Flow control system based on leakage

A control system for controlling aspiration of fluids within an ophthalmic surgical system, comprising:

• an ophthalmic device including a needle having a cannula therein through which fluid is aspirated from a surgical site, and a sleeve coaxially extending over the needle so as to define a flow passage between the sleeve and the needle, through which passage irrigation fluid is communicated to a surgical site, wherein the ophthalmic device is configured to be inserted into a medium through an incision of a predetermined size;
• an irrigation line through which irrigation fluid is communicated between a fluid container and the sleeve;
• the fluid container having the irrigation fluid therein, the container being configured to provide an adjustable infusion pressure for urging flow of the irrigation fluid through the irrigation line and sleeve to the surgical site;
• a measuring device for measuring a value indicative of the infusion pressure at the fluid container;
• an aspiration line through which fluid is communicated between the needle cannula and an aspiration pump;
• the aspiration pump configured to urge the flow of fluid aspirated from the surgical site through the needle cannula and aspiration line;
• a pressure sensing device for providing a signal indicative of the level of pressure being applied by the aspiration pump;
• a flow sensing device for providing a signal indicative of a flow rate of fluid being aspirated from the surgical site;
• a user interface for entering a needle size, a sleeve size, and the predetermined size of the incision;
• a controller in communication with the user interface, the measuring device, the flow sensing device, the pressure sensing device and the aspiration pump, the controller being configured to calculate an intraocular eye pressure based on the measured infusion pressure less a pressure drop caused by a predetermined resistance to an irrigation fluid flow, which irrigation fluid flow is a combination of the sensed fluid flow rate and a predicted leakage rate of fluid exiting the incision, where the predicted leakage rate is selected from a look-up table based on the needle size, the sleeve size, the incision size, and an estimated intraocular eye pressure;
• and
• wherein the controller adjusts either the infusion pressure or the aspiration pump based on the calculated intraocular eye pressure to maintain a desired intraocular eye pressure.

A method of controlling the operation of a controller for regulating fluid flow in an eye and through an ophthalmic device in an ophthalmic surgical system, comprising:

• the controller receiving an input of a needle size, a sleeve size, and an incision size;
• identifying in the controller, a predetermined resistance to a fluid flow associated with the ophthalmic device, including connected aspiration and irrigation tubing;
• obtaining in the controller an infusion pressure of the irrigation fluid at a container connected to the surgical system;
• selecting a predicted leakage rate of fluid exiting the incision from a look-up table stored in the surgical system, based on the needle size, the sleeve size, the incision size, and the infusion pressure;
• sensing in the controller a fluid flow rate of the fluid by a flow sensor placed in the aspiration tubing;
• determining an intraocular eye pressure based on the infusion pressure less a pressure drop caused by the predetermined resistance to the irrigation fluid flow, which irrigation fluid flow is a combination of the sensed fluid flow rate and the predicted leakage rate of fluid exiting the incision;
• and
• controlling the flow of fluid in the eye based on the determined intraocular eye pressure to maintain a desired intraocular eye pressure.

A method of controlling the operation of a controller for regulating fluid flow in an eye and through an ophthalmic device in an ophthalmic surgical system, comprising:

• the controller receiving the input of a needle size, a sleeve size, and an incision size;
• identifying in the controller a predetermined resistance to a fluid flow associated with the ophthalmic device, including connected aspiration and irrigation tubing;
• obtaining in the controller an infusion pressure of irrigation fluid at a container connected to the surgical system;
• sensing in the controller a fluid flow rate of the fluid by a flow sensor placed in the aspiration tubing;
• estimating an intraocular eye pressure value, based on the infusion pressure less a preliminary pressure drop caused by the predetermined resistance to fluid flow, which fluid flow does not include any predicted leakage flow;
• selecting a predicted leakage rate from a look-up table stored in the surgical system based on the needle size, the sleeve size, the incision size and the estimated intraocular eye pressure value;
• calculating a refined intraocular eye pressure based on the infusion pressure less a refined pressure drop caused by the predetermined resistance to the fluid flow, which fluid flow is determined as a combination of the sensed fluid flow rate and the predicted leakage rate;
• and
• controlling the flow of fluid in the system based on the refined intraocular eye pressure to maintain a desired intraocular eye pressure.