Patent Publication Number: US-6991629-B1

Title: Device and method for reducing corneal induced aberrations during ophthalmic laser surgery

Description:
This application is a continuation application of application Ser. No. 09/834,979 filed on Apr. 13, 2001, now U.S. Pat. No. 6,623,476, which is a continuation-in-part of application Ser. No. 09/172,819, filed Oct. 15, 1998, now U.S. Pat. No. 6,254,595. The contents of application Ser. No. 09/834,979 and application Ser. No. 09/172,819 are incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention pertains generally to surgical devices. More particularly, the present invention pertains to surgical lenses which are used in ophthalmic laser surgery. The present invention is particularly, but not exclusively, useful as a lens for temporarily reconfiguring the cornea from an imperfect shape which causes light passing through the cornea to experience aberration into a shape that allows light to pass through the cornea with little or no aberration. 
     BACKGROUND OF THE INVENTION 
     For ophthalmic laser procedures involving the photodisruption of eye tissue, it is extremely important for the laser beam to be properly focused to a spot at a prescribed location inside the tissue. To make accurate incisions with the laser, it is extremely important that the focal spot have good definition. Specifically, it is desirable that the laser beam reach the focal spot free from aberrations that can distort the definition of the focal spot. 
     For ophthalmic laser procedures involving the cornea, the beam of laser light is generally passed through the anterior surface of the cornea and focused with the cornea. Unfortunately, since the anterior surface of the cornea in its natural state is nearly spherical, once a beam of light passes through the anterior surface of the cornea, aberrations are introduced into the beam that cause the beam to distort. For light beams that are focused to a focal spot within the cornea, these corneal induced aberrations distort the definition of the focal spot. It follows that more accurate incisions can be performed by reducing or eliminating these corneal induced aberrations. 
     For light beams that are focused to a focal spot within the cornea, both spherical aberration and coma cause a loss of definition of the focal spot. Conversely, it is known that when a light beam passes through a flat interface between two mediums, no spherical aberration or coma is introduced into the beam. Similarly, when a light beam passes through a nearly flat or slightly curved interface between two mediums, the effects of spherical aberration and coma are much less pronounced than for a light beam passing through a nearly spherical interface, such as the anterior surface of the cornea. As recognized by the present invention, the effects of spherical aberration and coma on light beams passing through the anterior surface of the cornea can be reduced or eliminated by reconfiguring the anterior surface of the cornea from its nearly spherical natural shape to a flatter configuration. 
     Generally, no two corneas are identical. Rather, the exact shape and curvature of the anterior shape of each cornea is slightly different. Consequently, each cornea in its natural state introduces different amounts of aberration into a light beam passing through the anterior surface of the cornea. For a light beam focused to a focal spot within the cornea, the unique shape of each cornea affects the definition of the focal spot differently. The present invention recognizes that the effects of spherical aberration and coma on light beams passing through the anterior surface of the cornea can be predicted by flattening the anterior surface of the cornea against a surface of known curvature. By using a surface of known curvature, a focal spot of known definition can be obtained and this knowledge can be used to ensure the desired surgical effect. 
     In light of the above, it is an object of the present invention to provide a disposable lens which will reconfigure the cornea for surgical laser procedures into a configuration wherein the effects of spherical aberration and coma on a light beam passing through the anterior surface of the cornea are reduced or eliminated. Yet another object of the present invention is to provide a disposable lens which will stabilize and maintain a proper orientation of the eye during ophthalmic laser surgery. Still another object of the present invention is to provide a disposable lens which will beneficially maintain near-normal intraoccular pressure during ophthalmic laser surgery. Another object of the present invention is to provide a disposable lens which is easy to use, relatively simple to manufacture and comparatively cost effective. 
