In recent years, technical advances in the field of Augmented Reality (AR), coupled with the acceleration in computer and graphics processing power, have brought robust and affordable AR within the reach of the wider research community. While the technical issues of AR remain heavily researched, there is also a growing amount of work on user interface development and evaluation, heralding the convergence of traditional Human Computer Interaction (HCI) and AR. Magic Lenses are 2D interface components that provide alternative representations of objects seen through them. In this way, they can be used to provide Focus and Context in the interface, especially when visualising layered information. There are very few, if any, formal evaluations to guide the development of lens-based interfaces. This thesis describes the development and evaluation of Magic Lenses as a tool for AR interfaces. The work starts with a comprehensive survey of many Focus and Context techniques, which are classified based on the way they present views to the users { for example, a Magic Lens is a spatially separated multiple view technique. A formal evaluation of 2D Magic Lenses in a GIS scenario found that users strongly preferred the lens-based interaction technique to others, largely because it reduced the effort of interaction. Accuracy was high with the lenses, but a simple "global view" interface allowed significantly faster performance. This positive result motivated further work on Magic Lenses within AR, where the lens metaphor can reinforce the tangible interaction methods that link virtual and real content. To support rapid exploration of interaction alternatives with AR Magic Lenses, I describe the design and architecture of osgART, an AR development toolkit that is available to the research community as open-source software. Object selection and manipulation is a fundamental interaction requirement for all AR interfaces, and I establish an empirical foundation of performance in this task with a variety of AR interaction techniques, including Magic Lenses. Results show that performance with all techniques is successfully modelled by Fitt's Law, and that Magic Lenses outperformed other techniques. Finally, I examine new interaction techniques based on Magic Lenses, particularly a Flexible Sheet Lens, which allows concurrent bimanual specification of multiple parameters within the visualisation.

