Patent Publication Number: US-2022214541-A1

Title: Natural physio-optical user interface for intraocular microdisplay

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 62/846,443, filed May 10, 2019, which is hereby incorporated by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     This disclosure relates generally to ophthalmic devices, and in particular, relates to intraocular micro-displays. 
     BACKGROUND INFORMATION 
     Disease or injury to the cornea can lead to opacification or significant optical damage to the cornea, such that the individual is effectively rendered blind. The blindness may occur despite the patient having a fully functioning retina. For these patients with an intact retina but otherwise blind due to vascularization or damage to the cornea, implantation of an intraocular micro-display in the excised lens of the eye (e.g., capsular sack region) can restore image reproduction onto their fully functioning retina, thereby returning vision to the patient. 
     A proposed solution for an electronic intraocular micro-display involves the use of a transcutaneous tether that couples a transmitter positioned behind the ear to the intraocular micro-display. This tether provides power and data communication to the intraocular micro-display. The transcutaneous nature and complex surgery required for this proposed solution, likely makes this solution prone to physiological compatibility issues and inflammation. Since the tether protrudes outside of the eye and back into subcutaneous flesh on the side of the face, the tether also presents an infection risk. 
     To avoid the use of a transcutaneous tether, the intraocular micro-display and related circuitry must have a sufficiently compact form factor to fit entirely within the eye in the region of the capsular sack. As such, the electronics and user interface of such a small intraocular display present significant challenges. For example, when a user&#39;s natural crystalline lens is replaced with an intraocular micro-display, the user loses their natural ability to pan or tilt their forward vision (e.g., look around a scene) simply by moving their eyes. Furthermore, their ability to adjust their focal distance (e.g., accommodate) on different items at different offset distances is also lost. The loss of their natural mechanisms associated with healthy vision can substantially impact the user experience with an intraocular micro-display. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Non-limiting and non-exhaustive embodiments of the invention are described with reference to the following figures, wherein like reference numerals refer to like parts throughout the various views unless otherwise specified. Not all instances of an element are necessarily labeled so as not to clutter the drawings where appropriate. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles being described. 
         FIGS. 1A and 1B  are plan and side view illustrations of an intraocular micro-display (IOMD) system including an IOMD implant and an auxiliary head unit, in accordance with an embodiment of the disclosure. 
         FIG. 1C  is a cross-sectional illustration of the IOMD system with the IOMD implant implanted within an eye for projecting regenerated images onto a retina, in accordance with an embodiment of the disclosure. 
         FIG. 1D  illustrates use of the IOMD system along with a near-vision fiducial marker to control focal distance of an outward facing scene camera in the auxiliary head unit, in accordance with an embodiment of the disclosure. 
         FIG. 2  is a functional block diagram of an auxiliary head unit, in accordance with an embodiment of the disclosure. 
         FIG. 3  is a functional block diagram of an IOMD implant, in accordance with an embodiment of the disclosure. 
         FIG. 4  is a flow chart illustrating a process of operation of the IOMD system to provide pan/tilt and autofocus control over the IOMD system, in accordance with an embodiment of the disclosure. 
         FIG. 5  illustrates how a sub-portion of the higher resolution scene image is selected and transmitted from the auxiliary head unit to the IOMD implant for projection onto a retina, in accordance with an embodiment of the disclosure. 
         FIG. 6  is a flow chart illustrating blink control over the IOMD system, in accordance with an embodiment of the disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of a system, apparatus, and method of operation for an intraocular micro-display (IOMD) system that provides a natural physio-optical user interface are described herein. In the following description numerous specific details are set forth to provide a thorough understanding of the embodiments. One skilled in the relevant art will recognize, however, that the techniques described herein can be practiced without one or more of the specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring certain aspects. 
     Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. 
     Embodiments of the IOMD system disclosed herein are suitable for patients with intact retinas, yet are blind due to vascularization, occlusion, opacity, or otherwise damage of the cornea. The disclosed IOMD system seeks to restore sight to these patients by implanting an electronic micro-display (referred to as an intraocular micro-display or IOMD) into the eye, such as in the capsular sack region of the eye previously occupied by an excised lens. The IOMD is included within an IOMD implant to project regenerated images onto the patient&#39;s fully functioning retina. 
     Natural healthy vision comes with a real-time natural physio-optical user interface that provides the individual with a holistic user experience. For example, when the individual pans or tilts their eyes in a certain direction, the scene image delivered to their retina automatically changes as their gaze directions scans across the scene in front of them. Thus, immediate real-time feedback is provided to the user that synchronizes with, and otherwise confirms, their muscle action to pivot their eyes. Additionally, when a user directs their gaze upon a specific item, their eyes automatically accommodate (adjust their focal distance) to bring the item in the center of their foveal vision into focus. Finally, when an individual with healthy vision blinks or otherwise closes their eyelids, their vision of the external world is interrupted. All of these real-time physio-optical feedback mechanisms provide an individual with healthy vision a helpful physio-optical interface and holistic user experience that can be lost when their crystalline lens is replaced with an IOMD. 
