Abstract:
A slit lamp includes a rest for receiving a patient&#39;s face such as the patient&#39;s forehead. The slit lamp further includes an optical portion for observing the patient&#39;s eye. A fixation light is positioned near the optical portion to direct the patient&#39;s view toward the optical portion. A sensor secures to the rest and detects proximity of the user&#39;s face to the rest. The output of the sensor controls the fixation light such that the fixation light is turned on upon detecting the positioning of the user&#39;s face at the rest. In one embodiment, a shield secures to the optical portion and first and second fixation lights secure to the shield at either side of the optical portion. First and second flanges secure to the shield proximate the fixation lights and such that each fixation light is only viewable when directly in front of the patient&#39;s eye.

Description:
PRIORITY CLAIM 
   This application is a continuation of U.S. application Ser. No. 11/365,572 filed Mar. 1, 2006, Now U.S. Pat. No. 7,377,644 B2 which claims the benefit of U.S. Provisional Application Ser. No. 60/748,445 filed Dec. 8, 2005 and entitled THE SLIT LAMP FIXATION ALARM. 

   FIELD OF THE INVENTION 
   This invention relates generally to slit lamps for observing ocular features and, more particularly to fixation lights for slit lamps. 
   BACKGROUND OF THE INVENTION 
   The slit lamp is an instrument used in eye care that provides an illuminated and magnified view of a patient&#39;s eye. The slit lamp typically includes a light projected through a slit to allow for observation of optical cross sections of the eye using an optical portion. The light is typically mounted on an articulated arm that is adjustable for observation of different portions of the eye. During examination, the patient&#39;s face is positioned against chin and forehead rests. While one eye is being examined by the optical portion, the patient is instructed to focus the other eye on a fixation light such that the examined eye is properly oriented. A small shield secures to the slit lamp and protects the examiner from coughs and sneezes, though in prior systems the shield is much too small to be effective. 
   In prior systems, the fixation light is a single light mounted on an arm that is attached to the portion of the slit lamp bearing the chin and forehead rests. The examiner is required to move the fixation light from one side of the slit lamp to the other when examining both eyes. When moving the optical portion from focusing on one eye to the other, the fixation light and its mounting arm tend to cause obstruction. Furthermore, since the fixation light is constantly being moved between eyes, the mechanisms enabling articulation of its mounting arm become worn, resulting in drift of the fixation light. In prior system the fixation light is positioned close to the patient&#39;s eye such that bumping of the light or its mounting arm can cause injury to the patient. The mounting arm is typically movable to a storage position to the side of the slit lamp. However, the fixation light and its mounting arm are still an obstacle to movement of the optical portion and the examiner&#39;s hand. 
   Further complications during examination of a patient using a slit lamp occur as the patient&#39;s face moves. It is typical for a patient to move the forehead away from the forehead rest. As a result, the examiner must “chase” the eye. As the patient moves away the eye also moves out of the range of focus of the slit lamp. As a result, the examiner typically must frequently remind the patient to stay forward against the forehead rest. 
   In view of the foregoing it would be an advancement in the art to provide a slit lamp facilitating the convenient non-obstructive positioning of a fixation light. It would be a further advancement in the art to provide a convenient means for maintaining a patient&#39;s forehead against a forehead rest during examination. 
   SUMMARY OF THE INVENTION 
   A slit lamp includes a rest for receiving a portion of a patient&#39;s face, such as the patient&#39;s forehead. The slit lamp further includes an optical portion for observing the patient&#39;s eye. A fixation light is positioned near the optical portion to direct the patient&#39;s line of sight toward the optical portion. A sensor, such as a touch sensor, secures to the rest and detects proximity of the user&#39;s face to the rest. The output of the sensor controls the fixation light such that the fixation light is turned on upon detecting the positioning of the user&#39;s face at the rest. When the patient moves away from the rest, the fixation light is turned off, indicating to the patient to return to the rest. In some embodiments, the sensor is coupled to a wireless transmitter configured to transmit signals corresponding to the output of the transmitter to a receiver controlling the light. 
   In some embodiments a shield secures to the optical portion and first and second fixation lights secure to the shield at either side of the optical portion. First and second flanges secure to the shield and extend from the shield toward the rest. The first shade positioned proximate the first fixation light between the first fixation light and the optical device and the second shade positioned proximate the second fixation light between the second fixation light and the optical device. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Preferred and alternative embodiments of the present invention are described in detail below with reference to the following drawings. 
