This thesis describes the impact of contact lens-related microbial keratitis in terms of incidence and severity. Disease outcome is defined by visual outcome, costs to the healthcare system, costs to the individual and duration of disease. A successful 12-month surveillance study was conducted of the populations of Australia and New Zealand to detect all cases of contact lens-related microbial keratitis. A random telephone survey of 32,000 households in Australia and 7,500 in New Zealand accurately determined the level of use of various contact lenses in the community. The impact of new contact lens types: silicone hydrogels and daily disposables were investigated. Increased risk persisted in overnight wear with silicone hydrogel materials. Microbial keratitis associated with silicone hydrogel materials had slightly shorter disease duration however other factors had a stronger influence on severity. Rigid gas permeable and frequent replacement soft lenses when used for daily wear constitute the lowest risk. Cost analysis was developed in a hospital case series of microbial keratitis. This analysis was applied in the surveillance study including cases managed in the private health care sector. Disease duration and associated costs are novel indices of severity for contact lens-related disease. The most dramatic effects on disease severity were seen with the type of organism involved. Keratitis attributed to environmental organisms (Gram-negative bacteria, Acanthamoeba, fungi and Nocardia species) were 10x more likely to cause loss of visual acuity, had longer duration of symptoms and incurred higher costs. Importantly, delays in receiving treatment increased disease duration and associated costs. Greater awareness of the need for specialist healthcare is indicated amongst health care providers and contact lens wearers. The hypothesis that overnight wear in silicone hydrogel lenses would not increase the risk of infection has been disproven. This information is of value to practitioners who are responsible for informing contact lens wearers about the risk of contact lens-related infections and should be weighed against the benefits of continuous wear. The identification of factors which contribute to the outcomes of disease will be used in education campaigns amongst health care providers and contact lens wearers to minimise the impact of disease.

Silicone Hydrogel (SiHy) contact lenses are highly successful compared to previous soft lenses; they were developed to provide superior oxygen permeability. However, the hydrophobic natures of the silicone segments enhance lipid sorption which may diminish the lens surface wettability, clarity and comfort. While lens and lens care product are designed to remove lipid deposition, there is lack of experimental evidence to evaluate the actual performances with respect to lipid removal. An in vitro model using an artificial tear fluid containing radiolabeled lipids was employed in this thesis research to evaluate the efficacy of different multi-purpose lens care solutions in removing lipids from SiHy contact lenses. Additional rubbing with the lens care solution is often encouraged by professionals. Part of this research evaluated the effect of additional rubbing process on lipid removal. Overall, a multi-purpose solution (MPS) for lens care, Opti-Free PureMoist®, removed the most lipid deposition from lenses (senofilcon A, comfilcon A, and balafilcon A and one conventional hydrogel lens polymacon). The overall removal percentages were approximately 55% of DPPC and 28% of cholesterol from a conventional hydrogel. However, the MPSs did not remove lipids effectively from SiHy lenses. The highest percentages of removal were 3.08% of DPPC and 0.76% of cholesterol from SiHy lotrafilcon B lenses with Opti-Free PureMoist. The rubbing process increased the amount of removal in some MPSs, but the effects were small. The lack of removal of lipid suggests that the surfactants in the MPSs are not hydrophobic enough to remove lipids from SiHy lenses. Apparently a majority of deposited lipids absorbed into the lens matrix as rubbing did not enhance removal significantly. Future study on determining the concentration profile of lipid sorption throughout the lens thickness is encouraged. Another topic in this research thesis is the use of hydrogel lenses to deliver comfort agents or lubricating molecules from lenses. A screening study was performed in this research to select possible agents to be loaded into several SiHy macromer formulations. Experiments showed that comfort agents PNVP and Kollidon were the best candidates for such a procedure.