     Accordingly, embodiments described herein attempt to simulate one or more of the natural physio-optical interfaces described above to provide the user with a natural, holistic physio-optical user experience. In one embodiment, a gaze tracking module (e.g., eye-ward facing camera) is provided to monitor movements of the user&#39;s eye to generate gaze direction data that is indicative of the user&#39;s gazing direction and use this data to select a sub-portion of a scene image and present this sub-portion to the user&#39;s retina. In other words, a forward-facing scene camera module may acquire a high resolution scene image, from which a sub-portion is selected and delivered to the retina via the IOMD implant. Selection of the sub-portion from an otherwise larger scene image simulates the natural physio-optical interface of scanning a scene by panning or tilting just one&#39;s eyes. In addition, the eye-ward facing camera can look for saccades and “jitter” the image accordingly to prevent saturation of the stimulation of retinal cells. 
     In one embodiment, the physio-optical interface of accommodation is simulated with the use of a near-vision fiducial. The near-vision fiducial may be a visual marker that can be attached to items that are typically the focus of visual attention when brought sufficiently close to the center of our field of view (FOV). For example, when hands are brought into our FOV, they are often at the correct focal distance for what we are doing. In other words, an individual is using their hands to do something, such as holding a book while reading, tying their shoes, cooking, or otherwise. Accordingly, by wearing, or otherwise adhering a near-vision fiducial, on or near the wrist, hand, finger, or thumb, the near-vision fiducial provides a visual marker which may be identified and autofocused upon with high fidelity. 
     In one embodiment, the gaze tracking module (or other eye-ward facing camera) may be used to monitor the eye for eyelid closure (blinks or longer closures). The identification of these closures may be used to then temporarily cease projecting the regenerated image onto the retina. This physio-optical interface feature simulates blinking or otherwise closing the eyes. It should be appreciated that one, some, or all of the above physio-optical interface features may be implemented individually or collectively in a single embodiment. 
       FIGS. 1A, 1B, and 1C  illustrate an IOMD system  100  that includes an IOMD implant  105  and an auxiliary head unit  110 , in accordance with an embodiment of the disclosure.  FIGS. 1A and 1B  are plan and side view illustrations, respectively, while  FIG. 1C  is a cross-sectional illustration of IOMD system  100 . The illustrated embodiment of auxiliary head unit  110  includes a frame  115 , a scene camera module  120 , a gaze tracking module  121 , an autofocus module  122 , an antenna mount  125 , a charging antenna  130 , a data antenna  135 , embedded electronic circuitry  140 , and a user interface  145 . The illustrated embodiment of antenna mount  125  includes a flexible eye-safe enclosure  150  mounted to frame  115  via an articulating arm  155 . The illustrated embodiment of IOMD implant  105  includes an enclosure  160  in which electronics are disposed along with focusing optics  165 . 
     During operation auxiliary head unit  110  inductively powers IOMD implant  105  via power signal  131  output from charging antenna  130 . Auxiliary head unit  110  further captures forward facing images with scene camera module  120  and wirelessly transmits those images to IOMD implant  105  via data signals  136 . In one embodiment, this image capture and transmit is executed in real-time. IOMD implant  105  harvests energy from power signal  131 , uses that energy to power receiver and controller circuitry for decoding data signals  136  and display circuitry for projecting a regenerated image onto retina  170  of eye  175 . In one embodiment, the regenerated image is only a sub-portion of the scene image captured by scene camera module  120 . Again, in one embodiment, the reception, decoding, and display of the image data are executed in real-time and provide the user with virtual, real-time, forward facing vision. 
     Auxiliary head unit  110  includes frame  115  for mounting auxiliary head unit  110  to the user&#39;s head. Although  FIGS. 1A-C  illustrate frame  115  in the shape of eyeglasses, it should be appreciated that frame  115  may assume a variety of different shapes and configurations for mounting to the user&#39;s head including an eyepatch, goggles, visor, headgear, or otherwise. Scene camera module  120  is disposed in or on frame  120  and oriented to acquire scene images in the direction of the user&#39;s forward vision. Gaze tracking module  121  is disposed in or on frame  115  in an eye-ward facing orientation to monitor the user&#39;s eye  175  and generate gaze direction data. In one embodiment, gaze tracking module  121  is an eye-ward facing camera that generates eye images that may be analyzed to determine the user&#39;s gazing direction. In one embodiment, autofocus module  122  is a forward facing infrared (IR) camera that performs conventional autofocus functions. 
