Purpose: To evaluate the incidence of central hole-induced ring-shaped dysphotopsia after posterior chamber phakic implantable collamer lens (ICL) with central hole (hole ICL) implantation and to investigate the causes of central hole-induced dysphotopsia. MethodsThe clinical study enrolled 29 eyes of 15 consecutive myopic patients implanted with hole ICL. The incidence of ring-shaped dysphotopsia after hole ICL implantation was evaluated. In the experimental simulation study, non-sequential ray tracing was used to construct myopic human eye models with hole ICL and ICL without a central hole (conventional ICL). Simulated retinal images measured in log-scale irradiance were compared between the two ICLs for an extended Lambertian light-emitting disc object 20cm in diameter placed 2m from the corneal vertex. To investigate the causes of hole-induced dysphotopsia, a series of retinal images were simulated using point sources at infinity with well-defined field angles (0 to -20 degrees) and multiple ICL models. ResultsOf 29 eyes, 15 experienced ring-shaped dysphotopsia after hole ICL implantation. The simulation study using an extended Lambertian source showed that hole ICL-evoked ring-shaped dysphotopsia was formed at a retinal field angle of 40 degrees. Component-level analysis using a well-defined off-axis point source from infinity revealed that ring-shaped dysphotopsia was generated by stray light refraction from the inner wall of the hole and the posterior ICL surface. ConclusionHole ICL-evoked ring-shaped dysphotopsia was related to light refraction at the central hole structure. Surgeons are advised to explain to patients the possibility of ring-shaped dysphotopsia after hole ICL implantation.

A logical control extension surrounding cashless means of exchange is a permanent personal verification mark. An implanted micro chip such as ones that have been successfully implanted into humans could identify and store information. Connected with global positioning satellites and a computer system, a cashless monetary system could be formed in the future. The system would provide complete and continual real time records for individuals, businesses and regulators. It would be possible for all trading to occur in this way in the future. A modified Technology Acceptance Model was developed based on Davis' (1989) model and Fishbein and Ajzen's (1975) theory to test the acceptance level of the new monetary system by professional accountants in Australia. The model includes perceived ease of use, perceived usefulness, perceived risk, and a subjective norm component. 523 accountants were surveyed in December 2003 with a response rate of 27%. 13% either strongly agree d or agreed that they would accept the implantable chip. The analysis showed that Perception of Risk, Subjective Norm and Perception of Usefulness were all significant in explaining the dependent variable at the 95% confidence level. The Perception of Ease of Use was not proved to be significant. In consideration of response bias, it was found that with respect to the perception of usefulness at the 0.01 level, two elements were not significant, those being

Thesis (M.S.)--University of Florida, 2003. / Title from title page of source document. Includes vita. Includes bibliographical references.

Diabetes mellitus affects 25.8 million Americans (8.3%) and over 300 million people worldwide. Clinical trials indicate that proper management of blood glucose levels is critical in preventing or delaying complications associated with diabetes. Thus, there is a common need to monitor and manage blood glucose properly for people with diabetes. However, the patients’ compliance for recommended monitoring frequency is low due to the pain and inconvenience of current standard finger-pricking tests. To promote patient adherence to the recommended self-monitoring frequency, non-invasive/ minimally invasive glucose testing approaches are needed. Luminescent microparticle sensor is an attractive solution. For these sensors to be deployed in vivo, a matched optical system is needed to interrogate dermally-implanted sensors. This research project investigated the light propagation in skin and the interaction with implants using Monte Carlo modeling. The results of the modeling were used to design an optical system with high interrogation and collection efficiency (40~300 times improvement). The optical system was then constructed and evaluated experimentally. A stable skin phantom mimicking the optical properties of human skin was developed as a permanent evaluation medium to minimize the use of animals. The optical properties of the skin phantom matched the maximum published values of human skin in scattering and absorption over the spectral range of 540~700nm in order to avoid overestimation of the capability of the system. The significant photon loss observed at the connection between the designed system and a commercial spectrometer was overcome using two optimized designs: a two-detector system and a customized low-resolution spectrometer system. Both optimization approaches effectively address the photon loss problem and each showed good SNR (>100) while maintaining a sufficient system resolution for use with fluorescent materials. Both systems are suitable for luminescence measurement, because broad bands of the luminescent spectrum are of interest. In the future, either system can be easily modified into a more compact system (e.g. handheld), and it can be directly coupled to an analog-to-digital converter and integrated circuits offering potential for a single compact and portable device for field use with luminescent diagnostic systems as well as implanted sensors.

The goal of this thesis was to evaluate the cost-effectiveness of implantable Doppler technology (IDT) used to monitor free tissue transfer (FTT) procedures in the treatment of cancer of the upper aerodigestive tract (UADT). First, a systematic review of the literature on the effectiveness of traditional and IDT monitoring techniques was performed. Second, a utility survey using a time trade-off technique was created and administered. The results from this survey were used to establish utility values for health states common in patients undergoing FTT procedures. Third, a cost study using the microcosting data available through the Ottawa Hospital was performed. Finally, a decision analytic model was created and an economic evaluation from the payer perspective was completed. A probabilistic sensitivity analysis (PSA) and a value of information analysis (VOI) were performed. The thesis found that the currently available evidence supports IDT as a cost-effective intervention. Further research should be directed towards determining the effectiveness of both traditional and IDT monitoring.

