An ophthalmic surgical apparatus for use with an eye including a tube adapted to be in fluid communication with the eye, a pressure sensor adapted to measure an intraocular pressure value of the eye, a fluid reservoir comprising a moveable wall, the fluid reservoir adapted to be in fluid communication with the eye through the tube, and at least one processor coupled to the pressure sensor to receive the measured intraocular pressure value, the at least one processor operable to position the moveable wall in response to a difference between the measured intraocular pressure value and a target intraocular pressure value.