     Antenna mount  125  includes an articulating arm  155  to get at least power antenna  130  close to the user&#39;s eye  175  for effective wireless charging of IOMD implant  105 . As such, antenna mount  125  includes a flexible eye-safe enclosure  150  in which charging antenna  130  is disposed. In the illustrated embodiment, data antenna  135  is also disposed within flexible eye-safe enclosure  150  for close proximity to IOMD implant  105 . In other embodiments, data antenna  135  may be disposed elsewhere within frame  115 . In yet another embodiment, power antenna  130  and data antenna  135  may be the same physical antenna operated at different frequencies. Eye-safe enclosure  150  may be fabricated of a variety of soft, flexible, dielectric materials, such as molded silicone, etc. 
     Although  FIGS. 1A-C  illustrate auxiliary head unit  115  as a single contiguous frame, in other embodiments, auxiliary head unit  115  may be segmented into two or more body-wearable modular components that may be interconnected and mounted or worn in various locations about the body or clothing. Furthermore, although  FIGS. 1A-C  illustrate a monocular IOMD system, the illustrated components may be replicated to implement a binocular IOMD system. Furthermore, IOMD implant  105  may be operated with different external hardware having different functionality than described herein in connection with auxiliary head unit  110 . In fact, IOMD implant  105  may be operated without a head mounted auxiliary head unit, but rather receive wireless communications from a variety of sources to display a variety of different information. 
     As illustrated, IOMD implant  105  is entirely disposed within eye  175  and does not include electronic cables or tethers extending out of eye  175  to auxiliary head unit  110 . Similarly, auxiliary head unit  110  is an independent, discrete unit that is worn on the user&#39;s head. Auxiliary head unit  110  includes embedded electronics for powering and orchestrating the operation of IOMD system  100  including itself and IOMD implant  105 . 
       FIG. 1D  illustrates use of IOMD system  100  along with a near-vision fiducial marker to control the focal distance of scene camera module  120  in auxiliary head unit  110 , in accordance with an embodiment of the disclosure. When a user&#39;s hands are brought sufficiently into a central region of the user&#39;s FOV, it is often the case that the user will want to focus on a task that is using their hands (e.g., reading a book, cooking, tying a shoelace, etc.). Accordingly, in some embodiments, auxiliary head unit  100  is programmed to search for a near-vision fiducial in the FOV of scene camera module  120 . The near-vision fiducial may be implemented as an identifiable visual marker. When the identifiable visual marker is found in the FOV of scene camera module  120 , the focal distance of scene camera module  120  is automatically adjusted to a near-vision setting that brings the near-vision fiducial marker into focus. 
     The near-vision fiducial marker may assume a variety of different sizes, shapes, or form factors that are mounted in a variety of different places. For example, the near-vision fiducial marker may be worn on or near a wrist (e.g., bracelet  180 ), a hand (e.g., sticker or tattoo  185 ), a finger, a thumb (e.g., ring  190 ), or otherwise. The identifiable visual marker may be implemented as a visual code (e.g., QR code), an active emitter (e.g., IR emitter), or otherwise. Auxiliary head unit  110  may be programmed to continuously, periodically, or on-demand search for the near-vision fiducial marker. The act of searching for near-vision fiducial marker may include cycling through a plurality of different focal distance settings for scene camera module  120  and searching each scene image acquired at a respective setting for the identifiable visual marker. If the visual marker is identified in one or more of the images, the focal distance setting associated with the scene image having the near-vision fiducial in focus is selected or otherwise locked onto. 
       FIG. 2  is a functional block diagram of an auxiliary head unit  200 , in accordance with an embodiment of the disclosure. Auxiliary head unit  200  is one possible implementation of auxiliary head unit  110 . The illustrated embodiment of auxiliary head unit  200  includes a frame  201 , a power source  205 , a wireless power transmitter  210 , a scene camera module  215 , a gaze tracking module  216 , an autofocus module  217 , an auxiliary controller  220 , a data transceiver  225 , a clock  230 , a user interface  235 , a power antenna  240 , and a data antenna  245 . 
     Power source  205  is provided within frame  201  to power the internal electronics of auxiliary head unit  200  and IOMD implant  105  via inductive power transfer. In one embodiment, power source  205  is a rechargeable battery (e.g., lithium ion battery). IOMD implant  105  is inductively charged via wireless power transmitter  210  and power antenna  240 . In one embodiment, wireless power transmitter  210  emits power signal  131  as a continuous wave signal having a sufficiently low frequency f 1  (e.g., 13.5 MHz, 27 MHz, etc.) for efficient eye-safe power coupling. The frequency of wireless power transmitter  210  may be based upon clock  230 . In one embodiment, clock  230  is a high fidelity, low power resonator, such as a quartz crystal oscillator. 