Purpose To examine soft contact lens fitting characteristics using anterior segment imaging techniques and comfort. The specific aims of each chapter are as follows: Chapter 2: To calibrate the new ZEISS VisanteTM anterior segment optical coherence tomographer (OCT) using references with known physical thickness and refractive index equal to the human cornea and to compare the Visante measures to those from a previous generation OCT (Zeiss-Humphrey OCT II). Chapter 3: The first purpose of this study was to measure the repeatability of the Visante TM OCT in a normal sample. The second was to compare corneal thickness measured with the Visante TM OCT to the Zeiss-Humphrey OCT II (model II, Carl Zeiss Meditec, Jena Germany) adapted for anterior segment imaging and to the Orbscan II TM (Bausch and Lomb, Rochester New York). Chapter 4: Conjunctival displacement observed with the edges of the contact lens, when imaged may be real or may be an artefact of all OCT imagers. A continuous surface appears displaced when the refractive index of the leading medium changes at the edge of a contact lens. To examine this effect, edges of the contact lenses were imaged on a continuous surface using the UHR-OCT. Contact lens edges on the human conjunctival tissue were also imaged to see if the lens indentation on the conjunctival tissue is real or an artefact at the edge of the lens. Chapter 5: The main purpose of this study was to determine if we can predict end of the day discomfort and dryness using clinical predictive variables. The second purpose of the study was to determine if there was any relationship between lens fitting characteristics and clinical complications and especially to the superior cornea and conjunctiva with a dispensing clinical trial. Methods Chapter 2: Twenty two semi-rigid lenses of specified thicknesses were manufactured using a material with refractive index of 1.376. Central thickness of these lenses was measured using VisanteTM OCT and Zeiss-Humphrey OCT II (Zeiss, Germany). Two data sets consisting of nominal measures (with a standard pachymeter of the lenses and one obtained using a digital micrometer) were used as references. Regression equations between the physical and optical (OCT) measures were derived to calibrate the devices. Chapter 3: Fifteen healthy participants were recruited. At the Day 1 visit the epithelial and total corneal thickness, across the central 10mm of the horizontal meridian were measured using the OCT II and the Visante TM OCT. Only total corneal thickness across the central 10mm of the horizontal meridian was measured using the Orbscan II. The order of these measurements was randomized. These measurements were repeated on Day 2. Each individual measurement was repeated three times and averaged to give a single result. Chapter 4: (2-D) Images of the edges of marketed silicone hydrogel and hydrogel lenses with refractive indices (n) ranging from 1.41-1.51 were taken placing them concave side down on a continuous surface. Five images for each lens were taken using a UHR-OCT system, operating at 1060 nm with ~3.2um (axial) and 10μm (lateral) resolution at the rate of 75,000 A-scans/s. The displacement of the glass slide beneath the lens edge was measured using Image J. Chapter 5: Thirty participants (neophytes) were included in the study and the four lenses (Acuvue Advance 8.3, Acuvue Advance 8.7, Pure Vision 8.3, and Pure Vision 8.6) were randomly assigned for each eye. The lenses were worn for a period of two weeks on a daily wear basis for 8 to 10hrs per day. Lens performance was monitored over the 2week period. Assessment of subjective comfort was made using visual analogue scales. Total corneal and epithelium thickness was measured using the Visante OCT, the lens edge profiles of the contact lenses were observed using the ultra-high resolution OCT and the conjunctival epithelial thinning was measured using the RTVue OCT. Conjunctival blood velocity was measured at the baseline and 2 week visit using a high magnification camera. Results Chapter 2: Before calibration, repeated measures ANOVA showed that there were significant differences between the mean lens thicknesses from each of the measurement methods (p<0.05), where Visante measurements were significantly different from the other three (OCT II, MG and OP) methods (p<0.05). Visante thickness was significantly higher than the microgauge measures (453±37.6 µm compared to 445.1±38.2 µm) and the OCT II was significantly lower (424.5±36.1 µm both, p<0.05). After calibration using the regression equations between the physical and optical measurements, there were no differences between OCT II and Visante OCT (p<0.05). Chapter 3: Mean central corneal and epithelial thickness using the Visante™ OCT after calibration at the apex of the cornea was 536± 27 µm (range, 563-509 µm) and 55± 2.3 µm (range, 57.3-52.7 µm), respectively. The mean corneal and epithelial thickness using OCT II at the apex was 520±25µm and 56±4.9 µm, respectively. The mean of total corneal thickness measured with the Orbscan II was 609±29µm. Visante OCT was the most repeatable for test-retest at the apex, nasal and temporal quadrants of the cornea compared to OCT II and Orbscan II. COR’s of Visante OCT ranged from ±7.71µm to ±8.98µm for total corneal thickness and ± 8.72 µm to ± 9.92 µm for epithelial thickness. CCC’s with Visante OCT were high for total corneal thickness for test-retest differences ranging from 0.97 to 0.99, CCC’s for epithelial thickness showed moderate concordance for both the instruments. Chapter 4: Results showed that artefactual displacement of the contact lens edge was observed when the lenses were imaged on the glass reference sphere, custom made rigid contact lenses (1.376) and on the conjunctival tissue. The displacement measured on the conjunctival tissue ranged from 7.0±0.86 µm for the Air Optix Night and Day to 17.4±0.22 µm for the Acuvue Advance contact lenses. The range of displacement with the soft lens edges imaged on the rigid contact lens was from 5.51±0.03 µm to 9.72±0.12 µm. Chapter 5: The lenses with the steepest sag (Acuvue Advance 8.3, Pure Vision 8.3) resulted not only with the tightest fit, but with compromise to the superior conjunctiva. This was especially seen with the Acuvue Advance lenses. The steeper lenses caused more total corneal swelling, superior epithelial thinning, mechanical compression of conjunctiva, conjunctival staining, bulbar hyperemia, conjunctival indentation and reduced blood flow at the lens edge. Not many associations were observed between baseline clinical and 2 weeks sensory variables. However, significant associations were observed when comparing the baseline clinical variables to end of the day sensory variables. Baseline clinical variables compared to 2 week clinical variables also showed significant correlations. Conclusions Chapter 2: Using reference lenses with refractive index of the cornea (1.376) allows rapid and simple calibration and cross calibration of instruments for measuring the corneal thickness. The Visante and OCT II do not produce measurements that are equal to physical references with refractive index equal to the human cornea. Chapter 3: There is good repeatability of corneal and epithelial thickness using each OCT for test-retest differences compared to the between instruments repeatability. Measurements of epithelial thickness are less repeatable compared to the total corneal thickness for the instruments used in the study. Chapter 4: When contact lenses are imaged in-situ using UHR-OCT the conjunctival tissue appeared displaced. This experiment indicates that this displacement is an artefact of all OCT imagers since a continuous surface (glass slide) was optically displaced indicating that the displacement that is observed is a function of the refractive index change and also the thickness of the contact lens edges. Chapter 5: Discomfort is a complex issue to resolve since it appears to be related to ocular factors such as the corneal and conjunctival topography and sagittal depth; to lens factors that is 1) how the sag depth of the lenses relate to the corneal/conjunctival shape and depth and therefore how well it moves on the eye. 2) Also with the lens material; whether they are high or low modulus, low or high water content, dehydration properties, wetting agents used and its resistance to deposits, lens edge profile and thickness and its interaction with the upper eyelid.

