Patent Publication Number: US-2023146429-A1

Title: Biometric authentication in ophthalmic devices

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims the benefit of and priority to U.S. Provisional Patent Application No. 63/277,460, filed Nov. 9, 2021, the entirety of which is incorporated by reference herein. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates generally to devices and methods for performing biometric authentication of human eyes using ophthalmic devices, such as devices configured to measure intraocular pressure (TOP). 
     BACKGROUND 
     Ophthalmic systems such as those designed for diagnosing or treating ocular diseases are typically shared by multiple patients. In some instances, a patient may forget to load, or incorrectly load, his/her profile in the device, resulting in the testing and/or treatment results not processed or implemented correctly. If the patient&#39;s data is being collected for machine learning or analytics, errors in enrollment would also corrupt the dataset for training and analysis. In some instances, ill-intentioned individuals may impersonate other patients, compromising security of any medical records and/or personal information safeguarded by the systems. For at least these reasons, a biometrics-based authentication process associated with using these ophthalmic systems (or other systems shared by multiple patients or users) is desired. 
     Existing authentication technologies have relied on biometrics such as iris, fingerprints, facial features, and/or other suitable human features. Of these common biometric recognition regimes, iris recognition has been widely used due to its exceptional power to avoid false matches across a large sample population. The iris of a human eye has a fine and complex texture that is determined randomly during embryonic gestation. Such complexity combined with its random nature significantly lowers the chance that two individuals may share the same iris texture. Even genetically identical individuals, as well as the left and the right eyes of the same individual, have completely different iris textures that can be observed by iris imaging. While existing authentication processes by iris recognition are generally adequate, they have not been entirely satisfactory in all aspects. In some instances, absent a robust data discrimination algorithm, the system may fail to correlate an existing patient&#39;s iris code (which is derived from the patient&#39;s iris image) with his/her profile in the database, leading to the patient&#39;s test and/or treatment results being falsely rejected (i.e., a false-negative authentication result). In some instances, falsely accepted (i.e., false-positive) authentication results may also be possible when ill-intentioned individuals impersonate biometric data of existing patients, thereby compromising the security of the patient&#39;s personal information. Therefore, for at least these reasons, improvements in the performance of authentication processes by iris recognition are desired. 
     SUMMARY 
     According to one embodiment of the present disclosure, a system includes: an ophthalmic diagnostic device configured to obtain diagnostic measurements of a patient&#39;s eye, the patient&#39;s eye including an iris and a cornea; an imaging device configured to capture an image of the iris; an optical sensor integrated with the imaging module and configured to detect a position of the iris with respect to the optical sensor; and a computing device in communication with the ophthalmic diagnostic device, the imaging device, and the optical sensor, wherein the computing device is configured to: determine, based on the image of the iris and the position of the iris, whether the iris matches a known patient&#39;s iris; and perform a diagnostic measurement of the patient&#39;s eye based on the determining. 
     In some aspects, the ophthalmic diagnostic device is configured to measure intraocular pressure of the patient&#39;s eye. In some aspects, the system further includes an optical sensor configured to measure deflection of the patient&#39;s eye in response to pressure applied by the ophthalmic diagnostic device. In some aspects, the computing device is configured to determine deflection of the patient&#39;s eye in response to pressure applied by the ophthalmic diagnostic device using data obtained from the imaging device. In some aspects, the imaging device includes: a light source configured to illuminate the patient&#39;s eye with an incident light; and a camera configured to capture an image of the patient&#39;s eye that includes a reflection of the incident light. In some aspects, the imaging device is configured to detect a Purkinje image produced by the incident light reflected from the cornea of the patient&#39;s eye. In some aspects, the computing device is configured to calculate a curvature of the cornea based on the Purkinje image. 
     According to another embodiment of the present disclosure, a system includes: an iris imaging module including: a light source configured to illuminate iris of an eye with an incident light; and a camera configured to capture an image of the iris, the image including a reflection of the incident light on the eye; a proximity sensor in communication with the iris imaging module and configured to measure a size of the iris; and an iris authentication module including a memory and a processor in communication with the memory, wherein the iris authentication module is configured to: determine, based on the reflection of the incident light on the eye in the image, a curvature of the eye, and authenticate the iris based on the curvature of the eye. 
     In some aspects, the light source includes at least one light-emitting diode (LED). In some aspects, the system further includes an ophthalmic device integrated with at least one of the iris imaging module and the proximity sensor. In some aspects, the ophthalmic device is a non-contact tonometer. In some aspects, the ophthalmic device is an ocular drug delivery system. In some aspects, the light source is configured to emit the incident light in a defined pattern, and the image detected by the camera is a Purkinje image including a distorted reflection of the defined pattern off the cornea. 