     Power source  205  also powers scene camera module  215 , gaze tracking module  216 , autofocus module  217 , auxiliary controller  220 , and data transceiver  225 . Scene camera module  215  may include a charged coupled device (CCD) sensor, a complementary metal-oxide-semiconductor (CMOS) sensor, or otherwise that acquires the forward-facing scene images, which may then be relayed to IOMD implant  105 . In one embodiment, data transceiver  225  transmits the image data representing a sub-portion of the scene image acquired as data signals  136 . Data signals  136  are encoded on a carrier signal having a frequency  2  (e.g., 2.4 GHz). Data transceiver  225  may use any number of encoding techniques including one or more of frequency modulation, phase modulation, amplitude modulation, and/or time multiplexing. Frequency f 2  can be higher than frequency f 1 , since it can be transmitted at lower power for safety and provides a higher bandwidth for transmission of still or video images. In some implementations, the relative frequencies of f 1  and f 2  can be flipped. In one embodiment, frequency f 2  is generated based upon clock  230  as well. For example, frequency f 2  may be a multiplied or upscaled version of frequency f 1 , or frequency f 1  may be a divided or downscaled version of frequency f 2 . In either case, clock signals based upon f 1  and f 2  may be phase aligned to support synchronous data communications where f 2  is regenerated at IOMD implant  105  based upon f 1 . 
     Auxiliary controller  220  orchestrates the operation of the other functional components. For example, auxiliary controller  220  may receive and decode an acknowledgment (ACK) signal  250  from IOMD implant  105 , and in response, adjust the image data sent to IOMD implant  105  to throttle power consumption of IOMD implant  105 . ACK signal  250  may be received as a backscatter modulation of power signal  131  on power antenna  240 , or received as an actively transmitted signal over data antenna  245 . In either case, ACK signal  250  may operate as an acknowledgement that a given image frame has been received and displayed by the IOMD implant  105 . Additionally, ACK signal  131  may also include an indication of reception strength of power signal  131  by IOMD implant  105  and/or an indication of operational temperature of IOMD implant  105 . Thus, IOMD implant  105  may use a low bandwidth return channel to transmit acknowledgments along with power readings and temperature readings. The acknowledgments, power readings, and temperature readings may then be used by auxiliary controller  220  to throttle power consumption of IOMD implant  105  by adjusting the frame rate and/or color characteristics of the image data transmitted to IOMD implant  105 . By regulating the power consumption of IOMD implant  105 , auxiliary controller  220  is also regulating the power consumption of auxiliary head unit  200 , which is powering IOMD implant  105 . Accordingly, the image data may be adjusted due to power scarcity in one or both of IOMD implant  105  or auxiliary head unit  200 . 
     Auxiliary controller  220  may be implemented with hardware logic (e.g., application specific integrated circuit (ASIC), field programmable gate array (FPGA), etc.), implemented with software/firmware instructions stored in memory and executed by a microprocessor, or a combination of both. User interface  235  may include a variety of physical interfaces to enable the user to interact with IOMD system  100 . For example, user interface  235  may include a touchpad to receive gesture commands (e.g., swipe forward, swipe back, tap, double tap, etc.), one or more buttons, dials, switches, knobs, a microphone for voice commands, or otherwise. For example, user interface  235  may be enable the user to request on-demand searching for a near-vision fiducial in the FOV of scene camera module  215 . In one embodiment, auxiliary controller  220  may generate visual feedback overlays on the acquired images that are transmitted to IOMD implant  105 . These visual feedback overlays may include visual acknowledgments when the user interacts with user interface  235 , display power readings of power source  205 , display operational mode selections, display temperature readings, display a power coupling reading to aid the user in alignment of flexible eye-safe enclosure  150 , display acknowledgement of identifying a near-vision fiducial, or otherwise. Of course, IOMD system  100  may include audible feedback to aid alignment of flexible eye-safe enclosure  150  to eye  175 . 
     Gaze tracking module  216  may be implemented using a variety of different technologies for monitoring the user&#39;s eye. In one embodiment, gaze tracking module  216  is an eye-ward facing camera that captures eye images for iris or pupil tracking. The position of the iris or pupil in the eye images relative to a reference position may be used to calculate a gazing direction and identify when the user&#39;s gaze pans or tilts. In yet another embodiment, a tattoo may be placed on the user&#39;s cornea or iris and the position of the tattoo in the eye images used to identify the gazing direction. In yet another embodiment, gaze tracking module  216  may be an electromagnetic sensor (e.g., Hall effect sensor) that monitors an electromagnetic field emitted from IOMD implant  105  or another field emitter implanted in another portion of the eye (e.g., sclera). 
     Autofocus module  217  provides autofocus functionality to scene camera module  215 . In one embodiment, autofocus module  217  includes an IR emitter and sensor. Other known active, passive, or hybrid variants for providing autofocus functionality, either independent of, or integrated with, scene camera module  215  may be implemented. 
