Abstract:
A portable, integrated, hand-held visual examination apparatus for conducting a photostress test on the retina of the human eye. The apparatus includes, within the housing, a timing mechanism, a flash mechanism and an input device, for activating these mechanisms.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 60/142,965 filed Jul. 12, 1999. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to portable visual examination apparatus and, in particular, to a hand-held instrument for bleaching the macula of the human retina and measuring its recovery time. 
     2. Description of the Prior Art 
     The retina of the human eye consists of several layers, including a layer of nerve cells and fibers and a deeper layer of rods and cones. Cones differ from rods in that the cones provide a human with color and detailed vision, whereas rods differentiate black/white and motion. This layer of rods and cones is the light-sensitive layer. Located in a small central area of the retina is the macula, which houses the higher concentration of cones. Further, within the macula, the highest concentration of cones resides in the fovea. 
     Macular photostress testing is a sensitive method for detecting patients with macular disturbances, such as cystoid macula edema, central serous choroidopathy and senile macular degeneration. These disturbances have been shown to cause a significantly prolonged recovery from photostress. 
     It is well known in the art that exposing the macula of the human retina during an ophthalmoscopic examination to a bright light requires a certain amount of time for the human eye to recover useable visual acuity. This return time is commonly referred to as “recovery” time and varies from individual to individual. In many individuals, an unusually long recovery time is encountered after this photostressing or bleaching. This lengthened recovery time may be an indication of subliminal or developing maculopathy or other retinal disease. A recovery rate longer than normal helps the doctor identify persons at risk for developing macular degeneration or other retinal disease. In addition, a photostress test is particularly helpful in following intra-ocular surgery when cystoid macular edema is suspected. An increase in or lengthy recovery time indicates a maculopathy and helps to rule out other complicating factors, such as irregular astigmatism, early capsular opacification or optic nerve disease. 
     In assessing recovery time, there are various methods for definitively marking the point of re-focus (or recovery). A Snellen Eye Chart or an Amsler grid are two examples of tools used in marking the point of re-focus. A Snellen Eye Chart is a well-known chart consisting of lines of gradually reduced-sized letters. Typical Amsler grids, with focusing improvements, are disclosed in U.S. Pat. No. 5,646,710 to Caskey and U.S. Pat. No. 5,838,422 to Caskey. Further, U.S. Pat. No. 5,139,030 to Seay, Jr. discloses an Amsler grid with an illuminated center to assist the patient in focusing on the center of the grid. A Snellen Eye Chart may be utilized in determining the recovery time between bleaching of the retina to the return of visual acuity. While the Amsler grid may be used to assess recovery time, it is typically used as a screening device to ascertain loss or distortion of central or macular vision. 
     A flash unit, a timer and a focusing device have been previously combined together to create a visual examination apparatus for testing for macular degeneration. For example, U.S. Pat. No. 4,545,658 to Weiss discloses the use of such a combination for administering the photostress recovery test. However, the disadvantage of the Weiss apparatus is its requirement to be housed in a large, non-portable cabinet. While this cabinet-enclosed photostress instrument assists in normalizing the photostress procedure and simplifying the focusing process, the overall unit is large, cumbersome and is burdened with a split imaging mirror. In addition, such an instrument requires standalone optotype slides and continual administrative interaction. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide a portable, hand-held combined photostress testing apparatus that is easy and inexpensive in its manufacture. It is another object of the present invention to provide an apparatus that can be mass-distributed for use in both clinical and research situations. It is a further object of the present invention to provide an apparatus that is standardized to assist in advancing the art and determining retinal diseases. 
