Abstract:
A vitreous surgical apparatus in which an inner tubular blade is moved in an axis direction with respect to an outer tubular blade by supply and exhaust of compressed air to excise a part of a vitreous body in an eyeball and aspirate and discharge the excised part out of the eyeball, the apparatus including: a plurality of solenoid valves each of which is opened and closed for performing the supply and exhaust of the compressed air; and a control unit which synchronously drives the solenoid valves to open and close in order to move the inner tubular blade at a desired cutting speed.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a vitreous surgical apparatus for excising a part of a vitreous body in an eyeball, and aspirating and discharging the excised part out of the eyeball. 
     2. Description of Related Art 
     A vitreous body cutter used in vitreous surgery is operated to excise a part of a vitreous body in an eyeball of a patient&#39;s eye by moving an inner tubular blade in an outer tubular fixed blade while drawing the part of the vitreous body by aspiration into an aspiration port provided in one end of the outer blade. 
     As such moving system of the inner blade, there has been known a guillotine type which moves an inner blade to reciprocate. 
     Moreover, as systems for driving an inner blade, there are an electrical system using a vitreous body cutter which mounts therein an electric motor or electromagnet, and a pneumatic system which drives an inner blade by repeating supply and exhaust of compressed air. This pneumatic system intermittently performs supply of compressed air from a compression pump into a cylinder constituted of a piston, a diaphragm, and others and exhaust of the air from the cylinder by control of opening and closing of a solenoid valve. 
     In vitreous surgeries, in particular, operations on the periphery of a retina, speedup of a cutting speed (a cutting rate) of the vitreous body cutter is requested. Accordingly, the number of reciprocating motions of the inner blade per unit of time needs to be increased. 
     To realize high-speed actuation of the pneumatically operated cutter, the solenoid valve which controls the supply of compressed air to the cutter needs a high responsivity for the supply of compressed air. Thus, the solenoid valve has to be designed to have an air flow passage of a larger effective diameter (caliber) and to open and close at a high speed. There is, however, no solenoid valve satisfying those requirements at present. Newly designing a solenoid valve with an air flow passage of a larger effective diameter will result in high cost. Hence it is difficult to materialize a high-speed cutter for vitreous surgery. Furthermore, a large-sized solenoid valve is usually slow in response speed. It is therefore difficult to produce a solenoid valve with high responsivity and capable of allowing a large amount of flow. Also, the large solenoid valve generally has a high noise problem. 
     If the vitreous body cutter is driven at a high speed, an open time of the aspiration port in the end of the cutter (outer blade) in each cycle is reduced than when actuated at a low speed. This would cause problems that aspiration efficiency lowers and cutting sharpness of the cutter with respect to a vitreous body deteriorates. 
     SUMMARY OF THE INVENTION 
     The present invention has been made in view of the above circumstances and has an object to overcome the above problems and to provide a vitreous surgical apparatus capable of actuating a cutter for vitreous surgery at a high speed by a simple structure, and enhancing cutting sharpness of the cutter actuated at a high speed. 
     Additional objects and advantages of the invention will be set forth in part in the description which follows and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims. 
     To achieve the purpose of the invention, there is provided a vitreous surgical apparatus in which an inner tubular blade is moved in an axis direction with respect to an outer tubular blade by supply and exhaust of compressed air to excise a part of a vitreous body in an eyeball and aspirate and discharge the excised part out of the eyeball, the apparatus including: a plurality of solenoid valves each of which is opened and closed for performing the supply and exhaust of the compressed air; and control means which synchronously drives the solenoid valves to open and close in order to move the inner tubular blade at a desired cutting speed. 
