Keratorefractive system and method

A set of surgical instruments and a method for performing Keratorefractive eye surgery is disclosed. The set of surgical instruments includes two or more knife blades for making incisions of a precise depth in the cornea, and two or more footplate assemblies for holding each of the knife blades, the cutting portion of each knife blade extends from the footplate assembly by a precise fixed length corresponding to the precise depth of incision which can be made by that particular knife blade. Each footplate assembly includes a footplate which moves on the surface of the cornea to precisely control the depth of incision. Each footplate assembly also includes markers for indicating the range, fixed length and style of the knife blade, along with a handle for holding and manipulating each knife blade.

BACKGROUND OF THE INVENTION 
The current invention relates to surgical blades for use in 
Keratorefractive eye surgery or all forms of incisional Keratotomy and a 
novel method for performing same. More particularly, the invention is 
directed towards a system or sets of surgical instruments have fixed 
length knife blades that allow for safer and more precise corneal 
incisions. 
Keratorefractive surgery or incisional keratotomy involves changing the 
refraction of the eye's cornea by making incisions in, but not through the 
eye's cornea. In this type of surgery, the goal is to change the shape of 
the cornea by making plurality of incisions in the cornea. The procedure 
is known as either incisional Keratotomy or Keratorefractive surgery. The 
use of the term Keratorefractive surgery herein shall include all 
procedures involving corneal incisions made in order to affect or change 
the eye's vision or the cornea's refractive characteristics. 
The goal of Keratorefractive surgery is to result in emmetropia. In 
emmetropia, no optical defects exists, lights rays entering the eye focus 
clearly on the retina. Defects in visions are common and correctable to 
the point of defect free vision through Keratorefractive surgery. In 
hyperopia or farsightedness, the most common refractive error, the point 
of focus of the rays of light entering the eye lies behind the retina 
because the eye's cornea curvature is too shallow. This refractive defect 
usually has been corrected by using a convex(plus) lens in glasses or 
contact lenses. In myopia or nearsightedness, which affects about 
twenty-five percent of the adult population in the United States, the 
image entering the eye is focused in front of the retina because the eye's 
cornea is curved too steeply. This defect usually has been corrected by 
using a concave(minus) lens in glass or contact lenses. In astigmatism, 
the refraction is unequal in different meridians or quadrants of the eye. 
The cornea in this optical defect is shaped more like the surface a 
football, rather than like surface of a basketball when astigmatism is not 
found. This defect usually has been corrected through the use of cylindric 
corrective lens (a segment cut from a cylinder), that has no refractive 
power along one axis and is concave or convex along the other axis. 
In 1972, Dr. Syvatoslav Fyodorov introduced and began to practice a new eye 
surgery procedure that involved incisions in, but not through the eye's 
cornea. The Keratorefractive surgical procedure practiced by Dr. Fyodorov, 
primarily involved patients affected with myopia or nearsightedness. As a 
result of specific corneal incisions, Dr. Fyodorov was able to reduce or 
eliminate the myopia in many patients. By 1980, many successful 
keratorefractive surgical procedures were performed by Dr. Fyodorov. The 
surgical procedure developed by Dr. Fyodorov for treating myopia evolved 
with the corneal incisions being radial from the limbus to just before the 
optical zone. This procedure has become generally known as Radial 
Keratotomy (RK). Keratorefractive surgery has become very popular in the 
United States to correct vision problems. The RK, Astigmatic Keratotomy 
(AK) and the Hyperopia procedures are all growing in popularity as a way 
to correct defective vision. In some places and with some surgeons, the 
Hyperopia procedure has been designate as Hexagonal Keratotomy (HK) 
because in its initial practice the incisions in the cornea have been 
hexagonal. The Hyperopia procedure shall be referred herein through the 
use of HK, but it should not be read as being limited to hexagonal 
incisions because as Keratorefractive surgery develops the direction and 
the design or type of incisions will change. Therefore, HK shorthand 
herein will be for the general procedure or Hyperopic Keratotomy (HK). 