       FIG. 3  is a functional block diagram of an IOMD implant  300 , in accordance with an embodiment of the disclosure. IOMD implant  300  represents one possible implementation of IOMD implant  105 . The illustrated embodiment of IOMD implant  300  includes an enclosure  301 , a power antenna  305 , power harvesting circuitry  310 , an energy storage unit  315 , clock recovery circuitry  320 , a phase lock loop (PLL)  325 , an IOMD controller  330 , one or more sensors  335 , a transmit module  340 , a data antenna  345 , receiver circuitry  350 , a display controller  355 , a micro-display  360 , and optics  165 . The illustrated embodiment of power harvesting circuitry  310  includes a power rectifier  365  and a power converter  370 . The illustrated embodiment of receiver circuitry  350  includes a low noise amplifier (LNA)  375  and a demodulator  380 . 
     In the illustrated embodiment, the electronic components of IOMD implant  300  are housed within a biocompatible enclosure  301  that is sized and shaped for implantation into eye  175 . In one embodiment, enclosure  301  is sized for implantation into the region of the capsular sack of eye  175 . In one embodiment, enclosure  301  is a hermetically sealed enclosure fabricated of metal, polymers, or otherwise. 
     During operation, power signal  131  output from auxiliary head unit  110  is incident upon power antenna  305 . In various embodiments, power antenna  305  is disposed in or on enclosure  301 . In yet other embodiments, power antenna  305  may be externally attached or tethered to enclosure  301 , and implanted into another region of eye  175 , such as under the sclera. In one embodiment, power antenna  305  is a loop antenna suitable for harvesting inductive power operating at frequency f 1 . Power harvesting circuitry  310  is coupled to power antenna  305  to harvest the wireless power incident thereon. Power harvesting circuitry  310  includes power rectifier  365  and power converter  370 . In one embodiment, power rectifier  365  is implemented with one or more diodes for rectification while power converter  370  is implemented as a direct current (DC) to DC buck converter. Other power harvesting circuitry components may be used. Power harvesting circuitry  310  is used to charge energy storage unit  315 . In one embodiment, energy storage unit  315  is implemented with a capacitor, such as a supercapacitor. In yet other embodiments, a rechargeable battery may be implemented, though such implementations may have a shorter life span, and thus requiring periodic surgical replacement. Alternatively, energy storage unit  315  may be implanted into another region of eye  175  (e.g., under the sclera) and tethered to enclosure  301 . Placing a battery within the sclera may provide for less invasive replacement procedures. However, the components may all be implanted into eye  175 , and thus less susceptible to infection compared to a transcutaneous tether extending external to the eye. 
     Clock recovery circuitry  320  is also coupled to power antenna  305  to extract and recover a synchronous clock signal from power signal  131  from auxiliary head unit  200 . Accordingly, clock recovery circuitry  320  operates to recover the lower frequency f 1  from the carrier wave of power signal  131 . Frequency f 1  (or a partial/whole multiple thereof) is then provided to the other circuit components of IOMD implant  300  for synchronous timing. In particular, PLL  325  may be used to lock onto the phase of the synchronous clock output from clock recovery  320  and an upconverted frequency f 2  provided to receiver circuitry  350  to synchronously demodulate data signal  136  received from auxiliary head unit  200  over data antenna  345 . Receiver circuitry  350  includes LNA  375  to amplify data signal  136  and demodulator  380  to down convert and decode the higher frequency f 2  data signal  136 . Demodulator  380  may be implemented using a variety of decoding circuits, such as, an energy detect circuit, an IQ receiver, or otherwise. Data signals  136  may be modulated using one or more of frequency modulation, phase modulation, amplitude modulation, quadrature modulation, etc. 
     The decoded data signals  136  are then provided to display controller  355  as the image data to be displayed by micro-display  360 . Display controller  355  may be a discrete controller from IOMD controller  330  (e.g., integrated into micro-display  360 ) or may be logic functions/instructions executed on IOMD controller  330  for the purpose of controlling operation of micro-display  360 . In one embodiment, micro-display  360  is implemented as a multi-color light emitting diode (LED) display array. In other embodiments, micro-display  360  is a backlit liquid crystal display (LCD), a monochrome LED display array, an organic LED (OLED) display, or otherwise. In one embodiment, micro-display  360  has 5 mm diameter display while enclosure  301  has an overall 10 mm×10 mm size. Micro-display  360  outputs the image based upon the received image data, which is projected through focusing optics  165  onto retina  170 . 
     IOMD implant  300  also includes IOMD controller  330 , which serves to orchestrate the operation of the other functional components of IOMD implant  300 . As with auxiliary controller  220 , IOMD controller  330  may be implemented in hardware logic, implemented in software/firmware logic stored to a machine readable medium and executed by a microcontroller, or implemented in a combination of both. 
     In the illustrated embodiment, IOMD controller  330  is coupled to receive sensor readings from one or more sensors  335 . Sensor(s)  335  may include a temperature sensor to monitor the operational temperature of IOMD implant  300 . In this regard, the temperature sensor is a proxy reading for power consumption or power dissipation within IOMD implant  300 . The temperature sensor also serves as a safety measure to ensure the eye tissue surrounding IOMD implant  300  is not damaged due to elevated operational temperatures. 
