Abstract:
A pupilometer having a pupil irregularity or non-uniformity detection capability. The pupilometer may comprise an imaging sensor for generating signals representative of a pupil of an eye, a data processor; and a program executable by the data processor for enabling the data processor to process signals received from the imaging sensor and to thereby identify one or more regions of non-uniformity within an image of a perimeter of the pupil. The pupilometer may incorporate several innovative calibration and thresholding routines and may provide the basis for an innovative medical diagnostics system, when coupled to a network containing a suitable medical database and data processing hardware.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to pupilometry systems and, more particularly, to pupilometry systems having a pupil irregularity detection capability. In one particularly innovative aspect, the present invention relates to hand-held pupilometry systems having a pupil irregularity detection capability, to methods and processing sequences used within such systems, and to methods of using such systems. 
     In another innovative aspect, the present invention relates to a medical diagnostics system incorporating a pupilometer and medical database for correlating actual or derived pupilary image analysis data with stored medical data to formulate medical diagnoses, and to methods of implementing and utilizing such a diagnostics system. 
     BACKGROUND OF THE INVENTION 
     Systems for monitoring pupil size and pupil responsiveness characteristics are well known in the art and are generally referred to as pupilometry systems or, simply, pupilometers. One early pupilometer is described in U.S. Pat. No. 3,533,683, which issued to Stark et al. on Oct. 13, 1970 and is entitled &#34;Dynamic Pupilometers Using Television Camera System.&#34; The Stark et al. system employed a television camera system, a digital computer system, an infrared light source, and a visual light stimulator for determining the instantaneous size of a pupil as an eye (or neurologic pupilary control system) of a patient was exposed to various stimuli. Like the early Stark et al. system, conventional pupilometers measure, for example, the diameter of a pupil before and after the pupil is exposed to a light stimulus pulse and also measure the rates at which the pupil may constrict and dilate in response to the initiation and termination of the light stimulus pulse. Pupilometers may comprise hand-held units or, alternatively, may comprise desk or table-mounted, stand-alone units. Pupilometers also generally include some mechanism for ensuring that an imager within the pupilometer is properly positioned in relation to a pupil to be imaged. For example, U.S. Pat. No. 5,646,709, issued to Elbert P. Carter, describes an electronic centering system for ensuring that a pupilometer is properly positioned in relation to a pupil to be imaged. Similarly, U.S. Pat. No. 5,187,506, issued to Elbert P. Carter, describes an eye orbit housing for ensuring proper positioning between a pupilometer and an eye of a subject prior to the initiation of a pupilary scanning procedure. 
     Those skilled in the art will appreciate, however, that for a pupilometer to have maximum utility maximum flexibility should be provided for positioning the imager. For example, in the case of a hand-held system few, if any, restrictions should be placed upon the orientation of the imager prior to enabling an imaging function. The reason for this is that medical personnel at, for example, an accident site may have difficulty in positioning an imager in a prescribed position for acquiring pupilary response data. Thus, it is believed that, for hand-held units in particular, a need exists within the pupilometer field for improved data acquisition and processing systems and methods, as such systems and methods may substantially reduce system dependence on imager orientation and may allow pupilometers to become more user friendly. 
     Similarly, those skilled in the art will appreciate that a need exists for pupilometers that are capable of evaluating more than a mere pupilary response to light stimulus pulses. For example, it is believed that a substantial need exists for a pupilometer that is capable not only of measuring changes in pupilary diameter in response one or more light stimulus pulses, but also of evaluating pupil shape and/or segmental responses to a visual stimulus. Stated somewhat differently, it is believed that a substantial need exists for a pupilometer having a pupilary shape irregularity or non-uniformity detection capability. 
     Finally, it is believed that a substantial need exists for pupilometer-based diagnostics systems, as such systems may provide medical practitioners with a cost effective, non-invasive means for gathering and assessing numerous physiologic parameters. 
     SUMMARY OF THE INVENTION 
     In one particularly innovative aspect, the present invention is directed toward a pupilometer having a pupil shape irregularity detection capability. For example, a pupilometer in accordance with the present invention may comprise an imaging sensor for generating signals representative of a pupil of an eye, a data processor coupled to the imaging sensor, and a program executable by the data processor for enabling the data processor to process signals received from the imaging sensor and to thereby identify one or more regions of non-uniformity or irregularity within an image of a perimeter of the imaged pupil. 
     In one presently preferred embodiment, the one or more regions of pupilary non-uniformity or irregularity are identified by identifying a center point of a pupil and determining a plurality of radii representing distances from the center point to the perimeter of the pupil along a respective plurality of angles in a R,θ coordinate system. 
     In another innovative aspect, the present invention is directed to a medical diagnostics system incorporating a pupilometer and medical database for correlating actual or derived pupilary image analysis data with stored medical data to formulate medical diagnoses, and to methods of implementing and utilizing such a diagnostics system. 
     In still other innovative aspects, the present invention is directed to improved thresholding and image data processing algorithms for use within a pupilometer. For example, a pupilometer in accordance with the present invention may utilize a plurality of row and column histogram data sets in an iterative fashion to identify a preferred threshold value for locating the pupil of an eye within an image data frame. 