       FIG. 1  is a perspective view of a slit lamp in accordance with an embodiment of the present invention; 
       FIG. 2  is a perspective view of a sensor for use in a slit lamp forehead rest in accordance with an embodiment of the present invention; 
       FIG. 3  is a process flow diagram of a method for using a slit lamp in accordance with an embodiment of the present invention; 
       FIG. 4  is a perspective view of a shield in accordance with an embodiment of the present invention; 
       FIG. 5  is a perspective view of a fixation light in accordance with an embodiment of the present invention; and 
       FIG. 6  is a top plan view of a slit lamp examining a patient&#39;s eyes in accordance with an embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring to  FIG. 1 , a slit lamp  10  includes an optical portion  12  housing optical structures such as magnification lenses. The optical portion  12  is mounted to a base  14  facilitating movement of the optical portion  12  relative to a patient to enable examination of both eyes and different portions of the eye. A chin rest  16  and forehead rest  18  secure to a frame  20  and receive the face of a patient during examination. In the preferred embodiment, a forehead sensor device  22  may mount to the forehead rest  18  to facilitate sensing the proximity of the forehead to the forehead rest. A shield  24  secures to the slit lamp  10  between the examiner and the patient. In the illustrated embodiment, the shield  24  secures near the eye pieces  26  of the optical portion  12 . 
   One or more fixation lights  28   a ,  28   b  secure to the slit lamp  10  in positions to enable the lights  28   a ,  28   b  to project light into one of a patient&#39;s eyes while the other eye is being examined. In the illustrated embodiment, the fixation lights  28   a ,  28   b  secure to the shield  24  on opposite sides of the optical portion  12 . 
   Referring to  FIG. 2 , while still referring to  FIG. 1 , the forehead sensor device  22  includes a sensor  30  used to detect proximity of the patient&#39;s forehead to the forehead rest  18 . The sensor  30  may detect proximity of the patient&#39;s forehead in a variety of ways, for example, optically, thermally, or by detecting contact of the patient&#39;s forehead with the forehead rest, e.g., via a capacitance touch sensor. The sensor  30  may include membrane switches, small mechanical switches or motion sensing switches. The sensor  30  of the forehead sensor device  22  may mount to the forehead rest  18  at the point where the forehead rest  18  secures to the frame  20  or to another portion of the slit lamp  10 . For example, the sensor  30  may detect strain in the frame  20  to determine whether the patient has pressed the forehead against the forehead rest  18 . 
   In the illustrated embodiment, the sensor  30  is a touch sensor secured within a laminate  32  or like structure that secures to the forehead rest  18 . The sensor  30  may produce an output in response to the touch thereon or produce an output indicating proximity of the forehead when the pressure exerted thereon exceeds a predetermined threshold. The laminate  32  may have an adhesive backing  34  adhering the laminate  32  to the forehead rest  18 . A protective layer  36  may cover the adhesive backing  34  prior to securement to the forehead rest  18 . 
   In certain embodiments of the invention, the output of the sensor  30  controls power to the fixation lights  28   a ,  28   b  such that the lights  28   a ,  28   b  turn on when the patient&#39;s forehead is sufficiently close to the forehead rest  18 . The sensor  30  may connect to the lights  28   a ,  28   b  through a wire or a wireless communication channel. In alternative embodiments, the output of the sensor  30  is used to control an audible, tactile or optical indicator or alarm that is turned on when the patient moves away from the forehead rest  18  in order to notify the patient of the need to return to the forehead rest  18 . For example, a buzzer audible to the patient or a vibrating device in contact with the patient may be used. In such embodiments, the indicator may be configured to turn off when the patient returns to the forehead rest  18 . 
   In still other embodiments, a sensor (not shown) is mounted on or near the chin rest  16  such that the fixation lights  28   a ,  28   b  are turned on only when the patient&#39;s chin is within the chin rest and the patient&#39;s forehead is against the forehead rest. In certain embodiments, separate indicators are coupled to the sensor  30  and the sensor mounted to the chin rest. For example, contact of the patient&#39;s forehead may trigger turning on of the fixation lights  28   a ,  28   b  whereas lack of contact of the patient&#39;s chin with the chin rest triggers and audible, tactile or optical alarm. 
   In the illustrated embodiment, the sensor  30  is electrically coupled to a transmitter  40  transmitting signals causing the fixation lights  28   a ,  28   b  to turn on or off in correspondence with proximity of the patient&#39;s forehead to the forehead rest  18 . The transmitter  40  may transmit infrared, optical, radio frequency, acoustic or like signals. The output of the sensor  30  may be conducted to the transmitter  40  by means of a wire  42  coupled thereto. The output of the sensor  30  may be processed by a sensor circuit  44  and the output of the sensor circuit  44  provided to the transmitter. The sensor circuit  44  may condition the output of the sensor  30 , interpret the output of the sensor to determine whether the fixation lights  28   a ,  28   b  should be turned on or off, or both condition and interpret the output. The transmitter  40  and sensor circuit  44  may mount within a housing  46  secured to the frame  20  by means of clips  48  or the like. The housing  46  may also contain a battery  50  or other power source powering the transmitter and sensor circuit  44 . In an alternative embodiment, in order to conserve power life, a microprocessor (not shown) may be used to regulate power consumption. A switch  52  may secure to the housing and be used to turn off the transmitter  40  and sensor circuit when the slit lamp  10  is not in use or when the functionality of the transmitter  40  is not needed. 