     According to another aspect of the present invention, there is provided a vitreous surgical apparatus for excising a part of a vitreous body in an eyeball and aspirating and discharging the excised part out of the eyeball, the apparatus including: an outer tubular blade; an inner tubular blade movable in an axis direction with respect to the outer tubular blade; a piston to which the inner tubular blade is fixed; an air chamber in which the piston is movably disposed; a plurality of solenoid valves each having an output port being in communication with the air chamber, an aspiration port being in communication with a compressed air supply source, and an exhaust port through which the compressed air is exhausted, the solenoid valve being switched between communication between the output port and the aspiration port and communication between the output port and the exhaust port to alternately perform supply and exhaust of compressed air to and from the air chamber; and a control section which controls switching in each of the solenoid valves to move the inner tubular blade at a desired cutting speed. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings, which are incorporated in and constitute a part of this specification illustrate an embodiment of the invention and, together with the description, serve to explain the objects, advantages and principles of the invention. 
     In the drawings, 
     FIG. 1 is a schematic structural view of a vitreous surgical apparatus in an embodiment according to the present invention; 
     FIG. 2 is a schematic structural view of a solenoid valve of the apparatus in the embodiment; 
     FIG. 3 is a view of a setting panel screen for a vitreous surgical mode; 
     FIG.  4 A and FIG. 4B are graphs each showing a relationship between a driving speed of the solenoid valve and a driving pressure to the vitreous body cutter; and 
     FIG. 5 is an explanatory view showing examples of OPEN and CLOSE times of an aspiration port of the cutter and a ratio of the OPEN time to one cycle time with reference to a set value of a cutting speed. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A detailed description of a preferred embodiment of a vitreous surgical apparatus embodying the present invention will now be given referring to the accompanying drawings. FIG. 1 is a schematic structural view of a vitreous surgical apparatus in the present embodiment. 
     A cutter  1  for vitreous surgery (hereinafter, referred to as a vitreous body cutter), which is a handpiece, is constructed such that an outer tubular blade  3  with an aspiration port  3   a  in an end portion is partially and fixedly disposed in a housing  2 , an inner tubular blade  4  is fit in the outer blade  3  to be slidably in an axis direction, and a piston  5  is fixed on the inner blade  4 . This inner blade  4  is of a hollow-body shape and a cutting edge at one end. The piston  5  is movably connected in the housing  2  through a diaphragm  8 . Thus, the housing  2 , the piston  5 , and the diaphragm  8  define a compartment  9  and an air chamber  6 . 
     In the compartment  9 , a spring  7  is disposed urging the piston  5  toward the air chamber  6 . A moving force is thus applied to the piston  5  in a return (backward) direction, i.e., rightward in FIG.  1 . The housing  2  is provided with a hole  2   a  having one end which communicates with the compartment  9 . This hole  2   a  allows an air flow in/from the compartment  9 , so that the pressure in the compartment  9  can be maintained at atmospheric pressure even when movement of the piston S causes a change in volume of the compartment  9 , thus preventing unnecessary force from being applied to the piston  5 . 
     The air chamber  6  in the cutter  1  is connected to two solenoid valves  12   a  and  12   b  which intermittently supply compressed air to the chamber  6  through a tube  10 . FIG. 2 is a schematic structural view of one of the solenoid valves. Since both the solenoid valves  12   a  and  12   b  are of the same structure, only the solenoid valve  12   a  is explained below. 
     The solenoid valve  12   a  has a housing  19  in which two valves  16   a  and  16   b  are fixed on a shaft  17  having an end fixedly connected to a movable core  18 . A fixed core  20  is arranged adjacently to the movable core  18  and one end of the core  20  is fixed to the housing  19 . The two valves  16   a  and  16   b  are both urged by a force of a spring  14  in the direction opposite to an electromagnetic coil  13 . The housing  19  is provided with an aspiration port P, an exhaust port R, an output port A, and an output port B. 