     In one embodiment, sensors  335  also include a voltage sensor coupled to energy storage unit  315  to measure and monitor the voltage across the electrodes of energy storage unit  315 , and thus measure the stored energy. The measured voltage across energy storage unit  315  may also serve as a proxy for, or an indication of, the reception strength of power signal  131 . Alternatively, sensors  335  may be coupled to power harvesting circuitry  310  and/or power antenna  305  to directly measure received voltage. 
     In one embodiment, sensors  335  include an eyelid sensor for determining the open or closed state of the user&#39;s eyelid and even monitoring for eyelid blinks. The eyelid sensor may be implemented using an outward facing photosensor (e.g., photodiode) that monitors for changes in incident light intensity. In one embodiment, the photosensor may monitor for interruptions of an IR beam emitted from auxiliary head unit  110  and through the pupil onto IOMD implant  105 . Alternatively, the eyelid sensor may be implemented by monitoring the signal strength of power signal  131  and/or data signal  136  received from auxiliary head unit  110 . The intervening position of the eyelid may modulate these signals in an identifiable manner that may be correlated to eyelid position. In yet another embodiment, the eyelid sensor may be implemented using an impedance sensor that emits an electromagnetic field that is influenced by the open or closed state of the eyelid. Whatever the implementation, the eyelid sensor may be used to generate an indication of when the eyelid is closed, which indication may then be used to temporarily disable micro-display  360 , or otherwise cease projecting regenerated image  361  to simulate the temporary loss of light or vision when closing or blinking one&#39;s eyes. 
     Alternatively (or additionally), sensing eyelid closure may be executed at auxiliary head unit  200  using gaze tracking module  216  or another eye-ward facing camera and determined by auxiliary controller  220 . In this embodiment, data signals  136  may be encoded with the eye closure indication, or data signals  136  may simply cease transmitting, or temporarily transmit a black image instead of the scene image or sub-portion thereof. 
     IOMD controller  330  further includes logic for generating the ACK signal, which is transmitted back to the auxiliary head unit  200  via transmit module  340  as a feedback data path. Auxiliary head unit  200  uses the ACK signal to manage overall system power consumption by adjusting frame rates, color fading, and transmit power. The ACK signal may operate as an acknowledgment of each received image frame, an indication that the data frame was correctly received and displayed, an indication of the operating temperature of IOMD implant  300 , and an indication of reception strength (or a proxy thereof, such as voltage level on energy storage unit  315 ). 
       FIG. 3  illustrates two options for implementing the feedback data path. Option ( 1 ) illustrates transmit module  340  coupled to power antenna  305  to provide the feedback data path over the lower frequency f 1  wireless power charging path. With option ( 1 ), transmit module  340  operates as an RFID tag to modulate the impedance of power antenna  305  and generate ACK signal  250  as a backscatter modulation of power signal  131 . Option ( 2 ) illustrates transmit module  340  coupled to data antenna  345  to provide the feedback data path over the high frequency f 2  wireless data signal path. With option ( 2 ), transmit module  340  is an active transmitter for generating ACK signal  250 . Of course, options ( 1 ) and ( 2 ) need not be mutually exclusive, but rather, in some embodiments, both options may be implemented and used selectively based upon available power budget and bandwidth needs for the feedback data path. 
     In one embodiment, power antenna  305  is shaped as a loop antenna to harvest radio frequency or microwave frequency wireless power. However, it should be appreciated that power antenna  305  may assume a variety of sizes and shapes to harvest power from various frequencies of electromagnetic (EM) radiation. Similarly, data antenna  345  may assume a variety of different sizes and shapes to effectively receive (and optionally transmit) data signals  136  and/or ACK signal  250  at the higher frequency f 2  (e.g., 2.4 GHz or otherwise). For example, data antenna  345  may be a dipole antenna, a patch antenna, or otherwise. In one embodiment, data antenna  345  is an optical antenna (e.g., photo receiver or photo transceiver) and data signals  136  are optical wavelength EM radiation. In yet another embodiment, power antenna  305  and data antenna  345  may be implemented as a single physical antenna that is shared between power harvesting circuitry  310 , receiver circuitry  350 , and transmit module  340 . In this shared embodiment, power antenna  305  and data antenna  345  are graphical representations of the different functional uses for a single physical antenna. 
     Finally,  FIG. 3  illustrates optics  165 , which provide the optical power for focusing the regenerated image  361  output from micro-display  360  onto retina  170 . Optics  165  may include a high-power base lens (e.g., 100 diopters or more) along with one or more adjustable components. These adjustable components may include an adjustable power lens that provides an adjustable focal distance (z-axis adjustment) to regenerated image  361 . In various embodiments, optics  165  further include one or more adjustable prisms that provide beam steering for lateral adjustments (x and/or y axis adjustment) of the position of the projected image  362 . Lateral adjustments ensure that projected image  362  is properly positioned/centered on retina  170  including the user&#39;s fovea. Regenerated image  361  and/or projected image  362  may be referred to herein as the image, the regenerated image, or the projected image, but all refer to the image output from micro-display  360  whether or not it has been lensed or beam steered by optics  165 . 