     FIG. 3  describes a method for using the slit lamp  10  in accordance with one embodiment of the present invention. At block  56 , a patient is instructed to look at one of the fixation light  28   a ,  28   b  with the eye that is not being examined and to maintain the forehead against the forehead rest  18  such that the fixation lights  28   a ,  28   b  remains on. At block  58 , the patient&#39;s face is positioned such that the patient&#39;s forehead is against the forehead rest  18  and the patient&#39;s chin is on the chin rest  16 . At block  60 , the proximity sensors sense the proximity of the patient&#39;s face to the forehead rest  18 . If the proximity sensors determine that the patient&#39;s face is proximate, at block  62 , the fixation lights  28   a ,  28   b  are illuminated. At block  64 , the proximity sensors again sense the proximity of the patient&#39;s face from the forehead rest  18 . If the proximity sensors determine that the patient&#39;s face is no proximate, at block  66  the fixation lights  28   a ,  28   b  are turned off. 
   Referring to  FIG. 4 , the shield  24  may be embodied in any number of shapes such as a square or rectangular sheet and may be formed of PLEXIGLAS or like material. The shield  24  may have an aperture  68 , slot  68 , or like structure formed therein and sized to receive a portion of the optical portion  12  of the slit lamp  10 . In the illustrated embodiment, the aperture  68  is sized to secure to the optical portion  12  behind the eye pieces  26 . Fasteners  70 , such as set screws or the like, secure to the shield  24  proximate the aperture and fix the position of the shield  24  relative to the optical portion  12 . Fasteners  70  may also be embodied as VELCRO, adhesives, ring clamps, vise like attachments or the like. There are various types of slit lamps  12  having differently sized optical portions. Accordingly, the shield  24  may be formed of two or more pieces that are movable relative to one another and securable to one another in various configurations around the optical portion  12 . Alternatively, the aperture  68  may be shaped and sized to receive most optical portions  12  and have fasteners  70  sufficiently adjustable to accommodate different optical portions  12 . For example, VELCRO straps of adjustable length may be used. 
   Referring to  FIG. 5 , while still referring to  FIG. 4 , the fixation lights  28   a ,  28   b  may secure to the slit lamp  10  by various means including fixed or articulated arms secured to the slit lamp  10 . In the illustrated embodiment, the fixation lights  28   a ,  28   b  secure to the shield  24  on either side of the aperture  68 . The fixation lights  28   a ,  28   b  may include a light housing  72  having a light source  74  such as an LED, incandescent lamp or the like. A receiver  76  is coupled to the light source  74  and to a battery  78 . The receiver  76  receives signals from the transmitter  40  and permits electrical power from the battery  78  or other power source to reach the light source when the signals indicate that the patient has properly positioned the forehead against the forehead rest  18 . In an alternative embodiment, in order to conserve power life, a microprocessor (not shown) may be used to regulate power consumption. 
   A magnet  80  secured to the housing  72  and engages an opposing magnet  82 , preferably formed in a handle  84 . The handle  84  is positioned opposite the shield  24  from the housing  72 . In this embodiment, the attraction of the magnets  80 ,  82  maintains the housing and handles  84  in position. The handle  84  may be gripped by the examiner to move both the handle  84  and housing  72  in order to position the light source  74  relative to the eye of the patient. 
   Referring to  FIG. 6 , while still referring to  FIG. 5 , a flange  86  extends outwardly from the housing  72  to shield the light source  74  from view from certain angles in order to avoid confusing the patient being examined. For example, the fixation light  28   b  may have a flange  86  positioned between its light source  74  and the optical portion  12  whereas the fixation light  28   a  has a flange  86  positioned between its light source  74  and the optical portion  12 . In use, a patient&#39;s first eye  88   a  is positioned lying on the optical axis  90  of the optical portion  12  such that the eye  88   a  can be observed through the slit lamp. The patient&#39;s second eye  88   b  is positioned as illustrated such that light from the fixation light  28   a  is visible along the direct line of sight  92   a  of the second eye  88   b . However, along peripheral line of sight  94 , the fixation light  28   b  is not visible due to the flange  86  thereof. The flanges  86  of both fixation lights  28   a ,  28   b  shield the eye  88   a  being examined from the light sources  74 . When the second eye  88   b  is being examined the flanges  86  likewise shield the second eye  88   b  from the light sources  74  while permitting the first eye  88   a  to observe the fixation light  28   b.    
   Various alternative means of preventing a patient from viewing the incorrect fixation light  28   a ,  28   b  are possible. The fixation lights  28   a ,  28   b  may be positioned relative to the optical portion  12  such that the body of the optical portion  12  prevents viewing. One of the fixation lights  28   a ,  28   b  may be switched off manually or automatically by electrical or mechanical means when it is not needed. An LED with a small viewing angle may be used to prevent off-axis viewing. In an alternative embodiment, a Fresnel lens preventing off-axis viewing may be used. The fixation lights  28   a ,  28   b  may have different colors or shapes such that the patient can be instructed which light  28   a ,  28   b  to look at with the unexamined eye. 
   While the preferred embodiment of the invention has been illustrated and described, as noted above, many changes can be made without departing from the spirit and scope of the invention. Accordingly, the scope of the invention is not limited by the disclosure of the preferred embodiment. Instead, the invention should be determined entirely by reference to the claims that follow.