Surgical knife with controllably extendable blade and gauge therefor

Surgical knife with controllably extendable blade, the blade retained by a blade holder extending through an axial opening in the knife body and connected with a member threadedly retained within the knife body for axial adjustment and also connected to an adjustment knob at the rear end of the knife. Another feature of the knife is a foot configuration which facilitates precise use and control of the knife. Preferably the invention also comprises the knife, as disclosed, in combination with a gauge for visually inspecting blade projection, the gauge indicator consisting of a pair of eccentric circles or portions thereof, the blade projection being measured by comparison with the radial distance between the two circles.

INTRODUCTION 
This invention pertains to a surgical knife with controllably extendable 
blade, particularly adapted for use in radial keratotomy, together with a 
gauge for visually measuring the blade extension of such a knife. In 
particular, this invention pertains to such a knife of improved design 
with respect to convenience in the adjustment of the controllably 
extendable blade and in the use of the knife for more precise placement 
and manipulation thereof. 
In certain surgical procedures it is desirable to make an incision of a 
precisely controlled depth. In radial keratotomy, for example, an 
operation to which the present invention is particularly adapted, a 
plurality of radial incisions are made on the lens of an eye. It is 
important that the incision depth correspond to the lens thickness, and 
this has heretofore been accomplished by surgical knives, with diamond 
blades, in which the projection of the blade from a frontal surface of the 
knive is precisely adjusted and controlled to correspond to the desired 
incision depth. The frontal surface or bottom foot surface of the knife 
then is allowed to rest on the surface of the lens and the blade 
penetration and desired incision depth correspond to the length of blade 
projecting from the knife foot. 
Such a knife heretofore sold in this country by Micra North America, Inc. 
is described in a one page flier, entitled "New Radial Keratotomy Diamond 
Knife", a copy of which is submitted with this application for purposes of 
examination. As seen in the Micra North America literature, this knife 
also includes a calibrated rear knob adjustment, by which the front 
projection of the blade from the frontal or foot surface is controlled. 
This knife further includes a bayonet extension and retraction means by 
which the blade may be retracted entirely within the knife body for 
protection when not in use. Moreover, the Micra North America knife 
includes a slot opening on either side of the blade and a "window" in that 
slot at the rear of the knife straddling the blade or plane of incision 
made by the blade, to facilitate better visual observation of the knife 
position. 
Notwithstanding the state of the prior art with respect to surgical knives 
generally, and particularly with respect to such knives having features 
adapted for use in radial keratotomy, including that particularly 
disclosed in the Micra North America literature referred to above, there 
still remains a continuing need for a surgical knife improved with respect 
to convenience of use, controllable adjustment of the blade projection, 
foot locating and blade observation features, and a separate gauge for 
visually observing the blade projection from the knife. 
The general object of the present invention is to provide such an improved 
surgical knife and particularly to provide a surgical knife peculiarly 
adapted for radial keratotomy by the inclusion of one or more design 
features to facilitate and ensure proper knife adjustment and to 
facilitate more precise control of the knife in use. 
BRIEF DESCRIPTION OF THE INVENTION 
This object is met, briefly, by a surgical knife and gauge, comprising a 
generally cylindrical knife body housing a retractable blade holder and 
blade projecting from the front end of the body and urged rearwardly 
against a cam member axially adjustable by a threaded positioning member 
connected to a rear adjustable knob through a cylindrical sleeve within 
the knife body; a bayonet connection is provided between the cylindrical 
sleeve and the cam member. The surgical knife of this invention further 
includes a foot member, i.e., a member surrounding the blade as it 
projects from the front end of the knife body, including an axial slot on 
either side of the flat blade member and relief cuts intersecting the 
blade slot so that the various edges of the blade are open to view by the 
knife user. 