A typical RK surgical procedure will illustrate the problems encountered 
with current system and procedure, and will help illustrate the benefits 
of the current invention. RK is selected by way of example, but the 
current invention is applicable to all Keratorefractive surgical 
procedures, including but not limited to AK and HK. The use of the current 
systems and problems, as well as the current invention is applicable to 
all procedures where correction of vision defects are being made through 
any and all type of cornea incisions. In RK, the myopic condition is 
minimized or eliminated as the result of a series of corneal incisions. 
The current practice is to make the incision radially along and in the 
cornea. 
Exact incisions at a precise depth are critical to all the Keratorefractive 
surgical procedure. In Keratorefractive surgery the depth of penetration 
of the cutting blade must be controlled because the incision must not go 
through the cornea and perforate it. In Keratorefractive surgery, 
including RK, the cutting blade must cut to a depth of at least 
eighty-five percent of the total thickness of the cornea for the best 
result. The optimum incisions are those that are as deep as possible 
without causing the cornea to rupture, i.e., deep as possible without 
cutting all the way through the cornea. For practical reasons involving 
current practice, however, the depth of the incisions has been set at, at 
least eighty-five percent for a general rule of thumb. 
During the RK procedure at patient's eye is anesthetized with a local 
anaesthetic. The eye is then held open with a lid speculum. A microscope 
is then placed over the patient's eye and the surgeon marks the patient's 
optical zone with a optical zone marker utilizing a marking dye. The 
incisions in Keratorefractive surgery are usually made only outside of the 
optical zone of the cornea. Then the surgeon measures the center of the 
patient's corneal thickness using a pachymeter. That reading could 
typically be 0.540 mm. The surgeon then marks the eye with a radial zone 
marker (that can any number of marking protrusions with the typical number 
has been four to eight) to mark the cornea with dye for the incisions. The 
knife has a micrometer screw control in its handle that will extend or 
retract the knife blade that will make the incisions. The typical knife 
has a blade together with a foot plate surroundablly attached to the knife 
around and adjacent to the knife blade. The footplate has a highly 
polished surface and rides along the surface of the cornea as the knife 
blade extends beyond the footplate cutting the cornea to a depth that will 
not result in perforations, sutures and the end of the operation. 
The surgeon can take a number of measurements using a pachymeter in 
different areas of the cornea. The cornea's thickness changes from center 
to edge or limbus; the cornea getting thicker as the measurements are made 
from center to limbus. Also, the cornea changes thickness with quadrant, 
i.e. the quadrants being the areas defined by a simple x-y axis being 
superimposed over the cornea, The cornea thickness also changes due to the 
time of day, the humidity, and the quality of the air. Typically during 
the course of the day, the cornea will lose liquid or dehydrate and become 
thinner or increase its density. During the course of a Keratorefractive 
operation, the cornea can lose one percent of it thickness per minute. 
Therefore, the surgeon does not have a lot of time between measurements to 
make incisions. 
The length of the knife blade from the footplate to the tip is typical set 
with the micrometer screw control. Because of the problems associated with 
screw controls, the blade's protruding length is often checked at least a 
second time by a nurse or technicians and often a third time by the 
surgeon. These calibration checks are often made using a second sterile 
microscope in the operating room. This second sterile microscope has three 
sets of micrometer type adjustments in order to measure the knife blade's 
length. The first two being adjustment in the microscope's stage in the x 
and y plane. Then there is a micrometer scale in the reticle of the eye 
piece. The time consuming nature of the set-up to measure and calibrate, 
often requires a nurse and a technician to set and check the length of the 
knife's blade. Then, the surgeon will also check the length right before 
making the incision. 
The number of measurements and the micrometers used to measure all of a 
certain tolerance and variability. A stacking of tolerances due to device 
or person can result in incision that can be off as much as 0.100 mm or 
more. This calibration problem is and has been a problem in all types of 
Keratorefractive surgery. While the goal in Keratorefractive surgery is 
measure and cut for each incision and for each location on the cornea, the 
problems with calibration and the time delays has resulted in minimal 
measurement and a single depth of current being made for all incisions 
because setting the length of the knife once is so time consuming. 
