the change in the corneal surface using the surgical device of the present invention will be determined by an optical correction formed into a custom made member or insert based upon a doctor &# 39 ; s prescription . the prescription is similar to the prescription a doctor might give to an optical laboratory for the purpose of grinding lenses for eye glasses or for contact lenses . fig1 illustrates a particular prescribed corrective portion which is to be removed from a patient &# 39 ; s eye . this lenticular cut portion 40 which is to be removed from an eye has two surfaces 41 , 42 which form a positive meniscus ( crescent ) in shape . this prescriptive correction is mathematically converted to the optical equivalent 43 seen in fig2 . equivalent 43 has a planar side 44 and a convex side 45 . in accordance with the invention , the optical prescription is sculpted into a flat face 11173 of an insert 1117 shown in fig3 . the insert 1117 is then inserted into applicant &# 39 ; s instrument 1100 . the instrument is placed against the eye such that the eye is in contact with the insert . a knife edge is moved under the insert and an equivalent cornea portion of the eye is cut off thereby altering the curvature of the cornea by precisely the prescribed amount . the prescriptive member or insert 1117 as shown in fig3 has surface 11173 profiled to correspond to the plano convex shape of fig2 . as shown in fig3 corrective portion 11172 of the insert 1117 corresponds to the equivalent shape 43 . the insert 1117 is carried by a device 1100 shown in its entirety in fig7 and which is described in greater detail below . the device 1100 serves to hold the insert 1117 in position on an eye while a knife blade is passed under the insert and immediately adjacent thereto . in accordance with the invention a vacuum chamber is formed by a suction ring carried by the device 1100 and the eye adjacent to the lower surface of the insert 1117 . application of partial vacuum to this chamber raises the innerocular pressure of the eye causing the cornea of the eye to be urged into contact with the prescriptive portion of the insert 1117 . fig4 , and 6 illustrate the sequence of operation on an eye 50 in schematic form . the eye 50 is shown schematically without the device of the present invention in fig4 . in fig5 the surgical device 1100 which is not shown is placed into contact with the eye and a partial vacuum is applied to the sclera 52 . the vacuum is adjusted to a level such that forces are applied to the cornea 51 by the suction ring raising the innerocular pressure in the eye 50 and forcing the eye to bulge outwardly causing the cornea 51 to fill the prescriptive concave depression 11172 of the insert 1117 . the portion of cornea 51 filling the depression 11172 in the insert 1117 is rapidly but smoothly excised by a knife 1115 oscillating from side to side . knife 1115 is advanced across the eye at a predetermined rate in a plane parallel and adjacent to the flat face 11173 of the insert 1117 . the knife 1115 has a knife edge which is flat on its upper surface and beveled on its lower surface 11153 . after the cut has been made , the partial vacuum is released . as shown schematically in fig6 when the vacuum is released the cornea 51 will return to its normal shape less the disk portion 56 excised by the cut . the disk 56 is of a lenticular cut of the required refraction so that the remaining cornea 57 has precisely the proper refractive power for emmetropia ( normal vision ). all the components to assemble the device 1100 are shown in fig7 and the exploded assembly drawing of fig8 . as shown in fig7 and 8 , device 1100 includes a single piece body 1102 . body 1102 carries a pin registration plate 1103 . the plate 1103 has two registration pins 1105 which are press fit into apertures in the plate 1103 . plate 1103 is retained on base 1102 by means of a locking pin 1104 which is pressed into corresponding apertures in plate 1103 and body 1102 . a suction plate 1101 is assembled to the body 1102 at one end by means of two apertures which engage the pins 1105 . at the other end , the suction plate is retained on the body by means of a retaining screw 1119 which extends through the body 1102 . captured between the suction plate 1101 and the body 1102 is the optical insert 1117 and a knife 1115 . the knife 1115 and the insert 1117 are for purposes of clarity not shown in 29 in the actual positional relationship relative to the body 1102 and the plate 1101 . an actuator holder 1109 is fastened to the base 1102 by means of screw fasteners 1110 . a linear actuator 1112 is captured in and supported in the holder 1109 . a set screw 1111 is used to secure the actuator in position . the suction plate includes through bores which are in communication with apertures in the vicinity of the suction ring to form a suction chamber . the through bores exit the rear of the suction plate and are connected to a vacuum source by , for example , a vacuum manifold 1114 . the actuator 1112 has a piston 11121 extending from its one end . a motor holder 1106 is secured to the piston 11121 by means of fasteners 1107 . the motor holder 1106 carries a blade drive motor 1108 . the