These relief cuts provide the user with an expanded view of several 
reference edges of the knife blade so as to enable precise placement and 
manipulation of the knife blade at almost any angle. Further, the knife 
foot includes a frontal resting foot surface, beyond which the blade 
projects, the resting surface being of relatively short length in the 
cutting direction so as to avoid "plowing" of the cutting surface while 
nevertheless providing precise depth positioning of the blade. 
Calibrated marking on the rear adjustment knob and a mating outer surface 
of the knife body indicate the position of the blade relative to the blade 
body and thus the projection of the blade therefrom. 
To assure correct blade projection, a separate visual gauge may also be 
used. Preferably, the surgical knife of this invention is used in 
combination with such a gauge and particularly includes locator means 
adapted to mate with corresponding positioning means in a gauge stand for 
that purpose. Preferably also, the knife is used with a gauge, which 
separately comprises another aspect of the present invention. 
That gauge includes a gauge face with two offset circles or segments 
thereof, slightly spaced from one another and defining between them a 
continuously changing radial distance which, with proper indicator 
markings, is useful to measure the length of an element, by comparison to 
that radial distance. 
For a better understanding of this invention, reference may be made to the 
detailed description of the preferred embodiment thereof which follows, 
taken together with the accompanying figures and the appended claims.

DETAILED DESCRIPTION OF THE INVENTION 
With reference specifically to FIGS. 1-4, there is shown a surgical knife, 
particularly adapted for use in radial keratotomy, and including a knife 
body 10, comprised for purposes of manufacture of a front body segment 10a 
and a rear body segment 10b. Body 10 otherwise includes front end 12 and 
rear end 14 and a centrally disposed axial opening 16 running 
therethrough, axial opening 16 also including a reduced diameter section 
18 toward the front end thereof. 
Blade 50, which projects from the front end of body 10, comprises flat side 
surfaces 52, trailing edge 54, leading edge 56, and cutting edge 58. 
Enclosed angle .alpha., between the two side surfaces of cutting edge 58 
(as seen in FIG. 5), is generally on the order of 26.degree.-45.degree., 
preferably 26.degree.. Enclosed angle .beta., between trailing edge 54 and 
cutting edge 58 (as seen in FIG. 6), is generally on the order of 
15.degree.-45.degree., preferably 45.degree.. Blade 50, in the forward 
position of the blade (as constrasted with the retracted position, to be 
described later and as illustrated in FIG. 2) projects forward of frontal 
surface 49 of knife foot 40, a predetermined and adjustably controlled 
length, generally within the range of 0.4-0.8 mm for radial keratotomy of 
humans. The positioning of blade 50 is maintained by its retention in 
blade holder 60, at the front end of which blade 50 is secured, and which 
otherwise extends rearwardly through axial opening 16 of body 10 to a cam 
surface 62 at the rear end thereof. 
Preferably, radial alignment of blade 50 and blade holder 60 is maintained 
by one or more radial projections 64 matingly engaged in slots 66 on the 
inner surface of body 10. Still more preferably, axial alignment of blade 
holder 60 is maintained by an enlarged diameter section 68 thereof, 
slidingly engaged within the inner surface of axial opening 16 and body 10 
and from which projects radial projection 64. 
Blade 50 and blade holder 60 are urged rearwardly, preferably by compressed 
spring 72 trapped between enlarged diameter section 68 of holder 60 and 
reduced diameter section 18 of body axial opening 16. 
Countering the rearward urging of spring 72, the rear cam surface 62 of 
blade holder 60 is urged forwardly by a cam member 24 having a front cam 
projection 26. Cam member 24 in turn urges blade holder forwardly by its 
retention through bayonet projection 28 in a bayonet slot 76, including 
short circumferential extensions 78 at the front and rear ends thereof. 
Bayonet slot 76 in turn is located in a rearwardly extending axial sleeve 
74 of a blade positioner 70, threadedly retained within an internally 
threaded portion of body 10. Positioner 70 in turn is axially adjustable 
in its threaded retention within body 10 by rotation of adjustment knob 20 
secured at the rear end of cam member 24, to which adjustment knob 20 is 
adjustably secured by two perpendicularly oriented set screws 21, in the 
preferred form of the present invention. Internal knob 20 also includes an 
abutment shoulder 23. 