     The present invention is a hand-held, portable photostress visual examination device including a housing or body, which contains a controllable flash unit, a controllable timing unit, an optional back-lighting unit for an optotype chart, a controllable power source and electronic circuitry associated with these units. Connected to the housing may be an on/off switch, simultaneous flash and timer switch, a timer stop switch, a visual timing display for the timing unit and the recovery chart. Further, an Amsler or other grid may be provided on the body as an auxiliary tool. The recovery chart can be a Snellen Eye Chart or any suitable optotype chart for assessing an eye&#39;s return to a state of visual acuity. In addition, a color discrimination or contrast sensitivity test can be used. A measuring unit, such as retractable tape or string, may be attached to the top of the housing, allowing the examiner to quickly and accurately measure the appropriate distance between the device and the eye. 
     To use the invention, one of the patient&#39;s eyes is occluded and the patient reads, at a standard reading distance of 13-16 inches, the smallest definable line on the optotype chart on the face of the housing, using the patient&#39;s best optical reading correction. The measurement is recorded in near point Snellen or other standard ophthalmic terms. The patient&#39;s optical reading correction is removed, if such correction was required. The invention is moved to a closer, standardized distance from the non-occluded eye, using the measuring device, e.g., the retractable tape or string. The patient then gazes at the center of the flash unit, as viewed from the front side of the device. Next, the simultaneous flash and timer button is actuated, flashing the flash unit and starting the timing unit. Once “flashed”, the patient replaces any spectacle correction and attempts to read the line of optotypes immediately above the initially read line at the original reading distance. When the line of optotypes immediately above the initially read line is readable, the timer stop button is actuated, the timing unit ceases and the examiner reads the time from the visual timing display. 
     These and other advantages of the present invention will be clarified in the brief description of the preferred embodiments taken together with the attached figures wherein like reference numerals represent like elements throughout. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a front view of a hand-held visual examination device according to the present invention; 
     FIG. 2 shows a block diagram of the device shown in FIG. 1 illustrating the internal components and flow of the internal components of the device; and 
     FIG. 3 shows a front view of a second embodiment of a hand-held visual examination device according to the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention is a portable, integrated, hand-held visual examination device  10  and method of using the apparatus for detecting macular degeneration and other retinal diseases. As seen in FIG. 1, the device  10  of the present invention includes a housing  12  or body, which houses the internal components of the device  10 . Attached to the housing  12  is a simultaneous flash and timer switch  14 . Also attached to the housing  12  is a timer stop switch  16 . On the face of the device  10  is a flash unit screen  18 , an Amsler or other grid  20 , an optotype chart  22  (such as a Snellen Eye Chart) and a timer visual display  24 . Further, a measurement unit in the form of a retractable tape or string mechanism  26  can be mounted on or within the housing  12 , with a tape or string outlet  28  allowing a certain length of tape or string to be pulled from the outlet  28  and retracted back into the retractable tape or string mechanism  26 . This retractable tape or string mechanism  26 , is integral with (either attached to or within) the housing  12 , as shown in FIGS. 1 and 3. In addition, an on/off switch  30  is located on the housing  12 . While FIG. 1 shows one typical arrangement of the parts as attached to the housing  12 , it should be appreciated by one skilled in the art that various arrangements of the components are equally functional. 
     Turning to the internal components of the device  10 , FIG. 2 schematically illustrates the connection, flow and operation of the various components. The device  10  is powered by power source  32 , which communicates through a power controller  34 , producing a power output  80 . The power controller  34  communicates with the central logic controller  36 . This logic controller  36  controls the electronic and internal aspects of the device  10  and may be discrete logic devices or a ROM-based microcontroller. The logic controller  36  receives the power source status  38  from the power controller  34  and returns a “turn off” signal  40 , if required. The power output  80  is delivered to the various components that require power via a power input  42 . When the operator activates the on/off switch  30 , a “turn on” signal  78  is sent to the power controller  34 . It is also envisioned that different power controllers  34 , such as logic-controlled voltage regulators, may be used. While the logic controller  36  may always be on, as when not being used, the logic controller  36  enters a “sleep mode”, using a very low current. 