     According to another embodiment of the present disclosure, a method includes: providing an iris recognition system including at least an imaging module and a proximity sensor; capturing an image of a patient&#39;s iris using the imaging module; determining a distance of the iris from the proximity sensor; determining a size of the based on the determined distance and the captured image; determining, based on the captured image, a curvature of the patient&#39;s cornea; and comparing the captured image and at least one of the size of the iris or the curvature of the cornea with corresponding data stored in a database to confirm an identity of the patient, wherein the confirmation is based on a matching threshold. 
     In some aspects, the method further includes: providing an ophthalmic system configured to obtain a diagnostic measurement of the patient&#39;s eye, wherein the ophthalmic system is integrated with the iris recognition system; and obtaining, based on confirming the identity of the patient, the diagnostic measurement of the patient&#39;s eye using the ophthalmic system. In some aspects, the method further includes adjusting the matching threshold based on confirming the identity of the patient. In some aspects, the ophthalmic system includes a non-contact tonometer. In some aspects, the determining the curvature of the cornea includes analyzing a Purkinje image reflected from the cornea. In some aspects, the determining the size of the iris includes: calculating a relative dimension of the iris based on the captured image; determining a position of the iris with respect to the proximity sensor; and determining an absolute dimension of the iris based on the calculated relative dimension and the position of the iris. In some aspects, the matching threshold is a Hamming distance threshold, and the comparing the captured image and the at least one of the size of the iris or the curvature of the cornea includes comparing a difference between the captured image and a stored authentication image to the Hamming distance threshold. 
     This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to limit the scope of the claimed subject matter. A more extensive presentation of features, details, utilities, and advantages of the jet pump for noncontact tonometry, as defined in the claims, is provided in the following written description of various embodiments of the disclosure and illustrated in the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present disclosure is best understood from the following detailed description when read with the accompanying figures. It is emphasized that, in accordance with the standard practice in the industry, various features are not drawn to scale and are used for illustration purposes only. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion. 
         FIG.  1    is a diagrammatic view of an ophthalmic system, according to at least one embodiment of the present disclosure. 
         FIG.  2    is a functional block diagram of the ophthalmic system, in portion or in entirety, as depicted in  FIG.  1   , according to at least one embodiment of the present disclosure. 
         FIG.  3    is a schematic view of the ophthalmic system, in portion or in entirety, as depicted in  FIG.  2   , according to at least one embodiment of the present disclosure. 
         FIGS.  4 A,  4 B,  4 C, and  4 D  each illustrate a schematic view of the ophthalmic system, in portion or in entirety, as depicted in  FIG.  3   , according to at least one embodiment of the present disclosure. 
         FIG.  5    is a schematic view of a portion of a human eye interacting with an incident light, according to at least one embodiment of the present disclosure. 
         FIG.  6    is a schematic view of a portion of a human eye interacting with an incident light, according to at least one embodiment of the present disclosure. 
         FIGS.  7 A and  7 B  illustrate a flowchart of an example method for using the ophthalmic system as depicted in one or more of the  FIGS.  1 - 4 D , according to at least one embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     For the purposes of promoting an understanding of the principles of the present disclosure, reference will now be made to the embodiments illustrated in the drawings, and specific language will be used to describe the same. It is nevertheless understood that no limitation to the scope of the disclosure is intended. Any alterations and further modifications to the described devices, systems, and methods, and any further application of the principles of the present disclosure are fully contemplated and included within the present disclosure as would normally occur to one skilled in the art to which the disclosure relates. For example, while the present disclosure is described in terms of devices and systems configured to measure TOP or to deliver ocular drugs to a human eye, it is understood that the disclosure is not intended to be limited to these applications. The devices and systems are equally well suited to any application having an operation interface shared by multiple patients whose data are stored and processed in a common database. In particular, it is fully contemplated that the features, components, and/or steps described with respect to one embodiment may be combined with the features, components, and/or steps described with respect to other embodiments of the present disclosure. For the sake of brevity, however, the numerous iterations of these combinations will not be described separately. 
     Ophthalmic systems designed to diagnose or treat ocular diseases are typically utilized by multiple patients in settings such as a hospital or a doctor&#39;s office. A database of information is accessed each time before a patient, existing or new, is subject to testing and/or treatment by such systems, and the corresponding testing and/or treatment results are processed and stored in the database for further medical assessment. Accordingly, for purposes of safeguarding patients&#39; personal information (including, but not limited to, medical records) and implementing appropriate testing and/or treatments, a robust and secure authentication system is desired. 
