Abstract:
A viewing device usable by a surgeon to make an accurate corneal mark during an eye surgery procedure may be a face or head-mounted device to free the surgeon&#39;s hands. The device incorporates a light producing apparatus, such as an LED, that may be positioned to be coaxial or otherwise substantially co-aligned with a line-of-sight of the surgeon&#39;s dominant eye, and thus match the patient&#39;s line of sight with the surgeon&#39;s line of sight. The device include polarizing filters that cooperate with the light to minimize or even eliminate parallax viewing of a corneal light reflex by the surgeon&#39;s non-dominant or other eye. Further, the device may also include magnification lenses to enhance the view of the eye as seen by the surgeon.

Description:
PRIORITY CLAIM 
     This application claims the benefit of U.S. Provisional Application No. 61/211,271 filed Mar. 28, 2009, the subject matter of which is incorporated herein in its entirety. 
    
    
     FIELD OF THE INVENTION 
     This invention relates generally to a viewing device that minimizes parallax and, more specifically, to a head mountable viewing device that minimizes parallax to permit marking of a cornea. 
     BACKGROUND OF THE INVENTION 
     The surgical correction of astigmatism has become a common part of cataract surgery. Astigmatic intraocular lenses (IOL) and limbal relaxing incisions (LRI) are the most common methods used in conjunction with cataract surgery to correct the astigmatic error. Before the astigmatic error can be surgically corrected, the surgeon or assistant must mark the cornea to designate the horizontal and vertical axis, or preferably, the astigmatic axis, while the patient is sitting, since the patient&#39;s eye rotates slightly when the patient is lying down. Marking the cornea using the corneal light reflex and a gravity assisted astigmatic marker has been described in U.S. Provisional Patent Application No. 61/072,758, the subject matter of which is incorporated herein by reference in its entirety. Because most of the ophthalmic instrumentation for measuring the astigmatic error uses the light reflex, there are theoretical benefits to using the corneal light reflex to mark the cornea for the correction of the astigmatic error. 
     Using the corneal light reflex to mark the cornea, however presents several challenges. The light reflex on the cornea is actually quite small and dim. Consequently, it can be difficult for the surgeon or assistant to see it. This problem may be exacerbated if the surgeon is presbyopic. One known solution to this problem was recently developed by Mastel Precision out of South Dakota. The solution includes attaching a fixation light to a surgical magnifier worn by the surgeon. The fixation light facilitates marking the cornea when used with the gravity assisted astigmatic marker. Additionally, this solution frees the surgeon&#39;s hands so that an assistant is not needed to hold the patient&#39;s eyelids when the marks are being made. 
     SUMMARY OF THE INVENTION 
     At least one embodiment of the present invention is a viewing device that may be used by a surgeon or surgeon&#39;s assistant, for example, to make an accurate corneal mark during an eye surgery procedure. For purposes of this description, the term surgeon will be used, but it is appreciated that the device may be usable by a variety of persons to accomplish the same or similar tasks. The device may be a head-mounted device (e.g., head strap or eye glasses) to free the surgeon&#39;s hands, which in turn allows that person to hold the marking instrument and the patient&#39;s eyelids without the assistance of another person. The device incorporates a fixation light that may be positioned to be coaxial or otherwise co-aligned with a line-of-sight of the surgeon&#39;s dominant eye, and thus match the patient&#39;s line of sight with the surgeon&#39;s line of sight. The device include polarizing filters that cooperate with the fixation light to minimize or even eliminate parallax viewing of a corneal light reflex by the surgeon&#39;s non-dominant or other eye. Further, the device may also include magnification lenses to enhance the view of the eye as seen by the surgeon. 
     In one aspect of the present invention, an apparatus for marking a cornea of a patient&#39;s eye includes a first polarizing filter positioned in a line-of-sight of a first eye of a person prepared to mark the cornea; a light producing apparatus positioned on a first side of the first polarizing filter, the light producing apparatus adjustable to direct light through the first polarizing filter in a desired direction, the directed light becoming a polarized light after passing through the first polarizing filter; and a second polarizing filter positioned in a light line-of-sight of a second eye of the person prepared to mark the cornea, the second polarizing filter configured to substantially block the polarized light reflected from the cornea. 
     In another aspect of the present invention, a method for marking a cornea of a patient&#39;s eye includes the steps of (1) adjusting a direction of a light generated by a light producing apparatus to be in a desired direction, the light producing apparatus coupled to a head mounted viewing device worn by a person prepared to mark the cornea; (2) polarizing the light with a first polarizing filter coupled to the head mounted viewing device; (3) reflecting at least some of the polarized light from the patient&#39;s eye; (4) receiving the reflected, polarized light through a second polarizing filter coupled to the head mounted viewing device; and (5) marking a cornea of the patient&#39;s eye for purposes of making a surgical incision. 
