Abstract:
A device for mapping the visual field of an eye includes a projector for creating a light beam of visible light, a first light directing element for controlling the direction of the beam, and a reflection element for reflecting the light beam through a predetermined crossing point. The elements are arranged in such a way so that the light beam can be directed to well defined sites of the retina of the eye when positioned with the center of its lens substantially in the crossing point. The projector can be made to include a focusing element and a beam cross-section forming element for creating a disk of predetermined size on the retina of the eye.

Description:
FIELD OF INVENTION  
       [0001]     This invention relates to a device for mapping the visual field of the eye, more particularly a perimeter.  
       BACKGROUND-PRIOR ART  
       [0002]     Scanning or mapping the visual field of the eye is useful in detecting and diagnosing various eye diseases. Such diseases detected by visual field mapping include glaucoma. Markers of glaucoma are loss of peripheral vision, increased intraocular pressure, and changes in the optic disc. If untreated, blindness ensues. If detected at an early stage, however, treatment with drugs can usually arrest development of the disease and save the patient&#39;s vision.  
         [0003]     At present, glaucoma is diagnosed by eye specialists in a clinical setting. Instruments to map the visual field, measure intraocular pressure, and image the optic disc are bulky, complex, and expensive. These instruments require specialized skills to operate. Additionally, lengthy training is required to acquire the skills necessary to interpret results.  
         [0004]     An example of a method to detect glaucoma is measuring the intraocular pressure (IOP) of the eye. To measure the eye&#39;s intraocular pressure a tonometer is used, which through mechanical or air-puff contact flattens an area of the cornea. The amount of flattening as indicated by the pressure required to cause the flattened area correlates to the intraocular pressure. (By measuring corneal thickness, measurements may be adjusted to increase accuracy, but measurements are aimed not at precision measurement of IOP, which varies during the day, but that IOP is within a standard range, not too high, say not below 9 mm Hg, and not too much above 20 mm Hg.)  
         [0005]     Ideally, tonometry, measuring IOP, would be used on a routine basis to detect glaucoma in the earliest stages so that irreversible damage to the optic nerves/retina can be avoided. Then drugs could be administered to lower intraocular pressure and in most cases save the patient&#39;s vision.  
         [0006]     But tonometry is a clinical procedure requiring specialized skills. Air puff devices to measure IOP are expensive and difficult to use. Usual mechanical tonometry similarly requires expensive equipment, although a simple version is low cost but requires even more skill to use. Mechanical tonometry can also scratch the cornea of the eye thereby risking infection and vision impairment.  
         [0007]     In most of the world, including the advanced industrialized countries, specialized skill is not always available to detect incipient glaucoma. So the patient may not see a doctor until symptoms such as loss of peripheral vision (“tunnel vision”) become apparent to the patient. But at that point, noticeable loss of vision, the patient has already suffered irreversible damage to the retina.  
         [0008]     According to the Merck Manual (Fourteenth Edition) measurement of intraocular pressure and mapping the visual fields should be performed semi-annually as indicated. But screening to detect incipient glaucoma and determine who should be checked semi-annually is not a routine matter: such tests are complex and costly. Only a small percentage of the world&#39;s populations is screened for glaucoma. Yet, in persons over the age of 40, glaucoma is a common and serious eye disease.  
         [0009]     Clearly needed is a non-clinical, easy-to-use device for detecting glaucoma. This device must not only be easy to use (and low cost) but preferably non-contact. Non-contact means safe to use even by minimally skilled personnel. Ideally the device would measure IOP in a low-cost, safe, and effective manner. One type of devices for mapping the visual field in common use are the Humphrey or Octopus instruments. They project discs of varying brightness, size, or color, onto an evenly illuminated hemisphere for detecting and measuring contrast sensitivities.  
       SUMMARY OF THE INVENTION  
       [0010]     The present invention&#39;s objective is to provide a device for detecting changes in the visual field, e.g., scotomas characteristic of glaucoma.  
         [0011]     Another object consists in proposing a device capable to scan the visual field and to perform at least a measurement of the refraction of an eye.  
         [0012]     Accordingly, a device according to the invention produces a light disk on the retina. Preferably, the light spot is created by deflecting a corresponding beam into the eye by a concave mirror.  
         [0013]     More preferably, the light beam is created by a beam projector and the shape of the concave mirror is such that the light disk may be produced on any point of the retina beginning from the very center to the periphery of the retina without the beam projector needing to interfere with the line of sight of the eye.  