     A flash lamp  44  is connected with and in communication with a flash controller unit  46 , which includes a current converter  48 , a charge switch  50 , a trigger switch  52 , a trigger transformer  54 , a discharge switch  56 , and a storage capacitor  82 . Overall, the flash controller unit  46  communicates with the flash lamp  44  via an anode  58 , a cathode  60  and a flash trigger  62 . The logic controller  36  interfaces with the flash controller  46  (and its various components), transmitting and receiving a charge signal  64 , a trigger signal  66 , a discharge signal  68  and a trigger ready signal  70 . Also communicating with the logic controller  36  is the timer visual display  24 , which may be static or dynamic. The logic controller  36 , which interfaces with, or is integral with, a timing mechanism  76 , transmits a status/time data signal  72  to the timer visual display  24 . Finally, the logic controller  36  may control a back-lighting unit  74 , which, in turn, provides a light source that is transmitted through or around the Amsler grid  20  and/or the optotype chart  22 , allowing the patient to easily view the Amsler grid  20  and/or optotype chart  22  in darkened conditions. Overall, a centrally-controlled and internally communicating circuit is contained in the housing  12 . 
     The simultaneous flash and timer switch  14  and the timer stop switch  16  both interact, via the logic controller  36 , with the internal components of the device  10 . The simultaneous flash and timer switch  14 , when actuated, discharges dazzling light, via the flash lamp  44 , and begins a timing mechanism  76 , which is either part of or external to the logic controller  36 . A second control, the timer stop switch  16  both stops the timing mechanism  76 , allowing the operator to read the timer visual display  24 , and resets the timing mechanism  76  and timer visual display  24  with a second actuation. The on/off switch  30  allows the operator to sequence through the operations of device  10  to completion of the test on the patient. While the on/off switch  30  of the present invention  10  is a single-position-single throw, momentary closed push-button, used in controlling the device  10 , any suitable switch or control is envisioned. It is also envisioned that one switch may be utilized to control some or all of the on/off function, the flash function, the timer begin function, the timer stop function, and the timer reset function. In a second embodiment, the simultaneous flash and timer switch  14  and the timer stop switch  16  are controlled through one multi-purpose switch  84  or button, as shown in FIG.  3 . In this embodiment, all three functions are controlled by the multi-purpose switch  84 , which communicates directly with the logic controller  36 . 
     The logic controller  36  controls the sequencing of the operation of device  10 , and, further, controls or is integral with the timing mechanism  76  that measures the patient response. The logic controller  36  can be the decoded logic source or provide logic output to a dedicated controller that will control the timer visual display  24 . The timer visual display  24  may be a liquid crystal display or any suitable display type. Additionally, the logic controller  36  controls the charging, firing and safety discharge of the flash lamp  44 , and can also be used to monitor the electronic health of the device  10  and control and monitor the power to the device  10 . If, after a predetermined time, the logic controller  36  senses no function initiated by the operator, the logic controller  36  can discharge the flash lamp  44 , if needed, depending on the type of flash lamp  44  utilized, and turn the overall device  10  power off. 
     Device  10  may use a linear xenon flash tube, or any suitable substitute, together with a suitable reflector to generate a spectrally distributed flash of light of an intensity sufficient to stress the macula of the patient, projecting out to the patient through a flash unit screen  18 . Other light sources are envisioned, including an incandescent light or a light emitting diode. The light source can be comprised of a device that utilizes the photons that result from the transition of electrons from a higher energy state to a lower energy state as a result of exciting a suitable molecular or atomic structure. In using the linear xenon flash tube, the logic controller  36  sends a charge signal  24  to the flash controller unit  46 , which has a storage capacitor  82 . The flash controller unit  46  also triggers the flash lamp  44  at the command of the operator. The logic controller  36  may also be used to monitor the state of charge of the storage capacitor  82  and provide an indication to the operator when there is sufficient energy available to trigger the flash lamp  44 . Further, the logic controller  36  may be used to prevent triggering of the flash lamp  44  until a required energy level is reached. The logic controller  36  could also communicate with a circuit which would allow the logic controller  36  to discharge the storage capacitor  82  if the time after the last operator-controlled function exceeded a predetermined time. 