Purpose To study the impact of lactoferrin and lipids on the kinetic deposition and denaturation of lysozyme on contact lens materials. Methods The contact lenses investigated in this thesis included two silicone hydrogel lenses [AIR OPTIX AQUA; lotrafilcon B and ACUVUE OASYS; senofilcon A] and two conventional hydrogel lenses [ACUVUE 2; etafilcon A and PROCLEAR; omafilcon A]. All lenses were incubated in four solutions: a complex artificial tear solution (ATS); an ATS without lactoferrin; an ATS without lipids; and an ATS without lactoferrin and lipids. Following various time points, all lenses were prepared for lysozyme analysis using the methods below: • To quantify the kinetic uptake of lysozyme to different contact lens materials, I125-radiolabelled lysozyme was added to each incubation solution. Total lysozyme deposition was quantified using a gamma counter. • To study the activity of lysozyme deposited to contact lenses, a fluorescence-based lysozyme activity assay was compared to a turbidity assay. Potential interactions with lens materials and extraction solvents were evaluated. • To investigate the kinetic denaturation of lysozyme deposited to different contact lens materials, the fluorescence-based activity assay and the enzyme-linked immunosorbent assay were used. Results The presence of lactoferrin and lipids decreased lysozyme uptake to lotrafilcon B. Lysozyme deposition on senofilcon A was greater in the absence of lipids after day 21, however the opposite was seen with etafilcon A, where lysozyme uptake was lower without lipids in the ATS. Lactoferrin and/or lipids had no effect on lysozyme adsorption to omafilcon A. The fluorescence-based lysozyme activity assay demonstrated high sensitivity and a wide linear range of detection, which covers the amount of lysozyme typically extracted from contact lenses. Using this assay, lysozyme activity on both silicone hydrogel materials was lower in the presence of lipids in the ATS. In addition, lactoferrin had a protective effect on lysozyme activity for lysozyme sorbed to senofilcon A. Moreover, the presence of lactoferrin and/or lipids did not exhibit any effect on lysozyme denaturation with conventional hydrogel lenses. Conclusions The presence of lactoferrin and lipids in an artificial tear solution impacted lysozyme deposition and denaturation of lysozyme on various contact lenses. It is important for in vitro studies, when developing tear film models, to consider the effects of tear film components when investigating protein deposition and denaturation on contact lenses.