         [0014]     According to the other object, the concave mirror is transparent at least for light used for refractometry other than the light of the beam in the area where the line of sight crosses the mirror, so that the said light is able to pass the mirror.  
         [0015]     My invention is preferably intended to detect and map scotomas associated with glaucoma. (That glaucoma is not easily detected by a patient or even readily apparent to patients with glaucoma, is that about 40% of the retina is affected before the patient realizes he/she has a problem.)  
         [0016]     According to another aspect, my invention may be incorporated in an ultra-compact handheld autorefractor, either monocular or binocular. Incorporation of an autorefractor provides unique capabilities for my apparatus and methods for mapping the eye&#39;s visual field in the restricted sense of detecting and mapping scotomas associated with glaucoma.  
         [0017]     According to a further aspect, the present invention in its preferred embodiment provides entirely objective and automatic screening of the eye to detect and assist in the diagnosis of glaucoma. Objective and automatic operation is made possible by using a CCD and microprocessor to observe, record, and analyze responses of the pupil to light stimuli projected onto various areas of the retina of the eye.  
         [0018]     More preferably, this invention comprises an assembly consisting of a light source such as an LED and the light source is equipped with an adjustable aperture and lens so as to focus and project illuminated discs of various sizes and intensities onto the retina via a movable mirror or beam-splitter placed close to the eye, so that the illuminated discs can be projected onto any area of the retina, centrally or peripherally, by rotating the assembly and adjusting the position of the movable mirror, which is accomplished by small actuators or tiny motors such as manufactured by Sanyo. In conjunction with an integral autorefractor, position and refraction of the eye can be determined so that the subassembly LED/iris/lens can be adjusted to ensure that desired disc size and intensity is clearly focused and projected onto the targeted area of the retina.  
         [0019]     A micro-dot hemisphere edge-lighted provides even background illumination while allowing projection of light rays (stimuli) onto the retina. The ring assembly containing LED projector can be moved in x-axis and y-axis planes to center eye pupil.  
         [0020]     Another embodiment comprises an assembly of multiple fixed mirrors with corresponding multiple movable subassemblies comprising an LED, iris, and lens system, the subassemblies being adjustable by electromagnetic coils, and the assembly being rotated in steps by an actuator or step motor so that along with the adjustable sub-assembly illuminated discs of light can be projected onto areas of the central and peripheral retina.  
         [0021]     Still another embodiment comprises multiple mirrors fixed in position along with corresponding multiple subassemblies of LED, iris, and lens, positions of such subassemblies being adjustable.  
         [0022]     Still another embodiment comprises one or more tiltable light projectors, which can be moved by means of know mechanisms toward the center of eye (center of ring) so as to enable continued projection of light ray through center of pupil. Measuring z-axis distance (vertex distance) ensures that projection angles and location of projector unit from ring center continue to project light ray stimuli through center of pupil. An integral autorefractor with one or more microprocessors provides essential support such as monitoring eye center, CCD imaging of pupil, and recording/analysis of pupil size. Based on statistical analysis of initial pre-screening eye responses, microprocessors control and decide a further sequence of stimuli to eye so as to make screening efficient and rapid. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0023]     The invention will be further explained by way of exemplary embodiments with reference to the Drawing:  
         [0024]      FIG. 1  Schematical side view of a embodiment of the invention;  
         [0025]      FIG. 2  As  FIG. 1 , front view;  
         [0026]      FIGS. 3-4  Second embodiment of the invention with sets of fixed mirrors turned in 20 degree steps;  
         [0027]      FIGS. 5-6  A third embodiment of sets of fixed mirrors with fixed positions for corresponding six sets of LED/lenses;  
         [0028]      FIG. 7 A  further embodiment with movable light projectors;  
         [0029]      FIG. 8 A  fifth embodiment with tiltable projector mounted on rotatable ring;  
         [0030]      FIG. 9  Schematic longitudinal section of a sixth embodiment;  
         [0031]      FIG. 10  As  FIG. 8 , with the light projector more detailed and auto-fixation unit (AT unit);  
         [0032]      FIG. 11  Autorefractor unit of sixth embodiment, schematic side view;  
         [0033]      FIG. 12  Autotracking unit of sixth embodiment, schematic top (a) and side (b) view;  
         [0034]      FIG. 13  Operator view on patient, right eye (a) and left eye (b) measurement. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0035]     While mapping the visual field alone is not sufficient to diagnose glaucoma (tonometry and examination of the optic disc for changes such as “cupping” must also be performed), detecting changes in the visual field is an early marker. One would think that anyone with glaucoma would readily notice a loss of peripheral vision. This is not true. As described above, loss of vision may not be noticed until relatively late in the process of the disease.  
