Corneal insert, instrument for insertion of the same and method of correcting the refractive power of an eye

Abstract

A corneal ring for the correction of the refractive power of an eye consists of a part of metal or plastic which is formed into a split ring having at least one turn, or into a ring segment having a diameter or effective diameter matched to the periphery of the cornea of an eye. The ring or ring segment is inserted into a ring channel which is formed with a special instrument in the cornea of the eye and the radius of curvature of the ring or ring segment is subsequently adjusted by a laser beam, or by radiation, or electromagnetic induction, or magnetism to achieve a fine correction of the refractive power of the eye.

1 . A corneal insert in the form of a ring or ring segment for the correction of the refractive power of an eye consisting of at least one elongate part of metal or plastic which is formed into a ring with at least one turn, or into a ring segment, said ring or ring segment having a ring diameter which is matched to the diameter of the cornea and, for example, amounts to 6 to 12 millimeters, and said ring or ring segment being made of a material such that the spring characteristics of the ring or segment in the sense of at least one of an expansion or contraction of said ring diameter are adjustable or finely adjustable after insertion by the action of radiation, in particular electromagnetic radiation such as laser light, or by a magnetic treatment, or by an inductive treatment.  
     
     
         2 . Corneal insert in accordance with  claim 1 , characterised in that the ring is a split ring having only one turn, with the ends of the elongate part forming the split ring not being fastened to one another.  
     
     
         3 . Corneal insert in accordance with  claim 1 , wherein regions of a radially inner portion of the open ring or segment are heated by means of a laser to produce expansion only at the radially inner side of the ring or segment, whereby the stress in the ring or segment changes in the sense of opening of the ring or segment, i.e. an increase in said diameter.  
     
     
         4 . Corneal insert in accordance with  claim 1 , wherein regions of a radially outer portion of the open ring or segment are heated by means of a laser to produce expansion only at the radially inner side of the ring or segment, whereby the stress in the ring or segment changes in the sense of closing of the ring or segment, i.e. a decrease in said diameter.  
     
     
         5 . Corneal insert in accordance with  claim 1 , consisting of a material such as PMMA in which small bubbles can be generated by treatment with, for example, laser radiation, wherein the bubbles remain and can thus lead to an expansion of the material.  
     
     
         6 . Corneal insert in accordance with  claim 1 , wherein the insert is made of a material which shrinks permanently on being heated, such as for example PVC.  
     
     
         7 . Corneal insert in accordance with  claim 1 , characterised in that the ring comprises first and second layers, such as a radially inner layer and a radially outer layer of differing materials one of which shrinks irreversibly when heated, for example PVC with amorphous components.  
     
     
         8 . Corneal insert in accordance with  claim 1 , characterised in that the ring comprises first and second layers, such as a radially inner layer and a radially outer layer of differing materials one of which expands irreversibly when heated.  
     
     
         9 . Corneal insert in accordance with  claim 7 , wherein said first and second layers comprise radially inner and radially outer layers, wherein the other said layer is formed a material which expands permanently when heated, for example PMMA.  
     
     
         10 . Corneal insert in accordance with  claim 7 , wherein the layer which shrinks when heated is the radially outer layer.  
     
     
         11 . Corneal ring in accordance with  claim 10 , wherein the radially inner layer comprises a material which does not shrink when heated, such as PMMA, or of a material which shrinks to a lesser degree than the radially outer layer, or of a material which expands when heated.  
     
     
         12 . Corneal insert in accordance with  claim 7 , wherein the radially inner layer comprises a material which shrinks permanently when heated.  
     
     
         13 . Corneal insert in accordance with  claim 11 , wherein the radially outer layer consists of a material which does not shrink when heated, or shrinks less than the radially inner layer, or consists of a material which expands when heated.  
     
     
         14 . Corneal insert in accordance with  claim 1 , wherein it consists of a ring or segment of memory metal, such as tinitol.  
     
