Background of the Invention 1. Field of the Invention This invention relates to fluid collection cassettes used in surgical systems and, more particularly, to a scheme for identifying particular fluid collection cassettes.

2. RelatedArt Ophthalmic microsurgical systems typically are classified in accordance with the surgical area of the eye to which the system is directed. Therefore, certain ophthalmic microsurgical systems are considered to be anterior systems, while others are considered to be posterior systems. Occasionally, these systems may be combined into one system which operates in both the anterior and posterior regions of the eye.

In all ophthalmic microsurgical systems, some type of fluid collection reservoir is utilized to collect fluid byproducts of the surgical operation. The fluid reservoir may take various forms. One form which is well known in the art is a fluid collection cassette which is a hard plastic cassette defining a fluid collection reservoir.

The prior art associated with such fluid collection cassettes utilize a reflux bulb member attached at one end to the inlet of the fluid collection cassette and at the other end to a tube which is itself connecte to the hand piece.

Regardless of the type of operating procedure used, posterior or anterior, the size of the cassette remains constant. In fact, the only physical distinction that can be made between a cassette for posterior surgery and a cassette for anterior surgery is the

size of the volume contained within the respective reflux bulbs. The volume contained within the posterior surgery reflux bulb is approximately 1/10 (one tenth) the volume of the anterior reflux bulb. This difference in volumes is made necessary from the very nature of the surgery itself.

During surgery, the fluid line between the handpiece and the fluid collection cassette may occasionally become clogged. When this occurs, a preferred way to unclog the line is to exert a back pressure pulse within the fluid line. This is accomplished by punching a first finger down onto a first portion of the reflux bulb, to pinch off and separate the fluid line into two parts. A second finger immediately adjacent the first finger, between the first finger and the handpiece, descends to also pinch a portion of the fluid line. When the second finger descends, back pressure is exerted along the length of the fluid line towards the handpiece and"blows out"or unblocks the fluid line.

The posterior reflux bulb volume is necessarily smaller than the anterior reflux bulb volume because posterior surgery occurs in the retinal portions of the eye. A large stream of fluid ejected from the handpiece into the retinal portions of the eye due to the manipulation of the reflux bulb could damage the eye. Accordingly, the cross-sectional area of the fluid line comprehended by the posterior reflux bulb is sized much smaller than the volume of the reflux bulb used with anterior surgery. In effect, the posterior reflux bulb will eject a much smaller stream of fluid in order to unclog the fluid line, which in posterior surgery may contain Balanced Salt Solution (BSS), vitreous, and blood, and in anterior surgery may comprise (BSS) and emulsified cataract.

Because the difference in volume of the posterior and anterior reflux bulbs are virtually impossible to distinguish externally with the naked eye, each type of reflux bulb is given a specific color. For posterior surgery, the color of the reflux bulb is yellow. For anterior surgery, the color of the reflux is blue.

Ophthalmic microsurgical systems are unable to distinguish automatically (mechanically or electrically) whether a posterior cassette or an anterior cassette was in use. In this situation, a dangerous volume of fluid may be expelled with each reflux, potentially damaging the eye. To avoid this situation from developing, the only safeguard to date is a reminder by the ophthalmic microsurgical system in an onscreen prompt to check the cassette, or written warnings associated with the packaging of the cassette. Accordingly, it still remains possible for human error to allow an anterior cassette to be used in a posterior surgery.

Accordingly, there is a need in the art to provide an automatic identification scheme which will permit a machine to identify whether a posterior or an anterior cassette is in the machine.

Summary of the Invention It is in the view of the above problems that the present invention was developed. The invention is a method of identifying the type or class of a particular fluid collection cassette, such as posterior or anterior cassettes. A fluid collection cassette has a material disposed on, within, or inside it in a predetermined location.

When the fluid collection cassette is inserted into a housing, a sensor attached to the housing senses the existence, or non-existence of the material and sends a signal

conveying the information to a main controller which can disable the surgical machine from operating until the proper cassette is inserted.

Two separate predetermined locations may be used, together with two sets of material and two sensors for a posterior reflux bulb, whereas a single predetermined location, material and sensor may be utilized to covey the existence of an anterior reflux bulb. In addition, the identification system may be used to guarantee that the cassette originated from a source of known quality.

Further features and advantages of the present invention, as well as the structure and operation of various embodiments of the present invention, are described below in detail with reference to the accompanying drawings.

Brief Description of the Drawings The accompanying drawings, which are incorporated in and form a part of the specification, illustrate the embodiments of the present invention and together with the description, serve to explain the principles of the invention. In the drawings: Figure 1 illustrates an exploded view of a fluid collection cassette of the present invention; Figure 2 illustrates the fluid collection cassette of the present invention disposed within a housing; Figure 3 illustrates an exploded view of a fluid collection cassette of another embodiment of the present invention; Figure 4 illustrates the fluid collection cassette of Figure 3 disposed within a housing;

Figure 5 illustrates another embodiment of a fluid collection cassette of the present invention; and Figure 6 illustrates yet another embodiment of a fluid collection cassette of the present invention.

Detailed Description of the Preferred Embodiment Referring to the accompanying drawings in which like reference numbers indicate like elements, Figure 1 shows an exploded view of a fluid collection cassette shown generally at 10 of the present invention. Fluid collection cassette 10 comprises a main body portion 12, an inlet tube barb 14, an outlet tube barb 16, outlet tube portion 18, and outlet tube adapter 20.

