Knowledge of the mechanics of the lens capsule is crucial for improving cataract surgery as well as understanding better the physiological role of the lens capsule in the process of accommodation. Previous research on the mechanical properties of the lens capsule contains many gaps and contradictions due to experimental limitations and inappropriate assumptions. Thus, the goal of this work is to quantify fully the regional, multiaxial mechanical behavior of the lens capsule and to calculate the change in stress and strain fields as a result of cataract surgery. Determining in situ the multiaxial mechanical behavior of the lens capsule required the design and construction of an experimental device capable of altering stresses in the capsule while measuring localized surface deformations. Tests performed on this device reveal that the meridional and circumferential strains align with the principal directions and are equivalent through most of the anterior lens capsule, except close to the equator where the meridional strain is greater. Furthermore, preconditioning effects were also found to be significant. Most importantly, however, these tests provide the data necessary for calculating material properties. This experimental system is advantageous in that it allows reconstruction of 3D geometry of the lens capsule and thereby quantification of curvature changes, as well as measurement of surface deformations that result from various surgical interventions. For instance, a continuous circular capsulorhexis (CCC) is commonly used during cataract surgery to create a hole in the anterior lens capsule (typically with a diameter of 5 mm). After the introduction of a CCC, strain was found to redistribute evenly from the meridional direction (retractional strain) to the circumferential direction (extensional strain), where both directional components of strain reached magnitudes up to 20% near the edge of the CCC. Furthermore, the curvature was found to increase at the edge of the CCC and remain the same near the equator, indicating that the mere introduction of a hole in the lens capsule will alter the focal characteristics of the lens and must therefore be considered in the design of an accommodative intraocular lens.

Thesis (M. Phil.)--University of Hong Kong, 2010. / Includes bibliographical references (leaves 104-115). Also available in print.

ITC/USA 2012 Conference Proceedings / The Forty-Eighth Annual International Telemetering Conference and Technical Exhibition / October 22-25, 2012 / Town and Country Resort & Convention Center, San Diego, California / The NASA Remote Imaging System Acquisition (RISA) project is a prototype camera intended to be used by future NASA astronauts. NASA has commissioned the development of this engineering camera to support new mission objectives and perform multiple functions. These objectives require the final prototype to be radiation hardened, multispectral, completely wireless in data transmission and communication, and take high quality still images. This year's team was able to successfully develop an optical system that uses a liquid lens element for focus adjustment. The electrical system uses an Overo Fire computer-on-module (COM) developed by Gumstix. The OMAP processor onboard handles all communication with a monochromatic CMOS sensor, liquid lens control circuitry, pixel data acquisition and processing, and wireless communication with a host computer.

In this dissertation fully general conditions are presented to correct linear and quadratic field dependent aberrations that do not use any symmetry. They accurately predict the change in imaging aberrations in the presence of lower order field dependent aberrations. The definitions of the image, object, and coordinate system are completely arbitrary. These conditions are derived using a differential operator on the scalar wavefront function. The relationships are verified using ray trace simulations of a number of systems with varying degrees of complexity. The math is shown to be extendable to provide full expansion of the scalar aberration function about field. These conditions are used to guide the design of imaging systems starting with only paraxial surface patches, then growing freeform surfaces that maintain the analytic conditions satisfied for each point in the pupil. Two methods are proposed for the design of axisymmetric and plane symmetric optical imaging systems. Design examples are presented as a proof of the concept.

