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The ocular surface is extremely effective at protecting the eye through such physiological barriers as the cornea and tear film. The exposed nature of the cornea can still lead to a significant number of injuries and harm from the external environment. Management and treatment of ocular injuries involves a combination of a bandage contact lens (BCL) along with therapeutic eye drops that require frequent and strict dosing regimens that can be difficult to maintain and are inefficient due to the high clearance rate of the eye. Therapeutic contact lenses (TCL) with vitamin E (VE) incorporated have been shown to steadily release a desired therapeutic agent and potentially simplify a patient’s treatment process. Vat polymerization (VP), a form of 3D printing, was utilized in this work to explore a platform design for developing customizable VE-containing TCLs, using dexamethasone phosphate (DXP) as a model drug. VP was also used to explore the creation of a multi-material TCL, using a VE embedded ring that could be directly printed within the lens in a streamlined and automated manner. Three lens formulations consisting primarily of hydroxy ethyl methacrylate (HEMA) and polyethylene glycol diacrylate (PEGDA) with modified formulations containing methacrylated VE (VEMA) and Methacryloxypropyltris (Trimethylsiloxy) silane (TRIS) as a model silicone material were prepared. These lenses were synthesized and characterized to examine 3D printing for lens creation in comparison to commercial standards. The base and VEMA formulations were used to examine the feasibility of a multi-material (MM) lens with an embedded ring directly incorporated during the printing process. All three formulations showed shear thinning properties suitable for VP bioprinting applications. The base formulation produced a very homogenous print while VEMA prints showed defects and clear phase separation. The VEMA+TRIS formulation showed significant improvement as the prints were more homogenous with fewer defects. The MM lenses showed a mixture of properties between the base and VEMA formulations, with the center appearing more homogenous and the edge that included the embedded ring showing defects similar to VEMA prints. Surface wettability and water content decreased from the base formulation with an increasing presence of hydrophobic moieties in the modified formulations. The increased hydrophobicity can be correlated with an increase in stiffness seen from the base formulation. While all materials had high moduli due to the high crosslinking density and presence of PEGDA, the VEMA prints had a higher modulus than the base material but were quite brittle due to the increased hydrophobicity and poor print quality. The VEMA+TRIS prints showed a significant (p < 0.05) increase in stiffness without the brittleness of the VEMA prints due to the better print quality. The MM prints had the lowest moduli, most similar to the base material, indicating that this lens design could mitigate the brittleness seen with the VEMA prints. A comparison of 3DP and casting showed the cast material having a significantly (p < 0.05) higher modulus than the 3DP material presumably due to the bulk vs. layer-by-layer polymerization processes that the respective manufacturing methods utilize. The base material produced significantly more transparent prints, with transmissions (wavelength) that ranged between 80-88%, compared to the VEMA and VEMA+TRIS prints which ranged from 18-47%. The MM lenses showed promise for minimizing the effect of the poor transparency of the VEMA ring with transparency of 62-85%. Besides the formulations, the lens thickness, print quality and print plate surface were found to be major contributors to the printed lenses not meeting commercial standards. The VEMA+TRIS loaded lenses showed the greatest changes in the release kinetics with a larger burst release, attributed to the weaker affinity DXP has to the hydrophobic components, while the base and VEMA lens’ profiles were very similar. The weaker drug-polymer interaction and more mobile silicone-oxygen bonds of TRIS are likely the reason for the VEMA+TRIS formulation releasing significantly more DXP than the base or VEMA lenses, with 69.21 ± 3.62%, 44.09 ± 4.63% and 37.09 ± 4.81% released respectively. It is believed that the high degree of crosslinking within the lens polymer matrix causes high levels of physical entrapment, resulting in an incomplete release of DXP from the lenses. Another possibility is that some DXP reacted with the acrylate components of the lens formulations as the photopolymerization process creates free radicals which could lead to the formation of covalent bonds of DXP with one of the monomers in the formulation. The use of 3DP to develop customizable TCLs on-demand has a lot of potential as the biomedical and healthcare industries shift to more of a personalized rather than a one-size-fits all approach. The MM lens design allows for the incorporation of materials with poor lens properties without significantly impacting the lens’ functions such as its tensile stiffness and transparency. The freedom of design that 3DP provides will allow for tailor-made lenses that can meet a patient’s specific needs, including lens fitting, which would maximize the patient’s comfort. / Thesis / Master of Applied Science (MASc)