     The present disclosure provides systems, and methods of using the same, for performing a biometric authentication process that utilizes a series of iris recognition and matching processes. In the present embodiments, aspects of the patient&#39;s ocular metrics including, for example, the size of the iris and the curvature of the cornea, obtained from imaging the patient&#39;s eye are employed to confirm the patient&#39;s identity during the authentication process. When such a combination of metrics is collected and analyzed, an algorithm of the authentication process may be adjusted to accommodate possible variations in imaging conditions for purposes of reducing false rejection rate (FRR). Furthermore, information deduced from the combined metrics may also safeguard against illicit access of the database to reduce false acceptance rate (FAR). 
       FIG.  1    illustrates a schematic of using an ophthalmic system (hereafter referred to simply as system)  100  to treat a patient  200 &#39;s eye  202  according to various embodiments of the present disclosure. In the depicted embodiments, the system  100  is a non-contact tonometer designed to measure the IOP of each patient&#39;s eye(s). In other embodiments, the system  100  may include an automated ocular drug delivery system designed to dispense a drug according to each patient&#39;s personalized dosage and frequency. In some embodiments, the system  100  is configured to store and process multiple patients&#39; information. In some embodiments, the system  100  may be configured to store and process IOP data and associate the data with the corresponding eye of one or more patients. For example, the system  100  may include a memory configured to store a plurality of IOP measurements at various points in time. The system  100  may be further configured to connect with a network, such as a local area network (LAN), and wide area network (WAN), or any other suitable network. In some aspects, the system  100  is configured to communicate ophthalmic diagnostic data or measurements to a remote server, which can be accessed by the patient&#39;s physician. In some embodiments, the system  100  provides data safety features for a device that requires biometric authentication to function properly, such as a personal mobile device. It is noted that while the following description and the accompanying figures are directed to the system  100  being configured to perform non-contact tonometry, the present embodiments are equally suitable for other applications. Furthermore, although  FIG.  1    depicts the system  100  in a stationary, table-top configuration, embodiments of the present disclosure are equally applicable for portable, hand-held devices. In some embodiments, the patient  200 &#39;s eyes are tested one at a time, such that the IOP data specific to each eye is recorded separately in a database stored in a computing device, such as a computer. 
       FIG.  2    is a diagrammatic view of the system  100 . The system  100  may include a tonometer module  120 , an imaging module  140 , and a proximity sensor  160 , all of which are in communication with a computer  180  that is further connected to an output device  190 . In some embodiments, the tonometer module  120  includes devices configured to deliver a known amount of pressure to a patient&#39;s cornea and devices configured to measure deflection of the cornea in response to the applied pressure. In further embodiments, the imaging module  140  includes a plurality of light-emitting and light-sensing devices for illuminating and capturing images of the patient&#39;s eyes. Details of the various modules of the system  100  are discussed below. 
     In some embodiments, modules of the system  100  can be controlled independently by the computer  180 . In this regard, these modules may each include one or more user input devices not separately depicted in  FIG.  2   . In some embodiments, as discussed in detail below, these modules complement each other to complete the biometric authentication process. In some embodiments, these modules share one or more components in common to form an integrated system. For embodiments in which the system  100  performs functions other than measuring a patient&#39;s IOP, the tonometer module  120  may be replaced by other functional modules accordingly. For example, if the system  100  is configured to deliver an ocular drug, then the tonometer module  120  may be replaced by a dispensing module instead. Though not depicted, the system  100  may further include other components, such as power supply and user input device(s). 
     Generally, the tonometer module  120  may be configured to release a puff of air (e.g., air puff  130  depicted in  FIG.  3   ) at the cornea (e.g., cornea  206  as depicted in  FIG.  3   ) of the eye  202  (or  204 ) as in the case of non-contact tonometry, or to directly apply pressure to the cornea using a small probe (e.g., a piston), as in the case of contact (or applanation) tonometry, and subsequently measure the deflection of the cornea of the eye  202  in response to the puff of air. The air pressure required to temporarily flatten a region of the cornea is equal to the IOP of the eye  202 . In some instances, the IOP of the patient  200 &#39;s two eyes may differ. Accordingly, it may be beneficial to authenticate IOP data obtained for each eye, so that the data can be stored and/or analyzed separately. The imaging module  140  is configured to capture an image of the patient  200 &#39;s iris (e.g., iris  212  as depicted in  FIG.  3   ) and transmits the image to the computer  180 , which subsequently processes and converts the image into a bit pattern encoding information of the iris for comparison against an existing iris code in a database stored in the computer  180 . Operating in conjunction with the imaging module  140 , the proximity sensor  160  can determine an axial position of the eye relative to the system  100 , which then may be used to determine, based on the captured iris image, the size of the iris to scale. 
