured in eleven participants (53.5 ± 4.6 years, median monovision wearing time 5 years) as they repeatedly walked up to and onto a raised surface with either monovision or distance correction. Results: Compared to distance correction, monovision resulted in a large reduction in stereoacuity from 17¿ to 87¿, a slower walking velocity (p = 0.001), a reduced horizontal toe clearance of the step edge (p = 0.035) and, for trials when monovision correction occurred first, a 33% greater variability in vertical toe clearance (p = 0.021). Variability in some gait data was large due to certain study design features and learning effects. Conclusion: A slower walking velocity with monovision correction suggests participants became more cautious, likely as a result of the significantly reduced stereoacuity. The decreased horizontal toe clearance and increased vertical toe clearance variability suggests that monovision correction may cause a greater likelihood of hitting step edges and tripping during everyday gait. Recommended study design features are suggested for future adaptive gait studies to increase the precision of the data and to attempt to minimize the effects of learning from somatosensory feedback.

Yes / All neophyte contact lens wearers require training on how to handle contact lenses. Currently, almost no published information exists describing the most common approaches used by those involved in such training in soft contact lens wearers. This study aimed to gather information on the approaches taken by those conducting this training worldwide. An online survey was created in English and translated to Spanish and distributed internationally via social media, conference attendees, and professional contacts. The anonymous survey included information on workplace setting of respondents, information about the typical approaches used for application and removal of soft contact lenses, length of the appointment, and success rate with their approach. Survey responses were received between May 2021 and April 2022. A total of 511 individuals completed the survey and responses were received from 31 countries with 48.7% from the UK. The most common approach taught for application was to have the patient hold the upper eyelashes (84.7%) and to hold the lower eyelid with the same hand as the lens (89.4%). Lenses were applied directly to the cornea by 57.7% of the respondents. The most common approach taught for lens removal was to drag the lens inferiorly from the cornea prior to removal (49.3%). Most respondents did not use videos to aid the teaching appointment (62.0%); however, they felt that their approach was successful in most cases (90). Application and removal training sessions lasted a median of 30 min and contact lenses were typically dispensed after the instructor witnessing successful application and removal three times. Various methods are adopted globally for training of application and removal of soft contact lenses, with many advising a patient-specific approach is required for success. The results of this survey provide novel insights into soft contact lens handling training in clinical practice. / British & Irish University and College Contact Lens Educators (BUCCLE) receives sponsorship from CooperVision, Alcon, Bausch + Lomb and Johnson and Johnson. No specific grant was received for this study, and no sponsors had any input or involvement within this project. Nery Garcia-Porta is supported financially by a Maria Zambrano contract at USC under the grants call for the requalification of the Spanish university system 2021–2023, funded by the European Union—Next Generation EU.

No description available.

Contact lens performance depends on a number of lens properties. Many metrology systems have been developed to measure different aspects of a contact lens, but none test the surface figure in reflection to subwavelength accuracy. Interferometric surface metrology of immersed contact lenses is complicated by the close proximity of the surfaces, low surface reflectivity, and instability of the lens. An interferometer to address these issues was developed and is described here. The accuracy of the system is verified by comparison of glass reference sample measurements against a calibrated commercial interferometer. The described interferometer can accurately reconstruct large surface departures from spherical with reverse raytracing. The system is shown to have residual errors better than 0.05% of the measured surface departure for high slope regions. Measurements made near null are accurate to lambda/20. Spherical, toric, and bifocal soft contact lenses have been measured by this system and show characteristics of contact lenses not seen in transmission testing. The measurements were used to simulate a transmission map that matches an actual transmission test of the contact lens to lambda/18. (C) 2016 Society of Photo-Optical Instrumentation Engineers (SPIE)

Currently, most contact lenses are made with a silicone hydrogel (Si-Hy) blend that provides softness for comfort as well as high oxygen permeability. Silicone hydrogel lenses have both hydrophilic and hydrophobic areas, and the natural hydrophobicity of the material contributes to biofouling, which is the adsorption of proteins and lipids from the tear film of the eye. Published in vitro investigations into the quantity and spatial distribution of lipids deposited on contact lenses usually involve the use of artificial tear fluid (ATF) that is not changed or replenished over the course of the experiments. Yet, the natural tear film is constantly replenished by the meibomian and lacrimal glands. The intent of this study was to investigate the significance of replenishing the ATF over the study period on lipid absorption profiles and quantities. In part one, fluorescence confocal microscopy was used to observe the penetration profiles of lipids into nine different Si-Hy lenses. In part two, radiolabeling was used to quantify the amount of lipid absorbed by nine different Si-Hy lenses. Using a non-static exposure method was found to allow more absorption of cholesterol than the static method. The non-static method also provided more differentiation between lens types and brands in lipid absorption profiles and amounts than the static method. / acase@tulane.edu