This dissertation investigates challenges associated with optics in the 10-500 wavelength size regime. For the visible spectrum, this size range (5-250um) is classified as micro-optics, but is set apart from other size ranges by a noticeable lack of suitable simulation and metrology tools. Optics of this size are gaining popularity in applications such as solid immersion lenses (SIL) and laser beam shaping, but require more research into simulation, testing, fabrication, and assembly in order to be easily integrated into commercial applications.A survey of previous work on SILs and micro-optics simulation/testing is given, including past work with gallium phosphide (GaP) microlenses. A new SIL aberration treatment is described using spherical-parent 3rd order aberrations. Agreement is shown with previous work, and the lack of hemisphere approximations gives a broader understanding of aberrations for varying SIL thicknesses. Results show that aberration reduces with lens radius, but thickness tolerances become tighter as dimensions shrink. A study of GaP intrinsic birefringence and the theoretical impact on the induced polarization signal is also given.A survey of beam propagation simulators is given and a sequential piece-wise diffraction (SPWD) simulator is developed for arbitrary optical systems that overcomes the difficulties of simulation in the 10-500 wavelength size regime. A discussion of a future extension to the work to determine reflected and transmitted field amplitudes with a non-sequential method is presented with specific discussion on the challenges of electric field surface transfer.The design and operation of a micro-interferometer is discussed and testing results from the first sub-100um diameter GaP SILs are shown. A novel method for determining the shape profile of aspheric surfaces using information from annular fringes is presented. Theoretical beam shaping applications for micro GaP lenses is also discussed with results using the SPWD method. Experimental results are also shown for a 1x1x0.3mm beam shaper package that images a laser diode beam to an approximate size of 60um at a working distance of 4mm.Finally, designs and experimental results are shown for the integration of GaP micro-optics into conventional systems as SILs or beam-shaping elements including methods and equipment for lapping and polishing GaP.

E mokymo aplinkos padeda pasiekti efektyvesnį pažintinės veiklos vystimąsi ir suteikia galimybę kūrybiniam mokinių tobulėjimui. Fizikos pamokose galima naudoti kompiuterį, kuris gali atstoti dalį eksperimentui reikalingos įrangos, laboratorinį praktikumą. Tam reikalingos mokomosios kompiuterinės aplinkos, kurių pagalba demonstruojami bandymai papildo eksperimentinę fizikos kurso dalį, pamoka tampa efektyvesnė, lengviau įsisavinama. Tačiau dauguma mokymo tikslams naudojamų kompiuterinių programų yra užsienio kalba. Natūralu, jog programos yra nesuderintos su ugdymo turiniu, jos yra per sudėtingos mokytojams ir mokiniams. Dėl to reikia sukurti interaktyvią mokymo aplinką pritaikytą fizikos kursui „Lęšiai“ mokyti. Magistrinio darbo metu Atlikta kompiuterinių aplinkų, naudojamų fizikos mokyme, analizė. Jos metu nustatyta, kad kai kurios priemonės yra gana senos, pritaikytos MS - DOS aplinkai. Todėl kartais tai sukelia problemų naudojant šiuolaikiškas OS, nes dėl dalinio nesuderinamumo veikia nestabiliai. Atlikta mokytojų apklausos analizė. Jos metu nustatyta, kad naudojant mokomąsias kompiuterines priemones mokytojai susiduria su problemomis. Pagrindinės jų: nesuderintos su ugdymo programa, sudėtingas valdymas, daugelio vartotojo sąsajos kalba yra užsienio kalba. Atsižvelgiant į naudojamų kompiuterinių mokymo programų privalumus ir trūkumus, apibrėžta siekiama sukurti kompiuterinė mokymo priemonė, jos funkcijos. Atliktas mokomąja kompiuterinę priemonę sudarančių komponenčių... [toliau žr. visą tekstą] / E-teaching mediums help to reach more effective development of a cognitive work and gives an opportunity for the creative student’s perfection. A computer can be used in physics lessons, which can replace a piece of equipment needed for experiments and laboratories. Thereto teaching computer-based mediums are needed, with there help demonstration of experiments supplement experimental course of physics, lessons become more effective and easier to soak up. However majority of teaching computer-based programmes are in a foreign language. Naturally that programmes do not match the education content, they are too difficult for teachers and students. Therefore it is needed to create an interactive teaching medium fitted for teaching a physics course “Lens”. In master’s work The analysis of teaching mediums used in physics teaching is done. During it was found that some devices are quite old, adjusted to a MS – DOS medium. So sometimes it causes problems using modern OS, because of the partial incompatibility it works unstable. The teacher’s survey analysis was done. It was found that teachers face problems using the computer-based equipment. Basic of them: they do not match the education content, a complicated control and most of them user’s linking language is foreign. Considering the advantages and disadvantages of usable computer-based programmes, a computer-based teaching device and its functions are defined. A projection of a teaching computer-based device components was... [to full text]