     A pupilometer in accordance with the present invention also may process image frame data to determine a shape and/or diameter of the sclera/iris border of an eye and, thereafter, use the determined shape or diameter to evaluate an orientation of the eye of the patient and/or to correlate measured units with defined units of measurement. 
     Finally, when provided with an additional armature supporting, for example, a visible light emitting diode (LED), a pupilometer in accordance with the present invention may be used to measure afferent or consensual pupilary responses to visual stimulus pulses. In such embodiments, a visual stimulus is applied to an eye under examination, and the response of the monitored pupil is recorded and evaluated. Then, as the monitored pupil is allowed to dilate, a stimulus pulse is applied to the other eye of the patient, to see whether or not the monitored pupil again constricts. Following the second stimulus pulse, the monitored pupil is allowed again to dilate, and a final visual stimulus is applied to the eye under examination. During the final stimulus pulse, the constrictive response of the monitored pupil (or lack thereof) is again measured. By measuring the response of the monitored pupil to each stimulus pulse, it is possible to detect retinal impairment in each eye of the patient. 
     Other objects and features of the present invention will become apparent from consideration of the following description taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a cross-sectional view of a hand-held pupilometer in accordance with a preferred form of the present invention. 
     FIG. 2 is an illustration of a liquid crystal display and keypad that may be provided on a hand-held pupilometer in accordance with the present invention. 
     FIG. 3 is an enlarged cross-sectional view of an imaging section of a hand-held pupilometer in accordance with the present invention. 
     FIG. 4 is a three-dimensional plan view showing a preferred arrangement of a plurality of IR, blue and yellow LEDs that may be used for ocular illumination and stimulation within a pupilometer in accordance with the present invention. 
     FIG. 5 is a block diagram illustrating a group of programming objects that preferably comprise an operating program of a pupilometer in accordance with the present invention. 
     FIG. 6 is a timing diagram illustrating a typical stimulus/illumination sequence for the IR, blue and yellow LEDs that may be used within a pupilometer in accordance with the present invention. 
     FIGS. 7(a) and 7(b) are illustrations of histogram data sets that may be developed in accordance with a preferred thresholding algorithm utilized by a pupilometer in accordance with the present invention. 
     FIG. 8 is a flow chart illustrating a basic operating protocol for a pupilometer in accordance with the present invention. 
     FIG. 9 is an illustration of a pupilometer incorporating a consensual measurement attachment in accordance with the present invention. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     A. Hardware Components of a Pupilometer in Accordance with the Present Invention 
     Turning now to the drawings, FIG. 1 provides a cross-sectional view of a hand-held pupilometer 10 in accordance with the present invention. FIG. 2 provides an illustration of a liquid crystal display and key pad that may be provided on the hand-held pupilometer 10, and FIG. 3 is an enlarged cross-sectional view of an imaging section of the hand-held pupilometer 10. 
     As shown in FIGS. 1-3, the pupilometer 10 preferably includes a housing 12 wherein an imaging sensor 14, an objective lens 16, first and second beam splitters 18 and 20, a shield 22, four infrared (IR) LEDs 24, two yellow LEDs 26, a blue LED 28 (shown in FIG. 4), a reticle 30, a battery 32, an image signal processing board 34 and a liquid crystal display 36 are mounted. Stated somewhat differently, the pupilometer may comprise a viewing port (reticle 30 and shield 22), an imaging system (objective lens 16, imaging sensor 14 and related image processing electronics), an illumination system (IR LEDs 24, blue LED 28 and related control circuitry) and a stimulus system (yellow LEDs 26 and related control circuitry). 
     1. The Viewing Port 
     The viewing port (reticle 30 and shield 22) is provided to aid a user in properly positioning the pupilometer 10 for initial data acquisition. By looking through the reticle 30 and shield 22, the user of the pupilometer 10 is able to properly position the pupilometer 10 in front of an eye 38 of a patient, such that an image of the pupil of the patient&#39;s eye may be projected onto the imaging sensor 14. The reticle 30 preferably has circular targets (not shown) silk screened or etched on one surface. The targets are positioned along the user&#39;s line of sight so as to appear concentric with the iris and pupil of an eye 38 under observation. 
     Those skilled in the art will appreciate that the reticle 30 and shield 22 also serve as environmental barriers and function to minimize exposure of the imaging system to caustic cleaning agents, biological material and airborne dust, all of which can have a negative impact upon the performance of the imaging system. 
     2. The Imaging System 
     The imaging sensor 14 preferably comprises a N×M bit CMOS imaging sensor of a type that is commercially available. One such imaging sensor is the 384×288 bit, Model OV5017, CMOS imaging sensor manufactured and distributed by Omnivision Technologies, Inc. of Sunnyvale, Calif. The imaging sensor 14 is mounted to an imager board 31 of the pupilometer 10 and is coupled to a microprocessor (not shown) provided on a main processing or mother board 34 of the pupilometer 10. This allows for direct capture of digital images. Images in the form of 8 bit (or greater) gray scale bit maps are stored in system memory for image analysis and display on the liquid crystal display 36 (shown in FIG. 2). The microprocessor(not shown) preferably comprises an Elan SC 400 manufactured and distributed by Advanced Micro Devices, Inc., of Austin, Tex. 