Preferably, main body portion 12, inlet tube barb 14, outlet tube barb 16 and outlet tube portion 18 are integrally molded. Outlet tube adapter 20 is provided with a stem 22 which is press fit into outlet tube portion 18. Alternatively, outlet tube adapter 20 may be provided with a stem 22 which is threaded (not shown) to mate with matching threaded portion (not shown) of outlet tube portion 18.

A reflux bulb, shown generally at 26, comprises first end shown generally at 28 located in first body portion shown generally at 30, second body portion shown generally at 32, third body portion shown generally at 34, and second end shown generally 36 located in third body portion 34. At a first predetermined location shown generally at 38 on fluid collection cassette 10, a first material 40 is disposed on fluid collection cassette 10. At a second predetermined location shown generally at 42, a second material is disposed on fluid collection cassette 10.

Preferably, first material 40 and second material 44 are both metal strips, metal circles, or other geometric shape made from metal to permit use in connection with a capacitive proximity switch. Alternatively, first and second materials, 40,44, are of a material which would permit an alternate type of sensor to determine the existence or non-existence of first material 40 and second material 44 at first predetermined location 38 and second predetermined location 42, respectively.

First material 40 and second material 44 may be disposed in fluid collection cassette 10 (discussed in further detail below) which would raise the manufacturing cost, but would provide a greater guarantee of overall integrity. When first material 40 and second material 44 are both disposed on fluid collection cassette 10, preferably by adhesive, there is always some chance that one of the materials, 40,44, could become disassociated from fluid collection cassette 10. Indeed, as shown in Figures 1 and 2, first material 40 has only a portion thereof adhesively fixed to cassette 10, with the remaining portion freestanding. Second material 44 is similary situated as shown in Figure 1, although the view of Figure 2 does not permit a clear showing of the freestanding aspect.

As Figure 1 shows in exploded view, it is clear that the hole 54 defined by reflux bulb 26 extends through the length of reflux bulb 26. These holes are pushed onto and held by inlet tube barb 14 and outlet tube barb 16.

Reflux bulb 26 may assume a square cross-section measuring 5/16 (five- sixteenth) inch on each side.

In operation, as shown in Figure 2, fluid collection cassette 10 is disposed within housing 56. Housing 56 is located within an ophthalmic microsurgical system.

Attached to housing 56 is a first sensor 58 and a second sensor 60. First and second

sensors, 58-60, are preferably capacitive proximity switches and may be obtained readily from many electrical equipment manufacturers such as Balluff, Inc. of Florence, Kentucky. However, first and second sensors, 58-60, may also be of the sonic type (and the materials, 40,44, respectively, suitable for reflecting sonic waves), or may be of the light (LED, laser, etc.) type (and the materials, 40,44, respectively, suitable for reflecting light waves.

In operation, first and second sensors, 58-60, form the first side of a capacitor, respectively, and first and second materials, 40,44 form the second side of a capacitor, respectively. Alternatively, first and second sensors, 58-60, emit a signal such as light, a radio frequency, or some other frequency that his reflected back from first and second materials 40,44, and sensed by sensors 58-60. Accordingly, first and second sensors, 58-60, can sense the existence or non-existence of first material 40 and second material 44. The existence or non-existence information is communicated from each sensor 58-60 to a controller which can act on this information and either enable or disable the operation of the ophthalmic microsurgical machine, using a logical well known in the art.

Figures 3 and 4 illustrate an alternative embodiment of the present invention in which the first predetermined location 38 of first material 40 is at a different location than that indicated in Figures 1 and 2. Similarly, Figures 3 and 4 illustrate second predetermined location 42 of second material 44 is placed at a different location than that indicated in Figures 1 and 2. Further, first material 40 and second material 44 of Figures 3 and 4 are round disks geometrically, as opposed to arch-shaped disks suggested in Figure 1. Because of the different locations in Figures 3 and 4, the

location of first sensor 58 and second sensor 60 have also been moved consistent with the location of first predetermined location 38 and second predetermined location 42.

Figure 5 illustrates another alternative embodiment which illustrates that first material 40 may be embedded or encapsulated within the wall of fluid collection cassette 10.

Figure 6 illustrates yet another alternative embodiment which illustrates that first material 40 may be disposed inside fluid collection cassette 10. Thus, when disposing a material to be sensed"in"a predetermined location on the fluid collection cassette, the term"in"can mean"within"the wall of cassette 10 or"inside"cassette 10 itself.

In view of the foregoing, it will be seen that the several objects of the invention are achieved and other advantages are attained. The embodiments were chosen and described in order to best explain the principles of the invention and its practical application to thereby enable others skilled in the art to best utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. As various modifications could be made in the constructions and methods herein described and illustrated without departing from the scope of the invention, it is intended that all matter contained in the foregoing description or shown in the accompanying drawings shall be interpreted as illustrative rather than limiting. For example, the predetermined locations, 38 and 42, are not required to be on the same side of reflux bulb 26. Another modification falling within the scope of the present invention involves using three or more predetermined locations in conjunction with the application of sensing material at each location to assist in identifying a function other than anterior or posterior. Another modification

is that first and second materials may be the same material. Thus, the breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims appended hereto and their equivalents.