<p>Despite the long history of topical eye drops and their use in delivering therapeutic agents to the anterior of the eye, efficient sustained delivery continues to be an elusive goal. The robust and effective clearance mechanisms that the eye is endowed with are significant delivery challenges and result in short drug residence times and low ocular bioavailability. The work carried out in this thesis focused on developing, synthesizing and characterizing silicone hydrogels and evaluating their potential as drug eluting inserts for more effective delivery of ocular pharmaceuticals. The first strategy (Chapter 2) focused on incorporating a novel hydrogel additive, hyaluronic acid, to promote hydrogel-drug ionic interactions that can function to increase drug loading and subsequent release dosage. Hydrogels composed of a hydrophilic monomer, N,N-dimethlacrylamide (DMA) or 2-hydroxyethyl methacrylate (HEMA), and a hydrophobic monomer, methacryloxypropyltris(trimethylsiloxy)silane (TRIS), were used as model contact lenses. By combining ionic interactions with molecular imprinting techniques within a single hydrogel, it was shown that this can produce a compound effect on drug uptake and release. Although greater control over release dosage was achieved, there was limited capacity for these materials to delivery timolol for extended periods with drug release occurring rapidly over a period of 1-2 days. However, there were clear differences in the release duration from the p(DMA-<em>co</em>-TRIS) and p(HEMA-<em>co</em>-TRIS) hydrogel formulations. Therefore, the second study (Chapter 3) aimed to better understand the relationship between the hydrogel chemical composition and the resultant material properties on the drug release characteristics. A range of hydrogels were synthesized with varying hydrophilic and hydrophobic monomers, which were then characterized by their water content, transparency, optical haze and surface wettability. The previous generation materials were evolved by incorporating a modified siloxy methacrylate TRIS(OH), a methacrylated polydimethylsiloxane macromonomer (mPDMS) and a polymerizable silicone surfactant (ACR). The properties of the hydrogels were dramatically affected by the nature and relative contribution of hydrophobic and hydrophilic monomers. The release of dexamethasone (DEX), an anti-inflammatory medication, was shown to vary significantly depending on the hydrogel formulations; often displaying faster release in high water content materials and slow release in low water content hydrogels. The mechanism of diffusion for lipophilic DEX in these hydrogel systems appeared to be through the internal aqueous network channels within the bulk. Over the range of hydrogels formulations that were tested, the release from them varied from approximately seven days to greater than two weeks.</p> / Master of Applied Science (MASc)

When a biomaterial is inserted into the body, the interaction of the surface with the surrounding biological environment is crucial. Given the importance of the surface, the ability to alter the surface properties to support a compatible environment is therefore desirable. Silicone hydrogel contact lenses (CL) allow for improved oxygen permeability through the incorporation of siloxane functional groups. These groups however are extremely surface active and upon rotation, can impart hydrophobicity to the lens surface, decreasing lens wettability and increasing protein and lipid deposition. Lens biofouling may be problematic and therefore surface modification of these materials to increase compatibility is exceedingly recognized for importance in both industry and research. The current work focuses on the creation of a novel anti-fouling polymer surface by the incorporation of 2-methacryoyloxyethyl phosphorylcholine (MPC), well known for its biomimetic and anti-fouling properties. A controlled polymerization method was used to generate a unique double-grafted architecture to explore the effect of increasing surface density of polyMPC chains on corresponding anti-fouling properties. The novel free polymer was synthesized by a 3-step atom transfer radical polymerization (ATRP). First, poly(2-hydroxyethyl methacrylate) (polyHEMA) was polymerized by ATRP, where the hydroxyl (OH) groups of the polymer then underwent an esterification to create macroinitiating sites. From these sites, a second ATRP of poly(MPC) varying in length occurred, yielding the double-grafted polymer poly(2(2-bromoisobutyryloxy-ethyl methacrylate)-graft-poly(2-methacryloyloxyethyl phosphorylcholine (pBIBEM-g-pMPC). The polymer was designed for resistance to protein adsorption through a possible synergistic effect between the surface induced hydration layer by surrounding PC groups coupled with steric repulsion of the densely grafted chains. To test its potential as a surface modifier, the polymer was grafted from model silicone hydrogel CL through a 4-step surface initiated ATRP (SI-ATRP) in a similar manner to the free polymer. First, the ATRP initiator was immobilized from the HEMA OH groups of the unmodified CL, generating Intermedate-1. A polyHEMA brush was grafted from the initiating sites yielding pHEMA-50, followed by the generation of a second initiator layer (Intermediate- 2). A sequential ATRP of poly(MPC) then generated the target pMPC-50/pMPC-100 surfaces. For the free pBIBEM-g-pMPC polymer analysis, 1H-NMR and GPC determined polymers formed with a predictable MW and low polydispersity (PDI). For