TITLE: "DEVICE FOR DILATING A PUPIL AND/OR MAINTAINING A PUPIL
IN A DILATED STATE"
FIELD OF THE INVENTION
The present invention relates to a device for dilating a pupil and/or maintaining a pupil in a dilated state.
The invention has been developed primarily for use in ophthalmic surgery and
will be described hereinafter with reference to this application. However, it will be
appreciated that the invention is not limited to this particular field of use and can be
utilised in other medical procedures where an opening is required to be expanded and
maintained in the expanded state.
BACKGROUND OF THE INVENTION
It is advantageous in many ophthalmic surgical procedures for the pupil to be dilated as much as possible. A pupil is dilated when the iris retracts towards the outer
edges of the eye. This normally occurs when the eye is deprived of bright light, for
example, at night.
When performing ophthalmic operations, such as replacing the lens of a
patient's eye with an artificial intraocular lens, a dilated iris and pupil gives the
surgeon a larger area to manipulate surgical instruments in order to operate on the
human lens. The more area available to the surgeon reduces the risk of damaging the
iris or other components of the eye due to unintentional contact with the surgical
instruments.
A common method of dilating the pupil is the use of chemical eyedrops. The
eyedrops are formulated to trigger the expansion of the iris, resulting in a dilated pupil.
However, such eyedrops are not effective on all patients and more surgically
complicated measures are often required. Also, such eyedrops can "wear off during
an operation resulting in the iris retracting and reducing the pupil size.
One method to dilate and maintain a pupil in the dilated state involves making
four minor incisions at roughly 90° intervals around the periphery of the cornea and
inserting a small hook-like apparatus through each incision. The hooks engage with
the inner circumferential edge of the iris and when retracted, pull the iris outwards to
define an enlarged substantially square shaped opening. Another method, known as a
sphincterotomy, involves making an incision into the cornea through which a blade is
passed that makes radial cuts into the iris itself, thus allowing the iris to dilate and
expose more of the lens. Both the above methods add extra time to the actual
operation being performed and the latter involves considerable risk of damage to the
patients iris. Moreover, the damage done in segmenting the iris during a
sphincterotomy is irreversible and results in a permanently disfigured iris.
It is an object of the invention, to overcome or ameliorate at least some of the
deficiencies of the prior art.
SUMMARY OF THE INVENTION
According to a first aspect of the invention there is provided a device for
dilating a pupil and/or maintaining a pupil in a dilated state, said device including a
generally arcuate body having first and second ends, the outer peripheral edge of the
body having an engaging formation adapted to engage the inner peripheral edge of an
iris to retain the pupil in an expanded state, and at least one positioning arm extending
generally outwardly from one of the ends of the body so as to remain external to the
eye.
Preferably, positioning arms are provided at both the ends of the body.
Preferably also, the body is adapted to deform to a generally elongated or
folded configuration able to be passed through an exterior incision in the eye and
resiliently return to a substantially annular configuration engaging the iris edge.
Desirably, the body also includes a guide tab extending outwardly from and
generally parallel to a diameter of the body for aiding insertion of the device, for
supporting the body in engagement with the iris edge and also for preventing the body
from "falling" through the pupil opening.
In a preferred embodiment, the positioning arm or arms each terminate in a
gripping formation. The formation provides a convenient gripping point for the
device and also, if so desired, allows the positioning arms to be sutured to the eye.
The gripping formation or formations may include a hole through which a suture
thread may be passed.
In another preferred embodiment, each of the arm or arms include a proximal
portion adjacent the body and an offset distal portion extending to the gripping
formation or formations so as to allow the distal portion or portions to remain external
to the eye and above the level of the iris whilst the device is in use dilating the pupil.
The resilience of the body preferably provides a radially outwardly directed
force capable of urging into and maintaining the body in a substantially annular
configuration whilst engaging the iris to expand and/or maintain the pupil in the
dilated state.
In a preferred form, the engaging formation is desirably formed so as to define
a continuous recessed channel between the ends.
In a further embodiment, the body comprises a pair of circumferentially
aligned parallel axially spaced apart incomplete rings and a series of circumferentially
spaced apart curved joining members extending from one ring to the other to define
said engaging formation.
In another embodiment, the body is provided with a plurality of radially
outwardly angled pairs of flaps, each pair of flaps defining a portion of the recess
therebetween.
The body is preferably made from a material selected from the group including
prolene, poly methyl methacrylate, nylon, silastic, silicon polyimide, polyamide or a
combination thereof, or any other material having the requisite properties of resilience
and suitability for use in surgical procedures.
In a further embodiment, an insert of a second material is contained within the
body to give the required resilience.