Contact Lens Acute Red Eye (CLARE) and Infiltrative Keratitis (IK) are inflammatory responses of the eye associated with extended wear of soft contact lenses. Bacterial colonization of contact lenses with Gram-negative bacteria such as Pseudomonas aeruginosa is an important risk factor for the development of these adverse responses. Strategies that control the bacterial colonization of contact lenses may help prevent the occurrence of adverse responses. This thesis aimed to develop an animal model of CLARE/IK to test this hypothesis and to test the effectiveness of contact lenses containing antimicrobial compounds, namely silver and furanone compounds, in controlling corneal inflammation caused by Pseudomonas aeruginosa. A guinea pig model of contact lens wear was developed for the study and it was observed that the ocular responses to contact lens wear in the guinea pig were similar to those seen in human eyes wearing contact lenses. Also, three different models for CLARE/IK were developed and tested in the guinea pig eye. The pathological features of CLARE/IK in the guinea pig were virtually identical to those observed in human eyes. Bacterial contamination of contact lenses was confirmed to be a major risk factor for the development of CLARE/IK. Contact lenses containing nano-particles of silver demonstrated very good antibacterial activity against Pseudomonas aeruginosa in-vitro. The silver lenses were able to control the development of CLARE/IK responses in one of the models for CLARE/IK. Silver lenses might be most effective if used to prevent the establishment of a biofilm of bacteria on a lens such as might occur during storage in a contact lens case. Contact lenses were coated with different concentrations of the furanone compounds by physical adsorption and demonstrated good antibacterial activity at higher concentrations. However these concentrations were cytotoxic in-vitro and lower concentrations of furanones did not possess adequate antibacterial activity to control CLARE/IK responses in-vivo. This thesis has successfully demonstrated that guinea pigs can be used to test the effects of extended wear of contact lenses and developed models to test the pathogenesis of adverse responses such as CLARE/IK. The CLARE/IK models developed could be used to further our understanding of the pathogenesis of these inflammatory conditions and explore the activity of other antimicrobials.

Although there is considerable published research on the efficacy and corneal response to orthokeratology (OK) lenses that flatten corneal curvature to correct myopia, the effects of OK lenses that attempt to steepen corneal curvature to correct hyperopia are poorly understood. This project investigated the effects of hyperopic OK lens wear on corneal shape, refraction and vision. Open-eye and closed-eye overnight studies were conducted with proprietary hyperopic OK lenses, and these led to the development of an experimental hyperopic OK lens design which allowed manipulation of individual lens design parameters. Changes to refraction and best corrected visual acuity (BCVA), corneal topography (Medmont E300), and the profile of total and stromal corneal thickness (Holden-Payor optical pachometer) were measured over periods up to one week of overnight lens wear. Most refractive change occurred after the first night of wear, with increasing effect towards one week. Retention of effect at the end of the day increased with more nights of lens wear. BCVA decreased with longer periods of lens wear. Greater inter-subject variability in effect was found with higher refractive targets. The central cornea steepened and para-central cornea flattened producing a central steepening zone (CSZ) surrounded by a para-central annular flattened zone. CSZ diameter reduced with longer periods of lens wear, and this was significantly associated with decreases in high and low contrast BCVA. There was no change in central corneal thickness beyond the normal overnight lens induced hypoxic edema response. Once edema had resolved thinning of the para-central corneal epithelium was found which resulted in an overall thinning of the para-central cornea. Although central lens fenestrations did not affect the hyperopic OK response, a stronger relationship between changes to apical corneal curvature and refraction resulted. This supports the conclusion that the hyperopic OK effect is due to molding of the corneal surface towards alignment with the lens back surface. Similarities to the pattern of clinical change in myopic OK suggest that a similar corneal molding mechanism occurs in myopic OK. BCVA loss prevented longer term studies and needs to be resolved if hyperopic OK is to become established as a viable clinical technique.

In this work a finite element model is proposed to describe the swelling of poly(acrylic acid) hydrogels under the influence of an external electric field. The specific application of this model is for optical applications, but the design could be used equally well for other applications such as sensors and actuators.The model is proposed as five individual modules, which work in conjunction with each other but which can also function independently. This independence allows the model to provide intermediate results to the user, and also permits each module to be improved or adjusted individually without affecting the operation of the overall model. The first module is the Electrical module, which calculates the external electric field present in the hydrogel by solving Laplace's equation. The second module is the Chemical module, which uses the electric field to calculate the diffusion and migration of ions through the hydrogel/solvent regions. The third module is the Force module, which uses the change in ion concentrations to calculate the resulting change in osmotic pressure (force). This force is then used in the Mechanical module to calculate the deformation of the hydrogel, based on the assumption of linear elasticity. Finally, the fifth module is the Optical module, which uses the deformation to calculate the theoretical change in focal length.To verify the operation of the model, numerous experiments were conducted with the deformation of a poly(acrylic acid) hydrogel being measured under various external voltages with different electrode configurations. Overall, the model agrees quite well with the experimental results, but also highlights some interesting discrepancies that will need to be considered in future work. There is also some scope for improvement in the experimental method used, but again this is left for future work.

