An eye treatment system for performing an ocular surgical procedure contains an eye treatment probe or handpiece, a treatment console, an eye treatment cassette, and a pump formed by the engagement of the treatment cassette with the treatment console. The handpiece is configured to provide at least irrigation fluid to, and aspiration of fluid from, a subject eye. The treatment console comprises a controller configured to control the eye treatment probe. The eye treatment cassette engages the treatment console to couple the eye treatment probe with the treatment console. The pump comprises a pump head having a plurality of projections disposed to rotate about an axis, a ramp disposed near the rotating projections, and a resilient channel configured to transfer fluid when engaged by the ramp and the plurality of projections. The ramp is configured to reduce pressure fluctuations with the eye during a surgical procedure and comprises and entrance portion, a central portion, and an exit portion. The entrance portion has an arcuate extent over which the projections close the channel as the head rotates. The central portion has an arcuate extent over which the channel is sealed by the projections as the head rotates. The exit portion has an arcuate extent over which the projections open the channel as the head rotates. The ramp is configured such that the arcuate extent of the entrance portion is unequal to the arcuate extent of the exit portion.
