WO2015069189A1

WO2015069189A1 - An ocular surgical device

Info

Publication number: WO2015069189A1
Application number: PCT/SG2014/000525
Authority: WO
Inventors: Yin Chiang Freddy Boey; Chin Foo GOH; Tiang Hwee Donald TAN; Jodhbir SINGH MEHTA
Original assignee: Nanyang Technological University; Singapore Health Services Pte Ltd
Priority date: 2013-11-07
Filing date: 2014-11-07
Publication date: 2015-05-14

Abstract

An ocular surgical device comprising: a piezoelectric transducer (20); a blade (30) configured to be removably securable to the piezoelectric transducer; and a casing (16) configured to house at least a portion of the piezoelectric transducer therein.

Description

AN OCULAR SURGICAL DEVICE

FIELD OF THE INVENTION

This invention relates to a device for use in ocular surgery, and in particular, for cutting through the cornea or sclera.

BACKGROUND OF THE INVENTION

The cornea is a multi-layered transparent tissue (approximately 500pm thick) located in the front part of the eye as shown in Figs. 1 and 2A. Whenever vision is reduced from corneal disorders like infections, corneal injuries and degenerative diseases, a corneal transplant or keratoplasty can be an effective mean of restoring vision. Traditionally, a corneal transplant consisted of removing the full thickness of the cornea followed by transplantation of new corneal tissue, a procedure known as Penetrating Keratoplasty (PK), as shown in Fig. 2B. However, this procedure has a relatively high incidence of transplant rejection and only moderate long term graft survival rates.

In an effort to improve surgical outcomes, new corneal transplant procedures have recently been developed, in which only specific diseased layers of the cornea are exchanged or replaced. In Anterior Lamellar Keratoplasty (ALK), or Deep Anterior Lamellar Keratoplasty (DALK), as shown in Figs. 2C and 2D, only the anterior corneal stromal layers are exchanged, leaving the healthy inner Descemets layer and endothelial layer intact. ALK and DALK are transplant procedures indicated for corneal diseases affecting only the corneal stroma layers, such as keratoconus, anterior corneal scarring disorders and anterior stromal dystrophies, where the underlying Descemets and endothelial layers are still healthy. Conversely, for corneal diseases affecting primarily the inner endothelial cell layer and Descemets membrane, such as Fuchs' endothelial dystrophy, pseudophakic and aphakic bullous keratopathies and other acquired and congenital corneal endothelial disorders, the new transplant procedures of Endothelial Keratoplasty (EK) are newly emerging forms of corneal transplants which provide better visual and long term outcomes. The main EK surgical procedures performed today include Descemets Stripping Automated Endothelial Keratoplasty (DSAEK), where the donor tissue transplanted involves a thin (50-150 pm) posterior layer of corneal stroma, as shown in Fig. 2E, and Descemets Membrane Endothelial Keratoplasty (DMEK), as shown in Fig. 2F. DALK surgery and Lamellar Dissection Techniques

DALK has a major advantage of a much reduced risk of allograft rejection and consequent graft failure, as recipient corneal endothelium is not exchanged, but remains a highly technically challenging procedure, as deep lamellar stromal dissection is performed largely in a manual manner by the corneal surgeon, and great skill is needed for the manual dissection plane to be maintained. A major complication of DALK is inadvertent perforation of the Descemets layer, as surgeons attempt to reach the deepest layers of the stroma adjacent the Descemets layer, e.g. close to around 50-1 OOpm from the Descemets layer. Inadvertent perforation of the Descemets layer often necessitates conversion to the PK procedure instead. Uneven stroma! dissection which is performed across the natural stromal lamellar planes also results in poor stromal bed quality and resultant optically poor visual outcomes for the patient after surgery. As a result of the difficulty of DALK surgery, in the US, only about 2-3% of all corneal transplants undergo the DALK procedure.

In order to remove the outer layer of the stroma, a surgical cutting instrument as shown in Fig. 3a is currently used. This is essentially a sharp or semi-sharp crescent lamellar blade or lamellar dissector. The device consists of a simple angulated shaft to which a metal blade is attached. During surgical lamellar stromal dissection, the blade moves in an in-plane direction of the cornea as shown in Figs. 3b and 3c. Cutting depth, speed, thickness of outer layer and surface quality of the cut piece are mainly determined by the skill of the corneal surgeon who attempts to keep within the same lamellar stromal plane for optical smoothness, as shown in Fig. 4. The curved surface of the cornea provides added difficulty. Inexperienced surgeons are not able to maintain the surgical stromal plane and this results in poor stromal bed quality, as shown in Fig. 5, uneven thickness of the residual corneal stromal bed, increased postoperative scarring and inflammation, and poorer visual outcomes in terms of best spectacle-corrected visual acuity.