Although there is considerable published research on the efficacy and corneal response to orthokeratology (OK) lenses that flatten corneal curvature to correct myopia, the effects of OK lenses that attempt to steepen corneal curvature to correct hyperopia are poorly understood. This project investigated the effects of hyperopic OK lens wear on corneal shape, refraction and vision. Open-eye and closed-eye overnight studies were conducted with proprietary hyperopic OK lenses, and these led to the development of an experimental hyperopic OK lens design which allowed manipulation of individual lens design parameters. Changes to refraction and best corrected visual acuity (BCVA), corneal topography (Medmont E300), and the profile of total and stromal corneal thickness (Holden-Payor optical pachometer) were measured over periods up to one week of overnight lens wear. Most refractive change occurred after the first night of wear, with increasing effect towards one week. Retention of effect at the end of the day increased with more nights of lens wear. BCVA decreased with longer periods of lens wear. Greater inter-subject variability in effect was found with higher refractive targets. The central cornea steepened and para-central cornea flattened producing a central steepening zone (CSZ) surrounded by a para-central annular flattened zone. CSZ diameter reduced with longer periods of lens wear, and this was significantly associated with decreases in high and low contrast BCVA. There was no change in central corneal thickness beyond the normal overnight lens induced hypoxic edema response. Once edema had resolved thinning of the para-central corneal epithelium was found which resulted in an overall thinning of the para-central cornea. Although central lens fenestrations did not affect the hyperopic OK response, a stronger relationship between changes to apical corneal curvature and refraction resulted. This supports the conclusion that the hyperopic OK effect is due to molding of the corneal surface towards alignment with the lens back surface. Similarities to the pattern of clinical change in myopic OK suggest that a similar corneal molding mechanism occurs in myopic OK. BCVA loss prevented longer term studies and needs to be resolved if hyperopic OK is to become established as a viable clinical technique.

Although there is considerable published research on the efficacy and corneal response to orthokeratology (OK) lenses that flatten corneal curvature to correct myopia, the effects of OK lenses that attempt to steepen corneal curvature to correct hyperopia are poorly understood. This project investigated the effects of hyperopic OK lens wear on corneal shape, refraction and vision. Open-eye and closed-eye overnight studies were conducted with proprietary hyperopic OK lenses, and these led to the development of an experimental hyperopic OK lens design which allowed manipulation of individual lens design parameters. Changes to refraction and best corrected visual acuity (BCVA), corneal topography (Medmont E300), and the profile of total and stromal corneal thickness (Holden-Payor optical pachometer) were measured over periods up to one week of overnight lens wear. Most refractive change occurred after the first night of wear, with increasing effect towards one week. Retention of effect at the end of the day increased with more nights of lens wear. BCVA decreased with longer periods of lens wear. Greater inter-subject variability in effect was found with higher refractive targets. The central cornea steepened and para-central cornea flattened producing a central steepening zone (CSZ) surrounded by a para-central annular flattened zone. CSZ diameter reduced with longer periods of lens wear, and this was significantly associated with decreases in high and low contrast BCVA. There was no change in central corneal thickness beyond the normal overnight lens induced hypoxic edema response. Once edema had resolved thinning of the para-central corneal epithelium was found which resulted in an overall thinning of the para-central cornea. Although central lens fenestrations did not affect the hyperopic OK response, a stronger relationship between changes to apical corneal curvature and refraction resulted. This supports the conclusion that the hyperopic OK effect is due to molding of the corneal surface towards alignment with the lens back surface. Similarities to the pattern of clinical change in myopic OK suggest that a similar corneal molding mechanism occurs in myopic OK. BCVA loss prevented longer term studies and needs to be resolved if hyperopic OK is to become established as a viable clinical technique.

Thesis (MEng) - Swinburne University of Technology, Faculty of Engineering and Industrial Sciences, Centre for Micro-Photonics, 2006. / A thesis submitted for the degree of Master of Engineering, Centre for Micro-Photonics, Faculty of Engineering and Industrial Sciences, Swinburne University of Technology, 2006. Typescript. Includes bibliographical references (p. 74-77).

Thesis (M.S.)--New England College of Optometry, 2009. / Includes bibliographical references (p. 94-96).