     These ports are in communication with each other in the housing  19  as shown in FIG.  2 . Projections  19   a  are each formed in a circle in the housing  19  in which the valves  16   a  and  16   b  are moved. These projections  19   a  serve as a seal which comes into contact with the valves  16   a  and  16   b . Upon application of electric current to the electromagnetic coil  13 , the movable core  18  is attracted toward the fixed core  20  on the principle of electromagnet, moving the shaft  17  and the valves  16   a  and  16   b  rightward in the figure. When the valves  16   a  and  16   b  are moved rightward, the aspiration port P is brought into communication with the output port B (the solenoid valve  12   a  is opened). Upon stop of the application of electric current to the electromagnetic coil  13 , to the contrary, the valves  16   a  and  16   b  are moved leftward in the figure by the urging force of the spring  14 , providing communication between the exhaust port R and the output port B and between the aspiration port P and with the output port A (the solenoid valve  12   a  is closed). It is to be noted that the output port A is blocked with a blind stopper  15 . When the application of electric current to the coil  13  is stopped, therefore, the aspiration port P is put in a blocked state. 
     The tube  10  connected to the air chamber  6  in the cutter  1  bifurcates into two passages connected to the output ports B of the solenoid valves  12   a  and  12   b  respectively. The aspiration ports P of the solenoid valves  12   a  and  12   b  are connected to an air supply port of the compressed air pump  11 . The exhaust ports R of the solenoid valves  12   a  and  12   b  are connected to an air room  21  for reduction of exhaust noise. Conventionally, a muffler of a sponge type is attached to the exhaust port of a solenoid valve. This sponge type muffler provides only a small muffling effect and therefore high noise is produced when plural solenoid valves are provided. To enhance the muffling effect, in the present embodiment, the air room  21  of a cylinder type is attached as a muffler. 
     By opening and closing of the solenoid valves  12   a  and  12   b , compressed air is supplied (pumped) from the compressed air pump  11  in the air chamber  6  in the cutter  1  and exhausted from the air chamber  6 . Thus, the inner tubular blade  4  fixed to the piston  5  is reciprocated in the outer tubular blade  3 , thereby excising a part of a vitreous body V drawn by aspiration into the aspiration port  3   a.    
     An aspiration passage of the inner blade  4  is joined to an end of an aspiration tube  31 . The other end of the aspiration tube  31  is connected to a waste liquid bag  32 . When an aspiration pressure is applied into the inner blade  4  by an aspiration pump  33 , the excised part of the vitreous body V is aspirated from the aspiration port  3   a  and discharged into the bag  32  through the inner blade  4  and the tube  31 . 
     In FIG. 1, numeral  30  is a control section of the surgical apparatus in the present embodiment. This control section  30  controls and drives the solenoid valves  12   a  and  12   b , the compressed air pump  11 , the aspiration pump  33 , and others, in accordance with operation signals from a foot switch  35  and setting signals from a setting panel  36 . 
     Operation of the vitreous surgical apparatus structured as above is explained below. 
     For preparation of surgery, an operator (surgeon) sets various conditions for vitreous surgical operation with switches on the setting panel  36  of a touch panel type shown in FIG.  3 . To set an irrigation pressure, a set value  42  of a height of an irrigation pole is adjusted with an UP button  43  and a DOWN button  44 . Similarly, a set value  45  of a cutting speed (cutting rate) of the cutter  1  is adjusted with an UP button  46  and a DOWN button  47 , and a set value  48  of an aspiration pressure of the aspiration pump  33  is adjusted with a UP button  49  and a DOWN button  50 . 
     The operator injects irrigation fluid from an irrigation bottle into the eye of a patient and also inserts the outer blade  3  of the cutter  1  into the eye so that the aspiration port  3   a  is positioned in an affected part such as opacity. Then, the operator presses the footswitch  35  to drive the compressed air pump  11  and the aspiration pump  33 , thereby operating the cutter  1  at the cutting speed and aspiration pressure previously set as above. 
