A phacoemulsification system includes a phacoemulsification probe and a processor. The phacoemulsification probe includes (a) a needle configured for insertion into a lens capsule of an eye, and to be vibrated to emulsify a lens of the eye, (b) an irrigation channel for flowing irrigation fluid into the lens capsule, (c) an aspiration channel for removing material from the lens capsule, (d) a bypass channel fluidly coupled with the irrigation channel and with the aspiration channel, (e) a processor-controlled valve configured to control a level of fluid communication between the irrigation channel and the aspiration channel via the bypass channel, and (f) one or more sensors configured to measure fluid pressure at a distal portion of one or both of the irrigation channel and the aspiration channel. The processor is configured to adaptively adjust the valve based on the fluid pressure measured by the one or more sensors.