     SUMMARY OF THE INVENTION 
     In one embodiment for the present invention, a lens for use in ophthalmic laser surgery includes an optical element in combination with a suction means. More specifically, the suction means is connected in fluid communication with the optical element to selectively create a partial vacuum between the optical element and the cornea when the lens is positioned over an eye. In response to the partial vacuum, the cornea is forced against the optical element. This reconfigures the cornea for laser surgery and thereby reduces or eliminates optical aberrations that would otherwise be caused by the natural shape of the cornea. 
     In more detail, the optical element of the present invention includes a lens member which has two opposed surfaces; a substantially flat anterior surface and a substantially flat or slightly curved contact surface. Specifically, as intended for the present invention, the contact surface can be shaped flat or slightly curved to cause the shape of the anterior surface of the cornea to change when the anterior surface of the cornea is held against the contact surface. Preferably, the lens member is made of a substantially clear, medical grade plastic. Additionally, a skirt surrounds the contact surface and extends outwardly therefrom to establish and surround a recessed chamber and define an opening to the recessed chamber. In the preferred embodiment, the skirt is formed with a sealing surface for contacting the cornea. The sealing surface of the skirt is preferably formed having a concave shape extending into the recess. The concave shape of the sealing surface allows the skirt to establish a seal with the cornea when the lens is placed against the eye. Preferably, the sealing surface of the skirt is made of a soft medial grade plastic to further facilitate a strong seal between the skirt and the cornea during use. Inside the recessed chamber, a suction channel is provided at the interface between the contact surface and the skirt. 
     A suction device, such as a vacuum pump or a syringe, is connected in fluid communication with the recessed chamber via the suction channel. With this combination, a partial vacuum can be created in the recessed chamber whenever the opening to the chamber is covered. Specifically, as intended for the present invention, the opening to the chamber is to be covered by the cornea, and the cornea is to be drawn into the chamber where it is flattened against the contact surface of the lens. 
     As intended for the present invention, the lens can be mounted on a retainer ring which is attached to the laser system that is being used. More specifically, the retainer ring holds the lens in a predetermined orientation relative to the laser system so that the laser surgery can be performed. 
     In the operation of the present invention, the aplanatic lens is positioned over the eye so that the cornea of the eye is covered by the opening into the recessed chamber. The suction device is then activated to create a partial vacuum in the chamber. Due to this partial vacuum, the cornea is pulled or drawn into the chamber. Specifically, the cornea is flattened against the contact surface of the optical element. As indicated above, with the flattening of the cornea, spherical aberrations and comas which would otherwise be caused by the spherical geometry of the cornea are reduced or eliminated. After the particular ophthalmic laser procedure has been completed, the suction device is deactivated, the partial vacuum is dissipated, and the aplanatic lens is removed from the eye. The lens can be discarded and another new aplanatic lens may be used for the next patient. 
     In another embodiment for the present invention, the lens member as described above can be used in conjunction with a skirt formed with projections for holding the skirt and lens member in position relative to the eye. In this embodiment, the skirt surrounds the contact surface of the lens member and extends outwardly therefrom to establish and surround a recessed chamber and define an opening for the chamber. A plurality of projections are provided extending from the skirt near the opening for engagement with the cornea. A mechanism is provided to attach the lens member and skirt to a laser source. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The novel features of this invention, as well as the invention itself, both as to its structure and its operation, will be best understood from the accompanying drawings, taken in conjunction with the accompanying description, in which similar reference characters refer to similar parts, and in which: 
         FIG. 1  is a perspective view of a lens in accordance with the present invention shown with accompanying components; 
         FIG. 2  is a cross-section view of a lens in accordance with the present invention as seen along the line  2 — 2  in  FIG. 1  in position for engagement with the cornea of an eye; 