Further, even when the micrometer knife is set to a desired depth, there 
have been problems with that measurement being off and the resulting 
incision being off because of the tolerance stacking noted above. 
The incisions are made in quadrants of the cornea. The difficulty of 
calibration has resulted in a minimal number of measurements being made, 
in many cases only a single pachymeter measure being made at the cornea's 
center. The micrometer knife blade's length is attempted to be set at that 
particular pachymeter reading, then checked with the second microscope and 
by the surgeon, nurse and/or technician. Because the cornea's thickness 
increases from center to edge, the center reading used as a approximate or 
gross eighty-five percent of thickness of the cornea. With the tolerance 
stacking, the corneas change in thickness due to time and quadrant, many 
times the incisions are inadequate resulting in under correction or too 
deep resulting in perforation, sutures and the end of the operation. The 
knife blade calibration problems related to RK in particular, and 
Keratorefractive surgery in general, has resulted in many patients having 
to under go a second operation because the initial surgery was resulted in 
under-corrected vision or sutures due to cornea perforation. 
Some surgeons do not use a second microscope to check knife blade length, 
but use a physical block or coin gauge. This devices measure by using 
physical contact of the blade as a limitation. Unfortunately, these type 
of gauges because of their design and intended use, can damage the knife 
blade. 
While measure and cut is the goal, the reality of time consuming 
calibration of the knife blade and the cornea's thickness changing during 
the operation due to dehydration, precludes numerous and multiple 
measurements during an operation under the currently available systems. 
Further and in particular to RK, several RK procedures are popular in the 
United States. One is known as the American method, where the initial 
wound is formed by plunging initially in to the edge of the optical zone, 
so the possibility of impinging on the optical zone incision is minimized, 
and the incision is made in a direction radially away from the optical 
zone. Another method is known as the Russian method, where the initial 
wound is made at the edge of the cornea and the direction of the incision 
is toward the optical zone. The Russian method results in less pressure 
during cutting and cleaner incisions, but has the danger of cutting into 
the optical zone. Both methods also use a different blade style, i.e. 
angle of blade, number of edges of the blade -the overall knife blade 
configuration would be a particular style. No matter the style, however, 
in both of these procedures, as well as others, the depth of incision has 
been a problem because of the current calibration problems noted above. It 
has not been unusual for the depth of cuts to be off anywhere from 0.050 
mm to 0.100 mm or more. These calibration problems have been encountered 
in all types of Keratorefractive surgery, including AK, RK, HK and all 
incisional Keratotomy. 
For example in AK surgery the cuts are usually arcuate or have T-cut 
designs and depth is very critical. In HK surgery, there have been 
hexagonal and octagonal incision designs in the cornea that should be to a 
specific and accurate depth. The problems with depth and under cutting and 
perforation .have been encountered in all types of Keratorefractive 
surgery. As the techniques develop and the types of incisions change, as 
they will in order to affect the necessary change to a particular cornea's 
shape, the necessary precision will have to be present in the knives even 
more. 
Many of the current knives used diamond knife blades, where the diamond 
knife blade is usually 6 to 7 mm in length. This size necessary to 
accomplish this particular diamond size for the micrometer knife usually 
is manufactured from a two karat diamond. The very same size diamond that 
is the most popular in the world for its use in engagement rings and the 
like. The current invention will address the problem and cost of using 
such popular diamonds. 
The problem is calibration and despite efforts to check the cutting blades 
length through the use of a optical reticle in the operating room, the X-Y 
plane digital micrometer adjustments needed in that type of measurement 
often does not reduced errors, but actually has compounded the tolerance 
or cut-depth problem and increased the degree and extent of under 
correction and perforation. Improving the accuracy of the depth of 
incision is critical to improving the not only the efficiency of both the 
American and Russian method, but all cutting methods used in 
Keratorefractive surgery. The present invention is directed to solving 
these problems and other problems, while improving the result of 
Keratorefractive surgery. 
