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<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)

No / Orthokeratology (ortho-k) is the process of deliberately reshaping the anterior cornea by utilising specialty contact lenses to temporarily and reversibly reduce refractive error after lens removal. Modern ortho-k utilises reverse geometry lens designs, made with highly oxygen permeable rigid materials, worn overnight to reshape the anterior cornea and provide temporary correction of refractive error. More recently, ortho-k has been extensively used to slow the progression of myopia in children. This report reviews the practice of ortho-k, including its history, mechanisms of refractive and ocular changes, current use in the correction of myopia, astigmatism, hyperopia, and presbyopia, and standard of care. Suitable candidates for ortho-k are described, along with the fitting process, factors impacting success, and the potential options for using newer lens designs. Ocular changes associated with ortho-k, such as alterations in corneal thickness, development of microcysts, pigmented arcs, and fibrillary lines are reviewed. The safety of ortho-k is extensively reviewed, along with an overview of non-compliant behaviours and appropriate disinfection regimens. Finally, the role of ortho-k in myopia management for children is discussed in terms of efficacy, safety, and potential mechanisms of myopia control, including the impact of factors such as initial fitting age, baseline refractive error, the role of peripheral defocus, higher order aberrations, pupil size, and treatment zone size. / The CLEAR initiative was facilitated by the BCLA, with financial support by way of Educational Grants for collaboration, publication and dissemination provided by Alcon and CooperVision.

Yes / Objectives: To investigate the performance of a novel flat pack toric daily disposable contact lens compared with traditionally packaged toric lenses in a randomized, crossover study. Environmental attitudes to contact lens wear were also explored. Methods: Habitual contact lens wearers were recruited to wear a hioxifilcon A (Miru 1 day Flat Pack Toric, Menicon, Nagoya, Japan) test lens and a control lens: either nelfilcon A (Dailies AquaComfort Plus, Alcon, Geneva, Switzerland) or etafilcon A (1-Day Acuvue Moist, Johnson & Johnson, New Brunswick, NJ). Objective lens performance was assessed at fitting, and participants wore lenses in a randomized order for three consecutive days. Subjective measures of lens performance (comfort, vision, and handling) were then assessed by a questionnaire, with further questions on overall lens preference and environmental perceptions. Results: Objective measures of lens fit were similar for the test and control lenses, except for distance VA which was better with the control lenses (P<0.05; difference of two logMAR letters). End of day comfort was greater with the test lens, but this did not reach significance. Both lenses demonstrated similar scores for overall satisfaction. 87.5% of participants indicated the environmental impact of contact lenses to be important/extremely important to them, with 100% of participants identifying the flat pack packaging as having a smaller environmental impact. Conclusion: Overall, the lenses used in the study performed to similar levels. Environmental credentials are important to contact lens wearers, which may contribute to overall lens preference.

No / PURPOSE. To develop and validate a questionnaire for the measurement of the impact of contact lenses on quality of life (QoL): The Contact Lens Impact on Quality of Life (CLIQ) Questionnaire. METHODS. The questionnaire was developed and validated using conventional methods and Rasch analysis to assure content validity, repeatability, construct validity, and low respondent burden. Item identification and selection (647 items) were performed with an extensive literature review, professional advice, and lay focus groups. Item reduction used focus groups and data obtained from 161 subjects completing a 90-item pilot questionnaire. Validity and reliability, from data of 128 additional subjects, were assessed using Rasch analysis, intraclass correlation coefficient, and Bland-Altman limits of agreement. RESULTS. A 28-item CLIQ Questionnaire was developed and shown to have good validity and reliability by Rasch analysis statistics: real person separation, 2.02; model person separation, 2.17; reliability, 0.80; root mean square measurement error, 2.73; mean square ± SD infit, 1.01 ± 0.18; outfit, 1.01 ± 0.19. The items (mean score, 49.8 ± 4.9) were well targeted to the subjects (mean score, 51.2 ± 6.2) with a mean difference of 1.35 (scale range, 0-100) units. Test-retest intraclass correlation coefficient (0.86) and coefficient of repeatability (±8.00 units) demonstrated good repeatability. CONCLUSIONS. Rasch analysis and standard psychometric analyses demonstrated that the 28-item CLIQ Questionnaire is a valid and reliable measure of QoL in contact lens wearers. A scoring algorithm is provided for CLIQ Questionnaire users to convert raw scores into the Rasch analysis-derived linear person measures.

This PhD project investigated the ramifications of air-cured and nitrogen-cured manufacturing processes during silicone hydrogel contact lens manufacture in terms of lens surface characterisation and clinical performance. A one-hour contralateral clinical study was conducted for ten subjects to compare the clinical performance of the two study lenses. The main clinical findings were reduced levels of subjective performance, reduced surface wettability and increased deposition. Contact angle analysis showed the air-cured lenses had consistently higher advancing and receding contact angle measurements, in comparison with the nitrogen-cured lens. Chemical analysis of the study lens surfaces in the dehydrated state, by x-ray photoelectron spectroscopy (XPS) and time-of-flight mass spectrometry (ToF-SIMS), showed no difference due to surface segregation of the silicone components. Analysis of frozen lenses limited surface segregation and showed a higher concentration of silicone polymer components and lower concentration of hydrophilic polymer components at the surface of the air-cured lens, in comparison with the nitrogen-cured lens. Scanning electron microscope (SEM) imaging showed the nitrogen-cured lens to have a surface typical of a hydrogel material, whereas the air-cured lens had regions of apparent phase separation. In addition, atomic force microscopy (AFM) showed the air-cured lens to have a rougher surface associated with greater adherence of contaminants (often observed in materials with reduced polymer cross-linking). In conclusion, clinical assessment of the study lenses confirmed the inferior performance of the air-cured lens. Surface analysis suggested that the non-wetting regions on the air-cured lenses were associated with elevated level of silicone components, reduced polymer cross-linking and polymer phase separation.

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.