     
         15 . Corneal insert in accordance with  claim 14 , wherein a shape having a specific ring diameter was first impressed on the ring or segment at a temperature above the step temperature, and the ring was subsequently bent to a smaller radius below the step temperature, whereby on heating the ring to a temperature above the step temperature it attempts to adopt the impressed form with greater diameter, the precise change in radius of the ring or segment depending on the areas of the ring that are heated, to choose the step temperature.  
     
     
         16 . Corneal insert in accordance with  claim 1 , wherein is comprises a ring having a plurality of turns.  
     
     
         17 . Instrument for cutting a ring-like channel, in particular within the periphery of the cornea of an eye, characterised in that it has a working end which consists of at least one turn ( 33 ) of an least substantially helical wire ( 42 ) resembling one turn of a thread and having a parting or cutting tip ( 36 ) at its one end ( 34 ) and merging at its other end ( 38 ) into an actuating part or into a handle.  
     
     
         18 . Instrument in accordance with  claim 17 , characterised in that the wire part leading to the actuating part or handle extends at least substantially coaxial to the helix and merges into the helix via a section which extends at least partly radially.  
     
     
         19 . Instrument in accordance with  claim 17  or  18 , characterised in that the parting or cutting tip is formed for attachment to the one end of an elongate part which forms a corneal ring, or can be formed into a corneal ring, in order to draw this part into the ring-like channel on turning the instrument backwardly.  
     
     
         20 . Instrument in accordance with  claim 17 , characterised in that the handle is formed as an oscillation generator ( 40 ) in order to assist or facilitate the cutting action and the guidance of the instrument by the surgeon through oscillations of the cutting tip about the central longitudinal axis of the instrument or of the handle.  
     
     
         21 . Instrument in accordance with  claim 20 , characterised in that the oscillation frequency is higher than the natural frequency of the handle or of the eye and preferably at least substantially the same as the natural frequency of the cutting tool consisting of wire.  
     
     
         22 . Instrument in accordance with  claim 17  in combination with an image forming system or an optical enlargement system in order to facilitate the guidance of the instrument by the surgeon.  
     
     
         23 . Method of correcting the refractive power of an eye or for compensating for refraction errors, wherein a ring-like channel is cut into the periphery of the cornea and an elongate member of metal or plastic which can be formed into a segment of a ring having at least one turn with a diameter matched to that of the periphery of the cornea is introduced into the channel, and wherein at least the fine correction of refractive errors is effected after the insertion of the segment or ring, characterised in that the ring is comprised of a material which can be expanded and/or contracted after insertion by the action of radiation, in particular electromagnetic radiation such as laser light, thermal radiation, electromagnetic induction or magnetism, and in that the said fine correction is effected in situ in the eye by the use of such radiation in particular electromagnetic radiation such as laser light, thermal radiation, electromagnetic induction or magnetism.  
     
     
         24 . Method in accordance with  claim 23 , wherein the elongate part is preformed into a ring or segment prior to drawing it into the ring channel.  
     
     
         25 . Method in accordance with  claim 23 , characterised in that the insertion of the elongate part into the ring channel takes place by reverse rotation of the instrument used to cut the ring-shaped channel.  
     
     
         26 . Method in accordance with  claim 23 , wherein the coarse correction of the refractive error takes place by the insertion of a corneal ring or segment having a previously calculated diameter or spring tension.  
     
     
         27 . Method in accordance with  claim 23 , wherein said fine correction is effected after the healing of the ring in place in the eye and the disappearance of initially existing tissue strains.  
     
     
         28 . Method in accordance with  claim 23 , wherein the fine adjustment of the corneal ring or segment takes place with simultaneous checking of the optical parameters of the eye with the aid of a refractometer.  
     
     
         29 . Method in accordance with  claim 23 , characterised in that a microcomputer or a data processing plant is used to coordinate and control the fine adjustment, for example the active positions of a laser beam used to effect the fine adjustment while taking account of the measurement results of the refractrometer.