For DSAEK surgery, there are currently two clinical approaches to performing lamellar dissection of corneal donor tissue, which needs to be in the region of 50-150pm in thickness. The most popular approach is to use a dedicated semi-automated microkeratome device, such as the Automated Lamellar Therapeutic Keratoplasty (ALTK) surgical unit (Moria, France), as shown in Fig. 6. In this procedure, the donor cornea is first mounted on a pressurized artificial chamber maintainer device, and then a semi-automated gas turbine- driven microkeratome is mounted on the artificial chamber, and various changeable cutting heads of different cutting thicknesses are used to perform deep stromal lamellar dissection, thus creating the required posterior stromal lenticule which can then be transplanted into the patient during the DSAEK procedure. This procedure however requires an expensive microkeratome device such as the ALTK unit and has considerable inaccuracies in depth of lamellar cut, but remains the most popular approach to DSAEK donor preparation. Other DSAEK microkeratomes similar to the ALTK unit are also available. The second approach is a fully manual lamellar dissection performed by a corneal surgeon. In this approach, the cornea is mounted on an artificial cornea mount, and the surgeon attempts to perform deep manual stromal dissection using a lamellar blade, similar to the DALK procedure. This approach is subject to the same surgical challenges as encountered in DALK surgery, as discussed above, and is rarely used simply because of the relative surgical difficulty in attaining a smooth, deep lamellar dissection. Manual lamellar dissection is only generally performed today in less developed countries without good access to modern, but expensive microkeratomes, and visual outcomes are poorer.

The key to performing a perfect smooth stromal plane dissection within the deeper stromal layers of the cornea is to be able to stay within the same corneal stromal plane through the dissection area across the entire cornea. This is better achieved with a semi-sharp blade or blunt lamellar dissector, as a very sharp blade would tend to cut across the stromal lamellae, and lead to irregular dissection planes. Conversely, however, blunter surgical blades have inherently low tissue sectility and very high resistance to cutting, requiring excessive force to be applied which distorts tissue planes. Blunt blades also have a tendency to cause stromal fibre tearing through the cornea, rather than create a sharp plane of dissection, resulting in a rough fibrous surface which reduces optical quality.

In corneal and other forms of ophthalmic surgery, use of sharp surgical blades is required to effect clean and precise cutting of ocular tissues such as the cornea or sclera. Diamond knives are often used as they are sharper than metal blades and can cut smoothly across tissue planes with minimal force or distortion. However, diamond knives are costly to provide.

SUMMARY OF INVENTION

The present invention provides a device designed for cornea transplant surgery (e.g. PK, DSAEK, DALK), that can also be configured for use in other forms of ophthalmic surgery such as cataract wound construction, glaucoma surgery, retinal surgery, oculoplastic, orbital and squint surgery. This is achieved by providing a modular piezoelectric handpiece which can accept and be integrated with a wide variety of blunt or sharp surgical knife tips or blades which can be interchangeable and disposable according to the desired application.

In one aspect, for smooth stromal plane dissection, the present invention uses a blade that is not sharp at the tip so that the tendency to cut across lamellar stromal planes is much reduced, but which can effect a sectility efficacy similar to a sharp blade to effect less resistance as it is directed across the corneal stromal interface. Effecting a sectility efficacy similar to a sharp blade can be achieved as the blade is made to vibrate in an appropriate action which enhances stromal layer separation. A piezoelectric cornea stroma separating device is thus proposed, where a piezoelectric transducer is integrated into the shaft of a blade which is relatively blunt at the cutting edges. As a result, the blade vibrates in a controllable way, which will ensure the cutting of the tissue at a specific depth to cut the in- plane direction of the cornea precisely throughout the procedure, whilst the relatively blunt cutting edges of the blade reduces the risk of inadvertently traversing across lamellar stromal planes, which will also greatly reduce the risk of inadvertent perforation when at a very deep stromal plane.

