No description available.

M.Phil.(Optometry) / The concept of contact lenses was conceived over 500 years ago and has now evolved into a fundamental component of optometric practice. Soft contact lenses have become a convenient, aesthetically pleasing and comfortable alternative to spectacles that are becoming increasingly popular. The use of rigid contact lenses is imperative in the management of conditions such as keratoconus due to spectacles being insufficient in providing adequate vision. Placing a contact lens onto the cornea is an invasive procedure. The contact lens is a foreign body to the eye hence it is expected that the eye would react to that foreign body. Literature has revealed that the general reactions of the eye to contact lens wear are initial tearing, alteration of the tear layer and oedema due to reduced oxygen transmission but these are just a few of the known consequences amongst the multitude of the unknown consequences. What exactly goes on under a contact lens remains an enigma which contact lens researchers have strived to uncover over the past century. The consequence of contact lens wear is a vast area of research and can best be investigated by focusing on one aspect at a time. The aim of this study was to use dioptric power matrices and multivariate statistics to explore the effects of both gas permeable and gas non-permeable rigid contact lenses on corneal curvature. This study involves auto-keratometric measurements of the corneal curvature before and after lens wear to establish if there are any curvature changes induced by the contact lens. Keratometric data was collected with an automated keratometer (Nidek ARK-700) and was analysed correctly and completely using multivariate statistics. This thesis presents the findings of a study done in an effort to establish the short-term effects of rigid contact lens wear on keratometric behaviour by using complete methods of multivariate statistical analysis. Twenty four subjects were equally divided into three groups. One group wore polymethyl methacrylate (PMMA) rigid lenses, another group wore rigid gas permeable (RGP) contact lenses and the third group served as the control. The control group was included in the study to establish a reference for normal diurnal changes in keratometric behaviour. Fifty autoii keratometric measurements were taken before and immediately after three hours of rigid contact lens wear for the experimental groups and 50 auto-keratometric measurements were taken before and immediately after three hours of no lens wear for the control group. Data collected was analysed using multivariate statistical methods that in the past have been used infrequently in this area of research.

M. Tech. Pharmaceutical Sciences Tshwane University of Technology 2013. / Aims of the present study was to evaluate the inhibitory activities of essential oils against Fusarium isolates and their corresponding biofilms. In this study, the chemical compositions of the oils were established using gas chromatography with both mass spectrometric and flame ionization detection, for identification and quantification, respectively.

Thesis (Ph.D.)--University of Alabama at Birmingham, 2009. / Title from PDF title page (viewed on Sept 9, 2009). Includes bibliographical references (p. 120-125).

Background: Augmented Reality (AR) could be the next revolutionary technology after the personal computer, the internet and the mobile era. While AR Smart Glasses are already on the market, AR Contact Lenses (ARCL) are still in the stage of research and development, but likely to replace the smartphone in the near future. Purpose: The purpose of this thesis is the identification of key factors influencing the acceptance of ARCL from a potential user perspective to gather early-stage pre-market knowledge and extend the Technology Acceptance Model (TAM) literature to this novel wearable technology. Method: An explanatory online survey was conducted to test the hypotheses in an extended TAM. Data from 250 respondents up to an age of 34 years, representing the potential target group was collected. Partial Least Squares Structural Equation Modeling (PLS-SEM) was used to assess the measurement model in terms of validity and reliability and the structural model in terms of hypotheses testing and strength of relationships between proposed variables. In addition, a multigroup analysis was examined to identify significant differences among groups. Conclusion: The results show that the attitude, which is strongly influenced by perceived usefulness, is the major key determinant affecting potential users’ behavioral intention to adopt ARCL in the future, followed by subjective norms. Furthermore, a strong influence of personal innovativeness on both antecedents of attitude, perceived usefulness and perceived ease of use was identified. Moreover, moderating effects of educational background, knowledge of ARCL and usage of contact lenses were discovered.

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 description available.

Orthokeratology (OK) is the reduction, modification or elimination of myopia through application of contact lenses. With the development of high Dk/t lens materials, overnight therapy has become the modality of choice for OK. Overnight OK lens wear has been previously investigated in terms of its efficacy to reduce myopia. However, the underlying effects of overnight OK lens wear on the human cornea have received less attention. As well as the clinical efficacy of overnight OK, this study investigated the effects of overnight OK on topographical corneal thickness and the overnight corneal edema response, and corneal tissue changes with overnight OK. Eighteen subjects participated as the OK lens-wearing group, wearing BE lenses (UltraVision, Brisbane, Queensland) in both eyes. A further ten subjects participated as control subjects, wearing conventional rigid lenses (J-Contour, UltraVision) in the right eye (RE) only. The left eye (LE) acted as a non-lens-wearing control. Both groups wore lenses overnight only, with no lens wear during the day. Measurements were conducted at baseline then on day 1, 4, 10, 30, 60, and 90 for the OK lens-wearing eyes; and up to day 30 for the control group, in the morning (after overnight lens wear) and in the evening (after 8-10 hours of lens removal). Variables measured included best vision sphere (BVS), unaided logMAR visual acuity (VA), refractive astigmatism, apical corneal power (ACP), simulated K readings (Medmont E300 corneal topographer), topographical corneal thickness (Holden-Payor optical pachometer), and keratocyte and endothelial cell densities (ConfoScan2 confocal microscope). Approximately 75% of myopia was corrected after the first night of OK lens wear and the changes in refractive error stabilised by day 10. By day 90, myopia reduction averaged 2.54 ?? 0.63 D. This was associated with significant improvement in unaided VA of about 82% after the first night of lens wear. There was no change in refractive astigmatism over the 3-month period. There was significant reduction in ACP in the OK lens-wearing eyes after the first night of lens wear, which accounted for more than 70% of the total ACP change over the 3-month period (RE: -2.16 ?? 0.53 D; LE: -2.11 ?? 0.86 D). There was significant central epithelial thinning (about 30%) and significant thickening (about 3%) in the mid-peripheral stroma in the OK lens-wearing eyes. Significant central epithelial thinning was found after the first night of lens wear while thickening in the mid-peripheral stroma reached statistical significance by day 4. Further analysis suggests that topographical corneal thickness changes account for the refractive error changes with overnight OK lens wear, rather than corneal bending. The central overnight stromal edema response was significantly reduced in the OK lens-wearing eyes (1.2 ?? 0.5%) to a level lower than in the conventional RGP (6.2 ?? 1.2%) and non-lens-wearing eyes (2.5 ?? 0.9%) in the control group. Mid-peripheral and peripheral stromal edema responses showed similar levels to those predicted based on lens Dk/t. A single overnight wear of BE and Paragon Corneal Refractive Therapy (CRT) lenses showed that the edema response to BE lens wear is significantly less than in the CRT lens-wearing eyes (BE: 2.5 ?? 0.7%; CRT 3.5 ?? 1.3%) immediately on eye opening. No significant changes were found in either central stromal keratocyte or endothelial cell densities in either OK or control groups over the study period. In conclusion, overnight OK lens wear induces significant reductions in myopia after the first night of lens wear associated with improvement in unaided VA. Overnight OK lens wear causes significant thinning in the central epithelium and significant mid-peripheral stromal thickening which results in flattening of the central cornea and steepening in the mid-periphery. Although there were no significant changes in central stromal keratocyte and endothelial cell densities, thinning of the central epithelial layer raises concerns regarding the safety of the procedure, especially with the alarming number of corneal infections reported recently in the literature.