         [0036]     Loss of peripheral vision may not be noticed by the patient because the visual fields of the two eyes significantly overlap. Even inside a patient&#39;s field of vision scotomas (areas that do not receive or process images, that is, “blind spots”) the brain&#39;s visual processes may “fill in” and prevent the patient from being aware of the blind spots. An example of the brain filling in blind spots is the optic disc in each eye. Therefore, by detecting and mapping characteristic loss of peripheral vision, my invention aids in detecting incipient glaucoma.  
         [0037]     Mapping the visual fields of the eye carefully and precisely can take about thirty minutes, depending on the skill of the physician or technician. Screening for peripheral vision may require only a few seconds, and if careful screening with an actual instrument designed for such testing is performed, only about 45 seconds per eye, and then a further few minutes to verify screening results are needed. That is, verify no scotomas (blind areas) characteristic of glaucoma.  
         [0038]     Even simple screening of the eye requires a response from the patient, “Did you see a light, yes or no?” That is, the patient must press a button to indicate, yes, he/she saw a light stimulus. Moreover, the physician must look at the screening results and make a judgement as to whether there is a problem. My invention, however, uses physiological responses of the eye to make operation entirely objective and automatic.  
         [0039]     The non-contact nature of this invention&#39;s functioning ensures a high degree of safety. Positive indications of glaucoma can be used to refer patients to eye specialists for a more detailed series of tests.  
       FIRST EMBODIMENT  
     FIG.  1   
       [0040]      FIG. 1  shows eye  30  with light ray  1  from LED  2  with focusing lens  4  (arrow  3 ) and spot size adjuster iris  7 , with light ray  1  reflected from movable beam-splitter (or mirror, or dichroic beam-splitter)  8 . Beam-splitter  8  is shown in positions  10 ,  11 ,  12 , and  13  to project spots onto periphery of retina to central area of retina. That is, the combination of a rotating cylinder or ring  15  moved by motor  16  and moving mirror  17  has the capability to project illuminated discs onto any area of the retina  19 , beginning with the center up to the periphery.  
         [0041]     The assembly comprises a rotating ring, or rotating cylinder  15 , turned by a motor  16 , and with movable mirrors or beam-splitters  17  moved by motor  21 , and LED/iris/lens  4  for projecting clearly defined focused discs of light of various sizes and intensities onto the central and peripheral areas of the retina  19  of the eye  30 . Also shown are parts of the incorporated autorefractor including CCD  25  with adjustable lens  34  for imaging the eye  30 . A microprocessor serves controlling testing sequence, recording patient responses via e.g. a pushbutton switch for the patient, and outputting the visual field map and analysis of results (not shown).  FIG. 2  also shows a front view of the rotating cylinder assembly with the eye  30 . Shown are motor  21  for moving the mirrors  17  and motor  16  for rotating the assembly. Shown in the rotating assembly are LED/iris/lens  2 ,  7 ,  4  for projecting a disc of light onto the retina.  
         [0042]     The purpose of adjustable beam-splitter  8  (by action of motor  21 ) is to maintain a constant angle of incident and reflected light ray so that each light ray and resultant spot is projected through the pupil center  23 . This is shown as Θ 1  (incident light ray angle) equal to Θ 2  (reflected light ray). Shown also is beam-splitter  8  in positions  10 ,  11 ,  12 , and  13  for a multiplicity of positions wherein the light ray  1  passes each time through the pupil center  23 .  
         [0043]     Incident and reflected rays have the same angle so that the ray of light for projecting illuminated discs onto various areas of the retina always enters through the optical center of the eye.  
         [0044]     CCD  25  locates reflected spots  27  for determining curvature of cornea  28  so that with refractive power of the eye  30 , as determined by autorefractor, the iris  7  can be adjusted to project the appropriate size light spot onto the retina  19  with LED  2  being adjusted for intensity. (An ultra-sonic motor or similar device, not shown, drives the iris  7 .)  
         [0045]     The CCD  25  also monitors pupil size. Motor  32  drives imaging lens  34  so that reflected corneal spots  27 , or other features of the eye  30  such as the iris, are in sharp focus so as to help determine vertex distance Z. In the case of finding the distance to a point of light, maximum intensity on a minimum number of pixels indicates the CCD lens focal point and corresponding vertex distance Z.  
