The cornea is an avascular transparent tissue exposed to the environment and therefore highly susceptible to damage. With an increase in corneal refractive surgeries, corneal transplants, and corneal injuries, understanding and improving corneal healing mechanisms are extremely important. Impaired healing of corneal wounds can lead to decreased visual acuity and extreme pain. Serum eye drops, amniotic membranes, pharmaceutical agents, biopolymers, and cell transplants are just a few approaches that have been employed to improve wound healing. Bandage contact lenses (BCLs) have been proposed as a simple method to facilitate wound healing while reducing pain. The synthesis of a silicone hydrogel contact lens capable of surface binding hyaluronic acid (HA) for corneal wound healing was explored in the current work. HA was used as both a wetting agent and a therapeutic. The work presented describes the synthesis, characterization, and cell testing of the HA binding model silicone hydrogels, composed of the hydrophilic monomer, 2-hydroxyethyl methacrylate (HEMA) and a hydrophobic silicone monomer, methacryloxypropyltris (trimethylsiloxy) silane (TRIS). Three different methods were evaluated for increasing HA binding and improving surface wettability. “Caged lenses” utilized the same base polymer with the incorporation of methacrylated N-Hydroxysuccinimide (NHS). Hydrophilic polyethylene glycol (PEG) chains were then tethered from the NHS, forming a “cage” with the potential to physically entrap HA. Although surface wettability was improved, less HA was entrapped in the caged lenses compared to model silicone hydrogels, presumably due to the increased hinderance resulting from the PEG chains. “Tethered HA” lenses utilized PEG as a spacer to conjugate HA to the lens surface in order to improve surface hydrophilicity. Methacrylated HA conjugation resulted in a significant decrease in contact angle (p <0.01) compared to model pHEMA-co-TRIS whereas tethered thiolated HA did not lead to a significant decrease (p >0.05) in contact angle. It was clear that neither of these methods would lead to sufficient HA binding. Ionic interaction lenses utilize monomers and small molecules that contain a positive charge to bind to the negatively charged HA under physiological conditions. The monomer diethylaminoethyl methacrylate (DEAEM) was polymerized directly into the polymer backbone, but resulted in no significant decrease (p >0.05) in contact angle. In comparison, surface functionalization using thiolene “click” chemistry allowed conjugation of the small molecule, dimethylamino ethanethiol (DMAET) and diethylamino ethanethiol (DEAET). DMAET and DEAET modified lenses showed significantly higher (p <0.001) HA binding compared to model pHEMA-co-TRIS controls at all time points. The modified lenses improved release kinetics preventing an initial burst release and showed consistent release when unloaded and reloaded with HA. The contact angle was significantly decreased (p <0.05) for the modified lenses with HA without affecting the equilibrium water content. Optical transparency was reduced following lens modifications although the thickness of the disks prepared was higher than a typical contact lens. Finally, the modified lenses did not exhibit any cytotoxicity in vitro with human corneal epithelial cells (HCECs). The synthesis of silicone hydrogels capable of surface binding HA have potential to be used as a bandage contact lens while improving surface wettability and enhancing comfort. / Thesis / Master of Applied Science (MASc)

No description available.

No description available.

No description available.

No description available.

Silicone hydrogels haves been widely utilized in many in ophthalmic and other biomedical applications due to the its comfort of hydrogels, their excellent biocompatibility, high oxygen permeability and transparency. For use as a contact lens, the silicone hydrogel with interacts with the tear film, cornea, and eyelid;, thus surface properties of the gel are crucial to be considered. The highly oxygen permeabilitye performance of the silicone hydrogel contact lens materials mainly relies on the incorporationng of the siloxane functional groups., Hhowever these groups are extremely mobile and surface active, which can result in an increase in the of lens surface hydrophobicity, as well as protein and lipid deposition. Therefore, there is a need for surface modification of silicone hydrogel contact lenses. Otherwise users may might have to choose to decrease the frequency and length of wearing duration of silicone contact lenses due to dryness or bio-fouling related issues. A novel biomimetic methacrylate monomer which contains a phosphorylcholine group, 2-mMethacryloyloxyethyl pPhosphorycholine (MPC) is was grafted onto the surface of novel silicone hydrogel materials surface to create a thick hydration layer in order to enhance the protein resistance and surface wettability. Low temperature air plasma has beenwas chosen to initiate grafting polymerization of MPC monomers onto silicone hydrogel substrates. Hydrogels were treated with plasma and exposed to air flow to yield hydroperoxides on the surface; the, and peroxides group acted as a photo-initiators for further thermal MPC grafting polymerization. After surface modification, the silicone hydrogels were characterized by XPS and ATR-FTIR to confirm the structure and elemental composition. A significant amount of phosphorus element was found shown on the XPS spectra of the modified materialsum,, demonstrating that so the MPC monomers were successfully grafted onto the gel surface. According to water contact measurement results, the modified samples possessed very hydrophilic surfaces, with advancing angles of about 27°, while compared the unmodified samples at around 110°. After surface grafting, between a around 20% and to 50%’s reduction in protein deposition was also observed, which aligned with water contact angle results. Other properties such as oxygen permeability, transparency, water equilibrium, and elastic modulus remained unchanged after the air plasma exposure and thermal MPC polymerization. / Thesis / Master of Applied Science (MASc)

