A cam guided corneal trephine for selectively cutting a portion of an eye is provided herein. The cam-guided corneal trephine comprises a base, a coarse adjusting ring, interchangeable annular ring, interchangeable annular cams operatively supported by the adjusting ring, the annular cams having various inner round diameters or other than round dimensions, and a roller cage assembly adapted to be disposed and rotated within the annular cam, the roller cage assembly having a blade mounting means disposed therein for providing a continuous cut of the corneal tissue corresponding to the inner shape of the selected cam upon rotation of the roller cage assembly.

FIELD OF THE INVENTION 
The present invention is directed to a cam guided corneal trephine used to 
cut a circular or non-circular (or other than round) portion of the 
cornea. 
BACKGROUND OF THE INVENTION 
Corneal trephines have been used in lamellar and penetrating keratoplasty. 
Originally, such trephines have been in the form of a honed cylinder as 
developed by Castroviejo. Many surgeons have attempted to improve the 
techniques as developed by Castroviejo, see U.S. Pat. No. 4,423,728. Many 
surgical companies have attempted to make holders for such cylinders in 
order to improve the visualization of the cutting edge but such attempts 
have generally been insufficient due to lack of proper centering, 
obscuration of the cutting edge at sometime during the procedure, 
independent eye and trephine movements, and lack of ability to cut other 
than round windows in the corneal tissue. 
An improved corneal trephine was developed by David M. Lieberman, M.D., as 
described in the American Journal of Ophthalmology, May, 1976, pages 
684-685. As described therein, the surgical instrument was comprised of 
inner and outer cones, the inner cone revolving within the outer cone. The 
outer cone included an upper ridge held by the non-dominant hand of the 
surgeon, stabilizing the instrument on the eye, and a lower ridge 
containing an annular suction device which firmly held the eye with a 
pressure of from 10-15 mm Hg to assure centration of the device over the 
cornea. The inner cone revolved within the outer cone and carried a slide 
mechanism with an attached disposable razor blade. To perform the 
incision, the inner cone which carried the blade was rotated about the 
cornea. After each rotation, the blade was lowered a few thousandths of an 
inch by turning a screw and the inner cone was rotated again. The incision 
could be viewed through an operating microscope. The slide mechanism upon 
which the blade was mounted was controlled by an adjustment screw for 
varying the radial position of the blade. Two interchangeable cutters 
could be used, one at a time. The first provided the razor blade at a 
20.degree. angle. The second cutter mechanism held the blade vertically 
and was suitable for keratoplasty in which a donor cornea had been punched 
for reinsertion onto a patient's cornea. 
Although the single trephine described above represented a significant 
advance in the art, the device could only provide a round cut and, 
consequently, could not be employed whenever an other than round incision 
was required. 
A second improved corneal trephine was developed by David M. Lieberman, 
M.D., and is disclosed and claimed in U.S. Pat. No. 4,423,728 which 
disclosure is hereby incorporated herein by reference. The advantages of 
this trephine include the use of a circular or non-circular cam which 
guides the path of the cutting blade to provide either a circular or other 
than round cut of the cornea. As described therein, the surgical trephine 
comprises a base, a non-circular cam guide operatively connected to the 
base, and a rotation cone adapted to be disposed and rotated on the base, 
the rotation cone having a blade mounting means provided thereon. The 
blade mounting means includes a slide mechanism with an attached 
disposable razor blade and is further provided with a slave wheel which 
rides on the non-circular cam guide such that upon rotation of the 
circular rotation cone the blade means provides a cut of the cornea 
following the pattern of the annular cam guide. The razor blade is 
connected to the blade mounting means through a vertical adjustment screw 
such that upon adjustment of the screw, the blade could be moved 
vertically to control the depth of cut of the blade into the corneal 
tissue. 
The above device was also provided with an angled blade mounting means 
which operated similarly to the vertical blade means to provide a cut 
within the corneal tissue in an other than vertical manner. 
And, while the cam-guided trephine device described above and in U.S. Pat. 
No. 4,423,728 represented a significant advance in the art over the single 
point trephine described in the David M. Lieberman article, the cam guided 
trephine could still be improved. Specifically, the razor blade had a 
tendency to wobble during rotation of the blade, and the depth of cut of 
the cornea was difficult to accurately control. Further, since the 
complete cutting action of the corneal tissue was interrupted after each 
rotation of the blade means to incrementally lower the cutting blades, the 
cornea lamella is allowed to spread providing an uneven incision or 
"hour-glass" effect. Further, the process of making a complete cut through 
the corneal tissue was very slow. And, further, the sudden incremental 
lowering of the cutting blade for each new rotation of the blade means 
tended to displace the corneal tissue and thereby producing an uneven cut. 
SUMMARY OF THE INVENTION 
It is therefore an object of the invention to provide a cam-guided corneal 
trephine which overcomes the disadvantages of the prior art trephines. 
