Surgical cassette with multi area fluid chamber

1. A surgical cassette having an aspiration chamber disposed therein, said aspiration chamber comprising:

a fluid level sensing portion having a first transverse cross sectional area, said sensing portion providing accurate and precise evidence of continuous fluid level changes during use of said cassette; and

a storage portion fluidly coupled to said sensing portion during application of vacuum to said aspiration chamber and having a second transverse cross sectional area larger than said first transverse cross sectional area, said storage portion providing adequate fluid storage during use of said cassette;

whereby said sensing portion is disposed proximate a bottom of said aspiration chamber so that a surgical aspiration fluid first enters said sensing portion at a bottom of said aspiration chamber and substantially fills said sensing portion before entering said storage portion, said storage portion being disposed proximate a top of said aspiration chamber;

whereby said first transverse cross sectional area provides improved measurement sensitivity of both said continuous fluid level changes and a calculated aspiration flow rate of said surgical fluid; and

whereby said second transverse cross sectional area provides a sufficient amount of said surgical fluid to support a non-interrupted surgical procedure during exchange of a collection bag fluidly coupled to said aspiration chamber.

2. The surgical cassette of claim 1 wherein said second transverse cross sectional area is approximately 7.5 times larger than said first cross sectional area.

3. The surgical cassette of claim 1 wherein the angle between said sensing portion and said storage portion is about 90 degrees.

4. The surgical cassette of claim 1 wherein said aspiration chamber is not vented to atmosphere.