Vacuum loss detection during laser eye surgery

A method of detecting loss of vacuum in a patient interface of a laser eye surgery system, comprising:

• coupling the patient interface to an eye with suction provided to a suction ring in contact with the eye by a suction supply conduit so as to create an interface container over the eye defining an interface container volume, the suction supply conduit leading to a suction circuit having a source of suction;
• introducing a liquid to the interface container volume to create a transmissive medium of the liquid above the eye;
• coupling the patient interface to an ophthalmic laser surgery system;
• performing an ophthalmic laser procedure on the eye through the patient interface while maintaining suction to the suction ring;
• measuring a monitoring conduit pressure in a monitoring conduit connected to sense pressure in the suction ring, the monitoring conduit leading to a monitoring circuit having a substantially smaller volume than the suction circuit;
• and
• interrupting the ophthalmic procedure when the monitoring conduit pressure rises above a threshold amount.