     The computer  180  is operable to control one or more of the modules of the system  100 , store the information collected by the modules, and process such information for further assessment. For example, the computer  180  is configured to receive image data obtained from the imaging module  140  and/or the proximity sensor  160  and extrapolate and/or analyze metrics such as the a size of the iris, the deflection of the cornea, one or more Purkinje images, or other suitable metrics. The computer  180  may include one or more clock, memory, logic, or processing devices. Logic or processing devices may be application-specific or for general purpose. The computer  180  may employ any combination of hardware, software, and firmware to perform its functions. The computer  180  may further employ a fixed instruction set provided in read-only memory (ROM) or could have an updatable instruction set provided in programmable read-only memory (PROM), electrically erasable programmable read-only memory, flash memory, or any equivalent thereof. The computer  180  may be configured to communicate with a remote server, or a local device such as a laptop, tablet, or handheld device. In the present embodiments, the database containing registered iris codes that belong to multiple patients is accessed through the computer  180  to provide biometric authentication of a patient&#39;s identity. The authentication results, as well as the IOP measurements, may be displayed and/or reported to an authorized user (e.g., the patient  200  and/or a healthcare provider) via the output device  190 . 
     Referring to  FIG.  3   , a portion of the system  100  configured as the tonometer module  120  includes at least a chamber  122  that surrounds a piston pump  124  operatively connected to a motor  126 , which causes the piston pump  124  to force air through the chamber  122 , forming an air puff  130  through a nozzle  128  to strike the eye  202 . In some embodiments, the driving force for forming the air puff  130  is proportional to a current applied to the motor  126  and may be initiated and controlled by the computer  180 . The chamber  122  may be a portion of a stationary system or a hand-held system configured to measure the TOP of the patient  200 . In some embodiments, the tonometer module  120  optionally includes an optical system for measuring the deflection of the cornea  206 . 
     In the present embodiments, referring to  FIG.  3    and  FIGS.  4 A- 4 D  collectively, a portion of the system  100  configured as the imaging module  140  includes at least an image capturing device (ICD)  142 , such as a camera, positioned to face the eye  202 . The ICD  142  is configured to capture an image of the iris  212  illuminated by a light source  144  disposed at angle relative to the eye  202 . The ICD  142  may be any suitable device capable of capturing an image of the iris  212  at a resolution acceptable for generating an iris code for biometric authentication. For example, the ICD  142  may include a charge-coupled device (CCD), a complementary metal-oxide semiconductor (CMOS) imaging device, or any other suitable imaging device. The captured iris image may be subsequently transmitted to the computer  180  for further analysis as discussed in detail below. In some embodiments, the ICD  142  is configured to measure the deflection of the cornea  206  when measuring the IOP. In some embodiments, a spectral filter  143  is disposed in front of the ICD  142  to remove light having wavelengths that may cause specular reflections of the eye  202 . 
     The light source  144  emits an incident light  146  toward the eye  202 . The light source  144  is configured to illuminate the eye  202  in any suitable wavelength range, such as in the near infrared (IR) range (i.e., the incident light  146  having a wavelength in the range of about 700 nm to about 1100 nm) or in the visible light range (i.e., the incident light  146  having a wavelength in the range of about 400 nm to about 700 nm). In the present embodiments, the light source  144  illuminates the eye  202  for purposes of capturing an image of the iris  212  and/or producing one or more Purkinje images as discussed in detail below. In some embodiments, the light source  144  is a light-emitting diode (LED). In some embodiments, though not depicted, the system  100  includes more than one light source  144  disposed at different angles relative to the eye  202 . For example, a first light source  144  may be configured to illuminate the iris  212 , while a second light source  144  may be configured to illuminate the eye  202  to obtain one or more Purkinje images. In some embodiments, a filter (not depicted) may be placed in front of the light source  144  to reduce the optical power of the incident light  146  for the safety of the eye  202 . 
     After impinging upon the eye  202 , the incident light  146  is reflected through a lens  152  and detected by an optical sensor  154 . When used as a component of the tonometer module  120  according to some embodiments, the optical sensor  154  may facilitate the measurement of the deflection of the cornea  206 . In the present embodiments, the ICD  142 , the light source  144 , the optical sensor  154 , the lenses  150  and  152 , the spectral filter  143  and/or other components of the system  100  are collectively configured to enhance iris features not distinguishable in visible light to naked eyes and to remove specular reflections that would otherwise obscure such iris features in the captured iris image. 