In a further embodiment, the body is sized to provide an inner diameter in the
substantially annular configuration of between approximately 5.5mm and 7mm, the
body itself has a radial thickness of between about .75 and 1.25mm. In this
embodiment, the recess has an axial depth of about 1.12mm and the guide tab extends
from the outer edge of the body by about 1.25mm. The distal portions of the arms are
preferably offset from the proximal portions by about 1.5 to 2.0mm in the axial
direction.
In yet another embodiment, regions of weakness may be included in the body
to further facilitate resilient deformation between the expanded annular and the
elongated or folded configurations.
Desirably, the device is tinted for increased visibility to the surgeon.
In the annular configuration, the arcuate body has an included angle of
between approximately 270° and 340°.
BRIEF DESCRIPTION OF THE DRAWINGS
Preferred embodiments of the invention will now be described, by way of
example only, with reference to the accompanying drawings in which:
Figure 1 is a sectional side view of a human eye;
Figure 2 is a sectional side view of the eye shown in Figure 1 showing the
pupil being maintained in a dilated state by a first embodiment of the device according
to the invention;
Figure 3 is a plan view of the device shown in Figure 2 illustrated in an
annular configuration;
Figure 4 is a side view of the device shown in Figure 3;
Figure 5 is a plan view of the device shown in Figure 3 in the elongated or
folded configuration;
Figure 6 is a plan view of a second embodiment of the invention;
Figure 7 is a sectional side view of the device shown in Figure 6;
Figure 8 is a plan view of a third embodiment of the invention;
Figure 9 is a sectional side view of the device shown in Figure 8;
Figure 10 is a plan view of a fourth embodiment of the invention;
Figure 1 1 is a sectional side view of the device shown in Figure 10;
Figure 12 is a plan view of a fifth embodiment of the invention;
Figure 13 is a side view of the device shown in Figure 12; and
Figure 14 is an inverted partial plan view of the device shown in Figure 12.
PREFERRED EMBODIMENTS OF THE INVENTION
Referring to Figure 1 there is shown a human eye having a cornea 10, sclera
1 1, anterior chamber 12. lens 14, iris 16, limbus 17, retina 18 and optic nerve 20. The
iris 16 has an inner peripheral edge 22, the boundary of which defines the opening of
the iris known as the pupil 24 (the black circle in the centre of an eye).
As described previously, it is advantageous during surgery of the eye, for the
pupil opening 24 to be as large as possible to permit access to the lens and other parts
of the eye via incisions in the cornea or sclera.
Referring to Figure 2, there is shown in use a device 26 according to the
invention for dilating the pupil and/or maintaining the pupil in the dilated state. The
device 26 comprises a generally arcuate body 28 having first and second ends 35. The
outer peripheral edge of the body has a recess 30 adapted to engage the inner
peripheral edge 22 of the iris to retain the pupil in a dilated state. The device also
includes positioning arms 34 which extend generally outwardly from the ends 35 of
the body and remain external to the eye when the device is in use. The arms are more
clearly shown in Figures 3 and 4. The recess 30 forms a continuous channel 32
between the ends 35. Device 26 also includes guide tab 36 which extends from the
body 28.
Referring to Figures 3 and 4, the arms 34 can each be seen to include a
proximal portion 38 adjacent to the body and a distal portion 40 substantially parallel
to, but offset from the proximal portion 38. The arms 34 terminate in gripping
formations 44.
If desired, the formations 44 also allow the surgeon to suture the arms 34 to the
sclera 11. Holes can be provided through the formations through which the suture
thread may be passed.
Referring in particular to Figure 5, it can be seen that the body 28 is adapted to
resiliently deform to a generally elongated or folded configuration as shown which is
able to be passed through an exterior incision into the eye and, upon release, return to
a substantially annular configuration, as shown in Figure 4. Referring next to Figures
6 to 10, there are shown several alternative embodiments of the device according to
the invention. The embodiment of the device shown in Figures 6 and 7 comprises a pair of
circumferentially aligned parallel axially spaced-apart incomplete rings 46 with a
series of circumferentially spaced-apart joining members 48 extending from one ring
to the other to define the recess 30.
The embodiment of the invention shown in Figures 8 and 9 is similar to the
previously illustrated embodiments except that the body 28 is provided with a series of
radially extending flaps 50 around its periphery. Furthermore, this embodiment
includes regions of weakness 52 which facilitate resilient deformation between the
configurations shown in Figure 3 and Figure 5.
Referring now to the embodiment shown in Figures 10 and 1 1, the body of the
device is in the form of a single incomplete annular ring 54 provided with a plurality
of radially outwardly angled pairs of flaps 56. Each pair of flaps defines a portion of
the recess 30 therebetween.
A fifth embodiment of invention is shown in Figure 12 to 14. This
embodiment is similar to those previously described except the distal portions 40 of
each of the arms 34, which remain external the eye during use, are angled slightly
downwardly towards the eye surface to prevent the device from tilting towards the
cornea when the arms are pressed downwards. To allow easier suturing, the gripping
formations 44 are each provided with a pre-formed suture hole 54 which is adapted to
receive suture thread therethrough.