     The control section  30  controls and drives the solenoid valves  12   a  and  12   b  at the set cutting speed. When electric current is applied to the solenoid valves  12   a  and  12   b  (more specifically, to respective electromagnetic coils  13 ) in response to a control signal from the control section  30 , the aspiration port P is brought into communication with the output port B in each of the solenoid valves  12   a  and  12   b , thereby allowing the compressed air to flow from the compressed air pump  11  to the air chamber  6  through the tube  10 . This moves the piston  5  in a forward direction, thus moving the inner blade  4  fixed to the piston  5  along the outer blade  3 , cutting the part of the vitreous body V being drawn into the aspiration port  3   a . When the application of electric current to the solenoid valves  12   a  and  12   b  is stopped, the exhaust port R is brought into communication with the output port B in each of the solenoid valves  12   a  and  12   b , thereby allowing the compressed air to flow from the air chamber  6  to the air room  21  serving for noise reduction, and the air is then released into the atmosphere. Accordingly, the piston  5  is moved in a backward direction (rightward in FIG. 1) by the urging force of the spring  7 . With the backward motion of the piston  5 , the inner blade  4  is slid in the outer blade  3  in a return direction. This allows the aspiration port  3   a  to open, aspirating the vitreous body V into the aspiration port  3   a.    
     Now, differences between the case where a single solenoid valve is used and the case where two solenoid valves are used as in the present embodiment are explained below with reference to FIG.  4 . FIG. 4A is a graph showing a relationship between the driving speed of the solenoid valve and the driving pressure of the cutter  1  (i.e., the pressure of the compressed air to be supplied to the air chamber  6 ) in the case where the cutting speed of the cutter  1  is adjusted to a low setting (a cycle time ST 1 ). FIG. 4B is a graph showing a relationship between those in the case where the cutting speed is adjusted to a high setting (a cycle time ST 2 ). 
     When a driving signal S turns High, the solenoid valve  12   a  is energized, allowing the compressed air to flow from the compressed air pump  11  to the air chamber  6 . The driving pressure PR increases accordingly. When the driving signal S turns Low, to the contrary, the application of electric current is stopped, allowing the air chamber  6  to open to the atmosphere. The driving pressure PR then decreases. A conventional cutting speed is in a range from about 600 to 800 cpm. At such a cutting speed, as shown in FIG. 4A, even only a single solenoid valve could control the driving pressure PR in the range of variation P 1  sufficient to actuate the inner blade  4  in an enough stroke (travel). 
     If the cutting speed is requested to increase up to about 1200 to 1800 cpm, a solenoid valve capable of operating at a high speed is used. As the opening and closing rate of the valve  12   a  is increased, the cutting speed itself can be raised. 
     However, a typical solenoid valve capable of operating at a high speed has a small effective diameter of an air flow passage, which can neither feed the sufficient amount of compressed air to the cutter  1  in a short time nor exhaust the compressed air in a short time. As a result thereof, as indicated by a dotted line in FIG. 4B, the driving pressure PR descends before full ascent due to the stop of supply of the compressed air, while ascends before full descent due to the start of supply of the compressed air. In other words, the pressure PR is changed only by the range of variation P 2  in the figure. The inner blade  4  therefore could not be moved to reciprocate in an enough stroke. This prevents full open and close of the aspiration port  3   a  of the outer blade  3 , which deteriorates excision and aspiration (cutting sharpness) with respect to the vitreous body V. 
     On the other hand, the use of a plurality of the solenoid valves  12   a  and  12   b  makes it possible to carry out high-speed opening and closing operations and also increase the air flow passage. This enables quick start of supply of the compressed air to the cutter  1  and sufficient release of the air. The driving pressure PR is, as indicated by a solid line in FIG. 4B, controlled to change in the variation range P 3  (almost the same as P 1 ) enough for operating the inner blade  4  in a sufficient stroke, as in the case of the low-speed operation. Consequently, the excision and aspiration with respect to the vitreous body V can be ensured. 
     When two or more solenoid valves are used, even if one of those valves breaks down due to for example clogging, other valves are still workable. Even in case the trouble may arise, therefore, the surgery can be continuously performed at a low cutting speed (600-800 cpm). 
     As above, the cutter  1  can be driven at a high speed, enabling intermittent short-time aspiration in the surgery on the periphery of a retina. This makes it possible to reduce the behavior of the retina to smoothly excise the vitreous body without aspirating the retina. In the surgery on the center portion of the eyeball, on the other hand, the cutter  1  is used at the cutting speed in a range of 600-800 cpm which provides a good aspiration efficiency. The cutting speed set value  45  is changed by operation of the UP button  46  and the DOWN button  47 . 