SUMMARY OF THE INVENTION 
The invention is directed toward a novel system of surgical instruments for 
use in forming the requisite incisions for Keratorefractive surgery. The 
surgical system of the invention contains a set or series of sharp fixed 
length knife blades. The system contains a plurality of knife blades and 
handles. Instead of a single cutting blade being adjusted for incisions on 
different parts of the cornea and for different corneas, i.e. one tool to 
do everything badly. The current invention is a system having variable 
fixed length knife blades that are of a precise fixed length. Each fixed 
length knife blade being mounted on a handle, where the fixed length blade 
is fixed on the handle and in combination with the footplate, i.e. the 
footplate assembly, fixed on the handle of each instrument. The blade 
having a fixed length attachably connected to the footplate assembly. The 
knife blades of the current invention would be in a range having a minimum 
and a maximum length blade with various other length blades at fixed 
differential increments in between. A surgeon for example could have a set 
of knives in a range of 0.001 mm to 1 mm at 0.001 mm increments or a set 
of knives from 0.400 to 0.600 mm 
The increments will be as small and a large as necessary to accomplish the 
precision needed for the Keratorefractive surgical procedure in question. 
For example, the range of instruments in a set could have the lengths of 
cutting blades in a particular set could be 0.200 mm to 0.300 mm at 0.01 
mm increments. Another series of instruments could be set of instruments 
having a range of from 0.400 to 0.500 at 0.20 mm increments. Each set 
would have a range and each range of knives would vary in length by a 
predetermined increment. Therefore, the range and increments available to 
the surgeon would be sufficient to satisfy the various thicknesses and 
depth of incisions for any particular cornea. 
This system's preferred cutting blade will be made from diamond. Due to the 
hardness and the surface of diamond, the incisions are smoother and 
cleaner than other materials. New or other materials with the same or 
similar physical characteristics to diamond in cutting could also be used 
in this system. However, the current preferred embodiment uses diamond 
cutting blades. 
The system used by a surgeon can be a set having as many fixed length knife 
blades as necessary for a particular surgeon's needs. One surgeon may have 
a system of two knives and another surgeon may have a system of two 
thousand knives. The system envisions the use of multiple fixed length 
knife blades. Again, the needs of a particular surgeon will dictate the 
ranges, increments and number of sets. 
Another embodiment of the invention can incorporate at the footplate 
assembly be a particular color that would signify a style of blade. A 
style being for example the angle of the cutting edge, the number of 
cutting edges, the resulting configuration of the incision or whatever 
qualities that a particular style of knife blade may have, the current 
invention can incorporate any style of knife. Alternative embodiments to 
signify style would be any variation in the footplate assemblies surface 
or design that would make visually discernable from another footplate 
assembly having a blade of a different style. 
Another embodiment of this invention would have the handles for a 
particular range be a specific color and that color varying in the range 
in shading or intensity as the increment of the fixed length of the knife 
blade changes. For example and not as any limitation of this embodiment, 
the range of fixed length knives in the 0.400 mm to 0.500 mm could be blue 
and with each change increment from the minimum length to the maximum 
length would be a different shade of blue or intensity of blue. The shade 
can go from lighter to darker or darker to lighter, or greater or lessen 
the intensity of the color as the increments change. This embodiment would 
have a particular color to a range and a particular shading or intensity 
of that color to a particular length blade. 
Another embodiment would have the identity of the predetermined fixed 
length knife blade's length being etched by means of a laser or 
chemically. Also marking can be accomplished through stamping. 
Another embodiment of this invention could incorporate just the color of 
the range and not incorporate the shading or intensity. Another variation 
could be a machining of the handles or a knurling pattern to distinguish 
range and/or increment. These variations of this embodiment encompass any 
discernable change in the visual appearance of the handle indicate of a 
different range and/or increment of a particular length fixed length knife 
blade. 