The human eye is a complex optical system comprised of many components. The crystalline lens, an optical component with a gradient index (GRIN), is perhaps the least understood as it is situated inside the eye and as a result is difficult to characterize. Its complex nonlinear structure is not easily measured and consequently not easily modeled. Presently several models of the GRIN structure exist describing the average performance of crystalline lenses. These models, however, do not accurately describe the performance of crystalline lenses on an individual basis and a more accurate individual eye model based on anatomical parameters is needed. This thesis proposes an anatomically correct, individually customizable crystalline lens model. This is an important tool and is needed both for research on the optical properties of human eyes and to diagnose and plan the treatment of optically based visual problems, such as refractive surgery planning. The lens model consisted of an interior GRIN with a constant refractive index core. The anterior and posterior surface was described by conic sections. To realize this eye model, the optical and biometric properties of mammalian lenses were measured and the correlation relationships between these measurements were used to simplify the model down to one fitting parameter which controls the shape of the GRIN. Using this data, an anatomically correct individualizable model of the lens was successfully realized with varying parameters unique to each lens. Using this customizable lens model, customizable human eye models based on measurements of the entire human eye can be realized.

The human eye is a complex optical system comprised of many components. The crystalline lens, an optical component with a gradient index (GRIN), is perhaps the least understood as it is situated inside the eye and as a result is difficult to characterize. Its complex nonlinear structure is not easily measured and consequently not easily modeled. Presently several models of the GRIN structure exist describing the average performance of crystalline lenses. These models, however, do not accurately describe the performance of crystalline lenses on an individual basis and a more accurate individual eye model based on anatomical parameters is needed. This thesis proposes an anatomically correct, individually customizable crystalline lens model. This is an important tool and is needed both for research on the optical properties of human eyes and to diagnose and plan the treatment of optically based visual problems, such as refractive surgery planning. The lens model consisted of an interior GRIN with a constant refractive index core. The anterior and posterior surface was described by conic sections. To realize this eye model, the optical and biometric properties of mammalian lenses were measured and the correlation relationships between these measurements were used to simplify the model down to one fitting parameter which controls the shape of the GRIN. Using this data, an anatomically correct individualizable model of the lens was successfully realized with varying parameters unique to each lens. Using this customizable lens model, customizable human eye models based on measurements of the entire human eye can be realized.

The human eye is a complex optical system comprised of many components. The crystalline lens, an optical component with a gradient index (GRIN), is perhaps the least understood as it is situated inside the eye and as a result is difficult to characterize. Its complex nonlinear structure is not easily measured and consequently not easily modeled. Presently several models of the GRIN structure exist describing the average performance of crystalline lenses. These models, however, do not accurately describe the performance of crystalline lenses on an individual basis and a more accurate individual eye model based on anatomical parameters is needed. This thesis proposes an anatomically correct, individually customizable crystalline lens model. This is an important tool and is needed both for research on the optical properties of human eyes and to diagnose and plan the treatment of optically based visual problems, such as refractive surgery planning. The lens model consisted of an interior GRIN with a constant refractive index core. The anterior and posterior surface was described by conic sections. To realize this eye model, the optical and biometric properties of mammalian lenses were measured and the correlation relationships between these measurements were used to simplify the model down to one fitting parameter which controls the shape of the GRIN. Using this data, an anatomically correct individualizable model of the lens was successfully realized with varying parameters unique to each lens. Using this customizable lens model, customizable human eye models based on measurements of the entire human eye can be realized.

The human eye is a complex optical system comprised of many components. The crystalline lens, an optical component with a gradient index (GRIN), is perhaps the least understood as it is situated inside the eye and as a result is difficult to characterize. Its complex nonlinear structure is not easily measured and consequently not easily modeled. Presently several models of the GRIN structure exist describing the average performance of crystalline lenses. These models, however, do not accurately describe the performance of crystalline lenses on an individual basis and a more accurate individual eye model based on anatomical parameters is needed. This thesis proposes an anatomically correct, individually customizable crystalline lens model. This is an important tool and is needed both for research on the optical properties of human eyes and to diagnose and plan the treatment of optically based visual problems, such as refractive surgery planning. The lens model consisted of an interior GRIN with a constant refractive index core. The anterior and posterior surface was described by conic sections. To realize this eye model, the optical and biometric properties of mammalian lenses were measured and the correlation relationships between these measurements were used to simplify the model down to one fitting parameter which controls the shape of the GRIN. Using this data, an anatomically correct individualizable model of the lens was successfully realized with varying parameters unique to each lens. Using this customizable lens model, customizable human eye models based on measurements of the entire human eye can be realized.