     When the cutting speed set value  45  is changed, the control section  30  changes times for opening and closing the solenoid valves  12   a  and  12   b  and the ratio of a closing time thereof to a cycle time in accordance with the set value, as shown in FIG.  5 . In FIG. 5, a CLOSE time T 1  indicates a time interval to close the aspiration port  3   a  formed in the end portion of the outer blade  3 , namely, a time interval that the solenoid valves  12   a  and  12   b  are opened to supply the compressed air from the pump  11 , thereby moving forward the inner blade  4  to close the aspiration port  3   a . An OPEN time T 2  indicates a time interval to open the aspiration port  3   a , namely, a time interval that the solenoid valves  12   a  and  12   b  are closed to stop the supply of the compressed air, thereby moving backward the inner blade  4  to open the aspiration port  3   a . An OPEN ratio T 2 /ST shows the ratio of the OPEN time T 2  to a one cycle time ST, namely, the ratio of the closing time of the solenoid valves  12   a  and  12   b  to the one cycle time ST. 
     When the set value of the cutting speed CV is in a range of 50 to 450 cpm, the CLOSE time T 1  in one cycle time is determined to be 50 msec in order to ensure the amount of aspiration, and the OPEN time T 2  is adjusted to be shorter so that the one cycle time ST is reduced. 
     It is also desirable to control the CLOSE time T 1  at 50 msec even when the set value of the cutting speed CV is 500 cpm or more; however, the OPEN time T 2  will become shorter. Therefore, the CLOSE time T 1  is adjusted to be gradually shorter as a cutting speed set value is increased, thereby shortening the one cycle time ST. In this case, the OPEN ratio T 2 /ST is 60%, almost constant, for the cutting speed of 500-850 cpm. For a high-speed range of 900-1800 cpm, the OPEN ratio T 2 /ST is increased as the speed is raised. Thus, the ratio of reduction in the aspiration flow amount caused in association with the speedup of the cutter  1  can be prevented. In other words, the aspiration flow amount is ensured as much as possible during the high-speed operation of the cutter  1  as well to provide high aspiration pressure. This good aspiration with respect to the vitreous body V into the aspiration port  3   a  enables efficient excision of the vitreous body V. 
     Considering only the excision efficiency during the high-seed operation, the CLOSE time T 1  may be controlled to be 10 msec corresponding to the cutting speed of 1800 cpm. However, a vitreous body cutter incapable of operating if the CLOSE time T 1  is 10 msec can not be driven even if the cutting speed is adjusted to lower settings. Accordingly, the CLOSE time is controlled to become longer as the speed is decreased as shown in FIG.  5 . For example, a vitreous body cutter operable at the CLOSE time T 1  of 18 msec can carry out surgery at the speed of at least 1200 cpm. 
     It is to be noted that control of the vitreous body cutter may be performed by changing the ratio between the opening time and the closing time of the solenoid valves without changing the cutting speed. For example, in the surgery on the center portion of an eyeball, the ratio of the closing time to the opening time of the solenoid valves  12   a  and  12   b  is increased, thereby lengthening the open time of the aspiration port  3   a  to raise excision efficiency. In the surgery on the periphery of a retina, on the other hand, the ratio of the opening time to the closing time of the solenoid valves  12   a  and  12   b  is increase, thereby shortening the open time of the aspiration port  3   a  to suppress the behavior or the retina caused by intermittent aspiration. 
     As explained above, according to the present invention, a vitreous body cutter can be actuated at a high speed by a simple structure, thereby enabling smooth excision with respect to a vitreous body around the retina. Furthermore, the noise of the apparatus can be reduced, aspiration efficiency during high-speed actuation can be further enhanced with good cutting sharpness for surgery. 
     The foregoing description of the preferred embodiment of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of the invention. The embodiment chosen and described in order to explain the principles of the invention and its practical application to enable one skilled in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto, and their equivalents.