As the piezoelectric corneal stromal separating device provides better sectility with less manual forces, it is able to perform smoother and easier deep stromal dissection for DALK surgery, and it may similarly be used for DSAEK donor preparation which also requires a similar high bed quality in stromal dissection, with maintenance of the same deep stromal plane of dissection throughout the cornea. It is thus envisaged that an expensive semi- automated microkeratome will no longer be required by corneal surgeons and by eye bank techniques who perform pre-cut DSAEK tissue preparation, and the piezoelectric corneal stromal separating device can substitute for these expensive microkeratomes.

In ah alternative application to piezoelectric corneal stromal separation, for example, in corneal and other forms of ophthalmic surgery where use of sharp surgical blades is required to effect clean and precise cutting of ocular tissues such as the cornea or sclera, the present invention provides a piezoelectric transducer integrated into a sharp ophthalmic surgical blade to enhance sectility of that sharp blade to cut across ocular tissue planes with minimal force or tissue distortion, effectively making the already sharp blade even sharper, and is also less reliant on the durability of the sharp edge of the blade. This device, coupled with a variety of sharp keratome tips, will greatly enhance surgical cutting for a variety of eye operations, including corneal or scleral wound preparation for cataract surgery, glaucoma surgery (e.g. trabeculectomy), eyelid surgery, and other forms of ocular surgical procedures where precise cutting of cornea, sclera or intraocular tissues, and oculoplastic procedures are required. The device may also be used in corneal transplant circular trephination blades or devices, which are used to perform circular vertical trephination of the donor and host cornea. Enhancement of sectility reduces compression or distortion of the cornea during trephination, ensuring more vertical and undistorted trephination margins.

According to an exemplary aspect, there is provided an ocular surgical device comprising: a piezoelectric transducer; a blade configured to be removably securable to the piezoelectric transducer; and a casing configured to house at least a portion of the piezoelectric transducer therein.

The piezoelectric transducer af comprise a piezoelectric stack configured to generate vibrations and a displacement amplifier attached to the piezoelectric stack, the displacement amplifier configured to removably secure the blade thereto.

The blade may have a blunt cutting edge suitable for effecting stromal plane dissection. Alternatively, the blade may have a sharp cutting edge suitable for cutting across ocular tissue.

The ocular surgical device may further comprise an angled blade shaft to which the blade is attached, the angled blade shaft being removably securable to the piezoelectric transducer.

The blade shaft may be angled about an axis that is parallel to the plane of the blade and orthogonal to a longitudinal axis of the blade shaft.

The degree of angle of the blade shaft may range from 30° to 60°.

The blade and the angled blade shaft may be integrally formed.

The cross-sectional area of the blade shaft at where the blade shaft is secured to the piezoelectric transducer may be larger than the cross-sectional area of the blade shaft at where the blade shaft is attached to the blade. BRIEF DESCRIPTION OF FIGURES

In order that the invention may be fully understood and readily put into practical effect there shall now be described by way of non-limitative example only exemplary embodiments of the present invention, the description being with reference to the accompanying illustrative drawings.

Fig. 1 is an illustration of a perspective cross-sectional view of layers of the human cornea. Fig. 2 is an illustration of various types of corneal transplants.

Fig. 3a is a photograph of a prior art cutting device.

Fig. 3b is an illustration of a side view of the prior art cutting device of Fig. 3a in use.

Fig. 3c is an illustration of a top view of the prior art cutting device of Fig. 3a in use.

Fig. 4 is a photograph of rough deep stromal bed after attempted lamellar dissection by an inexperienced surgeon.

Fig. 5 is a photograph of deep stromal dissection technique in which the surgeon tries to keep within a same lamellar stroma! plane with surgicai dissector, to within 50-i00um of the Descemets layer without perforating the cornea.

Fig. 6 is a photograph of a ALTK microkeratome unit performing DSAEK donor lamellar dissection.

Fig. 7 is an illustration of a side cross-sectional view of an exemplary embodiment of the device of the present invention.

Fig. 8a is photograph of a prototype of the device of Fig. 7.

Fig. 8b is photograph of a close-up of a blade of the prototype of Fig. 8a.

Fig. 9 is a graph of mechanical displacement against frequency of vibration of the device of Fig. 8a.

Fig. 10 is a photograph of vibration effect of the blade of the device of Fig. 8a in water.

Fig. 11 is a photograph of intrastromal air in a human cornea at a leading edge of the vibrating blade of the device of Fig. 8a.