It is a further object to provide a cam-guided corneal trephine having an 
interchangeable blade means providing either a vertical or angled cut with 
respect to the corneal surface of the eye. 
It is a further object of the invention to provide a cam-guided corneal 
trephine which includes a blade which can provide either a "round" or 
"other than round" cut of the cornea. 
It is a further object of the invention to provide a cam-guided corneal 
trephine which includes a cutting blade and roller cage assembly that will 
decrease any wobble during rotation of the roller cage assembly within an 
interchangeable cam. The cams can have either an inner round cam guiding 
surface or an inner non-round cam guiding surface to allow the cutting 
blade to cut either a round or other than round hole in the corneal 
tissue. 
It is a further object of the invention to provide a cam-guided corneal 
trephine which includes an inner adjusting ring which supports the roller 
cage assembly and cutting blade to provide a course blade height 
adjustment relative to the surface of the corneal tissue. 
It is a further object of the invention to provide a cam-guided corneal 
trephine which includes a roller cage assembly supporting a cutting blade 
which provides a continuous cutting action during rotation of the roller 
cage assembly to provide a smooth, uninterrupted cut of the corneal 
tissue. 
And, it is a further object of the invention to provide a cam-guided 
corneal trephine which includes a blade holding means supporting a cutting 
blade which continuously advances the cutting blade towards the corneal 
tissue of the eye during rotation of the blade holding means to provide a 
smooth uninterrupted cut of the corneal tissue without wobble or 
deflection of the cutting blade. 
In accordance with the above objects, a novel cam-guided corneal trephine 
device is provided herein The cam-guided corneal trephine comprises a 
base, a course adjusting ring, interchangeable annular cams operatively 
supported by the adjusting ring, the annular cams having various inner 
round diameters or other than round dimensions, and a roller cage assembly 
adapted to be disposed and rotated within the annular cam, the roller cage 
assembly having a blade mounting means disposed therein for providing a 
cut of the corneal tissue corresponding to the inner shape of the selected 
cam upon rotation of the roller cage assembly. 
The blade mounting means provides a continuous adjustment of the blade 
height or blade advancement upon rotation of the roller cage assembly 
while grasping the end of the blade mounting means. This continuous blade 
advancement is accomplished by use of a differential thread arrangement 
provided within the blade mounting means to allow the tip of the blade to 
advance downwardly 0.096 mm per revolution of the roller cage assembly and 
blade mounting means as is further described below. 
More specifically, the roller cage assembly includes a generally circular 
cage having three rollers provided therein. A first roller is fixed within 
the cage and has the blade mounting means secured through its diameter. 
The other two rollers are affixed to the cage in radial slots and are 
biased outwardly from the cage to allow the roller assembly to be rotated 
about the inner cam surface. In this fashion the roller cage assembly can 
be rotated within a cam having an other than round inside dimension.

DETAILED DESCRIPTION OF THE INVENTION 
The cam-guided corneal trephine according to the present invention is shown 
in FIGS. 1-5. Specifically referring to FIG. 1, the cam-guided corneal 
trephine 10 as shown includes a suction ring 12 for conforming and 
securing the patient's eye E and trephine 10, an annular base 14 integral 
with the suction ring 12, a course adjustment ring 16, an interchangeable 
cam 18, a roller cage assembly 20 and a blade mounting means 22 mounted 
within roller cage assembly 20 for rotational movement relative to the 
annular base 14 integral with the suction ring 12. A locking or retaining 
ring 24 is secured into the top of the adjustment ring 16 to secure the 
cam 18 and roller cage assembly 20 within the adjustment ring 16. The base 
14 includes a pair of finger grips 26. In the device shown in the Figures, 
suction ring 12 and base 14 are connected by an outer cone 28, and 
elements 12, 14 and 28 are formed from a single integral piece. The blade 
mounting means 22 includes a moveable diamond tipped cutting blade 30 for 
cutting the corneal tissue. 
The course adjustment ring 16 is provided with an external thread 32 which 
is received within a mating internal thread 34 provided in the annular 
base 14. The course adjustment ring 16 provides for a 6 millimeter (mm) 
adjustment of the blade mounting means 22 relative to the corneal surface 
of the eye E. The top surface of the adjustment ring 16 is provided with a 
plurality of number indicators 1 through 6 positioned about the periphery 
of the ring and the base is marked with a "V" as shown at 36 to provide a 
reference point for marking the position of the adjustment ring 16. The 
adjustment ring 16 is provided with a locking screw 38. The locking screw 
38 is tipped with a nylon insert (not shown). When the course adjustment 
ring 16 is threaded into the base 14 such that the cutting blade 30 is 
positioned immediately adjacent the patient's cornea, the locking screw 38 
is threaded through the ring 16 until the nylon tip is in contact with the 
external threads 32 of ring 16 to hold the ring in position relative to 
the annular base 14. In one embodiment of the invention by way of example 
and not to be construed in a limiting manner, the external thread 32 of 
ring 16 and internal thread 34 of base 14 are of a truncated metric thread 
design having a diameter of 47 mm and a pitch of 6.35. 