surface grafting, using a sacrificial initiator, 1H-NMR and GPC indicated that the pHEMA-50 and pMPC-50/pMPC-100 polymers were well-controlled, with a MW close to the theoretical and a low PDI. For surface chemical composition, ATR-FTIR showed the presence of the ATRP initiator (Intermediate-1 and 2) by the appearance of a C-Br peak and disappearance of the OH peak. XPS confirmed the chemical composition of the 4-step synthesis by a change in the fraction of expected surface elements. Both the surface wettability and EWC of the materials increased upon pMPC modification, further improving upon increasing pMPC chain length. The contact angle was as low as 16.04 ± 2.37º for pMPC-50 surfaces and complete wetting for pMPC-100. Finally, the single protein adsorption using lysozyme and bovine serum albumin (BSA) showed significantly decreased protein levels for pMPC-50/100 lenses, as much as 83% (p 0.00036) for lysozyme and 73% (p 0.0076) for BSA, with no significant difference upon chain length variation. The aforementioned data demonstrates that the novel polymer has potential in providing an anti-fouling and extremely wettable surface, specifically regarding silicone hydrogel CL surfaces. / Thesis / Master of Applied Science (MASc)

The purpose of this study was to observe penetration profiles of lysozyme on a variety of contact lens materials by confocal microscopy, to analyze influential factors that are involved in these penetration curves and to suggest possible mechanisms related to the in-eye clinical performance of these materials. An FITC-lysozyme conjugate was synthesized in-house by amine reaction. Contact lenses were incubated in a lysozyme solution with a final concentration of 1.9 mg/mL for various periods before undergoing microscopic analysis. Optimal parameters for confocal scanning were successfully obtained to acquire desired fluorescence signals on various contact lenses. Measurement units were converted into absolute amounts of lysozyme using lysozyme data from ^(125)I gamma counting studies. A rhodamine labeled dextran solution was applied to distingush the surface of the contact lenses under examination. The data from these studies were then used to calculate the theoretical numbers of layers of adsorbed lysozyme on the lens surface. The results show that there were distinct differences in lysozyme penetration in the twelve hydrogel materials examined. A pure pHEMA lens, with a water content of 38%, deposited lysozyme primarily on the lens surface after 24 hours, with full penetration occurring after 4-weeks of incubation. Three types of non-ionic contact lens materials with water contents > 50% exibited rapid penetration within the lens bulk after 24-hours incubation, with increased deposition within the matrix after 4 weeks. Two ionic, high water content polymers (Acuvue 2 and Focus Monthly) exhibited markedly different penetration profiles, particularly after 24 hours, with very rapid and total penetration in Acuvue 2, as compared with partial penetration in Focus Monthly. Modern silicone hydrogel contact lenses can be nominally divided into first generation, plasma-modified materials and second generation materials which incorporate an internal wetting agent such as polyvinyl pyrrolidone (PVP). These materials exhibited different lysozyme deposition profiles. Lysozyme fully penetrated PureVision after 24 hours, whereas no lysozyme penetration occurred on lenses manufactured from Focus Night & Day or O_2Optix, even after 4 weeks. Lenses manufactured from Acuvue Advance and Acuvue OASYS, two second generation silicone hydrogel lenses, also displayed their own characteristic deposition profile. Acuvue Advance always exhibited a partial penetration of lysozyme within the matrix, even after 4 weeks of doping. Interestingly, Acuvue OASYS showed a similar profile to Focus Night & Day and O_2Optix, with predominantly surface deposition occurring. To confirm possible surface adsorption of lysozyme on surface-coated Focus Night & Day and O_2Optix, a rigid polymethylmethacrylate (PMMA) contact lens was used as a model of surface adsorption. A mounting medium containing rhodamine labeled dextran was scanned to distinguish the lens surface, as it was assumed that no surface penetration of the very high molecular weight dextran would occur. Using this model, it was confirmed that surface adsorption of lysozyme occurred on these plasmacoated lens materials, which is similar to that seen with PMMA. In a further experiment, it was seen that lysozyme sorption on Acuvue OASYS exhibits a penetration profile which is different to that seen in Focus Night & Day and O_2Optix, with lysozyme just penetrating the lens surface. The results from the studies described above demonstrated that in 24 hours lysozyme sorption did not achieve a complete monolayer. However, after 4 weeks multi-layer adsorption occurred, with the more hydrophilic materials depositing the most lysozyme. The quantitative measurement of lysozyme penetration on and into contact lens materials by confocal microscopy combined with ^(125)I labelling offers a valuable tool to discover the potential mechanisms of interactions between protein and polymer materials. This study reveals some important information that may be beneficial to contact lens development and will prove to be valuable in other more broad areas of biomedical research in which polymers and biological fluids come into contact. / Thesis / Master of Applied Science (MASc)