       FIG. 4  is a flow chart illustrating a process  400  of operation of IOMD system  100  to provide pan/tilt and autofocus control over IOMD system  100 , in accordance with an embodiment of the disclosure. Process  400  is described with reference to the system illustrated in  FIGS. 1A-D . However, process  400  is also applicable to the embodiments illustrated in  FIGS. 3 and 4 , and in certain instances, components illustrated in those figures are referenced. The order in which some or all of the process blocks appear in process  400  should not be deemed limiting. Rather, one of ordinary skill in the art having the benefit of the present disclosure will understand that some of the process blocks may be executed in a variety of orders not illustrated, or even in parallel. 
     In a process block  405 , a scene image of a user&#39;s forward facing FOV is captured with scene camera module  120 . In one embodiment, the scene image is a high-resolution image captured in real-time (or near real-time) as it is wirelessly conveyed to IOMD implant  105  and projected to the user&#39;s retina  170 . 
     Upon capturing a scene image, auxiliary controller  220  analyzes/searches the scene image for a near-vision fiducial (process block  410 ). Auxiliary controller  220  may continuously analyze all captured scene images, periodically analyze only select scene images (e.g., every Nth image frame), or analyze captured scene images on demand. On-demand searching may commence in response to the user requesting IOMD system  100  enter a near-vision mode of operation. Such a command may be received via user interface  145  (or  235 ). As mentioned above, auxiliary head unit  110  may cycle scene camera module  215  through a plurality of different focal distance settings while it searches for an instance of the near-vision fiducial. 
     If a near-vision fiducial is not identified (decision block  415 ), then process  400  continues to a process block  425  to perform gaze tracking. However, if a near-vision fiducial is identified (decision block  415 ), then process  400  continues to a process block  420 . In process block  420 , the focal distance setting of scene camera module  120  is adjusted to bring the identified near-vision fiducial into focus. In other words, the focal distance setting that brings the near-vision fiducial into focus is identified and automatically held, and/or continuously updated, to maintain acceptable or optimal focus. The near-vision fiducial provides a focusing target for scene camera module  120 . 
     In a process block  425 , gaze tracking is executed with the aid of gaze tracking module  121 . Gaze tracking module  121  is oriented to monitor the user&#39;s eye  175  and generate real-time gaze direction data. In one embodiment, the gaze direction data includes eye images acquired by an eye-ward facing camera implementation of gaze tracking module  121 . The eye images may be analyzed by auxiliary controller  220  to determine a gazing direction. The gaze direction may be determined based upon a position of the pupil or iris in the eye images relative to a reference position. Alternatively, a tattoo may be formed on the user&#39;s cornea and operate as an eye fiducial. The position of the eye fiducial may then be tracked relative to a reference position. The reference position may be factory set or user calibrated by performing a calibration or setup routine. Of course, other gaze tracking schemes may be implemented. For example, a Hall effect sensor may be used to track the position of a magnetic eye fiducial implanted into the sclera or other portions of the eye. In yet another embodiment, IOMD implant  105  itself may operate as the eye fiducial. In this embodiment, the IOMD implant  105  may be a passive fiducial or active fiducial that emits a trackable signal. 
     In one embodiment, the gazing direction is determined with reference to a single eye. In another embodiment, auxiliary head unit  110  may include a binocular gaze tracking module that monitors both eyes (e.g., two separate eye-ward facing camera modules). With a binocular gaze tracking module, gaze tracking not only determines the direction of a user&#39;s gaze but also identifies whether the user is using their near-vision based upon whether both eyes turn inward, as opposed to both tracking the same direction for distance vision. In one embodiment, an identification of the user attempting to use their near-vision may be an on-demand trigger to search for a near-vision fiducial in a scene image (process block  410 ). 
     Once a gazing direction has been determined, auxiliary controller  220  can use this information to identify a sub-portion of the high-resolution scene image for relaying to IOMD implant  105  (process block  430 ).  FIG. 5  illustrates an example of identifying a sub-portion  505  of a scene image  500 . In this example, auxiliary controller  110  has determined based upon the gaze direction data (e.g., one or more eye images) that the user is looking down and to the left. Accordingly, auxiliary controller  505  selects sub-portion  505  correlated to this gazing direction for wireless relay to IOMD implant  105  via data antenna  135 . The size of sub-portion  505  may be selected based upon the bandwidth/power constraints of the wireless data channel between auxiliary head unit  110  and IOMD implant  105  and/or the image resolution capabilities of micro-display  360  within IOMD implant  105 . By identifying and selecting sub-portion  505  of scene image  500  based upon the user&#39;s eye movement and gazing direction, the user&#39;s natural physio-optical response to pan and tilt eye movements is simulated, thereby providing a natural user experience. When the user&#39;s pans or tilts their eyes (decision block  435 ), sub-portion  505  is moved about the larger scene image  500  simulating natural eye movement. In other words, auxiliary head unit  110  adjusts and continuously readjusts the location of sub-portion  505  within scene image  500  in real-time. As changes in the user&#39;s gazing direction are determined, the position of sub-portion  505  within scene image  500  is revised (process block  440 ), thus updating the image data (i.e., revised sub-portion) that is relayed to IOMD implant  105  for projection onto retina  170  (process block  445 ). 