     In the present embodiments, the image module  140  further includes an image projector  155  that operates in conjunction with the light source  144  to project an image onto various optical planes of the eye  202 , resulting in one or more Purkinje images to be captured by the ICD  142  and subsequently transmitted to the computer  180  for analysis. The image projector  155  may produce a pattern including, for example, a line-grid pattern, a dot grid, crosshairs, concentric rectangles, concentric circles, or other suitable patterns. In an example embodiment, the image projector  155  is a dot projector. In some embodiments, referring to  FIG.  3   , the image projector  155  is disposed between the light source  144  and the eye  202 . In some embodiments, the image projector  155  is integrated with the light source  144 . 
       FIG.  5    schematically depicts four Purkinje images  156 A- 156 D produced by the eye  202  when illuminated by the incident light  146 . Purkinje images of an object are typically formed at various optical planes in an eye and may be used to analyze various features of the eye, such as the curvature of the cornea, based on their respective characteristics. Generally, the first Purkinje image  156 A is an image reflected from the anterior surface of the cornea  206 ; the second Purkinje image  156 B is an image reflected from the posterior surface of the cornea  206 ; the third Purkinje image  156 C is an image reflected from the anterior surface of lens  214 ; and the fourth Purkinje image  156 D is an image reflected from the posterior surface of the lens  214 . In some embodiments, the first Purkinje image  156 A may be captured by the ICD  142  and processed by the computer  180  to extrapolate the curvature (defined by a radius, for example) of the cornea  206 . 
     Referring back to  FIG.  3    and  FIGS.  4 A- 4 D , the system  100  further includes the proximity sensor  160 . The proximity sensor  160  may be coupled to, or integrated with, the tonometer module  120  and the imaging module  140 . In the present embodiments, the proximity sensor  160  may be used in tandem with the imaging module  140  to obtain an actual (i.e., true-to-scale) size of the iris  212  in terms of radius, diameter, and/or area based on the captured iris image, which may describe the size of the iris  212  in terms of pixels. In a non-telecentric imaging system, such as that provided by the system  100 , the size of the iris  212  varies with the distance at which the iris image is captured. In some examples, the diameter of a patient&#39;s iris may be about 11 mm to about 13 mm. In this regard, the actual size of the iris  212  may be deduced by measuring a separation distance along an axis between the iris  212  and the proximity sensor  160 . In some embodiments, the proximity sensor  160  is positioned on or near the same imaging plane as the ICD  142  to ensure accurate determination of such separation distance. In some embodiments, the proximity sensor  160  is placed along the optical axis of the ICD  142  with a known separation distance. The proximity sensor  160  may be any suitable optical sensor capable of detecting an axial position of the iris  212 . In the present embodiments, the proximity sensor  160  may be configured with a resolution on the order of a millimeter (mm), with sub-millimeter resolution, or with any suitable resolution. 
     In some embodiments, the proximity sensor  160  includes a source (not depicted separately) configured to emit radiation (e.g., electromagnetic radiation) and a detector (not depicted separately) configured to sense changes in the emitted radiation as a return signal, where such changes are processed by the computer  180  to obtain the axial separation distance between the iris  212  and the proximity sensor  160 . Subsequently, correlating such separation distance with the measured size of the iris  212 , which is calculated based on the captured iris image, provides the actual size of the iris  212 . In the present embodiments, the size of the iris  212  is equivalent to an area between an outer perimeter of the iris  212  defined by sclera  208  and an inner perimeter of the iris  212  defined by pupil  210 . 
     It is noted that the present disclosure does not limit the physical arrangement of the various components of the system  100  to any specific configuration. For example, the nozzle  128 , the ICD  142 , and the proximity sensor  160  may be arranged on the same frontal surface of the chamber  122  that is opposite to the eye  202 , as depicted in  FIG.  4 A . Alternatively, as depicted in  FIGS.  4 B- 4 D , one or both of the ICD  142  and the proximity sensor  160  may be disposed on a top surface of the chamber  122 , though they remain along the same imaging plane. 
     Referring now to  FIGS.  7 A and  7 B  collectively, a flowchart of a method  10  of using the system  100  is illustrated according to various aspects of the present disclosure. Method  10  is merely an example and is not intended to limit the present disclosure beyond what is explicitly recited in the claims. Additional operations can be provided before, during, and after method  10 , and some operations described can be replaced, eliminated, or moved around for additional embodiments of the method. 