As seen in FIG. 8, calibration markings 30 at the front edge of an 
overlapping portion 22 of knob 20 and the mating outer surface of body 10 
indicate the axial position of body 10, including foot 40 and frontal 
surface 49 thereof, relative to blade 50, retained by blade holder 60 and 
positioned through the connection of cam member 24 and threadedly retained 
positioner 70. (Dimension markings would ordinarily be associated with 
markings 30 but are not shown in FIG. 8.) Thus, rotational adjustment of 
knob 20 causes axial movement of threadedly adjustable positioner 70 and 
thus effects projection of blade 50 beyond frontal surface 49 of foot 40, 
associated with body 10. 
Forward adjustment of the blade holder assembly is limited by contact of 
abutment 23 with the rear edge of body 10. 
Typically, cutting edge 58 of blade 50 comprises a diamond particle cutting 
surface which is extremely sharp and vulnerable to misuse or abuse. Thus, 
when this surgical knife is not in use, blade 50 is desirably retracted 
within body 10, as shown in FIG. 2. In accordance with the preferred form 
of the present invention, this retraction movement is accommodated by the 
mating engagement of bayonet projection 28 and bayonet slot 76 with 
circumferential extensions 78 at the forward and rearward ends thereof. 
Extensions 78 each in turn include slight rearward axial extensions on 
their ends distal from the main slot 76 so that bayonet projection 28, for 
purposes of extension and retraction, is moved forward slightly by a 
forward movement of adjustment knob 20 and then circumferentially. This 
causes bayonet projection 28 to traverse the short circumferential 
extension 78 of slot 76. Then it is either urged rearwardly under the 
influence of spring 72, in the case of retraction, or urged forwardly by 
forward pressure on adjustment knob 20 by the operator, and it thus 
traverses the length of slot 76 to the opposing circumferential extension 
end slot 78 and into the short rearward axial extension at the distal end 
thereof. In this manner, the assembly of blade 50 and blade holder 60, 
together with cam member 24 and adjustment knob 20 is movable between two 
axially displaced positions. The rearward axial extensions of 
circumferential extensions 78 of bayonet slot 76 prevent further rearward 
movement of bayonet projection 28 at either position. 
Alternatively, circumferential extensions 78 of slot 76 may be inclined to 
form an angle with radial planes of sleeve 74 (i.e., planes perpendicular 
to the axis thereof), the enclosed angles between slot 76 and extensions 
78 being between 90.degree. and 180.degree.. Thus, such inclined 
extensions 78 provide a ramp whereby the primary axial activating 
projection and retraction forces on the blade holder assembly also move 
the bayonet projection along the angularly disposed slot end 
circumferential extensions to the distal end axially aligned locking slot 
extensions. 
As indicated previously, use and control of the surgical knife of this 
invention is facilitated by the configuration of knife foot 40 which 
provides views of reference edges of blade 50 in complementary reference 
planes, as better seen in FIGS. 5 and 6. More specifically, in the view of 
FIG. 5, the two flat side surfaces of blade 50 are seen substantially in 
their entirety through slot opening 44 in an axial slot segment 42 of foot 
40, just rear of frontal surface 49. Further, this view is enhanced by the 
expansion of slot 42 into the central axially aligned opening of a 
circular opening segment 46 of foot 40, at both the trailing edge 54 and 
leading edge 56 of blade 50. The former is provided by a cutaway section 
48 of foot 40 as best seen in FIG. 6. The latter enhanced view expansion 
of slot 42 is provided by a truncated conical shape at the forward end of 
the axial central bore of foot 40, the essential shape of which is shown 
by hidden lines 46a in FIGS. 6 and 7. 
