Patent Publication Number: US-6698886-B2

Title: Iridotomy and trabeculoplasty goniolaser lens

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Application No. 60/286,210, filed Apr. 24, 2001. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to contact lenses used by ophthalmologists for diagnosis and laser surgery of the eye, and more particularly to an iridotomy and trabeculoplasty goniolaser lens. 
     BACKGROUND OF THE INVENTION 
     Glaucoma is an eye disease that can lead to blindness if not properly treated. Elevated intraocular pressure is frequently an early sign of the disease. Reduction of the intraocular pressure may prevent loss of vision. The goniolaser lens may be designed to focus the laser light to treat two specific types of glaucoma. 
     Angle-closure glaucoma: In angle-closure glaucoma the intraocular fluids (aqueous humor) must pass through the pupil from behind the iris (posterior chamber) to a position in from of the iris (anterior chamber). The aqueous humor then escapes from the eye through microscopic channels located at the angle of the anterior chamber between the peripheral iris and cornea. In angle-closure glaucoma there occurs a block at the pupil so that the aqueous humor cannot pass from the posterior to the anterior chamber and the eye pressure becomes very elevated. 
     One method developed for relief of intraocular pressure caused by angle-closure glaucoma is to perform an iridotomy using laser ablation surgery. This surgical procedure is accomplished by positioning an appropriately configured contact lens on the cornea of an eye and delivering laser energy to the iris. The laser energy is focused on the peripheral iris to generate an opening through the iris. Intraocular fluid (aqueous humor) can then bypass the blocked pupil and move through the newly created iris opening from the posterior to the anterior chamber. This allows the aqueous humor to reach the outflow channels in the anterior chamber angle and relieve the pressure and symptoms of closed angle glaucoma. 
     Open-angle glaucoma: Open-angle glaucoma is caused by an abnormality in the microscopic channels, trabecular meshwork, that are located in the angle of the anterior chamber. Eyedrop medications may help the aqueous humor to pass through the meshwork, but not in all cases. 
     Another method for relieving the symptoms of open-angle glaucoma is to perform trabeculoplasty using laser ablation surgery. This procedure is accomplished by delivering laser energy to the trabecular meshwork to allow better passage of the aqueous humor through it. One theory suggests that the laser alters the intracellular and intercellular structures in the trabecular meshwork and allows the fluids to pass through with less obstruction. 
     Prior contact lenses employed for these purposes work efficiently for the application of laser energy to the eye. However, viewing the trabecular meshwork before and after an iridotomy procedure has necessitated removal of the laser lens and substitution of another viewing lens. While attempts have been made at combining a laser delivery lens and a viewing lens, the attempted combinations have not been successful for a variety of reasons. The major reason for lack of success has been the necessity to completely refocus the binocular microscope through which the surgeon is manipulating the laser energy and through which the surgeon views the trabecular meshwork. 
     During an iridotomy procedure, it is desirable to view the trabecular meshwork immediately after the delivery of laser energy to determine the efficacy of the procedure. If the aperture through the iris has been successfully completed, fluid pressure in the posterior chamber will be relieved and will allow the iris to flatten to its natural state rather than the anteriorly bowed configuration that occurs in the presence of excessive intraocular pressure in the posterior chamber. When laser iridotomy has been mechanically successful, the anterior chamber angle will open, as observed through the gonioscopy portion of the lens. However, if it is observed that the angle failed to open, then additional application of laser energy may be required. Thus, if the anterior chamber angle and trabecular meshwork could be viewed immediately after the initial delivery of laser energy through the same contact lens, an additional application of laser energy could be applied to the same or another location without removing the laser delivery lens, without substituting the viewing lens and without once again repositioning the laser delivery lens. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention, an iridotomy goniolaser lens is provided through which laser energy can be delivered to the eye and through which the treated area can be observed. In a currently preferred embodiment, the lens comprises four elements: a contact lens, a planar mirror, a first button lens, and a second button lens. The contact lens has an optical axis, a concave posterior contact surface, and an anterior planar surface. The contact lens element has an angled surface offset from its optical axis. The angled surface is planar and extends laterally and anteriorly from a location radially offset from the optical axis of the contact lens element and adjacent to the concave contact lens surface but anterior thereof. The surface forms an internally reflective planar mirror. The first button lens has a planar posterior surface and a convex anterior surface. The planar surface of the first button lens is in optical contact with the planar surface of the contact lens element and is offset from the optical axis of the contact lens element in a direction opposite from the offset of the angled surface. The magnification, curvature, and location of the first button lens is chosen to provide a virtual image in a first image plane of a predetermined location on the iris of a patient when the contact lens surface of the contact lens element is in optical contact with the cornea of the eye of the patient. The second button lens has a planar posterior surface and a convex anterior surface. The planar surface of the second button lens is in optical contact with the planar surface of the contact lens element. The second button lens is offset from the optical axis of the contact lens in the direction of the offset of the angled mirror surface and is positioned over the angled mirror surface. The magnification, curvature, and location of the second button lens is chosen to provide a virtual image in a second image plane of the trabecular meshwork of the eye of the patient when the surface of the contact lens element is in optical contact with the cornea of the eye of the patient. The magnification, curvature, and location of the first and second button lens are preferably chosen such that an optical microscope can be focused on the first and second image planes with little or no focus adjustment, thus allowing delivery of laser energy to the iris and viewing of the trabecular meshwork through the same lens. 