It is widely accepted in our society that people’s paralinguistic (i.e., non-semantic characteristics of the voice) and nonverbal (i.e., posture, gestures, and facial expressions) behaviours play an important role in conveying information about their personality traits. Two particularly relevant traits include one’s preferred levels of dominance and affiliation, which are the two major axes of the interpersonal circumplex. The current study investigates how dominance and affiliation are conveyed through paralinguistic and nonverbal behaviour using a lens model framework. Two major issues addressed by this framework include: 1) How do observers make inferences about people’s dominance and affiliation using paralinguistic and nonverbal behaviours and 2) How do people’s trait dominance and affiliation relate to these behavioural cues? To examine these two questions, we collected data from 114 opposite-sex dyads who worked together to complete a relatively unstructured collaborative task. The videotaped interactions were coded for specific paralinguistic (e.g., pitch, volume, resonance) and nonverbal (e.g., hand gestures, trunk posture, facial expressions) behaviours, in addition to coding more global displays of dominance and affiliation. Participants also completed several measures of trait dominance and affiliation, which tapped both their relatively conscious (i.e., explicit) and their relatively unconscious (i.e., implicit) levels of these traits. Our findings suggest that observers used mainly paralinguistic behaviour to infer dominance and mainly nonverbal behaviour to infer affiliation. In comparison to observers’ perceptions, there were fewer significant relations between individuals’ self-reported trait dominance and affiliation and the nonverbal and paralinguistic behaviours they expressed during the interaction, suggesting that people may have limited conscious awareness of how these behaviours convey information about their trait dominance and affiliation. In line with this idea, several behaviours showed relations to implicit measures of trait dominance and affiliation. We also conducted factor analyses of the measured paralinguistic and nonverbal behaviours, to examine whether or not these behaviours might co-occur as subsets or factors. We found that paralinguistic and nonverbal behaviours can be captured by overarching factors which relate meaningfully to measures of dominance and affiliation. Finally, we demonstrated that dyad members’ paralinguistic and nonverbal behaviours become interdependent as they interact with one another.

The Mexican tetra, Astyanax mexicanus, exists as two morphs of a single species, a sighted surface morph and a blind cavefish. In addition to eye regression, cavefish have an increased number of taste buds, maxillary teeth and have an altered craniofacial skeleton. I investigated the effect the lens has on the development of the surrounding skull by ablating the lens over early ontogeny. This unique long-term study sheds light on how early embryonic manipulations on the eye can affect the shape of the adult skull. The effects of lens ablation were analyzed using landmark based morphometric analyzes. Morphometric analyzes indicate that there is a significant difference in the shape of the supraorbital bone and suborbital bones four through six. These bones expand into the eye orbit exhibiting variability in their shape. Interestingly, the number of caudal teeth on the lower jaw is also affected by lens ablation. I compared these findings between morphs and across two teleost species. I conducted lens removal in the surface fish to determine if it would produce a cavefish phenotype. Lens removal in the surface fish only partially results in a cavefish phenotype, indicating that lens loss is not solely responsible for the phenotypic differences between the two morphs. The effects of lens removal were then compared in the Mexican tetra and zebrafish. Surprisingly, the results indicate that the same bones are variable in shape in both species, indicating that the variability of these bones is conserved across species. Finally, I compared laser lens damage and full lens removal, to investigate the capacity for both lens regeneration and healing in the Mexican tetra. Together, the lens healing and regeneration studies indicate that lens absence in early development does not influence the shape of the skull. Lens absence during later development influences the mechanical forces in the skull resulting in the bones of the orbital region changing in size and shape. This study highlights the dynamic nature of the skull and sheds light on the influence the eyes (a soft tissue) have on the surrounding skull (a hard tissue) a topic which has been overlooked in the literature.