This thesis investigates the feasibility of loading silicone hydrogel (SiHy) contact lenses with two different hydrophobic therapeutics, latanoprost and DMPC (1,2-dimyristoyl-sn-glycero-3-phosphocholine), for treatment of glaucoma and hyperemia respectively. The two methods of loading were 1) thermal loading in an aqueous medium and 2) convective loading in a solution of n-propanol. Dailies Total1® lenses prepared in this manner were tested for their loading and their release into artificial tears. Continuous release over 1-4 days at therapeutic levels is achievable from thermal loading of DMPC, convective loading of DMPC, and convective loading of latanoprost. The DMPC loading processes can be naturally integrated into standard manufacturing lines for Dailies Total1®. Both DMPC and latanoprost release at rates proportional to the amount loaded into a contact lens. Latanoprost loads into a contact lens strictly proportionally to the loading concentration and the time of loading. The convective loading step represents a significant improvement on both the time of loading (reduced from days to minutes) and the loading capacity of silicone hydrogel contact lenses. This thesis also compares the loading and release of latanoprost in the convective loading procedure using the SiHy contact lenses of Acuvue Advance® (Johnson & Johnson Vision Care, Jacksonville, FL) , Air Optix® (Alcon, Copenhagen, Denmark), Biofinity® (CooperVision), PureVision® (Bausch & Lomb), and Dailies Total1® (Alcon), and the polyHEMA lens, SofLens 38® (Bausch & Lomb), finding that silicone hydrogels load an order of magnitude more drug than the polyHEMA lens and release into artificial tears for an order of magnitude longer. Overall, these experiments provide a quantitative understanding of the dynamics of loading and release for both DMPC and latanoprost.

Purpose: Contact lens (CL) materials, modalities of wear and replacement, and care systems have changed considerably since the early studies of CL compliance were first conducted. Silicone hydrogel (SiHy) and daily disposable (DD) lenses are now the most popular lenses worn worldwide and the care systems that are currently available for them have been designed to be straightforward to use. The purpose of this research was to investigate patient knowledge of and compliance with the use of these contemporary CLs and care products, to determine whether non-compliant CL wearers experience ocular complications relating to lens wear more frequently and are more likely to discontinue lens wear, and to try to determine the factors that may constrain or enable patients to follow recommendations for appropriate lens wear and care. Methods: There are many ways in which compliance can be assessed in health care. Several different methodologies were employed during this research: A questionnaire was administered to just over 100 current lens wearers to determine whether photographic aids would help them to recognize which products they were using. More than 500 contact lens (CL) wearers were recruited by their eye care practitioners (ECPs) and mailed a questionnaire designed to evaluate their compliance with contact lens wear and care and to determine whether they had experienced any contact lens related complications which may have occurred as a result of non-compliance. Close to 5000 Current and lapsed CL wearers in Canada were recruited using Facebook to take part in an on line survey investigating CL wearing experiences during 2008 – 2010 and to establish the percentage of participants who temporarily and permanently discontinued CL wear during the period surveyed, the reasons for discontinuation and whether compliance with lens wear and care may have played a role. ECPs and patients independently completed more than 2000 linked questionnaires evaluating their contact lens wear and care. In addition the frequency with which patients attended their ECP’s office for eye examinations was assessed to determine whether there was a relationship between this and their patients’ compliance. More than 800 daily disposable contact lens (DDCL) wearers in four countries completed an online questionnaire designed to investigate how frequently they reused their lenses, the reasons for reuse and how the lenses were stored between uses. Quantitative (online questionnaire) and qualitative (focus groups) research methods were used to explore in detail the lens wear and care habits of adapted contact lens wearers in an attempt to seek a better understanding of what enables and constrains patient compliance with appropriate lens wear and lens care. Results: The rates of non-compliance with the wear of contemporary CLs were found to be similar to those previously reported. Non-compliance with recommendations for CL replacement was shown to be associated with a higher rate of CL related problems. CL wearers continue to “drop-out” for reasons of discomfort and dryness with their lenses but the drop out rates were not found to be different between compliant and non-compliant CL wearers. Patients who were non-compliant with lens replacement were found to attend their ECP’s offices less frequently. Wearers of DDCLs were the most compliant with lens replacement; however, some did report reusing these lenses and sleeping overnight in them. Focus group participants were able to provide a greater insight into why non-compliant behaviour occurs in CL wearers with the most frequently occurring themes identified as the “consequences” that may occur if patients are non-compliant