     Referring to  FIG.  7 A , method  10  at operation  12  provides the system  100  as discussed in detail above with respect to  FIGS.  1 - 4 D . The system  100  may be non-contact tonometry system equipped with the tonometer module  120 , the imaging module  140 , and the proximity sensor  160  in communication with the computer  180 , which may be further connected to the output device  190 . In some embodiments, instead of measuring the patient  200 &#39;s IOP, the system  100  may be configured to deliver an ocular drug to a patient and further equipped with the imaging module  140  and the proximity sensor  160 , all of which are in communication with the computer  180 . In some embodiments, the system  100  may be integrated into a device that provides personal data safety features, such as a personal mobile device. 
     Subsequently, method  10  at operation  14  captures an image of the patient  200 &#39;s first eye  202  using the imaging module  140 . In the present embodiments, the imaging module  140  is configured to illuminate the iris  212  of the first eye  202  with the incident light  146  provided by the light source  144 , such as an LED. In some embodiments, the incident light  146  has a wavelength in the IR range. In some embodiments, the spectral filter  143  is used to remove any ambient visible light, thereby enhancing relevant features of the captured iris image. In the present embodiments, the captured iris image is processed by the computer  180  to form a captured iris code (e.g., a bit pattern) that encompasses various features, such as color, texture, and size, of the iris  212 . In some embodiments, the computer  180  executes algorithms to remove any objects (e.g., eyelashes and eyelids) and/or specular reflections before converting the captured iris image into the captured iris code. 
     At operation  16 , method  10  determines the actual size of the iris  212  using the captured iris image and the proximity sensor  160 , which determines an axial position of the iris  212  relative to the proximity sensor  160 . The actual size of the iris  212  may be determined based on the principle that the measured size of the iris  212  (encoded in the captured iris image) is proportional to the separation distance between the iris  212  and the proximity sensor  160  in a non-telecentric imaging system. In some examples, the measured size of the iris  212  may be obtained in units of pixels, while the actual size of the iris  212  may be presented in units of mm, inches, and/or mm 2 , for example. 
     At operation  18 , method  10  determines the curvature of the cornea  206  of the first eye  202 . As discussed in detail above, the first Purkinje image  156 A produced by the first eye  202  may be used to determine the curvature of the cornea  206 , a method termed keratometry.  FIG.  6    schematically illustrates an example keratometry process, which includes placing an object  158  defined by a height X in front of the cornea  206 , the object  158  being illuminated by the light source  144  (not depicted) of the imaging module  140 . The first Purkinje image  156 A of the object  158  is formed behind the cornea  206  (a virtual image is shown here) and defined by a height Y at a distance S away from the object  158 . The radius R of the cornea  206  may then be calculated by using the following equation: 
     
       
         
           
             R 
             = 
             
               
                 
                   2 
                   ⁢ 
                   SY 
                 
                 X 
               
               . 
             
           
         
       
     
     Additionally or alternatively, a fixed pattern of LED illumination may be used to infer the curvature of the cornea  206 . For example, an array of LEDs could be fixed in a grid pattern and the corresponding Purkinje image(s) may be used to infer not only the curvature but also the topography of the cornea  206 . 
     In the present embodiments, an accurate measurement of the curvature of the cornea  206  is used in conjunction with the captured iris image and the actual size of the iris  212  to ascertain that the first eye  202  being authenticated is indeed from a real patient rather than a reproduced image of the patient&#39;s eye. Specifically, if a reproduced image of the patient&#39;s eye is presented before the system  100 , it is probable that some aspects of the captured iris code may be consistent with a registered iris code for the patient stored in the database; however, the actual curvature of the cornea  206  obtained using the first Purkinje image  156 A would not represent a meaning value, i.e., the radius R may be infinite. 
     The present embodiments do not limit the order in which operations  16  and  18  are implemented. For example, operation  16  may be implemented before operation  18 , or vice versa. Alternatively, operations  16  and  18  may be implemented simultaneously. 
     Thereafter, method  10  at operation  20  compares the measured iris and cornea metrics, including the iris code, the actual size of the iris  212 , and the curvature of the cornea  206 , with registered metrics stored in the database of the computer  180 . In some embodiments, the computer  180  compares the captured iris code against each registered iris code in the database on a bit-by-bit basis. A positive matching result occurs when at least a specific fraction of the total bits match, thereby satisfying a Hamming distance threshold predetermined for such a matching (i.e., authentication) process. In the present embodiments, the Hamming distance threshold (hereafter referred to as the threshold) is a concept commonly understood by persons ordinarily skilled in the art. By way of example, the threshold for the matching process discussed herein may be about 0.3. Typically, increasing the threshold increases the FAR (i.e., the false-positive results) of the matching process and decreases the FRR (i.e., the false-negative results), and decreasing the threshold decreases the FAR and increases the FRR. Advantageously, the present embodiments provide a system and a method of using the same for increasing the threshold to bring about a reduced FRR while also lowering the FAR, such that both the robustness and the safety features of the authentication process may be improved. 