La aberración de onda ocular está estrechamente vinculada con la calidad visual y presenta valores característicos en cada ojo. Su medida y corrección tienen un gran interés tanto en el ámbito de ciencia básica como en la práctica clínica. En el presente trabajo se desarrolla un sistema experimental de medida del frente de onda ocular con gran rango dinámico basado en un sensor Shack-Hartmann. Con él se miden las aberraciones oculares monocromáticas en dos grupos de sujetos: uno de jóvenes con ojos sanos y otro de sujetos que han sido intervenidos de transplante de córnea (queratoplastia penetrante). Los resultados muestran que el valor RMS medio de las aberraciones de alto orden es 10 veces superior en estos últimos. Además se encontró una alta correlación entre las aberraciones corneales (obtenidas de la topografía corneal) y las aberraciones oculares del grupo con patología corneal.Se estudia, de forma simulada y real, la corrección de las aberraciones por medio de lentes de contacto hidrofílicas, diseñadas a partir del patrón de aberraciones de cada sujeto. El estudio se realiza para tres tipos de ojos: normales, con queratoconos y con transplante de córnea. Los resultados muestran que las principales limitaciones de este tipo de corrección se originan debido a la posición y orientación media de la lente de contacto en el ojo. Si tenemos en cuenta desplazamientos realistas de la lente de contacto encontramos que los sujetos normales presentan una pérdida de calidad óptica respecto de la corrección estándar (corrección esfero-cilíndrica). Sin embargo, existen casos patológicos en los que a pesar de las típicas rotaciones y traslaciones de las lentes de contacto, se podría disminuir el RMS de las aberraciones y aumentar la calidad visual, como se comprueba experimentalmente en los queratoconos. / The ocular wave aberration is strongly related with the visual quality having specific values for each eye. Its measurement and correction is challenging for fundamental research as well as for clinical practice. In this work we develop an experimental apparatus to measure the ocular wavefront based on a Shack-Hartmann sensor with a high dynamic range. We use it for measuring monochromatic ocular aberration in two subject groups: a) normal young subjects (normal group hereafter) and b) penetrating queratoplasty eyes (pathologic group hereafter). The results show that mean RMS values of the high order aberrations in the pathologic group was ten times higher than that of the normal group. Further, there is a strong correlation between the corneal aberrations (obtained by corneal topography) and ocular aberrations in the pathological group. We study the aberration correction using soft contact lenses, custom designed from each subject aberrations, by mean of both experiments and theoretical predictions. The study is carried out for three types of eyes: normal, keratoconus and penetrating queratoplasty. Results show that the main factors limiting this correction method are owing to both the mean position and rotation of the contact lenses on eye. We found that the normal subjects show a loss of optical quality relative to standard correction (sphere and cylinder), caused by expected displacements of the lenses contacts. In spite of the rotations and translations expected of contact lenses, there are, however, pathologic cases in which it is possible to reduce the RMS and increase visual quality, such as it was experimentally demonstrated in the keratoconus eyes.

The wettability of contact lenses has become an area of intense research, with the belief that the more "hydrophilic" or wettable the lens surface is, the more comfortable the lens may be, as the posterior surface of the eyelid will move more smoothly over it, hence increasing comfort. <br /><br /> There are many ways to assess the wettability of a given material, namely sessile drop,¹ captive bubble ² or Wilhelmy plate. ³ This thesis used the sessile drop method to determine the surface wettability of various hydrogel contact lens materials, by measuring the advancing contact angle made between the lens surface and a pre-determined volume of HPLC-grade water. This was followed by measuring the surface wettability following periods in which the lens materials were soaked in various contact lens care regimens. Further studies determined wettability of lens materials after various periods of in-eye wear and finally a study was undertaken to evaluate if a novel biological technique could be used to differentiate proteins that deposit on hydrogel lens materials that may affect wettability and cause discomfort. <br /><br /> A variety of hydrogel lenses, taken directly from their packaging and after soaking in various care regimens, were analyzed to determine their sessile drop advancing contact angles, in vitro. These studies indicated that poly-2-hydroxyethylmethacrylate (pHEMA)-based lenses are inherently more wettable than silicone-based lenses, unless they have a surface treatment that completely covers the hydrophobic siloxane groups. Additionally, certain combinations of lens materials and care regimens produce inherently more wettable surfaces when measured in vitro. <br /><br /> Suitable methods to assess contact lens wettability ex vivo, or after subjects had worn lenses for set periods of time, were developed. It was determined that using latex gloves to remove lenses had no impact upon the lens surface wettability and that rinsing of the lens surface after removal from the eye was required to determine the wettability of the underlying polymer. <br /><br /> The final wettability studies involved an analysis of various lens materials from clinical studies conducted within the Centre for Contact Lens Research (CCLR). These studies investigated differences in wettability between silicone hydrogel lenses manufactured from differing polymers and variations in ex vivo wettability of several combinations of lens materials and solutions, worn for varying periods of time. <br /><br /> A novel method to investigate proteins extracted from lenses using 2D-Difference in Gel Electrophoresis (DIGE) found that this technique could be used to analyze proteins extracted from contact lenses. The data obtained showed that there was no difference between a group of subjects who were symptomatic of lens-induced dryness or a control group, and that care solutions had a minimal influence on the pattern of deposition seen. <br /><br /> The overall conclusion of these studies is that hydrogel lens wettability is affected by the polymer composition and that care regimen components can modify the surface wettability.