Another embodiment of the system incorporates in the footplate assembly 
having a scale. The scale would be similar to a optical recticle scale to 
have the surgeon double check the length of the cutting blade selected 
under the operating room microscope. The scale could be partially clear, 
completely clear or opaque. This would further ensure the selection of the 
right length cutting blade, but also to ensure that the cutting blade is 
not misaligned. Further the scale could be the footplate itself or a scale 
in addition to the footplate and incorporated in to the footplate 
assembly. 
Another embodiment of the instant invention would incorporate a system for 
protecting the knife blade by having the knife blade retract into the 
footplate assembly or have the footplate assembly retract into the handle. 
These embodiments would facilitate the protection of the fixed length 
knife blade. Further, these embodiments would facilitate the locking of 
the retractable knife or footplate assembly in to a closed or open 
position. 
Another embodiment, the handle could be disposable and the footplate 
assembly could be quickly releasable from a disposable handle or 
non-disposable handle. Handles of a particular angle or shape or contour 
could be incorporated with a attachable footplate assembly to satisfy the 
differences in one surgeon's hands to another surgeon's hands. 
All of the embodiments of the above could also, incorporate a portable 
pachymeter that would be light weight and incorporated in all and any 
embodiment of the invention. 
The resulting Keratorefractive system would utilize any and all similar 
embodiments. The surgeon would select a set out of a range or series of 
sets of knives and use the fixed blade system to ensure exact and precise 
incisions. The knives would be pre-calibrated. The surgeon could make 
multiple cuts of varying depths along a single incision or multiple 
incisions of varying depths incorporating multiple measurements in a 
timely fashion because the calibration problems associated with current 
used systems would not be encountered in the instant invention and its 
embodiments. The instant invention provides for precise, quick and 
accurate method for performing Keratorefractive surgery. The present 
invention and its various embodiments can be utilized in all current RK 
surgical techniques, including the American and Russian methods.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
FIG. 1 illustrates in brief the anatomy of the human eye. The eye is 
designated by reference number 10. The outer surface of the eye formed by 
the cornea 12 which terminates at the corneal margin or limbus 14 in the 
vicinity of adjacent the sclera spur 16. The ciliary muscle 18 joins an 
iris 20 and is connected to the crystalline lens 22. The lens 22 is flexed 
by the ciliary muscle 18 in order to focus a subject. 
FIG. 2 is a front view of eye 10, wherein iris 20 generally defines an 
optical zone, illustrated by dotted lines 24 within which light passes 
through the lens 22 onto the retina (not shown) for transmission of an 
image to the optic nerve and the brain. 
A person that is myopic or nearsighted, the cornea tends to have a 
curvature greater than is necessary. This excessive curvature of the 
cornea causes the focal point of images entering the eye to be offset from 
the retina. It has been found that myopia can be surgically corrected by 
making a number of incisions in the cornea, similar to those designated 
reference number 26 of FIG. 2 in a region outside the optical zone. FIGS. 
3 and 4 illustrates certain typical types of incisions made during AK and 
HK. As the techniques for Keratorefractive surgery develop and evolve, the 
direction, size and configuration of any and all incisions will change or 
modify for a particular type of procedure. For example in FIG. 3, "T-type" 
and "Arcuate-type" are illustrative as too the typical types of incisions 
which may be used for AK. Both or one or some variation may be utilized. 
These types of incisions are shown by way of example and not by way of 
limitation as to the type, design, and/or configuration of the incisions 
utilized in Keratorefractive surgery or the those made by the instant 
invention herein. 
For purposes of example and not of limitation, the embodiment discussed 
will be referenced in regards to RK for ease and simplicity. The present 
invention is applicable to any type of Keratorefractive or incisional 
keratotomy. RK is practiced through varying methods for making incisions 
26 of FIG. 3. These methods include the American method where the knife is 
plunged initially at the edge of the optical zone (which is marked by the 
surgeon with dotted lines similar to those referenced by 24 in FIG. 2) and 
moved toward the limbus 14, and the Russian method where the incision is 
formed by moving the knife from the limbus toward the optical zone. The 
present invention is not limited to any specified method, but these 
methods being the most popular at the instant moment, are used for 
example. 
