Patent Publication Number: US-2019183335-A1

Title: Ophthalmic surgical microscope image inverter

Description:
TECHNICAL FIELD 
     The present disclosure relates to ophthalmic surgery, and more specifically, to an ophthalmic surgical microscope containing a reflection inverter for inverting an image of an eye, particularly an eye undergoing ophthalmic surgery. 
     BACKGROUND 
     Ophthalmic surgery saves and improves the vision of tens of thousands of patients every year. However, given the sensitivity of vision to even small changes in the eye and the minute and delicate nature of many eye structures, ophthalmic surgery is difficult to perform and the reduction of even minor or uncommon surgical errors or modest improvements in accuracy of surgical techniques can make an enormous difference in the patient&#39;s vision after the surgery. 
     One type of ophthalmic surgery, vitreoretinal surgery, encompasses various delicate procedures involving internal portions of the eye, such as the vitreous humor and the retina. Different vitreoretinal surgical procedures are used, sometimes with lasers, to improve visual sensory performance in the treatment of many eye diseases, including epimacular membranes, diabetic retinopathy, vitreous hemorrhage, macular hole, detached retina, and complications of cataract surgery, among others. 
     During ophthalmic surgery, such as vitreoretinal surgery, an ophthalmologist typically uses a surgical microscope to view a magnified image of the eye undergoing surgery. Depending on the surgical microscope and optical system used, the magnified image viewed by the surgeon may be inverted as compared to the actual eye. For example, the eye, as it appears in the magnified image may be upside down or with left and right reversed as compared to the actual eye. The surgeon must then mentally correct the image in order to move surgical instruments in the eye properly, which can negatively impact the surgical outcome. 
     SUMMARY 
     The present disclosure provides an ophthalmic surgical microscope including a magnifying lens positioned in an optical path, a reflection inverter positioned in the optical path, and an ocular lens or eyepiece positioned in the optical path. 
     The ophthalmic surgical microscope may further be combined with any of the following features or any other features described in this specification, shown in the figures, or both, all of which may also be combined with one another unless clearly mutually exclusive: 
     i) the ophthalmic surgical microscope may have a stack height equal to or less than 5% longer than an otherwise identical ophthalmic surgical microscope lacking the reflection inverter;
 
ii) the reflection inverter may include a Schmidt-Pechan prism in the optical path, and the Schmidt-Pechan prism may be operable to invert an image traveling along the optical path;
 
ii-a) the Schmidt-Pechan prism may reduce the length of the optical path outside the Schmidt-Pechan prism by at least 20%;
 
ii-b) the Schmidt-Pechan prism may be operable to reflect light in the visible wavelengths internally at internal angles of incidence that are each 90° or less;
 
ii-c) the Schmidt-Pechan prism may be operable to exhibit at least 98% internal reflection of incident light in the visible wavelengths;
 
ii-d) the Schmidt-Pechan prism may exhibit internal reflection of at least 80% of a field of view of the ophthalmic surgical microscope;
 
ii-e) the Schmidt-Pechan prism may be made from a material transparent to the visible wavelengths of light and having an Abbe number of at least 40;
 
ii-f) the Schmidt-Pechan prism may be made from a material transparent to the visible wavelengths of light and having a reflective index of at least 1.40;
 
ii-g) the reflection inverter may be operable to preserve the polarization of any light in the visible wavelengths traveling along the optical path;
 
ii-h) the ophthalmic surgical microscope may not include a reduction lens in the optical path.
 
iii) the reflection inverter may include a right angle reflector having a first reflective face and a second reflective face, both in the optical path, a first inverting lens in the optical path, and a second inverting lens in the optical path, wherein the first reflective face of the right angle reflector may be operable to reflect light traveling along the optical path such that the light strikes and is transmitted by the first inverting lens then strikes the first reflector at a first angle of incidence, wherein the first reflector may be operable to reflect light at an angle 90° with respect to the first angle of incidence along the optical path such that the light then strikes the second reflector at a second angle of incidence, wherein the second reflector may be operable to reflect light at an angle 90° with respect to the second angle of incidence along the optical path such that the light then strikes and is transmitted by the second inverting lens, and then strikes the second reflective face of the right angle reflector, wherein the second reflective face of the right angle reflector may be operable to reflect the light along the optical path in a direction that is collinear with a direction in which the light struck the first reflective face, and wherein the reflection inverter may be operable to invert an image traveling along the optical path;
 
iii-a) the right angle reflector may include a right angle prism mirror;
 