Fig. 12 is a photograph of deep intrastromal lamellar dissection within the lamellar corneal planes with minimal tissue distortion.

Fig. 13a is an illustration of a top view of a first embodiment of a blade and blade shaft of the present invention.

Fig. 13b is an illustration of a side view of the blade and blade shaft of Fig. 13a.

Fig. 14a is an illustration of a side view of a second embodiment of a blade and blade shaft of the present invention.

Fig. 14b is an illustration of a perspective view of the blade and blade shaft of Fig. 14a.

Fig. 14c is an illustration of a close up of a top view of the blade and blade shaft of Fig. 14a.

DETAILED DESCRIPTION

Exemplary embodiments of the invention will be described with reference to Figs. 7 to 14c below. The device 10 comprises a piezoelectric transducer 20 and a blade 30 as shown in Fig. 7. The piezoelectric transducer 20 and the blade 30 can be connected by various means. In one embodiment, this is by means of a slot and screw arrangement, as shown in Fig. 7.

The transducer 20 comprises a piezoelectric stack 12, a displacement amplifier 14 and a casing 16. The casing 16 is configured to protect the device 10, housing the piezoelectric stack 12 and at least a portion of the displacement amplifier 14 therein. The piezoelectric stack 12 is configured to generate mechanical vibration that is transferred to the blade 30 through the displacement amplifier 14.

The blade 30 may be made either of metal, plastic or ceramic, may be coated with insulating materials to reduce heat transfer, and may comprise various shapes, dimensions, angulation, degree of sharpness and curvature. Non-metal blades are envisaged to be used for cutting tips which do not require sharp cutting edges 32. All blades 30 and blade shafts 40 are configured to minimize heat transfer to adjacent ocular tissues in direct contact with the blade 30.

Vibration direction of the blade 30 is configured to be controlled through the design of the piezoelectric transducer 20. For the blade 30 shown in Fig. 7, the vibration direction is indicated by the arrow 33, which is an out-of-plane direction to the cornea stroma layers. In another embodiment, the vibration direction can be configured to be an in-plane direction. In the prototype of the device 10 shown in Figs. 8a and 8b, the blade 30 is configured to vibrate in the out-of-plane direction.

Fig. 9 shows the displacement curve of the prototype device 10 shown in Fig. 8. The displacement is frequency dependent. At resonant frequency of around 22 kHz, the vibration displacement reaches its maximum. The maximum displacement is close to 50 umpp at an input voltage of 20 Vpp.

Fig. 10 shows the effect of the vibrating blade 30 when tested in water 99. The power input was about 1 W. Violent water agitation, vortex, bubbles and spray were observed. This further proves that strong vibration can be generated by the device 10.

In-vitro testing

An in-vitro experiment of the prototype device 10 was performed using human eye bank corneas 60 mounted on an artificial chamber maintainer. The cutting device 10 was driven at around 1 W power input. Two corneas were tested. The device 10 was found to generate lamellar stromal separation with ease, which was confirmed by the appearance of stromal air generation anterior to the cutting tip of the vibrating blade, as shown in Fig. 11 , where intrastromal air (observed as white feathery margins) 62 at the leading edge 32 of the vibrating head or blade 30 confirms intrastromal lamellar separation occurring ahead of the cutting tip of the blade 30. With vibration on, high tissue sectility was noted with minimal forward cutting movements required to separate the deeper layers of the cornea 60. When the vibration was turned off, as shown in Fig. 12, this high sectility was not present. Tissue planes examined after lamellar separation using the device 10 with vibrating biade confirmed the presence of a smooth interface conforming to the lamellar planes of the corneal tissue, establishing proof of concept of the device's ability to perform smooth lamellar intrastromal dissection. Vertical trans-lamellar cutting was also evaluated, and confirmed that the device 10 could effect highly precise wound profiles with high sectility and minimal cutting effort and tissue distortion. Preferably, the blade 30 is removably securable to the displacement amplifier via an angled blade shaft 40, as Figs. 13a to 14c. The blade 30 is thus securely attached to the blade shaft 40 while the blade shaft 40 is configured to be removably securable to the piezoelectric transducer 20. The blade shaft 40 is preferably angled about an axis X that is parallel to the plane of the blade 30 and orthogonal to the longitudinal axis Y of the blade shaft 40. The degree of angle of the blade shaft 40 may range from about 30° to about 60°

In the embodiment shown in Figs. 13a and 13b, the blade 30 has a generally rectangular shape with a rounded tip, while in the embodiment shown in Figs. 14a to 14b, the blade 30 has a generally circular shape. The edge 32 of the blade 30 may be blunt or sharp depending on the application that the blade 30 is designed for. In a preferred embodiment, the blade 30 and angled blade shaft 40 are integrally formed. For robustness, as shown in Figs. 14a to 14c, the blade shaft 40 may be configured to have a larger cross-sectional area at where the blade shaft 40 is secured to the piezoelectric transducer than at where the blade shaft 40 connects to the blade 40.