A prototype of a one-time implantable spinal cord stimulation (SCS) system is presented in this thesis. A pair of inductive coils is used to achieve wireless power transmission and bidirectional communication. A rechargeable Li-ion battery is used to extend the lifetime of the implanted SCS device. Therefore, the number of the battery replacement surgery could be reduced such that one-time implantation is feasible. Besides, the proposed system on chip (SOC) controller and many discretes are integrated on a printed circuit board (PCB). The size of the proposed SCS device is competitive compared to the currently commercial products. The proposed SOC controller adopts a dual supply voltage scheme to reduce power consumption. The proposed SCS system employs an amplitude-shift keying (ASK) technique to carry out the data modulation and power transmission. One of the critical factors to affect efficiency of ASK-based wireless power transmission is the oscillating frequency accuracy. A ROM-less direct digital frequency synthesizer (DDFS) is presented in this thesis to fulfill such a high accuracy demand. Since the supply voltages of the discretes are diversified on a system PCB, many level converters are needed to translate different signal output voltage levels. To resolve above problem, the chip, then, must be redesigned to meet the various voltage level requirement, or added level convertors among the SOC and the discretes. Obviously, it will cause a lot of cost. A wide-range I/O buffer, thus, is proposed to resolve the compatibility problem caused by different supply voltages of discretes.

This thesis includes two topics. The first topic is a low power design of 8-bit ANT-based pipelining CLA. The second one is a small digital to analog converter (DAC) used in an implantable neural stimulator. An ANT-based low-power 8-bit pipelining carry-lookahead adder (CLA) using two-phase all-N-transistor (ANT) blocks which are arranged in a PLA design style with power-aware pipelining is presented. The pull-up charging and pull-down discharging of the transistor arrays of the PLA are accelerated by two feedback MOS transistors between the evaluation NMOS blocks and the outputs. Both the added power-aware clock control circuit and clock generation circuit detecting data transition take advantage of shutting down the processing stages given identical inputs in two consecutive operations by keeping high clock level. The design keeps the advantage of high speed while having the effect of low power dissipation. The implantable neural stimulator assists patients to reconstruct transmission paths of neural signals by current stimulation. The proposed small DAC not only decreases the chip area and power dissipation by reducing transistor count, but also improves the linearity with higher current output performance. All of measured performances of the proposed DAC make the chip worthy of being implemented in a field application.

The first topic of this thesis proposes a neural stimulation, recording and impedance measuring system for implantable applications. It includes a stimulation DAC, a instrumentation amplifier, an ADC, and a digital controller which decides the operation of each block according to the required functions. The function provided by the system include micro-stimulation, neural signal recording, or impedance measurement. The second topic is to describe a dual-OPA coil driver for SOC heat dissipation. It includes two class AB complementary output drivers which can drive an inductance load, such as micro motors and fans. It also discusses the feasibility of a bipolar transistor in CMOS process.

When the nerve cell of human is damaged, the central neural system (CNS) can not work properly. Instead of sending commands by CNS, we can use a micro-stimulation method to send commands to hands, legs, or organs. The first part of this thesis presents a fully implantable system for neural micro-stimulation and neural signal monitoring, and introduces the communication protocol and baseband circuitry of the system. Due to the rapidly development of small and portable electrical equipments, low power becomes more and more important because of the limitation of the battery capacity. Meanwhile, the embedded memory in these devices consumes considerable power. In this thesis, we present a low-power sequential memory decoder to resolve the power-dissipation of embedded memories. We¡¦ll verify that the sequential decoder can reduce the power consumption compared to traditional decoders by implementing our idea with a 2-Kbit SRAM memory.

Today, there is an ever-growing demand for compact, and energy autonomous, implantable biomedical sensors. These devices, which continuously collect in vivo physiological data, are imperative in the next generation patient monitoring systems. One of the fundamental challenges in their implementation, besides the obvious size constraints and the tissue-to-electronics biocompatibility impediments, is the efficient means to wirelessly deliver power to them. This work addresses this challenge by demonstrating an energy-autonomous and fully-integrated implantable sensor chip which takes advantage of the existing on-chip photodiodes of a standard CMOS process as photovoltaic (PV) energy-harvesting cells. This 2.5 mm × 2.5 mm chip is capable of harvesting [mu]W’s of power from the ambient light passing through the tissue and performing real-time sensing. This system is also MRI compatible as it includes no magnetic material and requires no RF coil or antennae. In this dissertation, the optical properties of tissue and the capabilities of the CMOS integrated PV cells are studied first. Next, the implementation of an implantable sensor using such PV devices is discussed. The sensor characterizing and the in vitro measurement results using this system, demonstrate the feasibility of monolithically integrated CMOS PV-driven implantable sensors. In addition, they offer an alternative method to create low-cost and mass-deployable energy autonomous ICs in biomedical applications and beyond. / text