iii-b) the first reflective face and the second reflective face of the right angle reflector may both be operable to reflect at least 90% of incident light in the visible wavelengths;
 
iii-c) the first inverting lens and the second inverting lens may both be made from a material transparent to the visible wavelengths of light and having an Abbe number of at least 40;
 
iii-d) the first inverting lens and the second inverting lens may both be made from a material transparent to the visible wavelengths of light and having a reflective index of at least 1.40;
 
iii-e) the microscope may further include a reduction lens in the optical path that may be operable to reduce the optical path by at least 20%;
 
iii-f) the reduction lens may be made from a material transparent to the visible wavelengths of light and having an Abbe number of at least 40;
 
iii-g) the reduction lens may be made from a material transparent to the visible wavelengths of light and having a reflective index of at least 1.40; and
 
iii-h) the reduction lens may include a biconcave lens, a biconvex lens, a convex-concave lens, a plano concave lens, a plano convex lens, a positive/negative meniscus lens, an aspheric lens, a converging lens, a diverging lens, a liquid crystal lens, a diffractive lens, and any combinations thereof.
 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more complete understanding of the present invention and its features and advantages, reference is now made to the following description, taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is schematic diagram of an ophthalmic surgical microscope containing an inverter; 
         FIG. 2  is a set of schematic diagrams of a two views of Schmidt-Pechan prism reflection inverter suitable for use in the ophthalmic surgical microscope of  FIG. 1 ; internal prism angles are indicated in the left diagram; 
         FIG. 3  is a schematic diagram of a mirror/inverting lens reflection inverter suitable for use in the ophthalmic surgical microscope of  FIG. 1 ; and 
         FIG. 4  is a schematic diagram of how an image is inverted using the mirror/inverting lens reflection inverter or  FIG. 3 . 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure relates to ophthalmic surgery, and more specifically, to an ophthalmic surgical microscope containing a reflection inverter. Such an ophthalmic surgical microscope, by providing a magnified image of the eye undergoing surgery that is not inverted as compared to the eye, may decrease the difficulty of ophthalmic surgery an improve surgical outcomes for patients. In addition, the ophthalmic surgical microscope may have a stack height comparable to conventional ophthalmic surgical microscopes and, may, therefore, preserve ergonomic usability of the surgical microscope. In particular, the ophthalmic surgical microscope with the reflection inverter may have a stack height equal to or less than 5% longer, less than 2% longer, or less than 1% longer than an otherwise identical ophthalmic surgical microscope lacking the reflection inverter. 
     It will be understood that the component described herein as having certain properties with respect to light are operable to exhibit those properties when in the presence of light, such as during use of the ophthalmic surgical microscope. 
       FIG. 1  is a schematic diagram of an ophthalmic surgical microscope  100 . The ophthalmic surgical microscope  100  includes at least one magnifying lens  120  that is positioned in an optical path  110  (dotted line) that also extends through a reflection inverter  130  to an ocular lens or eyepiece  140 , which may be selectively positionable so that a portion of the eye  10  viewed by using the ophthalmic surgical microscope is in focus. Portions of the eye suitable for viewing can include the retina, macula, foveola, fovea centraalis, para fovea, perifovea, optic disc, optic cup, one of more layers of the retina, vitreous, vitreous body, or any portion in which a surgical instrument is also viewed. 
     During use of the surgical microscope  100  to view an eye  10 , the optical path  110  further extends to the eye  10  being viewed. The ophthalmic surgical microscope  100  also has a stack height,  150 , which is generally parallel to the optical path  110 , and which may extend from the portion of the ophthalmic surgical microscope  100  in the optical path  110  that is closest to the eye  10  during use through the ocular lens or eyepiece  140 . The stack height  150 , may be comparable to that of a similar ophthalmic surgical microscope containing only a reduction lens and lacking a reflection inverter  130 . 
     Due to the inverter  130  being a reflection inverter, light transmitted by the reflection inverter  130  has an axis that is collinear with and in the same direction as light incident on the reflection inverter  130 . 
     A portion of the eye  10 , which is shown upright with a surgical tool also present in position “A,” may be inverted when it passes through the magnifying lens  120 , to position “B.” Although ophthalmic surgeons can successfully operate even when viewing an inverted image in position “B,” doing so requires further mental processing and may increase surgery time or increase the chance of a less positive or even a negative surgical outcome. Accordingly, a reflection inverter  130  may be included in the ophthalmic surgical microscope  100  to invert the image back to position “A” as shown in  FIG. 1 . In addition, although various instruments exist that may invert an image, the reflection inverter  130  in ophthalmic surgical microscope  100  does so without an unacceptable increase in stack height or loss of image quality. 