     The imaging system of the present invention is designed such that, when the hand-held pupilometer 10 is positioned in front of the eye 38 of a subject, a properly illuminated and in-focus image of the pupil 43 of the subject&#39;s eye 38 is obtained at the sensor plane 40 of the pupilometer 10. The objective lens 16 and a first beam splitter (i.e., wavelength selective filter) 18 preferably are used to focus an image of the pupil 43 of the subject&#39;s eye 38 on the sensor plane 40. In a preferred form, the objective lens 16 comprises a five element lens having a focal length of 7.0 mm. The first beam splitter 18 preferably comprises a glass substrate having a thickness of 1.6 mm that is coated with a multi-layer dielectric coating (not shown) to form a wavelength selective filter. The subject side 42 of the beam splitter 18 is coated to enhance reflection at the blue and infrared (IR) wavelength bands with a 45° angle of incidence. The user side 44 of the beam splitter 18 is AR coated to minimize effects resulting from multiple reflections in the image path. 
     Thus, as shown in FIGS. 1 and 3, the beam splitter 18 functions to direct blue and/or IR light generated by the blue and IR LEDs 28 and 24, respectively, toward the eye 38 of a patient and to provide a return path to the imaging sensor 14 for blue and/or IR light that is reflected from the eye 38 ofthe patient. 
     The microprocessor (not shown) provided on the main signal processing board 34 controls the operation and function of the various components comprising the imaging system as described more fully below. 
     3. The Illumination System 
     The illumination system preferably comprises a blue light emitting diode (LED) 28 and four infrared (IR) LEDs 24. The IR LEDs 24 preferably are arranged symmetrically about the objective lens 16 of the imaging system. The IR LEDs 24 and blue LED 28 are coupled to a flex circuit 33 that is coupled to the main signal processing board 34. When activated by the microprocessor (not shown), the IR LED&#39;s 24 emit IR light preferably having a wavelength of substantially 850 nm. Thus, those skilled in the art will appreciate that the emission bandwidth of the IR LEDs 24 lies beyond the physiological response of the human eye but within the photoelectric response of the imaging sensor 14. Stated somewhat differently, while the human eye is unable to detect the IR light emitted by the IR LEDs 24, IR light generated by the IR LEDs 24 and reflected by the eye 38 of a subject may be detected by the imaging sensor 14. The four IR LEDs 24 preferably are arranged in diametrically opposed groups of two, as shown in FIG. 4. By arranging the IR LEDs 24 in the manner shown in FIG. 4, it is possible to more precisely control the IR illumination of a patient&#39;s eye 38 and, moreover, to achieve levels of 0, 50 and 100% illumination, if desired. 
     The blue LED 28 is used for ocular illumination in situations where the sclera/iris border of a patient&#39;s eye 38 may be difficult to detect with IR illumination alone. As shown in FIG. 4, the blue LED 28 preferably is placed on the same radial arc that is defined by the IR LEDs 24, which surround the objective lens 16. The blue LED 28, when activated by the microprocessor (not shown), preferably emits light having a wavelength of substantially 470 nm. It has been discovered by the inventors hereof that light in the blue color band may be used to substantially improve sclera/iris border image contrast because the iris 37 and sclera 41 of a subject&#39;s eye 38 generally have substantially different light absorption and reflection characteristics in the blue color band. Thus, the use of a blue LED 28 for sclera/iris border imaging is believed to be a particularly innovative aspect of the present invention. 
     Because the human eye is responsive to blue radiation, the blue LED 28 preferably is only activated for brief periods of time in relation to the temporal response of a subject&#39;s eye 38 or, alternatively, is used in conjunction with the stimulus LEDs 26 described below. Moreover, in a preferred form, IR and blue light illumination of the eye 38 of a subject may be performed in a multiplexed fashion, such that the eye of the subject is illuminated with IR light for a first period of time and, thereafter, illuminated with blue light for a second period of time. This is discussed more fully below with reference to FIG. 6. 
     The microprocessor (not shown) provided on the main signal processing board 34 controls the operation and function of the various components comprising the illumination system as described more fully below. 
     4. The Stimulus System 
     The stimulus system of the pupilometer 10 comprises two yellow LEDs 26 and a second beam splitter 20. The yellow LEDs 26 preferably are coupled to the flex circuit 33 and, when activated by the microprocessor (not shown), emit light having a wavelength of substantially 570 nm. Like the first beam splitter 18, the second beam splitter 20 preferably comprises a glass substrate having a thickness of 1.6 mm and is coated with a multi-layer dielectric coating (not shown) to form a wavelength selective filter. The subject side 50 of the beam splitter 20 is coated to enhance reflection at the yellow wavelength band with a 45° angle of incidence, and the user side 52 of the beam splitter 20 is AR coated to minimize effects resulting from multiple reflections in the user&#39;s observation path. The stimulus system of the pupilometer 10 preferably provides on-axis illumination of the pupil 43 of the eye 38 of a patient, as shown in FIG. 1. 