When viewed in plan, the arms 34 are angled slightly outwardly from the
incision which, in addition to the downward angling, provides extra clearance for
instruments passing through the incision. Also, the shape of the arms allows the
device to maintain a snug fit with the eye when in use dilating the pupil.
Additionally, as best shown in the inverted plan view of Figure 14, the body 28
of the device is recessed below the guide tab 36 so as to provide two regions of
weakness 52 which facilitate flexure of the device into the elongated position
described previously.
Further, to enhance the withdrawal of the device, the proximal portion 38 of
each of the arms 34 is provided with a smoothly tapered surface 56. This lessens the
likelihood of the device snagging or catching as the device is withdrawn through the
incision.
Referring back to Figure 2, there is shown a tunnel incision 42 used in, for
example, a lens replacement. The circumferential incision begins generally just
behind the limbus 17, is 2.5 to 5.5mm wide, and extends normally into the sclera for
about half it's depth (approximately 0.5 to 0.75mm). The incision then travels through
the sclera and then cornea for approximately 3 to 4mm then again is angled through
the cornea to finally open into the anterior chamber 12.
In use of the device, the incision 42, of approximately 2.5 to 5.5mm in width,
is made through the cornea and/or sclera of the eye. The device 26 is then elongated
or folded so that it can more easily be passed through this tunnel incision into the
anterior chamber 12 of the eye. The device may be inserted in the elongated
configuration by forceps such as angled "Mclntyre" forceps. The forceps grip the
device in recess 30 and so elongate the device for passing it through the incision. The
guide tab 36 aids the insertion process.
Preferably, the anterior chamber is filled with a visco-elastic fluid prior to
insertion of the device. As the device is being passed through the incision, the inner
peripheral edge 22 of the iris is partially located in recess 30. This location is helped by guide tab 36 sliding over, and resting upon, the upper surface of the iris. The guide
tab 36 also prevents the device from "falling" through the pupil opening during
insertion.
Once through the incision the resilience of the device then returns it to the
substantially circular configuration shown in Figure 3. As the device fully engages
edge 22 in recess 30 it provides sufficient radial force to expand the iris, thus dilating
the pupil. This radial force is also sufficient to maintain the pupil in the dilated state
shown in Figure 2.
It will be appreciated that due to the small size of both the device and the iris,
that occasionally some misengagement may occur which can be corrected by re-
positioning the device using arms 34. As a portion of each arm remains external to the
eye during pupil dilation, this repositioning can readily be effected. Also, the surgeon
can give additional dilation to the eye by pushing the arms towards the eye centre.
Since the proximal and distal portions, 38 and 40 respectively, are offset axially from
one another, the device can easily be positioned parallel to, and adjacent with, the iris
edge after the proximal portions have passed through the incision in the eye. The
surgical incision is generally offset so as to be above the plane of the iris edge.
The apparatus according to the invention provides several major advantages
over existing methods of dilating pupils. The first is that it will dilate and hold in a
dilated position a pupil that would not otherwise dilate under the influence of eyedrops
and the like. This gives the surgeon the space needed to perform the eye operation
without having to resort to more drastic measures to dilate the pupil. Moreover, since
the device is introduced into the anterior chamber of the eye by a single incision, there
is minimal surgical trauma to the patient.
Another advantage is that the device can be introduced through the usual
incision made for surgery. This allows the device to be used without any additional
incisions being made in the patients eyes. The incision may have to be made slightly
wider than normal to fit both the arms and also tools such as a phaco-emulsifier
simultaneously through the incision.
A further advantage provided by the device according to the invention is that
whilst maintaining the pupil in the dilated state, the device serves to effectively guard
the delicate edge of the iris against unintentional contact with surgical instruments.
A yet further advantage of the device of the invention is provided by arms 34
remaining partially external to the eye whilst the device is being used. This allows
easy re-positioning of the device and, more importantly, allows removal of the device
generally without introducing any surgical tools into the anterior chamber. This
greatly reduces the risk of damaging the eye during surgery. Additionally, formations
44 provide a convenient gripping point for a surgeon removing the device and also
allow the device to be sutured in the correct position whilst an operation is performed.
This can be important when surgical tools are continually being passed in and out of
the incision which may otherwise accidentally move or dislodge the device.
For reasons of convenience and sterilisation, the device will preferably be
disposable. The device can be manufactured in many sizes to cater for varying eye sizes
including, for example, animal eyes.
From the above, it will be appreciated that the device according to the
invention represents significant improvements over the previously used techniques
and devices for dilating a pupil and maintaining it in a dilated state.
Although the invention has been described with reference to specific examples.
it will be appreciated by those skilled in the art that the invention may be embodied in
many other forms.