The adjustment ring 16 is provided with an inner circular surface 40 and a 
bottom bearing surface 42. The interchangeable cam 18 as shown in FIGS. 4 
and 5 is positioned within the adjustment ring 16. The outer generally 
circular surface 44 of the cam 18 is configured to fit snugly against the 
inner surface 40 and is supported on the bottom bearing surface 42 of ring 
16. The cam 18 is further held in position within ring 16 by use of a set 
screw (not shown). The inner surface of the cam 18 can either be 
configured in either a generally circular or round shape as shown at 46 in 
FIG. 5 or an other than round shape as shown at 48 in FIGS. 2 and 4. 
The roller cage assembly 20 includes a cylindrical cage member 52 for 
supporting the blade mounting means 22 for rotational movement within the 
annular base 14 and ring 16. The cage member 52 includes a top member 53 
with three depending cylindrical side members 57 and a bottom member 55 
which can be affixed to the depending side members 57 to form an integral 
cage member 52. The cage assembly is provided with three (3) rollers 
positioned about the periphery of cage member 52 at approximately 
120.degree. from one another. Two of the rollers 54 and 56 are spring 
loaded and are received in radial slots 58 and 60, respectively provided 
in top and bottom surfaces 53 and 55, respectively on cage member 52. The 
spring loaded rollers 54 and 56 are biased radially outwardly from the 
cage member 52 by springs 62 and 64, respectively. A third roller 66 is 
provided in a fixed position about the cage and is configured to receive 
the blade mounting means 22 through the center of its diameter. This blade 
roller 66 has a larger diameter than rollers 54 and 56 to provide the 
necessary clearance for receiving the blade holding means 22. The rollers 
54 and 56 and blade roller 66 extend outside the periphery of cage 52 so 
that such rollers contact the inner cam surface 48 and bottom bearing ring 
surface 42, thereby allowing the roller cage assembly 20 to rotate freely 
within cam 18. 
The roller cage assembly is held in place within the ring 16 by use of a 
locking ring 24 which is threadably received within the top portion of 
ring 16. The locking ring 24 is provided with two indentations 70 in its 
top surface which can receive a spanner tool (not shown) for installing 
and removing the locking ring 24 from the adjustment ring 16. 
The blade mounting means 22 includes a body 74 having an externally 
threaded portion 76 extending up through a spacer member 78 provided in 
blade roller 66. The blade body 74 is secured to the roller cage 52 by an 
internally threaded collar 80 received on the externally threaded portion 
76 of blade body 74. The threaded collar also has an externally threaded 
portion 82 on its upper end. An axially moveable center rod 84 is 
positioned within body 74 and has an externally threaded portion 86 at its 
uppermost or distal end from body 74 extending above the threaded collar 
80. A blade holder 88 carrying the diamond tipped cutting blade 30 is 
positioned within body 74 and is secured to the lowermost or proximal end 
of center rod 84. A drive pin 90 is threaded through the body 74 and is 
received in a slot 92 provided in center rod 84 to prevent rotational 
movement of rod 84 while allowing for axial movement of rod 84 so that the 
cutting blade 30 can be raised and lowered relative to the roller cage 
assembly 20 and base 14. 
A thimble 96 having a knurled outer surface 98 is threaded onto the 
externally threaded portions 82 and 86 of threaded collar 80 and center 
rod 84, respectively. The thimble 96 is provided with two internally 
threaded portions 100 and 102 for receiving such externally threaded 
portions 82 and 86, respectively. Such an arrangement has been called a 
"micrometer" thread or a "differential" thread arrangement to allow for 
precise axial movement of the center rod upon rotational movement of the 
thimble. The center rod 84 is prevented from being unscrewed from the 
thimble 96 by use of a retaining screw 104. 
By way of example, the internal thread 100 of thimble 96 and the external 
thread 82 of collar 80 are a metric 5 mm diameter and having a pitch of 
0.5. The internal thread 102 of thimble 96 and the external thread 86 of 
rod 84 are a metric 3.5 mm diameter and having a pitch of 0.6. Therefore, 
upon clockwise rotation of the roller cage assembly 20 within the trephine 
10 but not allowing the thimble 96 itself to turn in the operator's 
fingers, the center rod 84 and consequently, the blade holder 88 and 
diamond tipped blade 30 will lowered by 0.096 mm per revolution of the 
roller cage assembly 20. 