motor holder also carries the knife 1115 on its bottom surface . the linear actuator 1112 serves to advance the knife 1115 such that knife 1115 traverse the area of the suction ring plate 1111 which carries the suction ring . while the knife 1115 is advanced , the blade motor 1108 drives the knife 11115 such that the leading edge of the knife oscillates from side to side . turning now to fig9 and 11 , the suction ring plate 1101 includes a suction ring 11011 . suction ring 11011 has a stepped portion produced by an inner aperture 11012 in the plate 1101 . a square corner or shoulder 11013 is formed which will exert a force against the sclera of an eye . this force in conjunction with the forces exerted by the peripheral edge of suction ring 11011 against the eye will cause the eye to generate equilibrium forces which urge the eye into contact with the insert 1117 . the aperture 11012 has a diameter which is smaller than the diameter of the prescriptive insert 1117 which is positioned above the aperture 11012 . the plate 1101 includes two through bores 11014 . bores 11014 have one end which opens into the interior of the suction ring 1101 at openings 11015 and at the other end each has a port 11016 which receives the vacuum manifold 1114 . as shown in fig1 , beveled edges are used at the edges of the suction ring 11011 and shoulder 11013 . the suction plate includes a recess 11017 in its top surface . the recess 11017 is sized to receive the knife 1115 and to retain the knife in planar position such that it may be moved forward and back in reciprocating movement within the plane immediately above the suction ring 11011 and immediately below the insert 1117 . the recess is of a width such that the knife 1115 may also pivot from side to side within the same plane as the reciprocating movement . a second recess 1108 is provided which allows the pivot pin 11061 which extends downward from the motor holder 1106 to freely slide back and forth as the knife 1115 is advanced and retracted . the one piece body assembly 1102 is shown in detail in fig1 , 13 and 14 . the body 1102 includes an insert receiving aperture 11021 . the rear portion of the body 1102 includes a recess 11022 which receives the pin registration plate 1103 . the recess is sized such that the plate 1103 is firmly held in place . a pin 1104 is inserted through apertures 11023 to retain the plate 1103 . the plate 1103 has two registration pins 1105 which are received in corresponding apertures in the suction plate 1101 . the other end of the suction plate 1101 is removeably retained against the bottom of the body 1102 by means of screw 1119 which is received in bore 11023 . body 1102 has a central aperture 11024 in which the motor holder 1106 and the blade drive motor 1108 may reciprocate back and forth . the body 1102 includes apertures 11024 which receive screws that fasten the actuator holder 1109 to the body 1102 . prior to assembling the suction plate 1101 to the body 1102 , the prescriptive insert 1117 is slid into the aperture 11021 . stop pins 1118 carried in the body 1102 limit the movement of the insert 1117 in the upward axial direction . when the suction plate 1101 is coupled to the base 1102 , the suction plate 1101 prevents movement of the insert 1117 in the axial downward direction . thus the insert 1117 is captured in the body 1102 . it should be noted that although stop pins are utilized in this embodiment , the through bore aperture 11021 could be stepped to provide a shoulder against which the upper surface of the insert 1117 rests . in addition , the knife 1115 is captured between the body 1102 and the suction plate 1101 . the insert is shown in fig1 , 16 and 17 . the insert 1117 of this embodiment includes an alignment scale 11171 which is laser etched into its upper surface , along with cross hairs . a keyway 11172 integrally formed in the insert 1117 engages a corresponding lug 11025 on the body 1102 to provide precise registration of the insert 1117 in the device 1100 . alternatively , the keyway or groove 11172 may extend axially only over a portion of the insert rather than along its entire length . in this alternate instance , the lug would be no longer than the keyway or groove and could be a pin rather than a lug . the motor holder is shown in fig1 , 18a , and 19 . motor holder 1106 includes a motor receiving ring 11061 to receive the blade motor 1108 . a linear actuator 1112 is secured to the device 1100 by utilizing the actuator holder 1109 . the linear actuator is a commercially available device and includes a piston 11121 which extends from the actuator 1112 and which is coupled to the motor holder 1106 by fasteners 1113 . the knife motor 1108 is shown in fig2 and 21 . the shaft 11082 of the motor 1108 terminates in eccentric 11081 which engages the aperture 11152 of the knife 1115 . the eccentric is formed by a bearing 11082 on shaft 11081 . the bearing 11082 is pressed onto the shaft 11081 such that it is off center to form an eccentric . alternatively the shaft 11081 could have its end machined into an eccentric . with the rear end of the knife pinned to the holder 1106 by pivot pin 11061 , the rotation of the eccentric in the slot 11152 in