     The ophthalmic surgical microscope  100  may further include other general components, such as additional lenses, mirrors, such as dichroic mirrors, digital light capture equipment, such as a digital camera, digital displays, and a processor programmed to process data from digital light capture equipment and display it on a digital display, or to insert images in a display, including in a display seen through ocular lens or eyepiece  140 . The ocular lens or eyepiece  140  may include a zoom lens, a liquid crystal lens, or any other suitable variable focal length lens, or a fixed focus length lens. 
     The ophthalmic surgical microscope  100  may also include other components specific for a particular procedure, such as a contact lens, particularly a macular contact lens, that may be coupled to the eye  10 , or an optical coherence tomography (OCT) system. A processor, if present, may further be programmed to perform functions associated with these more specific components, such as analysis of OCT data to create a two-dimensional or three-dimensional OCT image and to display the image on a digital display or to insert the image into a display. 
     The reflection inverter  130 , in one embodiment, may include a Schmidt-Pechan prism reflection inverter  130   a  as illustrated in  FIG. 2 . A light beam entering the Schmidt-Pechan prism reflection inverter  130   a  travels along optical path  110   a.  In the process, any image contained in the light beam is inverted, as indicated by the letter “R” in the diagram. 
     The Schmidt-Pechan prism reflection inverter  130   a  may be made from two prisms,  210  and  220 , positioned with respect to one another generally as indicated in  FIG. 2 . The Schmidt-Pechan prism configuration, unlike many other inverting prisms configurations, is mechanically stable and will not tend to cause the microscope to wobble or tip in any direction once mounted in the ophthalmic surgical microscope  100 . Furthermore, the optical path  110  in ophthalmic surgical microscope  100  often extends too long before an image of the eye  10  is in focus. A reduction lens is often currently used to shorten the total optical path  110  from the eye  10  to the ocular lens or eyepiece  140  so that the stack height  150  of the ophthalmic surgical microscope  100  is not too long. A reflection inverter  130   a  containing a Schmidt-Pechan prism has a relatively long internal optical path,  110   a,  within a short total length, L of the prism, such that a long optical path  110  can be accommodated by an ophthalmic surgical microscope  100  without a stack height  150  that is too high. The Schmidt-Pechan prism may effectively reduce the length of the optical path  110  outside of the Schmidt-Pechan prism by at least 20%, at least 30%, at least 40%, or at least 50%. 
     The Schmidt-Pechan prism in the reflection inverter  130   a  reflects light internally at internal angles of incidence as shown by the optical path  110   a  in  FIG. 2 . Because each internal angle of incidence is 90° or less, it may be possible to achieve at least 98% internal reflection of incident light in the visible wavelengths (390 to 700 nm), at least 99% internal reflection of incident light in the visible wavelengths, at least 99.5% internal reflection of incident light in the visible wavelengths, at least 99.9% internal reflection of incident light in the visible wavelengths, or even 100% internal reflection of incident light in the visible wavelengths (referred to as total internal reflection). This internal reflection may be for the entire field of view of the ophthalmic surgical microscope  100 , or for at least 80%, at least 90%, at least 95%, or at least 99% of the field of view. 
     The Schmidt-Pechan prism in the reflection inverter  130   a  may also be made from a material transparent to the visible wavelengths, such as a glass, having a high Abbe number in the visible wavelengths. The Abbe number, also referred to as the V-number, is a measure of the material&#39;s dispersion, or the variation of refractive index versus wavelength. In particular, the material may have an Abbe number of at least 40, at least 45, at least 50, or at least 60. If the material is a flint glass, it may have an Abbe number between 50 and 55. If the material is a crown glass, it may have an Abbe number of between 50 and 85. 
     The Schmidt-Pechan prism in the reflection inverter  130   a  may also be made from a material transparent to the visible wavelengths, such as a glass, also having a high reflective index in the visible wavelengths. The reflective index describes how fast light propagates through a material as compared to in a vacuum and is found using the equation n=c/v, where n is the reflective index, c is the speed of light, and v is the phase velocity of light in the material. In particular, the material may have a reflective index of at least 1.40, at least 1.45, or at least 1.50. If the material is a flint glass, it may have a reflective index of at least 1.50, such as approximately 1.52. If the material is a crown glass, it may have a reflective index of between 1.45 and 2.00. 
     Further, the Schmidt-Pechan prism in the mirror/inverting lens reflection inverter  130   a  may preserve any polarization of light in the visible wavelengths that passes through the reflection inverter  130   a  along the optical path  110   a.    