         FIG. 3  is a cross-section view of the lens shown in  FIG. 2 , engaged with the cornea of an eye; 
         FIG. 4  is a cross-section view of a lens in accordance with the present invention having an extended skirt, shown in position for engagement with the cornea of an eye; 
         FIG. 5  is a cross-section view of the lens shown in  FIG. 4  engaged with the cornea of an eye; 
         FIG. 6  is a cross-section view of a lens in accordance with the present invention having an extended skirt and a slightly curved contact surface, shown in position for engagement with the cornea of an eye; 
         FIG. 7  is a cross-section view of the lens shown in  FIG. 6  engaged with the cornea of an eye; 
         FIG. 8  is a perspective view of another embodiment of a lens in accordance with the present invention shown with accompanying components; 
         FIG. 9  is a cross-section view of a lens embodiment shown in  FIG. 8  as seen along the line  9 — 9  in  FIG. 8 ; 
         FIG. 10  is a bottom plan view of a lens embodiment shown in  FIG. 8 ; and 
         FIG. 11  is a cross-section view of the lens shown in  FIG. 8  engaged with the cornea of an eye. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring initially to  FIG. 1 , a lens system in accordance with the present invention is shown and generally designated  10 . As shown, the system  10  includes a lens member  12  which is mounted on a retainer ring  14 . Further, the retainer ring  14  is adjustably connected via an extension arm  16  to a laser source  18 . For purposes of the present invention, the laser source  18  is activated to generate a laser beam  20  which is directed through the lens member  12 . As will become more apparent with further disclosure, the lens member  12  is configured to eliminate, or substantially reduce any spherical aberration or coma that may otherwise have been caused by the spherical nature of the cornea  22  of an eye. 
     The actual structure of the lens member  12  will perhaps be best appreciated by reference to  FIG. 2  wherein it will be seen that the lens member  12  is formed with an anterior surface  24  and a contact surface  26 . It is to be appreciated that the anterior surface  24  can be substantially flat. Likewise, the contact surface  26  can be substantially parallel to the anterior surface  24 . In  FIG. 2  it will also be seen that the lens member  12  is formed with a skirt  28 . Specifically, the skirt  28  extends outwardly from the contact surface  26 , as shown, and surrounds the contact surface  26  to create a recessed chamber  30 . 
     Still referring to  FIG. 2 , it will be seen that the skirt  28  of lens member  12  establishes an opening  32  into the recessed chamber  30 . Further, the lens member  12  of the present invention is formed with a suction channel  34  which surrounds the contact surface  26 , and which is located between the skirt  28  and the contact surface  26 . As shown, the suction channel  34  is open along its length for fluid communication with the recessed chamber  30 .  FIG. 2  also shows an air passageway  36  is formed through the skirt  28  for fluid communication therethrough between a tube  38  and the suction channel  34 . Consequently, tube  38  is also in fluid communication with the recessed chamber  30 . As shown in  FIG. 1 , a suction device  40 , such as a vacuum pump, is connected with the tube  38  so that with activation of the suction device  40 , a partial vacuum can be created in the recessed chamber  30  of the lens member  12 . 
     The operation of the lens system  10  shown in  FIG. 2  can best be appreciated by cross referencing  FIGS. 2 and 3 . First, the lens member  12  is positioned above the cornea  22  of an eye substantially as shown in  FIG. 2 . The lens member  12  is then lowered into contact with the exterior surface of the eye (i.e., the cornea, limbus and/or sclera) until the skirt  28  comes into contact with the exterior surface of the eye. Preferably, at this point the cornea  22  completely covers the opening  32  into the recessed chamber  30 . With the lens member  12  positioned on the cornea  22  as described, the suction device  40  is activated to create a partial vacuum in the recessed chamber  30 . Due to the partial vacuum that is created by the suction device  40  in the recessed chamber  30 , the cornea  22  is drawn or pulled into the recessed chamber  30  substantially as shown in  FIG. 3 . Specifically, the cornea  22  is allowed to be pulled into the recessed chamber  30  until the cornea  22  has been flattened against the contact surface  26  of the lens member  12 . With this configuration for the cornea  22 , i.e., when the cornea  22  has been somewhat flattened against the contact surface  26 , the laser beam  20  from laser source  18  will be essentially free from the spherical aberrations and coma which would otherwise be caused by the cornea  22 . 