         [0046]     For a large pupil, vertex distance Z is not critical, but with a small pupil, vertex distance becomes critical. In regard to pupil size and vertex distance Z, the CCD/microprocessor monitors pupil size as well as position of the eye  30  (as determined by a corneal reflection generated by a visible fixation target, or alternately by non-visible IR) to ensure that light rays penetrate the eye through the optical center (line of sight)  23 , designated here for purposes of illustration as “pupil center.” 
         [0047]     Motor  16  fixed to instrument housing  36  turns rotating cylinder  15  so that every area of retina is mapped ( FIG. 2 , Arrow  38  shows assembly being rotated, Arrow  39  shows mirror  17  being moved up/down). Patient with push-button switch (not shown) indicates when a stimulus light (LED generated light spot) is detected by the patient. A processor controls testing sequences and functions to effect computerized perimetry. The resultant visual field maps assist in detecting glaucoma and related eye diseases.  
         [0048]      FIG. 2  shows the rotating cylinder  15  as indicated by arrow  38 , which is turned by motor  16  shown in cutaway. Motor  16  moves the movable mirrors  17  up/down.  
       ALTERNATE EMBODIMENT  
     FIGS.  3 ,  4   
       [0049]      FIGS. 3, 4  shows a second embodiment of the invention with one set of six sets of fixed mirrors in a rotating ring  17 . Shown are three mirrors  41 ,  42 ,  43  in 60 degrees  44  of the ring  17 . Also shown associated with each of the three mirrors  41 ,  42 ,  43  is a subassembly of LED/iris/lens  45  that is fixed in position. This means that by rotating the ring  17  in steps of 20 degrees, each of the three mirrors reflects a light ray  41 ,  42 ,  43  closer or further away from the periphery of the retina  19 .  
         [0050]     In  FIGS. 3, 4 , moreover, the subassembly LED/iris/lens  45  sits in an adjustable electromagnetic armature so the light ray  1  is adjustable to reach all areas of the central and peripheral retina  47  resp.  48 . A stepper motor  50  similar to the Sanyo T8LNP-60 is shown inside the rotating ring  17 , thus indicating the miniature size of the rotating ring assembly, which could be as small or smaller than 42 mm in diameter and 14 mm in depth.  
         [0051]      FIGS. 3, 4  shows only one of six sets  41 ,  42 ,  43  of mirrors and corresponding subassemblies of LED/iris/lens  45 . This means a total of  18  distinct points of the retina  19  reached, with areas between the points reached by adjusting positions of the LED/iris/lens subassemblies  45 . But it is understood that this is an example only, and the sets could be more or fewer in number, as is the case for the mirrors  41 ,  42 ,  43 .  
         [0052]     In  FIG. 3 , other features such as a pushbutton switch as in  FIG. 1  are also applicable.  
       ALTERNATE EMBODIMENT  
     FIGS.  5 ,  6   
       [0053]      FIGS. 5, 6  shows the most simple embodiment. It comprises a fixed system of six mirrors arranged as a six-sided polygon  53  with six corresponding LEDs/lenses  45 . Each LED/lens  45  projects a thin beam of light to the periphery of the retina  19 .  
         [0054]      FIGS. 5, 6  embodiment can be further developed by incorporating as shown in  FIGS. 3, 4  a second and third set of polygonal mirrors. These additional mirrors with the required Θ 1 =Θ 2  are added through using nested polygons or through moving the existing polygonal mirrors (separated into distinct sides) so that an iris-type mechanism with motor (not shown) rotates the mirrors into the additional positions. The additional mirror positions allow other areas of the retina  19  to be reached.  
         [0055]     In  FIGS. 5, 6 , other features such as a pushbutton switch as in  FIG. 1  are also applicable to the embodiment of  FIGS. 5, 6 .  
       OTHER EMBODIMENTS  
     FIGS.  7   a - 7   d , FIGS.  8   a - 8   b    
       [0056]      FIG. 7   a  shows the ring assembly  57  comprising elements of LED projectors  58  with lenses, and motors  ———  to rotate and cause LED projectors  58  to move closer to center of eyes vision. In  FIG. 7   a , ring assembly  57  is represented by a circle. At 45-degree intervals, the ring assembly  57  is suspended by springs  60  (four points) and at four points in between the four suspension points are coil/magnet assemblies  62  to move the ring  57  in x-y axes so as to cause the ring  57  to be centered relative to the pupil of the eye. Note that instead of a suspension system, the ring  57  could simply be moved in x-axis and y-axis by step motors or other means.  