As seen in the blade side plane profile of blade 50 and foot 40 of FIG. 6, 
cutaway portion 48 in foot 40, in the area of circular opening segment 46, 
provides both an outward expansion of the blade side opening visible in 
the plane of FIG. 5, and also a reference view of the trailing edge 54 of 
blade 50 rearwardly of frontal surface 49, and thus, with the knife in 
use, at a raised location above the incision surface. 
The improved features of the foot member and the surgical knife of this 
invention also include a relatively short frontal surface 49, in the 
cutting direction of the knife, i.e., essentially the plane of blade 50, 
by virtue of its extension from a first line at or just forward of blade 
trailing edge 54 to a second line 43 just ahead of that edge. A second 
surface of foot 40 slopes rearwardly from second line 43, to reduce the 
area of contact between the surface of foot 40 in contact with the surface 
being cut, and thus to reduce or minimize the tendency to plow or raise 
that surface during the cutting operation. 
Notwithstanding the convenient means provided in the surgical knife of this 
invention for the calibrated adjustment of the forward projection of blade 
50 by the mechanism described above, a second means to assure proper blade 
projection is often desirable. Preferably, this comprises a visual 
comparison gauge. In accordance with the present invention, such a gauge 
is also provided in combination with a knife of this invention and further 
includes a gauge stand and gauge holding means, by which the knife is 
retained in a fixed position relative to the gauge indicator. 
Preferably, the gauge provided, in accordance with the present invention, 
consists of (as seen in FIGS. 8-10) a gauge stand 80 with a flat disk 
indicator 82, having a cylindrical side surface 84 and a visual blade 
projection indicator consisting of a calibrated circumferential shape of 
variable width 92 at the edge of indicator 82. Calibrated circumferential 
shape 92 in turn is defined by two circles, one of which 86 comprises the 
outer circumference of flat disk indicator 82 and corresponds in shape to 
cylindrical side surface 84 thereof and the second of which 88 is 
eccentric thereto. Circumferential shape 92 in turn is provided with 
markings indicative of the radial distance between the respective circles 
86 and 88. Disk indicator 82, together with cylindrical side surface 84 
comprise a portion of gauge head 90, all of which is rotatable about the 
center of circles 86 and 88. Gauge head 90 is also axially adjustable in 
mounting slot 85, retained therein by a positioning screw 87. Thus, with 
the body of knife 10 supported on gauge stand 80 in supports 89 and 93, 
gauge head 90 is axially adjusted so that cylindrical side surface 84 
abuts frontal surface 49 of foot 40 associated with body 10 of the 
surgical knife, while blade 50 is disposed just over (but preferably does 
not rest on) the flat disk indicator 82 and projects over a portion of the 
calibrated circumferential shape 92. The projection of blade 50 from 
frontal surface 49 is thus determined by rotationally adjusting disk 
indicator 82 until the blade projection length corresponds to the radial 
distance between circles 86 and 88, at which point the markings 96 thereon 
indicate the length of blade projection. 
Alternatively, disk indicator 82 may comprise only segments of eccentric 
circle, rather than complete circles as shown. Such eccentric circle 
segments would, of course, define only a portion of circumferential shape 
92, and this portion would include markings 96. 
Preferably also, knife body 10 includes positioning means, by which the 
knife is retained at a particular position on gauge stand 10. 
Most preferably, this comprises, as shown in conjunction with support 89, a 
pair of flat bottomed indentations 91, on opposite sides of body 10 at a 
particular axial position thereof, indentations 91 matingly engaging the 
sides of a U-shaped opening 87 in plate support 89. In this manner, body 
10 is retained from both axial and radial displacement and the knife is 
particularly adapted for use in conjunction with a gauge of the type 
shown. 
While this invention has been described with reference to a particular 
embodiment thereof, it should be understood that it is not limited thereto 
and the appended claims are intended to be construed to encompass not only 
the form and embodiment of the invention shown and described but to such 
other forms and embodiments, and obvious modifications thereof, as may be 
devised by those skilled in the art without departing from the true spirit 
and scope of this invention.