     In another aspect of the present invention, a viewing device includes an adjustable head mountable assembly; two polarizing filters positioned adjacent one another, the filters coupled to the head mountable assembly; and a light producing apparatus coupled to the head mountable assembly, the light producing apparatus adjustable to direct light through a first polarizing filter in a desired direction, the directed light becoming a polarized light after passing through the first polarizing filter. Further, the first polarizing filter includes a polarization different than the second polarizing filter such that the polarized light is substantially blocked from travelling through the second polarizing filter after reflecting off of an object. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Preferred and alternative examples of the present invention are described in detail below with reference to the following drawings: 
         FIG. 1  is a perspective view of a viewing device having a light producing apparatus and a pair of polarizing filters in accordance with an embodiment of the present invention; 
         FIG. 2  is a schematic view showing an operation of the viewing device of  FIG. 1  in accordance with an embodiment of the present invention; and 
         FIG. 3  is a schematic view showing an operation of the viewing device of  FIG. 1  in accordance with an alternative embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     As discussed above, attaching a fixation light to a surgical magnifier worn by a surgeon to facilitate marking a cornea with a gravity-assisted astigmatic marker falls short of solving some other problems associated with corneal marking. For example, if the fixation light is attached in the center of the surgical magnifier, it would not be coaxial or substantially co-aligned with either of the surgeon&#39;s eyes. In turn, this may introduce error in that the optical axis of the patient is not aligned with the line-of-sight of the surgeon. Moreover, the surgical magnifier does not minimize the issue of parallax, which is generally defined as an apparent change in the direction of an object, caused by a change in observational position that provides a new line of sight. Accordingly, if the surgeon uses both of his eyes to focus on the corneal light reflex, the surgeon would see two marking instruments. But, if the surgeon focuses on the marking instrument then the surgeon would see two light reflexes. Either situation results in confusing images, which reduces the accuracy of the corneal marks. If the surgeon closes one eye to “sight the light reflex” with the marking instrument, the surgeon loses stereopsis, which then makes it difficult to judge how far the marker is from the cornea. 
       FIG. 1  shows a viewing device  100  having an adjustable head strap  102  and lens mounting assembly  104  pivotally coupled with a pin  106  to the head strap  102  according to an embodiment of the present invention. A light producing apparatus  108 , which may take the form of a light emitting diode (LED), is coupled and slidably movable relative to the lens mounting assembly  104 . A pair of polarizing filters  110  extends from the lens mounting assembly  104  such that they are positioned in a line-of-sight of a wearer. In addition, the viewing device  100  may include one or more magnifying lenses  112  positioned behind the light producing apparatus  108 . A battery compartment  114  and an ON/OFF switch  116  for the light producing apparatus  108  may be incorporated into a housing  118  of the lens mounting assembly  104 . 
     Polarization is a property of light waves that describes an orientation of their oscillations. The polarizing filters  110  preferably cooperate with one another such that one of them (e.g., a right filter  110   a ) blocks nearly all light of one polarization while the other (e.g., a left filter  110   b ) passes nearly all light of an orthogonal or perpendicular (i.e., right angles) polarization. In an alternative embodiment, other types of polarization, for example, circular polarization, may be used. For purposes of the description herein, polarized light may include fully polarized light, which is light having each and every wave crest oriented in the same direction, but more accurately includes partially polarized light in which one polarization predominates. It is appreciated that even with orthogonally oriented polarizing filters that all polarizations are typically present to some degree. 
     In the illustrated embodiment, the right polarizing filter  110   a  and the left polarizing filter  110   b  have opposite or orthogonal polarizations. Stated otherwise, the direction of polarization of the right side polarizing filter  110   a  is oriented at ninety degrees from the direction of polarization of the left side polarizing filter  110   b  (e.g., the orientation of the right side is 90 degrees while the left side is 0 degrees or the right side is 45 degrees while the left side is 135 degrees). 