     B. Software Components of a Pupilometer in Accordance with the Present Invention 
     Turning now to FIGS. 5-7, a pupilometer 10 in accordance with the present invention is a microprocessor based system and, therefore, preferably includes several software components or modules for controlling its operation. As is well know in the art, an operating system provides fundamental machine level interfaces between the hardware elements comprising the pupilometer 10. More specifically, various device drivers are used to provide an interface between the microprocessor (not shown) and the imaging sensor 14, IR LEDs 24, yellow LEDs 26, blue LED 28, keypad 39 and liquid crystal display 36. 
     The highest level of programming or code used within the pupilometer 10 is referred to herein as the P-Program, and the P-Program preferably is divided into five principal objects corresponding to different hardware and mathematical components. The five principal objects are illustrated in block diagram form in FIG. 5 and preferably include a graphic user interface (GUI) object 100, a stimulus/illumination object 102, a CMOS camera object 104, a feature extraction object 106 and an analysis object 108. All of the above-listed objects preferably are developed in Microsoft Visual C++ and Windows CE, and the graphic user interface (GUI) object 100 preferably is based on Win32 Api functions that are available in Windows CE. Visual C++ and Windows CE are software products distributed by Microsoft Corp. of Redmond, Wash. 
     1. Graphic User Interface (GUI) Object 
     The graphic user interface object 100 allows for data/information exchange between a user and the pupilometer 10. Information relating to the current status of the pupilometer 10 including mode of operation (i.e., direct or consensual response, left or right eye measurement etc.) and the battery level is displayed via the graphic user interface object 100. All inputs and outputs of the pupilometer 10 preferably are coordinated via the graphic user interface object 100. Verification of subject ID numbers and/or patient identification data may be accomplished under control of the graphic user interface object 100. Measurement parameters are determined and set with the assistance of the graphic user interface object 100. Instructions during measurement sequences and images of the iris 37 of the eye 38 of a subject are provided on the liquid crystal display 36 under control of the graphic user interface object 100. Similarly, results of measurement sequences are displayed on the liquid crystal display 36 under control of the graphic user interface object 100, and the option to transfer measurement results to a printer or network computer (not shown) is available through the graphic user interface object 100. 
     2. Stimulus/Illumination Object 
     The stimulus/illumination object 102 defines and controls the function of the yellow LEDs 26, IR LEDs 24 and blue LED 28 and, therefore, controls the stimulation and illumination of the eye 38 of a subject. The stimulus/illumination object 102 defines the various light profiles (i.e., yellow, IR and blue) as a function of time and controls activation of the yellow, IR and blue LEDs 26, 24 and 28, accordingly. In a typical stimulus/illumination sequence, the LEDs 26, 24 and 28 preferably are activated in the manner described below. However, those skilled in the art will appreciate that the stimulus/illumination sequence may be varied depending upon the circumstances of any given situation, and that variations in the stimulus/illumination sequence may be effected through the user interface object 100. 
     During a typical stimulus/illumination sequence, the LEDs 24, 26 and 28 may be operated as shown in FIG. 6. For example, during a typical measurement sequence, the yellow LEDs 26 may be activated and deactivated for successive 1 second intervals (i.e., &#34;on&#34; for 1 second and &#34;off&#34; for 1 second) for a period of 10 seconds total. Simultaneously, the IR LEDs 24 may be activated for all periods when the yellow LEDs 26 are &#34;off,&#34; and may be deactivated, activated and deactivated (i.e., turned &#34;off,&#34; &#34;on&#34; and &#34;off&#34;) for respective 0.04, 0.92 and 0.04 second intervals, while the yellow LEDs 26 are turned &#34;on.&#34; Similarly, the blue LED 28 may be activated, deactivated and activated for respective 0.04, 0.92 and 0.04 second intervals, while the yellow LEDs 26 are turned &#34;on,&#34; and may be deactivated during all periods when the yellow LEDs are turned &#34;off.&#34; This allows for the operation of the IR LEDs 24 and blue LED 28 to be multiplexed. In such an embodiment, the image frame transfer rate preferably would be set, for example, to 50 frames per second. 
     3. The CMOS Camera Obiect 
     The CMOS camera object 104 controls the transfer of image data frames between the CMOS imaging sensor 14 and memory associated with the microprocessor (not shown) provided on the main signal processing board 34 (i.e., between the imaging sensor 14 and the P-Program). Preferably, the rate of image frame transfer between the imaging sensor 14 and the memory associated with the microprocessor (not shown) may be programmably set within a range from 1 frame per second to 50 frames per second, depending upon the needs and/or desires of the user. However, those skilled in the art will appreciate that in some instances it may be desirable to provide for faster frame transfer rates, and that such rates might be as high or higher than 100 frames per second. The image frame acquisition or transfer rate is defined by the user under control of the graphic user interface object 100. 
