Patent Publication Number: US-2002010484-A1

Title: Microkeratome spring deceleration device

Description:
[0001] This application is based on U.S. provisional Application No. 60/219,609, filed on Jul. 21, 2000, and claims the benefit thereof for priority purposes. This U.S. Provisional Application is expressly incorporated herein by reference.  
       FIELD OF THE INVENTION  
       [0002] The invention generally relates to microkeratomes for use in laser eye surgery and, more particularly, to a microkeratome that includes a spring structure to ensure a soft stop at the end of the microkeratome&#39;s travel.  
       BACKGROUND OF THE INVENTION  
       [0003] In performing the primary lamellar cut for laser assisted in situ keratomileusis, before ablation of corneal tissue, a microkeratome is moved with respect to a suction ring assembly which holds eye tissue. Movement of the microkeratome slices corneal tissue. A conventional microkeratome includes a body carrying fine gearing that intermeshes with a gearing on the suction ring assembly to cause movement of the microkeratome with respect to the suction ring assembly. As the body reaches the end of its stroke, the body contacts a portion of the suction ring assembly in manner that can be considered to be a hard stop. The slice is therefore stopped before cutting entirely through the corneal tissue thereby forming a flap of tissue.  
       [0004] In contacting the suction ring assembly in this manner, the integrity of the fine gears of the microkeratome can be compromised. In some instances, due to the microkeratome&#39;s contact with the suction ring assembly, the gears can even “lock-up”. Thus, the contact of the microkeratome at the end of its stroke in the conventional hard stop manner reduces the life and function of the microkeratome.  
       [0005] There is a need to provide a microkeratome that includes spring structure ensuring that a soft stop of the microkeratome occurs at the end of the microkeratome&#39;s travel.  
       SUMMARY OF THE INVENTION  
       [0006] An object of the invention is to fulfill the need referred to above. In accordance with the principles of the present invention, this objective is achieved by providing a keratome having a body configured to be movable during a stroke thereof with respect to a suction ring assembly. The body includes spring structure constructed and arranged to resiliently contact a portion of the suction ring assembly at an end of the stroke of the body.  
       [0007] In accordance with another aspect of the invention, a method is provided for damping forces resulting from contact of a keratome with a fixed suction ring assembly at an end of a stroke of the keratome. The suction ring assembly includes a stop surface and the keratome has a body movable with respect to a suction ring assembly. The body includes a resilient stop surface. The method includes moving the body with respect to the suction ring assembly such that at the end of the stroke, the resilient stop surface of the body engages the stop surface of the suction ring assembly so as to dampen a contact force between the suction ring assembly and the body.  
       [0008] Other objects, features and characteristics of the present invention, as well as the methods of operation and the functions of the related elements of the structure, the combination of parts and economics of manufacture will become more apparent upon consideration of the following detailed description and appended claims with reference to the accompanying drawings, all of which form a part of this specification. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0009] The invention will be better understood from the following detailed description of the preferred embodiments thereof, taken in conjunction with the accompanying drawings, wherein like reference numerals refer to like parts, in which:  
     [0010]FIG. 1 is a side view of a gear plate of a microkeratome provided in accordance with the principles of the present invention.  
     [0011]FIG. 2 is a perspective view of the gear plate of FIG. 1.  
     [0012]FIG. 3 is a perspective view of a microkeratome including the gear plate of FIG. 2, shown associated with a suction ring assembly.  
     [0013]FIGS. 4A and 4B are schematic views of other embodiments of spring structure of the invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
     [0014] With reference to FIG. 1, a microkeratome gear plate, provided in accordance with the principles of the present invention is shown generally indicated at  10 . As shown in FIG. 3, the gear plate  10  is attached by a fastener  11  to a body  12  of a microkeratome, generally indicated at  14 . The gear plate  10  can be considered to be part of the body  12 . In the conventional manner, the microkeratome  12  includes gears  16 ,  16 ′ and  16 ″ carried by the gear plate  10  within a gearing recess  17 . The gear  16 ″ intermeshes with a gear  18  on a suction ring assembly  20  so that the body  12  of the microkeratome  14  can move during a stroke thereof with respect to the fixed suction ring assembly  20 . In particular, the suction ring assembly  20  is configured to be fixed to an eyeball such that the microkeratome  14  can slice corneal tissue. A motor and transmission shaft assembly  21  causes movement of the body  12 . The microkeratome  14  and suction ring assembly  20  may be of the type described in U.S. Pat. No. Re. 35,421, the entire content of which is hereby incorporated by reference into the present specification.  
     [0015] In order to prevent “hard stop” contact of the body  12  with a portion of the suction ring assembly  20  at the end of the stroke of the body  12 , in accordance with the invention, the gear plate  10  of the body  12  includes spring structure, generally indicated at  22 . In the illustrated embodiment, an open clearance channel  24  is defined at the bottom of the gear plate  10  such that the gear plate  10  can clear a gear support  26  of the suction ring assembly  20  during a stoke of the body  12 . The channel  24  is defined by surfaces  28  and  30  of the gear plate  10 . In the disclosed embodiment, the spring structure  22  is made integral with the gear plate  10  and is defined as a cantilever having a hinged end  31  and a free end  32  opposite the hinged end  31 . Thus, the free end  32  can flex about the hinged end  31 . The free end  32  extends into the channel  24  at an end of the gear plate  10  to define a resilient stop surface  34  of the gear plate  10 .  
     [0016] With reference to FIG. 3, the gear support  26  of the suction ring assembly  20  includes a stop surface  36 . Hence, when the body  12  reaches the end of its stroke, the resilient stop surface  34  of the spring structure  22  resiliently contacts the stop surface  36  of the gear support  26  of the suction ring assembly  20 , thereby providing a “soft stop” of the body  12  with respect to the suction ring assembly  20 . Due to the “soft stop”, a force created by contact between the body  12  and the suction ring assembly  20  is dampened. Thus, the mechanical integrity of the fine gears  16 ,  16 ′ and  16 ″ of the microkeratome  14  are preserved, thereby preserving the life and function of the microkeratome  14 . The “soft stop” also eliminates lock-up of the microkeratome  14  at the end of its stroke that can occur in conventional microkeratomes employing a hard stop.  
     [0017] With reference to FIG. 4A, instead of defining the spring structure  22  as a cantilever, the spring structure  22 ′ may comprise a compression spring  40  between a surface  42  of the gear plate  10 ′ and a stop member  44 . Thus, as the stop member  44  engages the stop surface  36  (FIG. 3) of the suction ring assembly  20 , the spring  40  compresses to ensure a “soft stop” of the microkeratome. Alternatively, as shown in FIG. 4B, the spring structure  22 ″ can be any resilient material such as silicone pad coupled to surface  42 . In either of these two embodiments, no hinged end is required.  
     [0018] The foregoing preferred embodiments have been shown and described for the purposes of illustrating the structural and functional principles of the present invention, as well as illustrating the methods of employing the preferred embodiments and are subject to change without departing from such principles.  
     [0019] Therefore, this invention includes all modifications encompassed within the spirit of the following claims.