Purpose: To test the viability of implanting the Artisan®/VerisyseTM lens in a low-income monocular aphakic African population with insufficient capsular support where contact lens wear is expensive and spectacle correction is not possible, by assessing the postoperative visual functions. To further assess whether adverse effects (e.g.: pigment dispersion with secondary glaucoma, prolonged uveitis) in patients with highly pigmented irises would be as low as with patients in European and American trials. Methods: A prospective, randomised, controlled clinical trial comparing outcomes in two groups of unilateral aphakic patients. The patients in the first group received an Artisan intra-ocular iris-claw lens as a secondary procedure while the second group remained aphakic (the current treatment status quo for public patients in KwaZulu-Natal province in South Africa). Follow-up was done for 1 year. Results: The study was terminated early due to ethical and statistical reasons. Nine treated and five control patients were included. Monocular uncorrected vision was significantly higher in the treatment group (P=0,012) and patient satisfaction was higher (p=0,002). Changes in other variables (intraocular pressure, angle pigmentation, change in cup-to-disc ratio, iris pigment changes and best spectacle corrected vision) were not significantly different between the two groups. Conclusion: The Artisan®/VerisyseTM lens is a feasible option for aphakic African patients with regard to visual outcome, safety and patient satisfaction. This form of refractive correction should be the standard for patients with no capsular support and where other options are too expensive or carry greater risk. / Thesis (M.Med.)-University of KwaZulu-Natal, Durban, 2007.

The aim of this project is to develop a computational model of the structure and function of the ocular lens, specifically the solute and fluid transport in the lens. The modelling framework was based on finite volume methods. The intracellular and extracellular solute fluxes were modelled using the Nernst-Plank equation with an extra term to capture solute fluxes due to advection. The modelling framework included equations describing the flux through the Na+ /K+ pumps and K+ channels in the surface membrane, and Na+ and Cl- channels in the fibre cell membrane. The intracellular fluid flow between adjacent fibre cells was modelled by a homogenised transmembrane fluid flow equation and the intracellular fluid flow along the fibre cell was modelled as Poiseuille flow. The extracellular fluid flow was modelled as Couette flow with an extra term to capture electro-osmotic flow. The fluid flow through the fibre cell membrane and surface membrane was modelled as transmembrane fluid flow. The governing equations account for the structural properties of the lens, such as the tortuosity of the extracellular cleft, the intracellular and extracellular volume fractions, and the membrane density. A one-dimensional model of the Na+ , K+ , Cl- and fluid transport in the frog lens was developed. This model was based on the analytic model developed by Mathias (1985b). The results were consistent with the results from the analytic model and experimental data. Two versions of the two-dimensional model were developed. In the first model, the parameters were spatially constant except for the distribution of the Na+ /K+ pump currents at the lens surface and the fibre cell angles. The second model was the same, except the extracellular cleft width and fibre cell height was spatially varied to represent the sutures and the diffusion barrier. These models were solved and compared with each other and with experimental data. Compared to the first, the second model predicted a significantly larger circulation of solutes and fluid between the pole and equator. It predicted a 12-20% increase in the penetration of Na+ , K+ and fluid into the lens. The second model also predicted a 300-400% increase in Cl- penetration and, unlike the first model, a Cl- circulation between the poles and equator. This is significant since Cl- is not an actively transported solute. These results highlight the strong structure-function relationship in the lens and the importance of an accurate spatial representation of model parameters. The direction of the current, solute fluxes and fluid flow that were predicted by the model were consistent with experimental data but the magnitude of the surface current was a tenth to a third of the values measure by the vibrating probe. To demonstrate the application of the lens model, the two-dimensional model was used to simulate age-related changes in lens physiology. This was done by increasing the radius of the lens to simulate growth with age. The model predicted an increase in the intracellular Na+ concentration, Cl- concentration and potential, and a decrease in the intracellular K+ concentration with age. These trends were consistent with those observed by Duncan et al. (1989), except for the intracellular K+ concentration, where they reported no change with age. The two-dimensional model forms a foundation for future developments and applications.