     4. The Feature Extraction Object 
     The feature extraction object 106 defines several image processing procedures that are used to isolate a pupil within an image and to extract several pupil features such as size, shape and position from each pupil image data frame. All processing procedures defined by the feature extraction object preferably are performed on each image data frame, with the exception of the automatic thresholding procedure described below. The automatic thresholding procedure is applied during an initial calibration phase and, therefore, does not need to be applied to each image data frame. Rather, the results of the automatic thresholding procedure are used during feature extraction processing for each image data frame. The results of the automatic thresholding procedure also may be used to set and/or adjust image exposure gain settings within the system. 
     The feature extraction object 106 employs a flying spot processing algorithm to identify the center of the pupil, a fitted circumference and/or radius of the pupil and, preferably, 48 radii representing the distance between the center and perimeter of the pupil at 48 separate angles in an R,θ coordinate system, where θ defines an angular orientation about the center of the pupil, and R represents the radius of the pupil at that orientation. The fitted radius of the pupil is determined by selecting a circumference that best fits a contour of the pupil and by solving the equation 2πr to obtain the radius value (r). 
     Those skilled in the art will appreciate that, by defining and evaluating 48 distinct radii about the center of the pupil, it is possible in accordance with the present invention to detect one or more non-uniformities or irregularities that may exist around the perimeter of the pupil. It also is possible to characterize the shape of the pupil as circular, elliptical etc. based upon the determined radii. It also is possible to evaluate selected sections of a pupil perimeter to determine whether or not those sections exhibit normal contour characteristics and/or normal responses to visual stimulus. It is believed that these capabilities represent significant improvements over conventional pupilometry systems, as these features allow not only for the performance of conventional pupil aperture and response evaluations, but also for the performance of pupil shape and sectional contour evaluations. Thus, where a particular affliction may produce a defined irregularity in pupil shape or defined sectional response to visual stimulus, the affliction may be identified through the use of a pupilometer in accordance with the present invention. 
     The inputs to, and outputs obtained from, the flying spot algorithm may be defined as follows: 
     Input Parameters: 
     Frame=eye image frame generated by the CMOS imaging sensor 14 
     Threshold=gray level threshold value; any pixel having a gray scale value greater than the threshold value is considered to be part of the pupil. 
     Output Parameters: 
     Output=fitted radius and center of pupil, 48 radii. 
     It is assumed herein that within the gray scale used by the pupilometer 10 the color black will be associated with a high gray scale value, such as 255, and the color white will be associated with a low gray scale value, such as 0. However, those skilled in the art will appreciate that the relative maximum and minimum values could be reversed. 
     It is believed that the use of flying spot algorithms are well known in the art and, therefore, that the flying spot algorithm need not be described in detail herein. Nonetheless, the basic flying spot procedure may be described as follows. The flying spot procedure starts with a large circumference centered on the image of an eye and iteratively reduces the size of the circumference. In reducing the size of the circumference and adjusting the center location of the circumference, for each iteration the following momentums will be computed: ##EQU1## where N represents the number of pixels having coordinates x,y in the circumference contour; gray --  level --  sign(x,y) is +1, if the gray level value of the pixel (x,y) is greater than the threshold value; gray --  level --  sign(x,y) is -1, if the gray level value of the pixel (x,y) is less than the threshold value; and x0,y0 are the center coordinates of the circumference. 
     The x and y coordinates of the circumference center and the radius are updated as follows: 
     
         x0=x0+μx* Gain.sub.-- x 
    
     
         y0=y0+μy* Gain.sub.-- y 
    
     
         radius=radius+μr* Gain.sub.-- r. 
    
     As indicated above, the updating procedure is applied iteratively, each time calculating the momentum and then changing the center and radius of the flying spot, such that the circumference finally converges to a circumference that best fits the contour of the pupil. 
     Once the fitted radius and center of the pupil are determined, 48 radii representing the distance between the center and perimeter of the pupil at 48 separate angles in an R,θ coordinate system preferably are determined, where θ defines an angular orientation about the center of a pupil, and R represents the radius of the pupil at that orientation. By evaluating the 48 determined radii, it is possible to characterize the overall shape of the pupil and to determine whether or not any sectional non-uniformities or irregularities are present about the perimeter of the pupil. Such processing may be performed either by the feature extraction object 106 or the analysis object 108. 
     Another principal function performed by the feature extraction object is thresholding. The thresholding function automatically identifies a gray level value that separates the pupil from the background in an image data frame. Moreover, when an appropriate threshold value is determined, all pixels having a gray level value greater than the threshold value are considered to comprise part of the image of the pupil, and all pixels having a gray level value less than the threshold are considered to correspond to background. 
     Preferably, the defined threshold value represents the average of a maximum hypothetical threshold value and a minimum hypothetical threshold value. The maximum and minimum hypothetical threshold values are derived through respective histogram analysis routines. Moreover, as shown in FIGS. 7(a) and 7(b), for each hypothetical threshold value two histograms are evaluated, one for the rows of pixels within an image frame, and one for the columns of pixels within the image frame. The histogram value for a given row or column is determined by counting the pixel locations in that row or column that have a gray level value that exceeds the hypothetical threshold level. Thus, the number of values within a histogram preferably corresponds to the number of rows or columns in the image data frame, and each value represents the number of pixels in the specific row or column that have a gray level exceeding the hypothetical threshold value. 