with one or more aspects of their contact lens wear and the importance of receiving “instructions” regarding the most appropriate way to wear and care for their lenses. Most of the themes that emerged from this qualitative research study were both constraints to, and enablers of, compliance. Conclusions: Compliance with contemporary CLs and care products remains poor. Non-compliant behaviour can result in serious complications and patients may not always be aware of this. Careful counseling and education on the risks associated with CL wear is required to provide patients with a better lens wearing experience and continued successful contact lens wear. ECPs and the contact lens industry can hopefully apply this greater understanding of why patients fail to wear and care for their lenses as they should and to help them develop strategies and tools to aid compliance and success in contact lens wear.

Purpose: Contact lens (CL) materials, modalities of wear and replacement, and care systems have changed considerably since the early studies of CL compliance were first conducted. Silicone hydrogel (SiHy) and daily disposable (DD) lenses are now the most popular lenses worn worldwide and the care systems that are currently available for them have been designed to be straightforward to use. The purpose of this research was to investigate patient knowledge of and compliance with the use of these contemporary CLs and care products, to determine whether non-compliant CL wearers experience ocular complications relating to lens wear more frequently and are more likely to discontinue lens wear, and to try to determine the factors that may constrain or enable patients to follow recommendations for appropriate lens wear and care. Methods: There are many ways in which compliance can be assessed in health care. Several different methodologies were employed during this research: A questionnaire was administered to just over 100 current lens wearers to determine whether photographic aids would help them to recognize which products they were using. More than 500 contact lens (CL) wearers were recruited by their eye care practitioners (ECPs) and mailed a questionnaire designed to evaluate their compliance with contact lens wear and care and to determine whether they had experienced any contact lens related complications which may have occurred as a result of non-compliance. Close to 5000 Current and lapsed CL wearers in Canada were recruited using Facebook to take part in an on line survey investigating CL wearing experiences during 2008 – 2010 and to establish the percentage of participants who temporarily and permanently discontinued CL wear during the period surveyed, the reasons for discontinuation and whether compliance with lens wear and care may have played a role. ECPs and patients independently completed more than 2000 linked questionnaires evaluating their contact lens wear and care. In addition the frequency with which patients attended their ECP’s office for eye examinations was assessed to determine whether there was a relationship between this and their patients’ compliance. More than 800 daily disposable contact lens (DDCL) wearers in four countries completed an online questionnaire designed to investigate how frequently they reused their lenses, the reasons for reuse and how the lenses were stored between uses. Quantitative (online questionnaire) and qualitative (focus groups) research methods were used to explore in detail the lens wear and care habits of adapted contact lens wearers in an attempt to seek a better understanding of what enables and constrains patient compliance with appropriate lens wear and lens care. Results: The rates of non-compliance with the wear of contemporary CLs were found to be similar to those previously reported. Non-compliance with recommendations for CL replacement was shown to be associated with a higher rate of CL related problems. CL wearers continue to “drop-out” for reasons of discomfort and dryness with their lenses but the drop out rates were not found to be different between compliant and non-compliant CL wearers. Patients who were non-compliant with lens replacement were found to attend their ECP’s offices less frequently. Wearers of DDCLs were the most compliant with lens replacement; however, some did report reusing these lenses and sleeping overnight in them. Focus group participants were able to provide a greater insight into why non-compliant behaviour occurs in CL wearers with the most frequently occurring themes identified as the “consequences” that may occur if patients are non-compliant with one or more aspects of their contact lens wear and the importance of receiving “instructions” regarding the most appropriate way to wear and care for their lenses. Most of the themes that emerged from this qualitative research study were both constraints to, and enablers of, compliance. Conclusions: Compliance with contemporary CLs and care products remains poor. Non-compliant behaviour can result in serious complications and patients may not always be aware of this. Careful counseling and education on the risks associated with CL wear is required to provide patients with a better lens wearing experience and continued successful contact lens wear. ECPs and the contact lens industry can hopefully apply this greater understanding of why patients fail to wear and care for their lenses as they should and to help them develop strategies and tools to aid compliance and success in contact lens wear.