Microbial contamination of contact lenses is a significant risk factor leading to adverse responses. Adhesion of microorganisms to a contact lens is the first step in a series of events that leads to contact lens-related infections or inflammation. Recently, some of the non-steroidal anti-inflammatory drugs (NSAIDs) have been shown to have the ability to interfere with microbial biofilm formation. In this project, antibacterial properties of commonly used NSAIDs (salicylic acid, sodium diclofenac and ketorolac) were assessed and characterised using biological assays and molecular biological techniques. Salicylic acid, ketorolac and diclofenac reduced adhesion of a range of bacterial species isolated from corneal infection and inflammatory events to contact lenses in a dose-dependent manner. Salicylic acid also decreased the adhesion of Pseudomonas aeruginosa and Staphylococcus epidermidis to human corneal epithelial cells in a dose-dependent manner. Results further demonstrated that NSAIDs had a significant impact on the production of virulence factors such as Type IV pili mediated (twitching) motility, flagella mediated swimming, elastase, protease IV and alkaline protease and affected the production of acylated homoserine lactones of P. aeruginosa. Salicylic acid and ketorolac affect the expression of P. aeruginosa outer membrane proteins. In the presence of the salicylic acid and ketorolac more than 85% of all detectable outer membrane proteins changed and most were down-regulated. Moreover, in the presence of salicylic acid at least five gene products, including Na+ - translocating NADH (Nrq1), choline dehydrogenase (CHDH), a hypothetical protein of unknown function, a gene product with no similarity to any known sequence in the database and a sequence similar to 23S rRNA of P. aeruginosa, were down-regulated. The results of this study clearly demonstrated that NSAIDs have a significant impact on virulence factors and the expression of acylated homoserine lactones by P. aeruginosa. This thesis has illustrated the potential of NSAIDs for preventing bacterial contamination of contact lenses by ocular pathogens and highlights the potential for NSAIDs as antibacterial agents. Therefore, this class of compound should be investigated further for their therapeutic efficacy in vivo.

The primary objective of this study was to quantify and characterise lipid deposition on soft (hydrogel) contact lenses, particularly those containing siloxane components. Studies involving a variety of <em>in vitro</em> doping and <em>in vivo</em> worn contact lenses were undertaken, in which lipid deposition was analyzed by either TLC or HPLC. Specific experiments were completed to optimize a method to extract the lipid from the lens materials, to compare the total lipid deposition on nine different hydrogel lenses and to analyze the effect that lipid deposition had on wettability. A method for extracting lipid from contact lenses using 2:1 chloroform: methanol was developed. This study also showed that siloxane-containing contact lens materials differ in the degree to which they deposit lipid, which is dependent upon their chemical composition. Small differences in lipid deposition that occur due to using variations in cleaning regimens were not identifiable through TLC, and required more sophisticated analysis using HPLC. Contact lens material wettability was found to be influenced by <em>in vitro</em> lipid deposition. Specifically, conventional hydrogels and plasma surface-treated silicone-hydrogel materials experienced enhanced wettability with lipid deposition. Reverse-phase HPLC techniques were able to quantify lipid deposits with increased sensitivity and accuracy. From the HPLC studies it was found that contact lens material, concentration of the lipid doping solution, and the composition of the lipid doping solution in <em>in vitro</em> deposition studies influenced the ultimate amount and composition of lipid deposits. <em>In vivo</em> HPLC studies showed that the final lipid deposition pattern was influenced by the interaction between the composition of the tear film and the various silicone hydrogel contact lens materials. In conclusion, HPLC analysis methods were more sensitive and quantitative than TLC. Lipid deposition was ultimately influenced by the concentration and composition of the lipid in the tear film and the contact lens material. Contact lens wettability was influenced by the presence and deposition of lipid onto the contact lens surfaces. Finally, this reverse-phase HPLC lipid analysis protocol was not the most sensitive, robust, or accurate. In the future, other methods of analysis should be explored.