     Turning now in particular to FIGS. 7(a) and 7(b) the hypothetical maximum and hypothetical minimum threshold values are determined by iteratively altering a hypothetical threshold value until a prescribed histogram profile is achieved. An acceptable profile is illustrated in FIG. 7(a) and is one in which a null-high-null pattern is achieved for both a row histogram (y Hist) and column histogram (x Hist). More specifically, an acceptable profile preferably comprises a single &#34;high&#34; bordered by a pair of &#34;nulls.&#34; Unacceptable profiles are illustrated, for example, in FIG. 7(b). 
     The hypothetical maximum threshold value is determined by selecting an absolute maximum value and iteratively decreasing that value and deriving corresponding histogram data sets until acceptable row and column histogram profiles are achieved. Similarly, the hypothetical minimum threshold value is determined by selecting an absolute minimum value and iteratively increasing that value and deriving corresponding histogram data sets until acceptable row and column histogram profiles are achieved. Once the hypothetical maximum and minimum threshold values are determined, those values are averaged to determine the defined threshold value that will be used by the feature extraction object 106. Those skilled in the art will appreciate that the defined threshold value may correspond to the maximum hypothetical threshold value, the minimum hypothetical threshold value, or any value that is between those values. Thus, in alternative embodiments, the defined threshold value could be determined, for example, based on a weighted average of the maximum and minimum hypothetical threshold values. In such an embodiment, the defined threshold value may comprise a value corresponding to the sum of the minimum hypothetical threshold value and 2/3 of the difference between the maximum and minimum hypothetical threshold values. 
     5. The Analysis Object 
     The analysis object 108 analyzes the configuration characteristics of a pupil as a function of time. Preferably, the analysis object 108 receives, as inputs, from the feature extraction object 106 a plurality of data sets for each captured image data frame. The data sets preferably include the time of image capture in msec, x and y coordinates of the pupil center, radius of the flying spot circumference, 48 radii representing the distance between the center and border of the pupil for 48 selected angles within an R,θ coordinate system, and an applied stimulus record for the relevant entry. Upon receiving the input data sets, the analysis object 108 preferably derives at least the following information from the data sets: minimum pupil aperture, maximum pupil aperture, difference between maximum and minimum pupil apertures, latency of pupil response to yellow light stimulus, pupil constriction velocity, first and second pupil dilation velocities and, if desired, pupil irregularity magnitude and location information. Where pupil irregularities are detected, the location of the irregularity preferably is identified by its θ coordinate. However, graphical indications also may be provided on the display 36 of the pupilometer 10. 
     Further, in alternative embodiments, the analysis object 108 may include programming for effecting a multi-varied analysis wherein a plurality of selected variables including, for example, latency indicia, constriction velocity indicia, first and second dilation velocity indicia, segmental static and/or dynamic analysis indicia, constriction/dilation velocity ratio indicia, and maximum and minimum diameter indicia are evaluated for one or both eyes of a patient to arrive at one or more scalar values that are indicative of an overall physiologic or pathologic condition of the patient or, alternatively, to arrive at one or more scalar values that are indicative of an overall opto-neurologic condition of the patient. 
     With regard to the information derived by the analysis object 108, the maximum pupil aperture, minimum pupil aperture and difference determinations require the identification of the maximum pupil aperture and minimum pupil aperture within a set of image data frames and, thereafter, computation of the difference between those values. The latency determination provides an indication in milliseconds of the time that it takes for a pupil to begin to respond to a visible (i.e., yellow) light stimulus pulse. Further, those skilled in the art will appreciate that, when a pupil is exposed to a visual light stimulus pulse, the pupil generally will, after some latency period, constrict and, once the stimulus is discontinued, dilate and return to its original size and configuration. Thus, the analysis object 108 evaluates the response of a pupil to a visual stimulus to determine a pupil constriction velocity and evaluates the response of the pupil to termination of the stimulus to determine first and second dilation velocities. First and second dilation velocities are evaluated because a pupil generally will dilate quickly for a first period of time and, thereafter, will dilate more slowly until its original size and configuration are achieved. Finally, as explained above, an analysis object 108 in accordance with the present invention also preferably identifies any irregularities in the shape of the pupil. Such irregularities may be either static or dynamic in nature. For example, a static irregularity may take the form of an irregular pupil shape in ambient light, whereas a dynamic irregularity may take the form of increased latency for a particular section of the pupil during a response to a the initiation or termination of a visual stimulus. With regard to static irregularities, such irregularities may be identified by identifying the angular orientations of radii that do not fall within prescribed limits, differ from other calculated radii by a predetermined deviation or differ from the fitted radius by a predetermined amount, deviation or percentage. 