Non-mechanical variable lenses are important for creating compact imaging devices. Various methods employing dielectrically actuated lenses, membrane lenses, and liquid crystal lenses were previously proposed [1-4]. In This dissertation the design, fabrication, and characterization of innovative flat tunable-focus liquid crystal diffractive lenses (LCDL) are presented. LCDL employ binary Fresnel zone electrodes fabricated on Indium-Tin-Oxide using conventional micro-photolithography. The light phase can be adjusted by varying the effective refractive index of a nematic liquid crystal sandwiched between the electrodes and a reference substrate. Using a proper voltage distribution across various electrodes the focal length can be changed between several discrete values. Electrodes are shunted such that the correct phase retardation step sequence is achieved. If the number of 2πzone boundaries is increased by a factor of m the focal length is changed from f to f/m based on the digitized Fresnel zone equation: f = rm²/2mλ, where r(m) is mth zone radius, and λ is the wavelength. The chromatic aberration of the diffractive lens is addressed and corrected by adding a variable fluidic lens. These LCDL operate at very low voltage levels (±2.5V ac input), exhibit fast switching times (20-150 ms), can have large apertures (>10 mm), and small form factor, and are robust and insensitive to vibrations, gravity, and capillary effects that limit membrane and dielectrically actuated lenses. Several tests were performed on the LCDL including diffraction efficiency measurement, switching dynamics, and hybrid imaging with a refractive lens. Negative focal lengths are achieved by adjusting the voltages across electrodes. Using these lenses in combination, magnification can be changed and zoom lenses can be formed. These characteristics make LCDL a good candidate for a variety of applications including auto-focus and zoom lenses in compact imaging devices such as camera phones. A business plan centered on this technology was developed as part of the requirements for the minor in entrepreneurship from the Eller College of Management. An industrial analysis is presented in this study that involves product development, marketing, and financial analyses (Appendix I).

The goal of this project is to obtain quantitative images of the lens and the ciliary body to validate EVAS-II (Second generation Ex Vivo Accommodation Simulator). To accomplish this goal it was necessary to develop methods, instrumentation and image processing techniques to acquire 3D images in EVAS-II, using UBM (Ultrasound Bio Microscope), and to apply these techniques to non-human primate eyes. The lens studies included measurement of speed of sound in the lens to reconstruct accurate images of the lens, development of instrumentation to measure the un-distorted lens shape and development of a mathematical model to quantify the whole lens shape. Speed measurements showed that the speed of sound exhibits a gradient profile in the equatorial plane, similar to refractive index and protein distributions in the lens. Lens shape measurements showed that the UBM can be used to accurately measure thickness, diameter, cross-sectional area, volume and surface area of the lens. The ciliary body studies included development of instrumentation and algorithms to obtain 3-D images of tissue in EVAS-II and development of methodology to quantify ciliary body movement during stretching. Studies showed that the accommodation process in young baboon eyes in EVAS-II is comparable to the in vivo process in rhesus monkeys. The UBM can be used to obtain reliable quantitative information about the lens and the ciliary body. 3-D UBM enables monitoring of ciliary body motion of the entire accommodative apparatus.

We fabricated the liquid crystal cell which had the property of the diffraction optical element. The concentric electrode had been fabricated on an indium-tin-oxide (ITO) substrate by etching technology. With the application of a proper voltage, it produces an inhomogeneous grating-like electric field in space to form phase Fresnel liquid crystal lens. Because of liquid crystals (LCs) are excellent electro-optic materials with electrical and optical anisotropies. Their optical properties can easily be modulated by the external electric field. Hence based on the electro-optic properties, the function of the as-constructed phase Fresnel liquid crystal lens has been studied in this paper. In this study, we discuss the diffraction efficiency of Fresnel LC lenses and collocated plano-convex to form dual focal length optical element.