The present invention is generally directed to improved methods, devices, andsystems for eye surgery. In some embodiments, the invention may provide new and/orimproved devices, systems, and methods for detecting surgical fluids in a fluidicscassette, particularly cassettes which are used to couple an eye treatment probeto an eye treatment console. Rather than relaying on internal reflection by agas-liquid interface, the fluid detection techniques described herein maymake use of the changes in propagation of light through a portion of the holdingtank when the portion varies between empty and full. For example, light may propagatedirectly through the holding tank portion when there is no surgical fluid, butmay be directed away from a light detector when the portion of the holding tankis filled with surgical fluid. As the light may be controllably refracted usingthe interface between the transparent holding tank material and the surgicalfluid, the propagation properties of the light may be more reliably predictedand controlled. While the sensor may not determine the actual liquid level withinthe holding tank, a plurality of individual liquid detectors may be sufficientto determine when it is appropriate to (for example) turn drain pumps on and off,when the holding tank is in danger of being overfilled, and the like. Other aspectsof the invention may provide devices, systems, and methods for producing differenttypes of fluidics cassette using a single cassette body type.