     Finally, an analysis object 108 in accordance with the present invention preferably includes programming for identifying statistical anomalies within derived results. This allows an analysis object 108 in accordance with the present invention to discard either actual pupilary response data sets (i.e., fitted radius, center and radii calculations) or derived data sets (i.e., max aperture, min aperture, latency, constriction rate or dilation rates) when a selected value differs from other values by a statistically significant degree. When such anomalies are identified, the relevant data sets are not included in averaging functions, and where many anomalies are identified, an imaging sequence will be invalidated and must be repeated. 
     C. Operation of a Pupilometer in Accordance with the Present Invention 
     Turning now to FIG. 8, operation of a pupilometer 10 in accordance with the present invention proceeds as follows. Generally the pupilometer 10 will be configured according to a default mode of operation. The default mode defines a set of values for basic operation of the device. The defined values may include, for example, values for scan duration, illumination duration and/or profile, stimulus duration and/or profile and stimulus intensity level. However, it will be appreciated that all of the above-listed values may be programmably set under control of the graphic user interface object 100. Thus, it will be appreciated that default programming values generally will be utilized by the pupilometer 10 absent entry of an override by the user in a scan sequence program mode. 
     A typical image acquisition and analysis procedure may proceed as follows. If the pupilometer 10 has been idle for a predetermined period of time (e.g., 120 seconds), the pupilometer 10 is automatically placed in a battery-conserving sleep mode (step 202). By depressing the &#34;scan&#34; button 45 (shown in FIG. 2), the user causes the pupilometer 10 to enter a &#34;ready&#34; mode (step 200). At this time, the user is prompted to enter an alphanumeric subject or patient identification number via the keypad 39 or to download any necessary patient information from a network computer via an infrared data interface, such as an IrDA interface that is provided on numerous conventional personal computer products (step 204). Once any requisite patient identification data has been entered into the system, the user is prompted via the liquid crystal display 36 or an audio prompt to hold down the &#34;scan&#34; button 45 and to position the pupilometer 10 in front of the eye 38 of a subject (step 210). 
     When the user depresses the &#34;scan&#34; button 45, the microprocessor (not shown) initiates an imaging test sequence. The yellow LEDs 26 preferably are not activated during the test sequence. During the test sequence the images that are acquired by the imaging sensor 14 may be displayed on the liquid crystal display (LCD) 36. Preferably, the P-program analyzes the image data frames that are acquired during the test sequence, determines whether or not the pupilometer 10 is properly positioned for obtaining measurements, and determines if all necessary parameters are met to ensure high-quality data recovery. If the test criteria are not met, the user is prompted to reposition the pupilometer 10. After any requisite test criteria are met, the P-program will continue to run the test sequence until the &#34;scan&#34; button 45 is released. 
     Once the scan button 45 is released, the P-program preferably will initiate a prescribed measurement sequence and will activate the illumination system of the pupilometer 10 as needed during the measurement sequence. Upon completion of the measurement sequence, the user is informed via the LCD 36 or an audio prompt that the measurement sequence has been completed (steps 226-228). 
     Following completion of the measurement sequence, the P-program preferably will analyze the image data frames that have been obtained and will display the results of the analysis on the LCD 36. If the results are satisfactory (i.e., are statistically sound), the user may then be prompted to download the results to a printer or related network via the IrDA interface (not shown) (step 246). If the results are not satisfactory, the user is prompted to repeat the measurement sequence (step 222). 
     Finally, after an initial set of measurement are obtained, the user may be prompted for a decision to measure the pupilary characteristics of the other eye of the subject/patient, or the user may be prompted for a decision to make a consensual response measurement (steps 238, 242). The consensual response measurement may take the form of a &#34;swinging flashlight&#34; measurement discussed more fully below. If a consensual measurement is to be performed, the user may be prompted to couple a consensual measurement attachment (shown in FIG. 9) to the pupilometer and to position a yellow LED 52 mounted on the attachment in front of the appropriate eye of the subject/patient. If the consensual measurement attachment is permanently affixed to the pupilometer 10, the user may only need to deploy and/or properly position the attachment. 
     D. Incorporation of Consensual Measurement Apparatus in a Pupilometer in Accordance with the Present Invention 
     Turning now to FIG. 9, a pupilometer 10 in accordance with the present invention may incorporate a consensual measurement apparatus or armature 50 to enable consensual pupilary responses to be analyzed. In a preferred embodiment, the armature 50 may detachably engage a main body 11 of the pupilometer 10. However, as explained above, the armature 50 also may be permanently affixed to the main body 11 of the pupilometer 10. 
     One test for analyzing consensual pupilary responses is commonly referred to within the medical community as a &#34;swinging flashlight test.&#34; During a typical swinging flashlight test one eye of a subject is monitored, and a visible light stimulus is applied first to the eye of the patient that is being monitored, then to the eye of the patient that is not monitored and, finally, again to the eye that is monitored. If the eyes of the patient are normal, the pupil of the monitored eye should constrict in response to all of the light stimulus pulses (regardless of which eye the stimulus pulse is applied to). Following application of the first light stimulus, the pupil of the monitored eye should begin to dilate, and upon application of the second light stimulus (i.e., upon application of stimulus to the non-monitored eye), the pupil of the monitored eye should again constrict. If the monitored pupil does not respond adequately to the second stimulus pulse, it may be inferred that the retina of the non-monitored eye somehow may be impaired. If the monitored pupil does not respond adequately to the third stimulus pulse, it may be inferred that the retina of the monitored eye somehow may be impaired. 