     The logic controller  36  can disable power to the device  10  if there is no operator-initiated control after a predetermined time (i.e., five minutes of non-use). Also, the logic controller  36  can be used to indicate to the operator that the power source  32  is not sufficiently energized for operation of the device  10 , or that the power source  32  is near a point of energy depletion. The power source  32  may be batteries, direct connection to external power, rechargeable batteries, or other well-known power sources. 
     Turning to the method of using the present invention  10 , the device  10  is turned on via the on/off switch  30 . Once activated, and if so desired, the backlighting unit  74  illuminates the Amsler grid  20  and the optotype chart  22  from within the device  10 . When the flash controller unit  46 , communicating with the logic controller  36 , displays, communicates or otherwise indicates to the operator that the device  10  is ready for use, the operator engages the patient. 
     One of the patient&#39;s eyes is occluded, and the patient is asked to read the smallest line that the patient finds definable on the optotype chart  22 . This step is completed while the patient continues wearing his or her adequate reading correction, if required. In addition, the optotype chart  22  is read at a typical reading distance, i.e., approximately 13-16 inches. The operator may use the retractable tape or string mechanism  26  to measure the distance from the device  10  to the patient; pulling out the tape to measure from the tip of the device  10  to the middle of the patient&#39;s eyes. The line that the patient is able to read is recorded in near point Snellen or any other standard ophthalmic terms. 
     Next, the patient removes his or her optical reading correction, if required. The device  10  is moved to approximately six inches, or another standardized distance, from the non-occluded eye, again using the retractable tape or string mechanism  26 . The operator then instructs the patient to gaze to the center of the flash unit screen  18 , and the operator then actuates the simultaneous flash and timer switch  14 , discharging the flash lamp  44  and starting the timing mechanism  76 , as indicated on the timer visual display  24 . The patient is then instructed to replace any optical reading correction. 
     The device  10  is then placed back at its original “reading” distance, as measured by using the retractable tape or string mechanism  26 . The patient&#39;s dazzled eye begins recovery, and the patient is directed to attempt to read the line immediately above the initially-read line of optotypes on the optotype chart  22 . For example, if the patient read the 20/25 line on the optotype chart  22 , the subject is now directed to focus on and attempt to read the 20/30 line on the optotype chart  22 . When the patient is able to read the line, the operator actuates the timer stop switch  16 , which stops the timing mechanism  76  and displays the recorded time on the timer visual display  24 . The timer stop switch  16  is depressed again, resetting the timing mechanism  76  and clearing the timer visual display  24 . The process is then repeated with the other formerly occluded eye. 
     Overall, the present invention  10  provides a portable, hand-held photostress testing apparatus that is elementary in operation and inexpensive in construction. Further, the present invention  10  is of the size and cost so as to allow for mass distribution to doctors, operators, acadamiens, and other parties in both clinical and research settings. Through such standardization and distribution of the present invention  10 , it is anticipated that great strides in retinal disease studies may be made through the collection and study of the data received from the widespread use of the device  10 . In addition, the portability and ease of use of the present invention  10 , coupled with its inexpensive manufacture and standalone capabilities, will assist in advancing the art in the areas of macular degeneration and other diagnosable retinal disorders. Use of this device  10  will allow the doctor to detect and forewarn patients with a tendency to maculopathy. 
     The invention itself, both as to its construction and its method of operation, together with the additional objects and advantages thereof, will best be understood from the previous description of specific embodiments when read in connection with the accompanying drawings. It will be evident to those of ordinary skill in the art that various changes and modifications may be made to the present invention without departing from the spirit and scope thereof. For example, the portable housing may be formed with a table supported base and flip-top display similar to a laptop computer design. The specific embodiment described is intended to be illustrative of, and not restrictive of, the present invention. The present invention is defined by the appended claims and equivalents thereto.