As a stroma separator, the piezoelectric transducer 20 provides vibrational energy to the blade 30 which improves high tissue sectility due to vibratory separation of corneal stromal lamellae, ensuring that the plane of dissection follows the exact lamellar separation plane provided by the vibratory function. Sectility becomes less reliant on the sharpness of the cutting edge 32 of the blade 30, so that blunter blades can be utilized, which then greatly reduces the risk of cutting across the corneal lamellar planes, resulting in smooth and predictable lamellar separation across the cornea, and less risk of inadvertent perforation of Descemets membrane. By allowing vibration direction of the blade 30 to be controllable, the device 10 can also vibrate in the out-of-plane direction when it moves in the in-plane direction in any x-y-z configuration or combination, as opposed to conventional non-vibrating devices that mainly move in the in-plane direction. In an envisaged embodiment of use, i.e., in-plane movement is hand-controlled while vibration provided by the piezoelectric transducer 20 is in the out-of-plane direction. This fully takes advantages of the lamina nature of the stroma to effectively separate the stroma with minimum damage or risk of perforation.

Consequently, the stromal bed surface will be smoother and optically more precise than that achieved by standard lamellar dissectors. As the piezoelectric vibration will reduce the friction between the blade 30 and tissue, and effect clean lamellar separation, the quality of the cutting surface will be improved, and this should result in better visual outcomes.

·

As opposed to other sharp blades which effect greater tissue sectility by presenting a very sharp cutting edge, the piezoelectrically vibrated blade 30 of the present invention can be made much less sharp, i.e. having a blunt cutting edge 32, since sectility is effected mainly by the vibrational energy separating the corneal lamellae. The present device 0 also has major advantages over conventional blunt lamellar dissectors which have poor tissue sectility leading to a high resistance to dissection, tissue distortion, and stromal fibre tearing. Since sectility is now less of a function of the cutting tip or blade 30 in the present device 10, the choices of the blade profile will be more flexible as the tip or blade material may now not need to hold a sharp edge 32. Accordingly, metal, sapphire or diamond materials are no longer essential, and alternative non-cutting materials may be utilized for the blade 30, which includes various forms of plastic polymers and ceramics. Although it is envisaged for the blade 30 to be disposable, it may be reused if need be, unlike sharp blades which will blunt with repeated use. The device 10 thus allows ophthalmic surgeons to manually perform corneal stromal dissection with greater ease and precision to create an optically smooth dissection plane which more precisely follows the corneal stromal lamellar planes, whilst using a more blunt- edged blade tip so as to prevent inadvertent traversal across lamellar planes. For DSAEK donor preparation, the device 10 enables manual dissection preparation with minimal instrumentation to achieve the same precision and stromal bed quality as the microkeratome. The device 10 will also reduce surgical time during DSAEK donor preparation, either in the eye bank for precut donor preparation, or during the DSAEK surgical procedure in the operating theatre.

For DALK surgery, the device 10 will significantly reduce surgical time, and reduce the long period of surgical training required to perform DALK surgery due to the enhanced ease of lamellar dissection. The device 10 will transform DALK into a mainstream surgical procedure which all surgeons can master, which will greatly improve corneal transplant outcomes in terms of visual results, reduction of intraoperative complications, and reduction of corneal transplant rejection and enhanced graft survival rates, as DALK becomes the preferred form of corneal transplantation over penetrating keratoplasty.