     The light producing apparatus  108  is illustrated as a small white LED fixation light  108  and is approximately behind the left side polarizing filter  110   b  such that a light from the LED may be directed along a visual axis of a patient&#39;s left eye (not shown). The light producing apparatus  108  may produce light of any color, but white may advantageously allow for illumination of the patient&#39;s eye, as well as making it easier to determine a patient&#39;s optical axis. The light producing apparatus  108  is attached to an elongated arm  120  received in a guide channel  122  a frame structure  124  of the lens mounting assembly  104 . The arm  120  may be moved along the guide channel  122  so that the light producing apparatus  108  may be positioned in front of either of the surgeon&#39;s left or right eye (whichever is dominant), and may also be adjusted for individual variations of the papillary distance. The arm  120  may be secured to the frame  124  with a thumbnut  126 , as shown, or another type of securing device (e.g., clip, pin, etc.) 
     The viewing device  100  may further include a binocular magnifying lens  128  positioned behind the light producing apparatus  108 . The binocular magnifying lens may include right and left portions to correspond with the patient&#39;s right and left eyes, respectively. In one embodiment the lens  128  takes the form of 2× binocular magnifying lens and is directly attached to the frame  124  of the lens mounting assembly  104 . Further, the polarizing filters  110  are aligned with the right and left portions of the lens  128 . 
       FIG. 2  shows a schematic diagram of how the polarization filters  110  minimize the parallax condition that may be experienced by a surgeon when making a corneal marking. In the illustrated embodiment, it is merely exemplary that a left eye  130  is the surgeon&#39;s dominant eye and a right eye  132  is the non-dominant eye. Because the right and left polarizing filters  110   a ,  110   b  are opposite in polarization, like three-dimensional glasses, the light producing apparatus  108  shines through the left side polarizing filter  110   b , which polarizes a light  134  directed toward a patient&#39;s eye, and more specifically toward a patient&#39;s cornea  136 . The light  134  reflects off of the cornea  136  and at least some of the polarized light  134   a  passes back toward the polarizing filters  110  through the magnifying lens or lenses  128 . The polarized light  134   a  reflected back toward the left side polarizing filter  110   b  may pass through the same and be processed by the surgeon&#39;s left eye  130 . The polarized light  134   a  reflected back toward the right side polarizing filter  110   a  is substantially, if not completely, blocked such that it cannot be seen by the surgeon&#39;s right eye  132 , which is also not coaxial or substantially co-aligned with a direction of the light  134  as it leaves the light producing apparatus  108 . 
     With the patient looking at the light producing apparatus  108 , beaming light  134  that is coaxial or substantially co-aligned with the surgeon&#39;s left eye  130 , the surgeon can only process light  134   a  that is reflect back through the left side polarizing filter  110   b  even though the surgeon is viewing the patient with both eyes. Consequently, even if the surgeon focuses on a marking instrument, there is minimal, if any parallax, which allows the surgeon to make a more accurate corneal marking. In addition, the polarized, reflected light  134   a  may be magnified by the lens  128  to further assist the surgeon in viewing the patient&#39;s eye. 
     In yet another embodiment, shown with reference to  FIG. 3 , a modified polarizing filter  110   c  may be positioned substantially over the light producing apparatus  108  but not substantially over the surgeon&#39;s left eye  130 . In yet an alternative embodiment, the apparatus may combine both the modified polarizing filter  110   c  (shown in  FIG. 3 ) with a polarizing filter  110   b  (shown in  FIG. 2 ), preferably both having the same polarity. 
     Referring back to  FIG. 1 , to use the viewing device  100  the surgeon powers on the light producing apparatus  108  using the switch or button  116 . The surgeon adjusts the head strap  102  and lens mounting assembly  104 . Then, the surgeon adjusts the light producing apparatus  108  by loosening the thumbnut  126 , and moves the arm  120  along the guide channel  122  until the light is coaxial or substantially co-aligned with the surgeon&#39;s dominant eye, but not blocking the view of the dominant eye. The position of the light producing apparatus  108  is secured using the thumbnut  126 . The patient may then be asked to sit up and look at the light producing apparatus  108 . The surgeon uses a corneal marker (not shown), which may take the form of a gravity assisted astigmatic marker, which has the ability of orienting its centration to the corneal light reflex. The surgeon aligns the marker with the corneal light reflex and marks the corneal axis with the marking instrument. 
     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. By way of example, other embodiments may include telescopic surgical loops instead of simple magnifiers. Instead of polarizing filters, other mechanisms may be used to block light to one eye, such as red/green lenses, shutter mechanisms, circular polarization filters, etc. Further embodiments could be applied to the operative microscope or surgical loupes. Another embodiment may include a light source of different shapes and sizes, such as an illuminated “x” or a small ring light, which would give the light reflex a geometric shape and may facilitate centration of the marker and improve illumination at the same time. 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.