     In the present embodiments, besides comparing the bit pattern of the captured iris code with those of the registered iris codes, method  10  at operation  20  may including comparing the actual size of the iris  212  obtained from the measurements of the proximity sensor  160  with actual sizes of irises stored in the database to further ascertain the identity of the patient  200 . Advantages of this additional process of comparison, which increases the threshold, are at least two-fold. Firstly, the increased threshold would improve immunity of the authentication process against unfavorable ambient lighting conditions, focus blur associated with the captured iris image, angle dependence of the captured iris image, and/or other conditions that would otherwise produce false-negative authentication results, leading to a more robust and user-friendly authentication process. Secondly, the increased threshold would require any person pretending to be the patient  200  or presenting a reproduced image of the patient  200 &#39;s first eye  202  to match the actual, true-to-scale size of the iris  212  with a high degree of accuracy, thereby improving the security of the authentication process. Alternatively or additionally, method  10  at operation  20  compares the curvature of the cornea  206  obtained from the first Purkinje image  156 A with values of corneal curvature stored in the database to raise the threshold and obtain similar advantages. 
     Subsequently, method  10  at operation  22  evaluates whether the measured metrics match the registered metrics according to the predetermined threshold. If a match has occurred, method  10  proceeds to operation  28  as depicted in  FIG.  7 B ; otherwise, method  10  proceeds to operation  24  to determine whether the measured metrics, such as the curvature of the cornea  206  determined by the first Purkinje image  156 A, suggest a real patient is present. If such a condition is met, i.e., the measured curvature of the cornea  206  is a value typical of a human cornea, then method  10  proceeds to operation  27  as depicted in  FIG.  7 B . If such a condition is not met, (i.e., the measured curvature of the cornea  206  is not a value typical of a human cornea, then method  10  is terminated at operation  26 . Scenarios leading to termination of operation may include, for example, if the measured curvature of the cornea  206  is infinite, which suggests that a flat substrate (e.g., an image of a human cornea printed on a piece of paper), rather than a curved object (e.g., an actual human cornea), is present. In some embodiments, the actual size of the iris  212  may also be used to determine whether a real patient is present, since the size of the iris on a printed image must closely match that of an actual iris to scale, which may be difficult to achieve. 
     Referring now to  FIG.  7 B , on condition that the measured curvature of the cornea  206  is a value typical of a human cornea, method  10  may proceed to operation  27  by creating a new patient profile in the database to store the measured metrics. This operation may be optional and may be omitted according to protocols set forth by an authorized user of the system  100 . 
     On condition that the measured metrics match with registered metrics in the database, e.g., a positive match has occurred, or after confirming a new patient is present, method  10  may proceed to operation  28  to adjust the threshold of the matching process implemented at operations  20  and  22 . In some embodiments, the threshold of the matching process may be increased such that incorporating the actual size of the iris  212  and/or the curvature of the cornea  206  into the conventional iris code matching process results in a lowered FRR and thus a more robust authentication outcome. Advantageously, if the size of the iris  212  and/or the curvature of the cornea  206  of a given patient is an outlier, then adjusting the threshold at operation  28  allows such patient to be authenticated with greater accuracy in the future. In some embodiments, the degree by which the threshold is increased is determined through simulation and experimentation for the system  100  under typical testing conditions that incorporate the measurements of the various iris and cornea metrics discussed herein. Unless desired by an authorized user of the system  100 , operation  28  may be implemented a single time after a successful match for a given patient is completed, such that the adjusted threshold is kept constant for subsequent authentication processes. In other embodiments, operation  28  may be implemented multiple times after a successful match. In some embodiments, operation  28  may be omitted, i.e., the threshold remains unchanged for the patient  200  (as well as other patients using the system  100 ), such that incorporating the actual size of the iris  212  and/or the curvature of the cornea  206  into the conventional iris code matching process leads to a reduced FAR, thereby improving the data security associated with the authentication process. In this regard, obtaining the additional metrics improves the overall efficacy of the authentication process and further allows the authentication process to be tailored to a greater number of users by incorporating customizable comparison parameters. 
     If the system  100  functions as an ophthalmic system, such as one configured to perform non-contact tonometry or to deliver an ocular drug, method  10  then proceeds to operation  30  and performs any relevant test and/or treatment on the first eye  202  of the patient  200 . Subsequently, method  10  at operation  32  processes any data associated with such test and/or treatment and stores them in the database for record-keeping and/or further assessment. 