         [0057]     Still referring to  FIG. 7   a , a fixation target light generator fixed at optical infinity in combination with a CCD  64  with lens  65  provides a corneal reflection/detection system to know center of eye  30 , and a microprocessor observes and records eye&#39;s position so that the microprocessor can accordingly adjust ring&#39;s  57  x-y position so as the center the eye. Note, too, finding vertex distance z allows the ring  57  to be either moved forward or backward so projection rays  66  pass through center of pupil  23 . Alternately, position of ring  57  in z-axis can be fixed and projection angles of LED  58  adjusted so as the ensure LED rays  66  pass through center  23  of pupil.  
         [0058]      FIG. 7   b  shows a semi-transparent hemisphere  68  fixed in front of ring assembly  57 . The hemisphere  68  is edge-lighted, preferably illuminated with low-intensity yellow light. Projected ray  58 , preferably blue color and of relatively high intensity, passes through the hemisphere  68  and the center  23  of pupil as previously described.  
         [0059]      FIG. 7   c  shows a detail of semi-transparent hemisphere  68 . It is suitably thin so as to not introduce optical effects but allow projected ray  58  to pass through with minimal refractive effects. Note that the semi-transparent hemisphere  68  is coated with microdots  70  so that part of the projected ray  58  is blocked and the remainder of the ray passes unattenuated to the eye  30 . Microdots  70  allow edge lighting of hemisphere  68  to produce a uniform lighting background. Amount of microdots  70  may vary from a few percent to fifty percent or more of hemisphere area. Microdots may be painted, etched, or applied in a number of different ways to hemisphere surface in order to produce a surface suitable for edge lighting to produce a uniform lighting background.  
         [0060]      FIG. 7   d  shows apparatus and methods to automatically record and map scotomas in the retina. A lens CCD  64  images eye pupil  72  and observes changes in pupil size. A microprocessor (not shown) records sizes of eye pupil  72  in a series of pupil size measurements, say, every 10 ms to every 100 ms.  
         [0061]     Again referring to  FIG. 7   d , as previously described, rays of light  66  are projected onto various areas of the retina  19 , and times that rays  66  are projected, and times may be random or sequenced uniformly, are observed and recorded. The microprocessor then through a statistical analysis compares pupil sizes at times with rays projected and with rays not projected. For rays projected onto scotomas  74  there is little or no pupil change. For rays projected onto healthy retina there is change in pupil response. Knowing the area of the retina that each ray was projected for pupil response and no pupil response allows detection of scotomas  74  including scotomas  74  characteristic of glaucoma.  
         [0062]     Still referring to  FIG. 7   d , note that software can perform a quick screening to detect any large scotomas  74 , and then the software can allow re-examination of areas of interest, that is, areas indicating potential scotomas. Note, too, that in my invention, the intensity of projected rays as well as size of disc of projected rays onto the retina and background illumination levels are all adjustable so that subtle changes in retinal fields are more likely to be detected and mapped. Detecting subtle changes is significant in detecting and diagnosing incipient glaucoma.  
         [0063]      FIG. 8   a  shows a ring assembly  17  similar to previous descriptions. This ring assembly  17  has been automatically centered in the ring  17 . One subassembly  78  of actuator (micro step motor or similar device) for a pivoting light ray projector  80  is shown. As indicated in  FIG. 8   a  this subassembly  78  can be moved toward the center of the eye  30  (arrow  79 ), moving in x-axis or y-axis, so as to access less peripheral areas of the retina, and more specifically for locating the eye&#39;s blind spot, a reference point for locating and mapping scotomas. Ring&#39;s rotary motion is indicated by a double-headed arrow  38 . The ray projector is tiltable (arrow  83 ) around pin  85  by actuator  87 . The actuator  87  imparts an essentially linear movement (arrow  88 ) on rod  89  attached to the back end of projector  80 . (Actuators moving the ring toward eye center and causing rotation of ring are not shown.)  
         [0064]      FIG. 8   b  shows details of subassembly  78  for rotating light ray projector  80 . As light source, an LED  2  is provided. Significant is that diameter of LED light ray (and subsequent size of stimulus light disc on retina) is selectable by a variable size iris  7 . Focus of disc on retina can be achieved by adjusting focal length of LED lens  4 . To properly adjust focal length of LED lens  4  means knowing distance of LED from eye  30  and knowing eye&#39;s refractive measurement.  