     By using a consensual measurement attachment 50 in accordance with the present invention, it is possible to perform a &#34;swinging flashlight&#34; test using the pupilometer 10. For example, the when performing a &#34;swinging flashlight&#34; test, the P-program may first cause the yellow LEDs 26 within the pupilometer 10 to be activated for a period of, for example, 1 second. The P-program then may deactivate the yellow LEDs 26, and 0.5 second following deactivation of the yellow LEDs 26 may activate for 0.5 second the yellow LED 52 located at the distal end 54 of the consensual attachment. Finally, after deactivating the yellow LED 52 and waiting for a period of, for example, 0.5 second, the P-program may again activate the yellow LEDs 26 for a period of 1 second. Image frames may be obtained by the imaging sensor 14 at a rate of, for example, 10 frames per second and for a total period of 5.0 or more seconds to evaluate the consensual response of the imaged eye. If desired, the process may be repeated a predetermined number of times. 
     E. Miscellaneous System Calibration and Pupil Identification Processing Techniques 
     In alternative embodiments, the P-program of a pupilometer 10 in accordance with the present invention may incorporate a calibration algorithm that uses acquired data descriptive of the perimeter of the iris 37 of the eye 38 of a patient to define a relationship between pixel spacing data and real world measurement parameters and/or to evaluate an orientation of a patient&#39;s eye 38 in relation to the pupilometer 10. 
     For example, in one innovative aspect, the P-program of a pupilometer 10 may cause the iris of the eye of a patient to be illuminated by blue light (i.e., may activate the blue LED 28) and, while the patient&#39;s eye is so illuminated, may obtain an image of the sclera/iris border of the patient&#39;s eye. A flying spot or similar processing algorithm may then be used to identify a best fitting elliptical circumference for the sclera/iris border of the patient&#39;s eye, and the radii or horizontal and vertical diameters of the circumference may be compared to or correlated with assumed sclera/iris border radii or diameters to provide a correlation between a pixel count and a real world measurement. For example, if the horizontal diameter of a sclera/iris border is assumed to be 11.7 mm, and the sclera/iris border measures 117 pixels in diameter, the P-program of the pupilometer 10 may derive a pixel measurement to real world correlation factor of 10 pixels/mm, and that correlation factor may be used to provide the user with pupil measurement information. In accordance with one preferred form of the present invention, the horizontal diameter of the sclera/iris border is assumed to be 11.75 mm for in all subjects. However, those skilled in the art will appreciate that a different diameter, such as 11.0 mm or 12.0 mm, may also be assumed. 
     Similarly, by evaluating the shape of the sclera/iris border of an eye it is possible to estimate the angular orientation of the eye with respect to the pupilometer 10 and, moreover, to evaluate the orientation of an eye with relation to a vertical axis of the eye. Preferably, this may be done by evaluating a degree of ellipticity of the imaged sclera/iris border and assuming that the shape of the sclera/iris border has a predetermined elliptical shape. Such, measurements may be further refined by comparing the shape of a pupil to the shape of a surrounding sclera/iris border to determine whether variations in the shape of a pupil arise from angular orientation of the eye in relation to the pupilometer 10, or from non-uniformities or irregularities in the perimeter of the pupil. 
     In another innovative aspect, a pupilometer 10 in accordance with the present invention may include software for utilizing physical landmarks to assist in locating a pupil within an image data frame. In such an embodiment, the feature extraction object 106 of the P-program executed by the microprocessor (not shown) may include code for identifying characteristic structures of ocular tissue such as eyelids and/or eyelashes within an image data frame, and for using the location of those structures to predict the location of a pupil within the image data frame. Additional landmarks that may be located in accordance with the present invention include the lachrymal punctum, lachrymal caruncula, and lateral and medial papebral commisures of a patient&#39;s eye. These landmarks also may be used to identify which eye of a patient is being monitored. 
     F. Diagnostics Systems and Methods in Accordance with the Present Invention 
     In still another innovative aspect, the present invention is directed to improved diagnostics systems and methods incorporating a pupilometer 10 and medical database (not shown). For example, it is contemplated in accordance with the present invention that data representative of a plurality of pupilary response or configuration characteristics associated with one or more physical or pathological conditions may be stored within a medical diagnostics data base, that a pupilometer 10 may be used to obtain data descriptive of one or more pupilary response or configuration characteristics from a patient, and that the obtained data may be compared to the stored data within a data analysis system to identify one or more physiologic or pathologic characteristics or conditions of the patient. Further, in a preferred form, the obtained and/or stored pupil configuration data may be descriptive of one or more static or dynamic regional non-uniformities that may exist within the perimeter of a patient&#39;s pupil. 
     While the invention is susceptible to various modifications and alternative forms, specific examples thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the invention is not to be limited to the particular forms or methods disclosed, but to the contrary, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the appended claims.