     The same lens can be employed for trabeculoplasty. For this procedure, laser energy is directed toward the angled mirror surface and reflected to the trabecular meshwork. The results of the trabeculoplasty can be viewed along the same optical path. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated as the same become better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein: 
     FIG.  1  and FIG. 2 are respective elevation and top views of a contact lens constructed in accordance with the present invention; 
     FIG. 3 is a longitudinal sectional view of the lens along section line  3 — 3  of FIG. 2 shown in contact with the cornea of a patient&#39;s eye and illustrating the optical path for the delivery of laser energy; and 
     FIG. 4 is a view similar to FIG. 3 after laser energy has been delivered and showing the optical path for viewing the trabecular meshwork. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to FIGS. 1 and 2, a preferred embodiment of the laser surgery lens  10  of the present invention is housed in a holder comprising a lower frustoconically shaped shell  12  and an upper retaining ring  14 . Housed within the holder is a contact lens element  16 , a mirror  18 , and first and second button lenses  20  and  22 , respectively. 
     Referring now to FIG. 3, the contact lens element  16  has a concave posterior surface  30  that has a curvature that approximates the curvature of the cornea  32  of an eye  34  of a patient. The iris  36  of the eye is shown in an anteriorly distended position that is typically symptomatic of closed angle glaucoma. It is the purpose of iridotomy surgery to relieve the intraocular pressure on the iris so that it can relax to its normal position (shown in FIG.  4 ). The anterior surface  38  of the contact lens element is planar and is oriented perpendicularly to the optical axis  40  of the contact lens element  16 . When the contact lens  10  is positioned on the patient&#39;s eye  34 , the optical axis  40  is also positioned generally along the optical axis of the eye. 
     The first button lens  20  has a planar posterior surface  44  and a convex anterior surface  46 . The planar posterior surface of the first button lens  20  is placed in optical contact with the anterior planar surface  44  of the contact lens element  16 . By optical contact it is meant either direct surface-to-surface contact or contact with an optical glue or other bridging material that minimizes refraction and reflection otherwise caused at the junction of two optical surfaces. The first button lens  20  is offset laterally in a first direction from the optical axis  40  of the lens. The lateral positioning of the button lens  20  as well as its curvature and magnification are chosen such that laser energy can be delivered along the site line  48  parallel to the optical axis  40 , through the cornea  32  and onto the iris. The lens is designed to focus the laser energy on the iris so that the heat generated will ablate the tissue of the iris and create an aperture or hole  50  through the iris. One of ordinary skill will recognize that the anterior surface of the first button lens  20  may be spheric, aspheric, diffractive, or a combination thereof depending upon the particular design and material parameters chosen. 
     The contact lens element  16  also has a planar surface  60  that is offset in the opposite direction from the offset of the first button lens  20 . The lower edge of the planar surface  60  is positioned above but adjacent the contact lens surface  30 . The planar surface  60  extends laterally and anteriorly from that position to a location near the upper planar surface  38 . This planar surface  60  functions as mirror  18  to reflect light rays internal to the lens in a manner as discussed below. If desired, a reflective coating can be applied to the surface  60 . Alternately, a mirror element having a planar mirrored surface may be positioned in optical contact with the planar surface  60  on the contact lens element. 