         [0065]     Again referring to  FIG. 8   b , a micro step motor or similar micro actuator causes light ray subassembly to rotate around a pin so the light ray can be projected at selected angles to reach different areas of the retina. Arrow  79  shows that the subassembly can be moved toward center of ring (eye  30 ) in x- or y-directions so light ray  66  continues to pass through eye&#39;s center  23  with different angles of light projection. Note that area above pin  85  to which actuator  87  is attached is not necessary, and the actuator  87  could be attached to an area of projector  80  below the pin  85  so as to make the subassembly  78  more compact.  
       SIXTH EMBODIMENT  
       [0066]      FIGS. 9-12  illustrate a sixth embodiment comprising inter alia a visual field mapping (VM) unit  101 , an autorefractor unit (AR)  103  and a target fixation (TF)  ———  and auto-tracking (AT) unit  107 .  
         [0067]     The VM unit  101  comprises a light beam projector unit  109  and concave reflector  110 . As in the embodiments explained above, the projector  109  generates a beam of light  112  (a, b indicating to exemplary paths of beam  112 ), which is directed to reflector  110 . Reflector  110  deflects the beam  112  into eye  30 . More specifically, the beam  112  has to pass as exactly as possible the center  23  of the lens of the eye  30  so that the site  113  (a, b corresponding to light path  112   a  resp  112   b ) where the beam hits the retina is known. If the retina is light sensitive at this site, the patient sees a light disk and confirms by pressing a button or by answering. As mentioned, with an additional unit for observing the iris of eye  30 , an automatic detection if the light beam hits a light sensitive site of the retina is achieved: If the beam  112  is switched on and is seen, the iris will adapt to the increased brightness by closing, resp. it will open slightly if the beam  112  is switched off or the beam enters a non-sensitive area and vice versa.  
         [0068]     The whole VM unit  101  is rotatable around the z-axis  114  (arrow  115 ), which is identical with the line of sight of eye  30  if the device is perfectly adjusted. From the foregoing it is evident that the VM unit  101  has to centered with respect to the eye  30 , resp. the eye has to kept fixed to the axis of rotation of the VM unit  101  as best as possible. However, a small deviation of the lens of sight of the eye  30  and the thereby created displacement of the actually illuminated site of the retina may be numerically corrected.  
         [0069]     The projector  109  comprises a source  116  of visible light of wavelength λ s  (e.g. a LED), an iris  117  for adjusting the width of beam  112 , a lens  118  for adjusting the beam to the refraction properties of the eye  30  (the beam when hitting the retina should create a disk of constant proportions), a filter  119  for further reducing the spectrum of the light beam  112 , and a movable scanning mirror  120 . The lens  118  is movable as indicated by arrow  122 .  
         [0070]     By the movement of the mirror  120 , the light beam  1129  can be directed to different sites on concave reflector  110 . One extreme point is point  124  from which the beam is reflected exactly along the line of sight of the eye  30 , i.e. the beam hits the retina in its center. The other extreme location on reflector  110  has to be a point from which the beam is directed to a peripheral area of the retina. The distance of this area from the center of the retina is not as well defined. Yet, preferably, it shall at least correspond to the most peripheral zone of the retina which should still be sensitive to light for an eye having a normal or larger area of sight.  
         [0071]     Generally, however, both extreme positions may be chosen according to special conditions. Hence, it may be possible to pass the center of the retina or to choose other values for the peripheral boundary.  
         [0072]     The shape of the concave reflector  110  is calculated such that the beam  112  can be directed into eye  30  as explained above. Accordingly, though apparently about elliptic or parabolic, the shape is neither of both. A reflector of such a peculiar, numerically or analytically determined shape, can be manufactured nowadays with acceptable efforts. Still to be mentioned that is particularly necessary to have the reflector  110  reflect light impinging from a direction significantly different from the z-axis into the z-axis. This allows to keep the projector  109  out of the line of sight of the eye and of the observation lines of other units like autorefractor, TF, AT unit. Furthermore, a specifically adapted shape of reflectors  110  allows as well an optimisation in order to simplify the movement of scanning mirror  120  and/or the relationship between the position of the scanning mirror  120  and the coordinates of the illuminated site of the retina of eye  30 , etc.  
         [0073]     The reflector  110  is further provided with a surface reflective in the extreme only to wavelength λ s  of beam  112 . However, the reflector  110  is transparent in the area  126  about symmetrical to the z-axis, so that it is possible to examine and observe eye  30  through the reflector  110 .  