       FIG. 4  shows another embodiment of a lens  12  in accordance with the present invention. As shown in this embodiment, the skirt  28  is extended and includes a ring portion  42  and an extension  44 . As shown, the extension  44  is attached to the ring portion  42  and projects therefrom. Also shown, the skirt  28  surrounds a recessed chamber  30  and establishes an opening  32  to the recessed chamber  30 . The extension  44  of the skirt  28  is formed with a sealing surface  46 . As shown, the sealing surface  46  is preferably formed having a concave curvature extending into the recessed chamber  30 . This concave curvature facilitates a tight seal between the exterior surface of the eye and the skirt  28  during use. 
     The operation of the lens  12  shown in  FIG. 4  can best be appreciated by cross-referencing  FIGS. 4 and 5 . First, the lens member  12  is positioned above the cornea  22  of an eye substantially as shown in  FIG. 4 . The lens member  12  is then lowered into contact with the exterior surface of the eye until the sealing surface  46  of the skirt  28  comes into contact with the exterior surface of the eye. At this point the cornea  22  completely covers the opening  32  into the recessed chamber  30 . With the lens member  12  positioned on the cornea  22  as described, the suction device  40  is activated to create a partial vacuum in the recessed chamber  30 . Due to the partial vacuum that is created by the suction device  40  in the recessed chamber  30 , the cornea  22  is drawn or pulled into the recessed chamber  30  substantially as shown in  FIG. 3 . Specifically, the cornea  22  is allowed to be pulled into the recessed chamber  30  until the cornea  22  has been flattened against the contact surface  26  of the lens member  12 . With this configuration for the cornea  22 , i.e. when the cornea  22  has been substantially flattened against the contact surface  26 , less spherical aberration and coma will be introduced into a light beam passing into the reconfigured cornea  22  than would be introduced into an identical light beam passing into a cornea  22  that is not reconfigured. 
       FIGS. 6 and 7  show another embodiment of a lens  12  in accordance with the present invention. As shown, in this embodiment, the contact surface  26  is slightly curved. Although the substantially flat contact surface  26  shown in  FIG. 2  provides an interface with the cornea  22  that introduces little or no spherical aberration and coma into a light beam passing through the interface, the slightly curved contact surface  26  shown in  FIGS. 6 and 7  greatly reduces spherical aberration and coma, and does so at a reduced intraocular pressure. Stated differently, reconfiguring the cornea  22  against a substantially flat contact surface  26  results in a slightly higher intraocular pressure than reconfiguring the cornea  22  against a slightly curved contact surface  26 . As can be seen by cross referencing  FIGS. 6 and 7 , the cornea  22  has a substantially flatter curvature after reconfiguration against the slightly curved contact surface  26  ( FIG. 7 ) than before reconfiguration ( FIG. 6 ). Further, since the contact surface  26  in this embodiment is only slightly curved, when suction is applied at passageway  36  adjacent to the slightly curved contact surface  26 , the cornea  22  is still drawn into the recessed chamber  30  and flattened against the slightly curved contact surface  26 . 
     Referring now to  FIG. 8 , another embodiment of the lens system in accordance with the present invention is shown and designated  10 ′. In this embodiment, the lens member  12  includes a skirt  28  formed with projections  48 . As shown with cross reference to  FIGS. 9 and 10 , the skirt  28  is formed with an annular surface  50 . As further shown, the plurality of projections  48  are preferably distributed around the circumference of the skirt  28 , with each projection  48  extending from the annular surface  60  of the skirt  28 . Referring now to  FIG. 11 , the lens member  12  is shown after being pressed onto the eye to reconfigure the cornea  22  against the contact surface  26 . As shown, the projections  48  are provided to engage the cornea  22  and prevent the cornea  22  from moving relative the lens member  12 . 
     While the particular invention as herein shown and disclosed in detail is fully capable of obtaining the objects and providing the advantages herein before stated, it is to be understood that is merely illustrative of the presently preferred embodiments of the invention and that no limitations are intended to the details of construction or design herein shown other than as described in the appended claims.