     The second button lens  22  is offset from the optical axis  40  in the same direction as the planar surface  60 . The curvature, magnification and location of the second button lens  22  are chosen so as to provide a sight path  64  that extends from anterior to the button lens  22  along a path that is first parallel to the optical axis  40  of the composite lens and is then reflected by the surface of the mirror  18  formed by surface  60  at an angle that allows the trabecular meshwork adjacent and around the aperture  50  to be viewed by the ophthalmologist performing the surgery. The angle of the surface  60  and of course, the mirror  18  are chosen so as to provide the appropriate sight path  64 . One of ordinary skill will recognize that the anterior surface of the second button lens  22  may be spheric, aspheric, diffractive, or a combination thereof depending upon the particular design and material parameters chosen. 
     The combination of the button lens  20  and the contact lens element creates a virtual image at a virtual image plane  70 , which lies within the eye. Similarly, the combination of the button lens  22  mirror and contact lens element forms a second virtual image of the trabecular meshwork at a virtual image plane  72 , which is also within the eye. In accordance with the present invention, the power and curvature of the respective button lenses  20  and  22  are chosen so that the virtual images  70  and  72  are preferably simultaneously in focus to the user of the lens  10 . That is, the virtual image formed along sight path  48  and the image formed along sight path  64  and  64   a  preferably lie in substantially the same plane. This allows the ophthalmologist performing the laser surgery to focus the binocular microscope in a single plane so that both the laser energy can be focused at the base of the iris  36  and the trabecular meshwork can be viewed simultaneously or serially without moving or replacing the contact lens element and without the need to substantially refocus of the binocular microscope. 
     While it is most preferred that the images  70  and  72  lie substantially in the same plane, one of ordinary skill will readily understand that the visual images may be separated by a small distance which may require only slight refocusing of the binocular microscope through which the surgeon normally views the images. A separation of the images  70  and  72  by 5 mm is quite acceptable, requiring little refocusing during a procedure. 
     As shown in FIG. 4, the aperture  50  has been successfully created. When the trabecular meshwork is viewed along optical path  64 , it is clear to the surgeon that the iris  36  has relaxed to its natural position because intraocular fluid has been allowed to escape from the posterior chamber into the anterior chamber through aperture  50 . 
     The lens of the present invention can also be used to treat open angle glaucoma with trabeculoplasty. In this procedure, the trabecular meshwork is viewed along the sight path indicated by dashed line  64  using the internally reflective surface  60 . In this procedure, however, the laser energy is also delivered along the same path to ablate or burn the trabecular meshwork to render it perforate to intraocular fluid. After surgery, the meshwork can again be viewed along path  64 . 
     In a preferred embodiment, the curvature of the contact lens surface  30  is defined by a radius of curvature (R 1 ) equal to 7.4 mm and distance D 1  is 14.4 mm. The curvature of the anterior surface of button lens  20  is defined by a radius of curvature (R 2 ) equal to 18.6 mm. The optical axis of the button lens  20  is offset by 4.5 mm from the optical axis  40  of the composite lens. The thickness D 2  is 2.5 mm. The second button lens  22  has a thickness D 3  of 2.5 mm. The curvature of the anterior surface of the button lens  22  is defined by a radius of curvature (R 3 ) equal to 31.0 mm. The optical axis of the button lens  22  is coincident with the optical axis  40  of the contact lens. The mirrored surface  60  forming mirror  18  is set at an angle of 28 degrees relative to the optical axis  40  of the composite lens. One of ordinary skill will readily recognize that the powers of the lens so defined, the angles of the mirror and other pertinent parameters can be changed so long as the functionality provided by the present invention is retained. 
     One of ordinary skill will also recognize that the individual lens elements comprising the preferred embodiment of the lens of the present invention may be created in one or more multifunctional elements. It is possible, for example, albeit more expensive to machine the equivalent of the button lenses from the same optical element as the contact lens. Moreover, if separate elements are employed, the surfaces between the elements such as surfaces  38  and  44  may not only be planar, as is preferred, but spherical or aspherical as desired. 
     While the preferred embodiment of the invention has been illustrated and described, it will be appreciated that various changes can be made therein without departing from the spirit and scope of the invention.