         [0074]      FIG. 10  shows additionally a vision unit  128 , the TF unit  105  and part of AR and AT unit. Actuator  130  serves to rotate the VM unit  101  on the z-axis  114 . The angular actuator  130  is coupled to the carrier  129  by e.g. toothed-wheel gearing  133 . Actuator  131  moves the scanning mirrors  120 . In comparison with  FIG. 7  the beam generator (light source  116  up to filter  119 ) produce a beam which is deflected by an auxiliary mirror  132 . This layout yields a more compact unit.  
         [0075]     Still to mention that mirror  110  is only an angular segment, i.e. has the general shape of a two-dimensionally bent strip. Depending on the shape of the impinging beam, it may also be possible to use a one-dimensionally bent strip.  
         [0076]     Hence, by rotating the whole VM unit  101  over at least 360°, the angular position of the illuminated spot on the retina of eye  30  is determined, and by moving the scanning mirror  120 , the radial position, i.e. the distance to the center of the retina.  
         [0077]     The vision unit  128  mainly serves to adjust the device as exactly as possible centered before an eye  30 . It comprises a system holder  135  (possibly a PCB), on which a micro-camera  137  provided with an illumination ring  139  is mounted. The line of sight of the vision system  128 , i.e. micro-camera  137 , extends through a splitting mirror  141  and as explained above, through the concave reflector  110 . Splitting mirror  141  is partly (e.g. 50%) transparent to visual light and reflective to IR light used by inter alia AR, AT, and TF unit. It is movable by the auto-tracking x-axis actuator  143  in the x-axis  145  vertical to the z-axis  114 .  
         [0078]     The light coming from the eye  30  and deflected by mirror  141  is deflected by mirror  146  downwards into the y-axis vertical to x-axis  145  and z-axis  114 . Mirror  146  is movable by auto-tracking y-actuator  148  in direction of the y-axis. The auto-tracking actuators  143  and  148  are of a type allowing rapid movements. Preferably they are of a type comprising a movable element kept in equilibrium between two solenoids having opposedly to each other a repellent effect on the moving element.  
         [0079]     A second splitting mirror  147  separates visual light created by the TF unit from the generally invisible IR light of AR and AT unit. The TF unit  105  comprises a target projector  151 , a Badal optic  152  and a TF relay lens  153 . Depending on the results of refractometry (cf. below), the target projector  151  is moved in x-direction in order to keep the target at virtual infinity. Additionally, by moving the target testwise to a distance virtually farer away, e.g. corresponding to a ¼ more hyperopic eye than measured, accommodation of the eye to infinity can be checked. If refractometric measurement yields other values thereafter, the eye has accommodated to the new distance. The process is repeated until constant refractometric values are observed meaning an as perfect as possible accommodation of the eye to infinity. TF unit is moved by the TF actuator  155 .  
         [0080]     In the light path after splitting mirror  147  follows a further splitting dichroic mirror  160  which separates the light of the AR unit  103 , e.g. IR of a first, suitable wavelength, from the IR of another wavelength used by the AT unit  107 .  
         [0081]     The AR unit  103  comprises a double-sided PCB  162 . On its lower side, a light source  163  is arranged. Its light is deflected and bundled by an optical element  164  toward mirror  166 . Mirror  166  redirects the light to polarizing beam-splitter  168 , where the light is again deflected to dichroic mirror  160 .  
         [0082]     The AR light, when reflected by the retina of eye  30  or other reflective elements, travels the same way back up to polarizing beam-splitter  168 . Hence, only light whose polarization has changed or is lost which is the case with light being reflected by the retina which acts as a secondary light source, may pass beam-splitter  168 . Light reflected by other elements mostly retains its polarisation and does not pass.  
         [0083]     After beam-splitter, the light passes a refractor lens  170  and is splitted by semitransparent mirror  172 . A part is deflected to near CCD sensor  174 , the other part passes relay lens  176 , is deflected by mirror  177  and hits far CCD sensor  178 . The signals delivered by the two sensors  174 ,  178  are evaluated by a processor (not shown) and used to determine refraction properties of eye  30  and to adapt to the properties of the eye the system by: 
    moving the AR PCB  162  along axis  180 ;     moving the TF unit by means of actuator  155 ; and     moving lens  153  in the light projector  151 .    