The incisions of either method require precise control in the depth of 
incision. The present invention is an improvement over on the current 
typical keratorefractive knife used in RK procedures, and shown generally 
in FIG. 5, where a blade 28 is formed of a sharp hard material, in this 
example diamond and is mounted in a footplate assembly 30. The footplate 
assembly has footplates 29 that straddle the blade 28 and are designed to 
slide along the outer surface of the cornea 12 during procedures for all 
types of Keratorefractive surgery. For controlling the depth of cut the 
depth of cut the length of the blade 28 projects beyond the footplates 29 
being controlled by a micrometer setting of a known design and shown at 
27. The calibration and measurement problems and the resulting incision 
error has been detailed above with use of this current system. 
The present invention prevents the incision errors associated with the 
typical knife system of FIG. 5. FIG. 6 is a partial side view of a knife 
40, that is exemplary of the current of the current invention. FIG. 6 
illustrates a side view of the footplate assembly 50 having blade 52, 
being attachably connected by mounting piece 54 and pair of footplates 56 
straddle the blade 52. The length of the blade 52 that protrudes from 
beyond the footplates to the tip is a predetermined length 58. The 
predetermined length 58 is established for each knife in the system of 
knives that is incorporated in the current invention. The predetermined 
length would be set in manufacturing the footplate assembly and attached 
to a handle 42. The footplate assembly can be permanently attached to a 
handle 42 or detachable from handle 42 for the purposes of being 
disposable. Further, handle 42 can be customized for a particular surgeon 
hand or configured a specific design, angel or whatever configuration is 
desired. The handle can also incorporate a quick disconnect type 
connection between the handle 42 and the footplate assembly 50, so that a 
surgeon can change handles or footplate assemblies in a quick an easy 
manner. 
The predetermined length 58 will change from knife to knife in the system 
of knives of the current invention. The system can be as few as two knives 
to almost an infinite number of knives, depending on the incremental 
change between the predetermined length from knife to knife. The system 
can be utilized in system of knives having a particular range and that 
particular range having a fixed increment from knife to knife. For 
example, the system of the present invention could be a set of knives in a 
range having a minimum predetermined length of 0.300 mm to a maximum 
predetermined length of 0.500 mm at 0.010 mm increment length variation 
from knife to knife. As a result, these series of knives would be in a 
system of 21 knives having 21 different predetermined fixed length blades. 
The predetermined length in this illustration would vary from 58a to 58u. 
Furthermore, the total available knives in a set could vary in number 
anywhere from two to however many knives are required by a particular 
surgeon. 
An embodiment could include a series of knives 40 have a knife blade of a 
predetermined length starting at a minimum of 0.001 mm to a maximum 
predetermined length of 2 mm at 0.001 mm increments or a series of 200 
knives within the system of the current invention. Obviously, the 
variation of the number of knives in a system can vary further by the 
different styles of blades. 
For the purpose of example, the footplate assembly 50 could be varied by 
angle of the knife blade 52's edge, the number of knife blade edges that 
knife blade 52 may have, the thickness of knife blade and the 
configurations of knife blade 52 can be varied to meet any particular 
need. The current invention is suitable for any configuration for knife 
blade 52 because the present invention to directed towards that knife 
blade having a fixed predetermined length, so that the incision made in 
the cornea is at the depth of the predetermined length 58. Further the 
footplate assembly 50 can be constructed to have a single footplate 
straddling blade 52. The system of the current invention is flexible to 
meet the knife configuration requirements for any particular 
Keratorefractive procedure. 
An alternative embodiment of the current invention is illustrated by FIGS. 