Dry eye syndrome has been associated with the lack of phospholipids in the tear film, leading to disruption of the tear film and subsequent irritation. Characterization of the transport and release of phospholipids from a silicone hydrogel contact lens is required to assess the possible use of these lenses for phospholipid delivery to increase patient comfort. This thesis examines the use of silicone hydrogel contact lenses as phospholipid delivery devices. Contact lenses of silicone hydrogel composition were loaded with varying amounts of radiolabeled 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) from a solution of n-propanol. These lenses were eluted at 35°C into artificial tear fluid (ATF) or ATFcontaining varying amounts of DMPC. The amount of DMPC loaded into a lens is a linear function of the time of exposure to the DMPC/propanol solution. The initial rate of elution into ATF appears to be diffusion controlled for at least 10 hrs and is proportional to the amount of DMPC loaded. The ease of loading and the controllable release of DMPC from silicone hydrogels present the possibility of using such lenses to counter eye discomfort caused by inherently low levels of phospholipid in tears. To reduce manufacturing steps and concern for residual n-propanol in the lens, it is beneficial to incorporate the DMPC into the monomer formulation and then photopolymerize the lens. Results showed that using this process, DMPC can be placed in the lens and then eluted at faster rates than when it was loaded from n-propanol.

Cytotoxicity of Multi-Purpose Solutions (MPS) is commonly tested on cells using diluted MPS or extracts from MPS soaked contact lenses. There is evidence that lens type will affect uptake and release of compounds contained in MPS. To assess the cytotoxicity of agents contained in MPS that would be released by contact lens, an in vitro “onlay” model was used, whereby MPS soaked silicone hydrogel lenses were directly set onto a confluent monolayer of corneal cells. Chapter 4 describes the impact of MPS released from contact lenses on immortalized human corneal epithelial cells. MPS-soaked lens interactions with cells were characterized by studying cell viability, cell adhesion and caspase assays. In Chapter 5, mechanisms of cell death induced by exposure to MPS from contact lenses were determined through evaluation of apoptotic markers, such as activation of caspase 3 and 9. In Chapter 6, the impact of the physical properties of silicone hydrogel lenses, specifically surface treatments, on cytotoxicity of MPS were investigated. The development of methods for characterizing the release of MPS from lenses, using absorbance spectra, is also described. The results indicate that exposure to contact lenses soaked in Opti-Free Express (OFX) and ReNu not only induces cell death in vitro, but also has an adverse effect on adhesion phenotype, suggesting that the remaining cells may have a compromised epithelial structure. Borate- buffered MPS were found to be more cytotoxic than phosphate-buffered base solutions. Investigation of the mechanisms of cell death revealed that ReNu and OFX induced corneal epithelial cell death in vitro using different pathways, whereby ReNu induced a necrotic pathway while OFX-induced cell death was mediated by the intrinsic pathway of apoptosis. The in vitro model was also able to identify differences between silicone hydrogels with different surface treatments: the different surface treatments and chemistries of silicone hydrogels lens will affect the release profile of MPS and hence their potential cytotoxicity. By investigating the induction of cell death processes by solution-lens combinations in vitro, we aim to prevent potential adverse effects in the cornea, which may ultimately compromise various visual and barrier functions. The findings indicate the wealth of information in vitro cytotoxicity testing can provide when evaluating the toxicological profile of MPS.