 
         [0087]     The remaining part is the auto-target AT unit  107 . It comprises an AT light source  185 , e.g. an LED emitting IR light of a frequency different from light source  163  of the autorefractor unit. Its light is deflected by partial (e.g. semi-transparent mirror  189  and by mirror  190 . Then it passes mirror  160  which is substantially transparent for this light. On return, the light follows the same path as the emitted light, and a part passes mirror  189 , is deflected by mirror  191  and hits AT sensor  192 . The sensor  192  comprises four sensor elements  194  having each a light sensitive surface which does not need to be further subdivided. A correct, i.e. centered adjustment of the device produces substantially the same illumination of all sensor elements  194 , and a misalignment, e.g. by a rapid movement of the eye, produces differing illumination, hence signal variations. These variations used to energize actuators  143  and  148  to recenter the light paths of TF, AR, and AT unit  105 ,  103 , and  107  respectively. Regarding the VM unit  101 , a movement of the eye produces another illuminated site on the retina which is corrected numerically.  
         [0088]      FIG. 13  shows a patient  195  with the visual field mapping device  196  arranged before his eyes. The correct position is secured by a strap or belt  197  tightened to the head on patient  195 , preferably together with a headrest or the like for securing a fixed distance of the device  196  from the eyes of the patient. The correct position is observed by the image on the screen  198  furnished by the vision unit  28 . The keyboard  199  allows controlling the device by the operator.  
         [0089]     The device further comprises an acceleration or gravity sensor. As  FIG. 13  shows, the device is turned upside down if used for the other eye. The gravity sensor allows to detect automatically if a left or right eye is measured, and besides adapts the image on screen  198  and rearranges the functions of the keys of keyboard  199  accordingly.  
         [0000]     Advantages  
         [0090]     An advantage of the present invention is its ultra-compact size, that is, reducing current visual field instruments from bulky table-top apparatus to an ultra-compact device.  
         [0091]     A further advantage of the present invention is that it is relatively low-cost compared to present expensive instruments, so that affordability makes visual field mapping apparatus available and accessible to large populations in vast geographical regions.  
         [0092]     Still another advantage is that this ultra-compact and battery-powered invention allows the invention to be carried and used almost anywhere.  
         [0093]     Another advantage is that the easy-to-use handheld size enables non-specialists such as internists, family physicians, and paramedicals to perform vision testing for patients with hitherto limited or no access to eye care.  
         [0094]     Other advantages not detailed here will become apparent as the present invention is more fully described in the ensuing pages.  
         [0000]     Operation  
         [0095]     As indicated in the above descriptions and in the Drawings and to wit: The physician or other practitioner asks the patient to look into the invention, and look at the fixation target. The patient is asked to press a pushbutton, held in the patient&#39;s hand, each time the patient perceives a flash of light, all the while looking forward at the fixation target. Sequence of targets and recording and analysis as well as print-out or other display of the data is thenceforth automatic.  
         [0096]     Operation of my invention to detect glaucoma not requiring patient response is entirely automatic. Pupil response is recorded and compared to light ray stimuli objectively and automatically to detect and map scotomas characteristic of glaucoma.  
         [0097]     In a regular patent application, operation will be described in detail using specifications described in these pages.  
         [0000]     Conclusions, Ramifications, and Scope  
         [0098]     Conventional visual field mapping instruments are difficult to use and accessible to only a very small percentage of the world&#39;s population, yet in most of the world eye diseases such as glaucoma are common but undetected and undiagnosed until the patient has irreversible damage to the eye, usually leading to blindness.  
         [0099]     My invention, ultra-compact apparatus and methods for detecting and mapping scotomas characteristic of incipient glaucoma, has the advantages of small handheld size, complete portability, easy use, and low cost. Moreover, operation can be made entirely objective and automatic, not requiring patient response.  
         [0100]     In conclusion, this invention helps make eye care accessible and affordable to large populations in vast geographical regions. Detection and diagnosis of an eye disease such as glaucoma can then be treated with drugs to help arrest the disease and prevent blindness.  
         [0101]     From the description of embodiment given above, numerous variations and alternations are accessible to the one skilled in the art without leaving the scope of protection which is defined solely by the claims. One modifications may be to design the convex reflector  110  as a sequence of plane mirrors. This allows to only stepwise move the beam in radial direction, i.e. only rings of discrete distances from the center of the retina can be scanned. However, construction of this mirror may be less complicate.  
         [0102]     As is mentioned in the introduction, it is further conceivable to have the device contain two mapping units so that two eyes may be mapped without moving and readjusting the device. Evidently, the distance between the two mapping units has to be adjustable in order to adapt the device to the interpupillary distances differing between persons.  
       Glossary  
       [0000]    
       
          AR auto-refractor  
          AT auto-tracking  
          IR Infra-red  
          PCB printed circuit board  
          TF target fixation  
          VM visual field mapping