     The reflection inverter  130 , in one embodiment, may be a reflection inverter  130   b  shown in  FIG. 3 . The reflection inverter  130   b  includes a right angle reflector, such as the right angle prism mirror  310  illustrated. Other objects containing two reflective faces at right angles to one another and position with respect to the other components of the reflection inverter  130   b  as shown in  FIG. 3  may also be used in place of the right angle prism mirror  310 . Light traveling along the optical path  110   b  strikes a first face of the right angle prism mirror  310  and is reflected to a first inverting lens  320   a,  then strikes a first reflector  320   c.  The light strikes the first reflector  320   c  at a first angle of incidence and is reflected from the first reflector  320   c  at angle that is 90° with respect to the first angle of incidence. The light reflected from the first reflector  320   c  then strikes the second reflector  320   d.  The light strikes the second reflector  320   d  at a second angle of incidence and is reflected from the second reflector  320   d  at angle that is 90° with respect to the second angle of incidence. The second reflector  320   d  also reflects the light at an angle that is 90° with respect to the second angle of incidence. The light then strikes the second inverting lens  320   b . The light transmitted by the second inverting lens  320   b  then strikes a second reflective face of the right angle prism mirror  310  and is reflected along an optical path in a direction that is collinear with the direction in which light struck the first reflective face of the right angle prism mirror  310 . 
     While traveling through the inverting lenses  320   a  and  320   b,  an image contained in the light is inverted as illustrated in  FIG. 4 . Two (as shown in  FIG. 3 .) or more reflectors can be added to redirect the beam as desired and form an inverted image. 
     Because the portion of the optical path  110   a  through the right angle prism mirror  310  and the inverting lenses  320   a  and  320   b  is typically short it does not significantly reduce the total optical path  110  within the ophthalmic surgical microscope  100 . Accordingly, a reduction lens  340  may further be included, which may be fixed or selectively positionable to change the focus position such that the a portion of the eye  10  may be viewed in focus. The reduction lens  340  can include one or more optical components, such as a biconcave lens, a biconvex lens, a convex-concave lens, a plano concave lens, a plano convex lens, a positive/negative meniscus lens, an aspheric lens, a converging lens, a diverging lens, a liquid crystal lens, a diffractive lens, other suitable lenses, and any combinations thereof. 
     The reduction lens  340  may reduce the length of the optical path  110  by at least 20%, at least 30%, at least 40%, or at least 50%. 
     The total length, L between the edge of the reduction lens  340  closes to the ocular lens or eyepiece  140  and the edge of the right angle prism mirror or first inverting lens  320   a,  whichever is further, that is furthest from the reduction lens  340 , may be such that the stack height of the ophthalmic surgical microscope  100  is not too long. 
     The right angle prism mirror or other right angle reflector may reflect, on both faces, at least 90%, at least 95%, at least 99%, or at least 99.9% of incident light in the visible wavelengths. Similarly, both of inverting lenses 320 may transmit at least 90%, at least 95%, at least 99%, or at least 99.9% of incident light in the visible wavelengths. In addition, both of inverting lenses may have Abbe numbers and reflective indices the same as those described above for the Schmidt-Pechan prism and may be made of the same materials. Similarly, the reduction lens  340  may transmit at least 90%, at least 95%, at least 99%, or at least 99.9% if incident light in the visible wavelengths and may have Abbe numbers and reflective indices the same as those described above for the Schmidt-Pecham prism and may be made of the same materials. Polarization may also be preserved. 
     An ophthalmic surgical microscope  100  as described herein may be used in any sort of ophthalmic surgery in which a portion of an eye  10  is magnified. Typically magnification may be between  5   x  and  40   x,  more particularly between  5   x  and  15   x.  The ophthalmic surgical microscope  100  may not only provide an image of the eye  10  through the ocular lens or eyepiece  140 , it may be coupled with other microscope components or a processor to provide the same image on a digital viewed, such as a screen used by an assistant, to provide an digitially enhanced image of the eye  10 , to provide additional information, such as OCT image, or any combinations of these images and any other images presented to the surgeon performing ophthalmic surgery, any assistants, or both. 
     The above disclosed subject matter is to be considered illustrative, and not restrictive, and the appended claims are intended to cover all such modifications, enhancements, and other embodiments which fall within the true spirit and scope of the present disclosure. Thus, to the maximum extent allowed by law, the scope of the present disclosure is to be determined by the broadest permissible interpretation of the following claims and their equivalents, and shall not be restricted or limited by the foregoing detailed description.