     With respect to using the system  100  to measure a patient&#39;s TOP during non-contact tonometry, the present embodiments allow the patient&#39;s two eyes to be identified and tested separately, such that the TOP of each eye may be recorded correctly and categorized automatically. In addition, if the authorized user fails to first load the patient&#39;s profile, i.e., bypassing the authentication process discussed above with respect to operations  14 - 24 , the system  100  will alert the authorized user to do so first before proceeding to the TOP measurements. With respect to using the system  100  to deliver an ocular drug, the present embodiments ensure that the correct dosage of the correct ocular drug is delivered to each eye of a patient at a prescribed time and frequency, thereby improving the accuracy of the drug delivery process. 
     Thereafter, method  10  at operation  34  may proceed to repeating operations  14 - 32  on the second eye  204  of the patient  200  if such test and/or treatment is necessary. In some embodiments, operations  30 - 34  are optional and may be omitted if the system  100  does not perform the functions of an ophthalmic system. In some embodiments, after adjusting the threshold of the matching process at operation  28 , method  10  may proceed directly to operation  36  and perform additional operations relevant to the functions of the system  100 . For instances, if the system  100  is integrated with a device that requires biometric authentication to gain access, then after adjusting the threshold of the matching process at operation  28 , method  10  at operation  36  may allow the authorized user to unlock the device and perform additional operations. 
     Communication (including but not limited to software updates, firmware updates, or readings from the device) to and from the system  100  could be accomplished using any suitable wireless or wired communication technology, such as a cable interface such as a USB, micro USB, Lightning, or FireWire interface, Bluetooth, Wi-Fi, ZigBee, Li-Fi, or cellular data connections such as 2G/GSM, 3G/UMTS, 4G/LTE/WiMax, or 5G. For example, a Bluetooth Low Energy (BLE) radio can be used to establish connectivity with a cloud service, for transmission of data, and for receipt of software patches. 
     The logical operations making up the embodiments of the technology described herein may be referred to variously as operations, steps, objects, elements, components, or modules. It should be understood that these may be performed or arranged in any order, unless explicitly claimed otherwise or a specific order is inherently necessitated by the claim language. It should further be understood that the described technology may be employed as a standalone device or as a component of other devices. 
     All directional references, e.g., upper, lower, inner, outer, anterior, posterior, upward, downward, left, right, lateral, front, back, top, bottom, above, below, vertical, horizontal, clockwise, counterclockwise, proximal, and distal are only used for identification purposes to aid the reader&#39;s understanding of the claimed subject matter, and do not create limitations, particularly as to the position, orientation, or use of the system  100 . Connection references, e.g., attached, coupled, connected, and joined are to be construed broadly and may include intermediate members between a collection of elements and relative movement between elements unless otherwise indicated. As such, connection references do not necessarily imply that two elements are directly connected and in fixed relation to each other. The term “or” shall be interpreted to mean “and/or” rather than “exclusive or.” Unless otherwise noted in the claims, stated values shall be interpreted as illustrative only and shall not be taken to be limiting. 
     Furthermore, when a number or a range of numbers is described with “about,” “approximate,” and the like, the term is intended to encompass numbers that are within a reasonable range including the number described, such as within +/−10% of the number described or other values as understood by person skilled in the art. For example, the term “about 5 nm” encompasses the dimension range from 4.5 nm to 5.5 nm. Still further, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed. 
     The above specification, examples and data provide a complete description of the structure and use of exemplary embodiments of the jet pump for noncontact tonometry as defined in the claims. Although various embodiments of the claimed subject matter have been described above with a certain degree of particularity, or with reference to one or more individual embodiments, those skilled in the art could make numerous alterations to the disclosed embodiments without departing from the spirit or scope of the claimed subject matter. For example, the jet pump could be used to produce controlled puffs of other gases than ambient air, including but not limited to oxygen, nitrogen, helium, and argon, or of gases that contain colorants, odorants, medications, or other materials. Additionally, some or all of the components of the jet pump may be contained within a housing, either alone or with other components such as a battery and/or power supply. 
     Still other embodiments are contemplated. It is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative only of particular embodiments and not limiting. Changes in detail or structure may be made without departing from the basic elements of the subject matter as defined in the following claims. Persons skilled in the art will recognize that the devices, systems, and methods described above can be modified in various ways not explicitly described or suggested above. Accordingly, persons of ordinary skill in the art will appreciate that the embodiments encompassed by the present disclosure are not limited to the particular exemplary embodiments described above. In that regard, although illustrative embodiments have been shown and described, a wide range of modification, change, and substitution is contemplated in the foregoing disclosure. It is understood that such variations may be made to the foregoing without departing from the scope of the present disclosure. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the present disclosure.