       FIG. 6  is a flow chart illustrating a process  600  for blink control over IOMD system  100 , in accordance with an embodiment of the disclosure. Process  600  is described with reference to the system illustrated in  FIGS. 1A-D . However, process  600  is also applicable to the embodiments illustrated in  FIGS. 3 and 4 , and in certain instances, components illustrated in those figures are referenced. The order in which some or all of the process blocks appear in process  600  should not be deemed limiting. Rather, one of ordinary skill in the art having the benefit of the present disclosure will understand that some of the process blocks may be executed in a variety of orders not illustrated, or even in parallel. 
     In a process block  605 , IOMD system  100  monitors the closure state of the user&#39;s eyelid. In one embodiment, the closure state of an eyelid may be monitored by auxiliary head unit  110  using gaze tracking module  121 . For example, an eye-ward facing camera may visually monitor an eyelid for eyelid closures or blinks. In one embodiment, the closure state of the eyelid may be monitored by IOMD implant  105  from the inside out. Eyelid monitoring by IOMD implant  105  may be implemented using an outward looking photosensor (e.g., photodiode) that tracks changes in light intensity or monitors interruptions of an IR beam broadcast from auxiliary head unit  110 . Alternatively, IOMD implant  105  may sense fluctuations in the signal strength of data signals  136  and/or the coupling strength of power signals  131  from auxiliary head unit  110  (or  200 ). Fluctuations in these signals may correlate to whether the eyelid is open or closed. In yet another embodiment, IOMD implant  105  may include an impedance sensor capable of monitoring fluctuations in an oscillation circuit that inductively couples to the eyelid of the user. Of course, one or more of the above techniques, or other eyelid sensing techniques, may be implemented. 
     In a decision block  610 , if the eyelid is determined to be open, then auxiliary head unit  110  wirelessly relays data signals  136 , including sub-portion  505  of scene image  500 , to IOMD implant  105  (process block  615 ). In turn, IOMD implant  105  projects a regenerated image of sub-portion  505  onto the user&#39;s retina  170  (process block  620 ). On the other hand, if the user&#39;s eyelid is determined to be closed (decision block  610 ), then the regenerated image is temporarily interrupted while the eyelid is deemed closed. The regenerated image may be temporarily interrupted at the behest of auxiliary head unit  110  or IOMD implant  105 . In process block  625 , if auxiliary head unit  110  determines that the eyelid is closed, then auxiliary head unit  110  can either not transmit sub-portion  505 , transmit an indication that the eyelid is currently deemed closed, and/or transmit a black image in place of sub-portion  505  of scene image  500 . Correspondingly, if IOMD implant  105  determines that the eyelid is closed (e.g., using one of the on-board sensors  335 ), then IOMD implant  105  (or  300 ) may independently disable micro-display  360  while the closed state is deemed to persist (process block  630 ). Of course, in some embodiments, both auxiliary head unit and IOMD implant mechanisms for determining eyelid closures and temporarily ceasing projection of the regenerated image may be implemented together. 
     The processes explained above are described in terms of computer software and hardware. The techniques described may constitute machine-executable instructions embodied within a tangible or non-transitory machine (e.g., computer) readable storage medium, that when executed by a machine will cause the machine to perform the operations described. Additionally, the processes may be embodied within hardware, such as an application specific integrated circuit (“ASIC”) or otherwise. 
     A tangible machine-readable storage medium includes any mechanism that provides (i.e., stores) information in a non-transitory form accessible by a machine (e.g., a computer, network device, personal digital assistant, manufacturing tool, any device with a set of one or more processors, etc.). For example, a machine-readable storage medium includes recordable/non-recordable media (e.g., read only memory (ROM), random access memory (RAM), magnetic disk storage media, optical storage media, flash memory devices, etc.). 
     The above description of illustrated embodiments of the invention, including what is described in the Abstract, is not intended to be exhaustive or to limit the invention to the precise forms disclosed. While specific embodiments of, and examples for, the invention are described herein for illustrative purposes, various modifications are possible within the scope of the invention, as those skilled in the relevant art will recognize. 
     These modifications can be made to the invention in light of the above detailed description. The terms used in the following claims should not be construed to limit the invention to the specific embodiments disclosed in the specification. Rather, the scope of the invention is to be determined entirely by the following claims, which are to be construed in accordance with established doctrines of claim interpretation.