Besides being configured for use as a corneal stromal lamellar separator, the device 10 may alternatively be configured as an ultrasharp ocular knife (using other tip shapes similar to other ocular surgery blades and knives) for use in corneal surgery, cataract surgery, glaucoma procedures, retinal surgery, orbital and oculoplastic procedures for a variety of ocular tissues including cornea, sclera, intraocular tissues, orbital/periorbital tissues and periocular skin. As the piezoelectric transducer 20 provides vibrational energy to the blade 30, this improves higher tissue sectility due to vibratory separation of ocular tissue planes, with minimal manual forces or tissue distortion, ensuring a sharper, more even cut. Integrating a piezoelectric transducer 20 with an already sharp surgical blade 30 will therefore further enhance sectility of a sharp metal blade, making the blade 30 even sharper (ultrasharp). The device 10 configured as an ultrasharp ocular knife thus requires less cutting forces to be applied by the surgeon, resulting in less tissue distortion during ophthalmic surgery, and will provide for higher quality cutting planes along and across tissue planes, with greater accuracy.

Furthermore, as sectility is less of a function of the cutting tip or blade, the choices of the blade profile will be more flexible. Integrating the piezoelectric transducer 20 with an already sharp blade 30 may replace the need for more expensive diamond blades to achieve a same required sharpness, thereby reducing costs. The blades 30, although envisaged to be disposable, may alternatively be reused if need be, as sectility is less dependent on the sharpness of the cutting tip or blade.

In the USA, the ophthalmic devices global market has been estimated to roughly $ 12 billion dollars and is predicted to grow with a CAGR of 3.3% for 2011-1018. In the US, approximately 45,000 corneal transplants are performed annually, and it is estimated that the rest of the world performs a similar number of transplants. It is estimated that up to 30% of transplants may benefit from a DALK surgical procedure for various indications including keratoconus, corneal stromal scarring, and anterior stromal dystrophies. In the US, only 2% of transplants are performed using the DALK procedure, due to surgical difficulty of the procedure. With present device 10, the percentage of DALK procedures could be increased to 30%. Approximately 50% of all transplants in the US are currently performed using the DSAEK procedure and this could rise to 75% in time. At the Singapore National Eye Centre, which performs approximately 300 transplants a year, 80% of transplants are lameiiar keratoplasty procedures: DSAEK constitutes over 50%, while DALK constitutes over 25%. In mature advanced corneal transplant programs therefore, these lamellar keratoplasty procedures which will thereby benefit from the device 10 of the present invention could thus constitute up to 80% of all corneal transplants.

Commercially, it is envisaged that the device 10 may be supplied as a low cost, modular ophthalmic surgical unit for corneal stromal lamellar separation having a disposable handpiece comprising a blade 30 attached to a modular piezoelectric motor unit 20, with the potential for attaching different disposable blunt tips or varying tip configurations. This modular unit may also have other attachable, exchangeable handpieces for other ocular surgical functions, such as sharp blades for configuring the ultrasharp ocular knife, and even phacoemulsification and capsulotomy handpieces.

Whilst there has been described in the foregoing description exemplary embodiments of the present invention, it will be understood by those skilled in the technology concerned that many variations in details of design, construction and/or operation may be made without departing from the present invention.

Claims

A ocular surgical device comprising:

a piezoelectric transducer;

a blade configured to be removably securable to the piezoelectric transducer; and a casing configured to house at least a portion of the piezoelectric transducer therein.

The ocular surgical device of claim 1 , wherein the piezoelectric transducer comprises a piezoelectric stack configured to generate vibrations and a displacement amplifier attached to the piezoelectric stack, the displacement amplifier configured to removably secure the blade thereto.

The ocular surgical device of claim 1 or claim 2, wherein the blade has a blunt cutting edge suitable for effecting stromal plane dissection.

The ocular surgical device of any preceding claim, wherein the blade has a sharp cutting edge suitable for cutting across ocular tissue.

The ocular surgical device of any preceding claim, further comprising an angled blade shaft to which the blade is attached, the angled blade shaft being removably securable to the piezoelectric transducer.

The ocular surgical device of claim 5, wherein the blade shaft is angled about an axis that is parallel to the plane of the blade and orthogonal to a longitudinal axis of the blade shaft.

The ocular surgical device of claim 5 or 6, wherein the degree of angle of the blade shaft ranges from 30° to 60°.

The ocular surgical device of any one of claims 5 to 7, wherein the blade and the angled blade shaft are integrally formed.

The ocular surgical device of any one of claims 5 to 8, wherein the cross-sectional area of the blade shaft at where the blade shaft is secured to the piezoelectric transducer is larger than the cross-sectional area of the blade shaft at where the blade shaft is attached to the blade.