The blade mounting mechanism 22 is positioned through the roller cage 
assembly 20 on an angle to allow for maximum viewing by the surgeon 
through the center of the device. The blade holder 88 is angled with 
respect to the center rod 84 so as to present the cutting blade 30 in a 
vertical orientation to the corneal tissue E to be cut by the trephine. By 
way of the specific example above, the 0.096 mm of axial movement per 
revolution of the roller cage assembly 20 will translate into 0.1 mm 
movement of the blade 30 into the corneal tissue. 
The roller cage assembly 20 freely rotates within cam 18 of trephine 10 on 
spring loaded rollers 54 and 56 and the blade roller 66. Since the spring 
loaded rollers are biased radially outwardly at all times, these rollers 
force the blade roller 66 to closely follow the inner surface 48 of cam 
18. As is shown in FIGS. 4 and 5, it is possible for the inner cam surface 
to be of various diameter round configurations as shown at 46 in FIG. 4 or 
to be of an other than round or possibly oval configuration as shown at 48 
in FIGS. 2 and 5. In this fashion the blade mounting means 22 and cutting 
blade 30 will closely follow the geometric pattern provided on the inside 
surface of cam 18. 
Suction ring 12 of trephine 10 functions by virtue of the void space left 
between inner and outer suction rings 108 and 110, which void space 
communicates with a tube 112 adapted to be connected to a source of 
suction. Suction ring 12 may be identical to the one provided in the 
cutting device disclosed in the aforementioned U.S. Pat. No. 4,423,728, 
and accordingly may have a frustoconical shape with a constant height 
throughout. It is also contemplated that the suction ring may be slightly 
tilted in such a way that its height varies between maximum and minimum 
values at about 180.degree. opposed locations in order to compensate for 
the variation in corneal thickness between the inferior (minimum corneal 
thickness) and superior (maximum corneal thickness) cornea. 
The various included pieces and parts of which trephine 10 is comprised may 
be prepared by conventional methods, for example casting, machining, etc., 
from a suitable metal or metal alloy (e.g. stainless steel). 
Alternatively, injection molded plastic pieces and parts may be utilized 
in a disposable embodiment of the invention. 
The operation of trephine 10 will be described with reference to an 
ophthalmic surgical procedure for removing a piece of corneal tissue in 
contemplation of a corneal transplant operation. First, the surgeon or 
operator would grasp the trephine 10 by finger grips 26 and place the 
suction ring upon the corneal surface E of the eye. An appropriate suction 
would be applied to suction ring 12 to secure the trephine 10 to the 
corneal surface. To start an incision, the operator would first rotate the 
thimble 96 clockwise to its lowest position which would raise the cutting 
blade 30 to its fully up position. Then, by rotation of course adjustment 
ring 16, the operator would lower the blade mounting means 22 and diamond 
tipped blade 30 to a position immediately adjacent to the corneal tissue 
E. The locking screw 38 would then be secured to prevent further rotation 
of the adjusting ring 16. 
The operator would then grasp the thimble 96 firmly within the fingers of 
his or her other hand and rotate the roller cage assembly 20 in a 
clockwise direction about the annular base 14 without allowing the thimble 
96 to rotate. Consequently, the blade 30 would be lowered into the corneal 
tissue 0.1 mm per revolution of the roller cage assembly 20 until the 
corneal tissue E has been completely dissected. In this manner, the 
cutting blade 30 of the trephine 10 provides a continuous cutting action 
of the tissue providing a smooth annular hole therein. To raise the 
cutting blade 96, the operator would rotate thimble 30 clockwise while 
holding the roller cage assembly 20 still until the thimble 96 is screwed 
back down against the roller cage member 52 which would raise the blade 30 
back to its original position. 
To change from one interchangeable cam 18 to another, the operator would 
unscrew the locking ring 24 with spanner wrench (not shown). The roller 
cage assembly 20 would then be removed from the course adjustment ring 16 
and set aside. The adjustment ring 16 would then be removed from the 
annular base 14. The retaining screw (not shown) in the side of ring 16 
would be loosened and cam 18 would be removed from the ring 16. A 
different cam having a different inside dimension could be put back into 
the ring 16 and the steps outlined above reversed to place the trephine 10 
back in working condition. 
Thus, the cam-guided trephine in accordance with the present invention 
provides a technique for allowing a vertically disposed blade 30 to 
provide an annular cut of essentially any practical shape, diameter and 
depth. However, it should be noted that while a vertical blade 30 has been 
shown in use, it would be equally possible to utilize an angled blade to 
be used in its place. And, although the trephine in accordance with the 
present invention is disclosed for use in a procedure for a corneal 
keratoplasty operation, it will be readily apparent to those skilled in 
the art that other surgical procedures may be performed by the present 
invention as well. 
Although the present invention has been described with respect to a 
specific embodiment of the apparatus, it is also readily, apparent that 
modifications, alterations, or changes may be made without departing from 
the spirit and scope of the invention as defined by the following claims.