the knife 1115 will cause the front edge of the knife 1115 to swing from side to side in an arc . the knife 1115 is shown in detail in fig2 and 21 . the knife includes a pivot hole 11151 which engages a pivot pin 11061 of the motor holder 1106 . the knife also includes aperture 11152 which receives eccentric 11081 on the output shaft 11082 of motor 1108 . the aperture or slot 11152 is of a width corresponding to the diameter of the eccentric 11081 and a length which is at least twice the distance of the center of the eccentric to its furthest point . by utilizing an eccentric 11081 in conjunction with a pivot pin , as the motor shaft 11082 turns , the knife 1115 will swing side to side through an arc to enhance cutting as the knife is reciprocally advanced . it has been found that the knife 1115 is ideally formed of zirconium . zirconium is particularly advantageous because with zirconium , an extremely smooth and flat upper surface may be obtained on the knife 1115 . with zirconium the top of the cutting edge may be made flat and the bottom surface 11151 may be beveled so that a chisel edge is found to achieve extremely smooth cuts . in contrast , with stainless steel , as the knife is sharpened a wire is formed along the cutting edge . this wire may be eliminated by back stropping of the edge . however , after backstropping , the top edge of the knife will be concave as shown in fig2 . with the top edge concave , cuts of the cornea will not have the prescriptive accuracy desired . operation of the device is simple . the physician places a custom made insert such as insert 1117 into the cutting instrument 1100 . the physician then places the instrument 1100 over the patient &# 39 ; s eye with the insert 1117 , which is made of a clear material , over the cornea . the physician centers the insert on the eye and activates a vacuum source so that the suction size will retain the eye in position relative to the insert . the physician then activates knife motor 1108 , and activates the linear actuator 1112 which automatically advances the knife a preset distance at a predetermined speed which is approximately 0 . 5 to 1 . 0 mm / sec . when the knife advances to the preset point , the knife motor 1108 and linear actuator 1112 are automatically turned off and the partial vacuum is released . the entire procedure from centering of the optical zone to the completion of the cut should take no more than 30 seconds . a patch is placed over the patient &# 39 ; s eye and the operation is complete . with the present invention , highly precise corrections may be made because highly precise sculpting or grinding apparatus are commercially available to form the prescriptive corrective recess in the inserts . these apparatus in combination with computer technology allow forming the recess 11172 of the insert 1117 to exactness within two tenths of a micron . visual positional alignment is achieved using crosshairs 11171 as shown in fig1 which allows the surgeon to look through the insert to align the crosshairs 11171 with the optical center of the eye after which the vacuum is applied . insert 1117 is transparent and is preferably made of an acrylic plastic such as the well known pmma . equivalent materials include materials used for the manufacture of eye glasses or hard contact lens . the insert 1117 may be alternatively provided with a convex , planar or irregular correction formed into the flat face 11173 of the insert 1117 to provide corresponding corrective cuts in the cornea . irregular corrections for such defects as astigmatism may be formed into the insert 1117 by means of a laser or by use of optical grinding machines . the resulting insert is shown in fig2 . thus , the refractive correction for any degree of myopia , hyperopia , or astigmatism can therefore be precisely and predictably formed into an insert . fig2 illustrates a negative meniscus cut which will correct for hyperopia and the resulting cut 471 which is produced in an eye 50 is shown in fig2 . fig2 illustrates an insert which will produce a lamellar cut . fig3 illustrates how an insert which provides multifocal corrections may be shaped . the foregoing description of a preferred embodiment has been presented for the purposes of illustration and description . many modifications and variations may be made without departing from the spirit or scope of the invention . it is intended that the scope of the invention be limited by the claims appended hereto .
a surgical device for altering the curvature of an eye includes a base which carries a transparent insert , a drive device , a knife edge coupled to the drive device and movable to a plane immediately adjacent the under surface of the transparent insert . the transparent insert includes a face having a surface portion shaped according to a predetermined correction . the base further includes a suction ring which forms a vacuum chamber with the eye . the suction ring is placed against the eye . application of vacuum results in the cornea of the eye being urged into engagement with the shaped surface portion . actuation of the drive device moves the knife edge whereby the cornea is cut . only the knife edge traverses the insert .