No description available.

No description available.

QC 351 A7 no. 54 / It is possible to use a target of two coherent point sources, with a separation much greater than the resolution limit of a diffraction -limited lens, to determine the best focus of a photographic system. The interference pattern formed is a function of the focus error. Measurement of its characteristics (fringe period, fringe number, etc.) for different focus errors should indicate the best focus. Since the measurement is made at a long distance from focus, there is no ambiguity as to the direction of the best focus position relative to the film. An experiment, in which known focus errors were introduced on both sides of a visual best focus for a two -coherent -point- sources target, was designed and carried out for a 35 -mm camera system to determine the usefulness of such a method of determining best focus. A comparison test was made against a standard resolution vs focus error method. The experiment showed an unambiguous best focus within an error of 10 pm. The focus position was unambiguous because the final relationship studied was linear, and only one value was obtained. In general the new method appears to be faster, simpler, cheaper, and more accurate than the standard resolution method, and it requires no special instrumentation on the camera being tested.

D.Phil. / That the eye is essentially a first-order optical instrument is evidenced by the success Gaussian optics has met with in optometry and ophthalmology. An unfortunate consequence of this approach is that a brief review of the literature on the topic of intraocular lens power calculation gives one the impression that the character of such a lens is described fully by its dioptric power. This is not so. Indeed, the idea that a thin refracting interface can somehow embody the optical character of the thick intraocular lens can, and in many ways has, limited the scope of intraocular lens power formula. The purpose of this dissertation is to apply the methods of linear algebra to the investigation of the first-order optical character of the stigmatic and astigmatic pseudophakic eye. This work attempts to lay a solid foundation for the study of the pseudophakic eye in the context of first-order astigmatic optics. While the majority of concepts and results of this dissertation are directly applicable to the study of the pseudophakic eye, an attempt has been made to ensure that the methods outlined in this work may be applied to the study of optical systems in the broader context of first-order optics. Central to this work are the members of the non-abelian symplectic group Sp(2n) under the operation of conventional matrix multiplication. The elements are evendimensional, non-singular symplectic matrices with unit determinant which are referred to here as ray transferences. These matrices act on the members of even-dimensional vector spaces so as to preserve a particular skew-symmetric, non-degenerate bilinear pairing referred to as the symplectic form. The laws that govern the operation of these matrices, the three symplectic relations, flow naturally from the structure of the symplectic group. From the ray transference four 2„e 2 fundamental properties of an optical system may be defined, the dilation A , the disjugacy B , the divergence C and the divarication D. A number of additional optical properties can be derived from the fundamental properties. Examples of derived properties include the dioptric power F , the negative of the divergence C and refractive state 0 F . The ray transference is used here in the derivation of a set of new intraocular lens formulae for the pseudophakic eye. These formulae are entirely general, working equally well in both stigmatic and astigmatic pseudophakic eyes in which additional (possibly astigmatic) intraocular devices may already be present. Formulae for both distant and near objects are provided. The constraints under which the divergence of a thick (possibly bitoric) intraocular lens is conserved despite changes in the lens are investigated. Furthermore, the constraints under which the refractive state of the pseudophakic is conserved in spite of changes in the thick intraocular lens are investigated. We find that there exist an infinite number of thick intraocular lenses that will produce a given refractive outcome, say emmetropia, in the pseudophakic eye. The basic theory of matrix differentiation with respect to a scalar variable is utilized in the study of the changes in the optical character of the pseudophakic eye following axial translation of a variety of intraocular lens systems. A novel method of representing the changes in the stigmatic and antistigmatic properties of refraction on account of axial translation and rotation of a toric intraocular lens in the astigmatic eye is presented and numerical examples are provided. The analysis permits the calculation of the ideal axial lens position and orientation in the astigmatic pseudophakic eye. Such methods will prove increasingly important in refractive data analysis, particularly in light of the development of continuously adjustable intraocular devices. / Prof. W.F. Harris