10, 11, and 12. FIG. 10 illustrates a knife 60 of the current invention 
wherein the footplate assembly 70 can retract into handle 65 and be locked 
in a closed position as illustrated by FIG. 10. FIG. 10 shows the knife 60 
where the footplate assembly 70 is retracted in the handle 65 and the 
footplate assembly is locked in place inside the handle by the locking 
configuration 80. The locking configuration incorporates a pin 82 and a 
channel 84 wherein the retractable cover piece 66 can be slidably moved in 
to the closed position of FIG. 10. 
The footplate assembly 70 can be extended and exposed for use by turning 
piece 66 and slidably retracting piece 66 along channel 84 into an open 
position as illustrated by FIG. 11. The pin 82 would lock in place at the 
other end of channel 82 to fixablly hold piece 66 in the open position for 
use during Keratorefractive surgery. 
In another embodiment of the invention, the range of the knives within a 
series of the system can be identified by a discernable visual differences 
on the surface of the knives handles. This embodiment can be illustrated 
at FIG. 13, wherein FIG. 12 shows knife 100 having a surface finish 120. 
Surface finish 120 could be a particular color for a specific range. The 
increment change in the range can be signified by varying the shading or 
intensity of the particular color for a range. For example, the range for 
the series of knives in the range 0.400 mm to 0.500 mm may be blue and the 
handle at 120 could go from a lighter blue to a darker blue as the 
predetermined fixed length blade 115 of footplate assembly 110, goes from 
a minimum of 0.400 mm to 0.500 mm at whatever increment that is desired. 
The color at 120 would signify the particular range of a blade and the 
size of the predetermined length 115. Further, the knife 100 could have 
laser or mechanically stamped or similar means of identification the 
actual length of the predetermined fixed length blade at 125 and at end 
126. 125 and/or 126 would be marked with the identifying length, i.e., 
0.450 mm. The visual identification of predetermined length of blade from 
knife to knife could be by color or etching or knurling or any manner 
where one knife can be visually discernable from another knife to signify 
the particular predetermined length. 
Another embodiment could have the foot plate assembly identify the style of 
the predetermined fixed length blades incorporated in those assemblies. 
The identification would be any visually discernable way to distinguish 
one foot plate assembly from another in order to identify a different 
style of knife as to angle of blade, design of footplate assembly, or any 
configuration as to the relationship of the incision and the instrument. 
The visual discernable difference could be accomplished through the use of 
color or etched pattern or knurling or any physically discernable 
identification that would illustrate a difference and signify one style 
from another. 
FIG. 13 illustrates a scale 200 incorporated on the perpendicular axis of 
the footplate 210 relative to the predetermined fixed length knife blade 
225 of a footplate assembly 230. The scale can also be incorporated on the 
parallel axis at 202 of the footplate 210. Further, the footplate could be 
partially or completely clear so that the predetermined fixed length knife 
blades could be read right through the clear scale with the use of the 
reflection of light off the predetermined fixed length knife blade. 
All of the knife blades are preferably to be manufactured from diamonds at 
this time, but the invention is suitable for use with predetermined fixed 
length knife blades manufactured from any and all surgical knife 
materials, including stainless steel; high alloy steel; other precious 
stones such as, but not limited to ruby, sapphire, and emerald; and any 
material which will result in an incision of the type that will affect the 
eye's cornea in order to improve .vision defects in the eye. It has been 
determined that diamonds and similar materials are currently utilized 
because there use result in clean and precise incisions. It could develop 
that Keratorefractive surgery will require less precise wounds, but still 
at a precise depth and the current invention would be suitable for those 
instances. 
A benefit, however, of the current invention is that each knife will use 
significantly smaller diamond than the knife 40 of FIG. 3. The knives of 
the type of FIG. 3 are often manufacture from 2 karat diamonds, the most 
popular diamonds in the world because they are used for engagement rings 
and the like. The current invention can utilize diamond chips, 
re-processed diamonds or re-cut diamonds because of the use of the 
predetermined fixed length knife blade. As a result, the current invention 
broadens the available supply of usable diamonds for knife blades. 
It should be understood that there can be improvements and modifications 
made to the embodiments of the invention described in detail above without 
departure from the spirit or scope of the invention, as set forth in the 
accompanying claims.