A pneumatically driven vitrectomy probe system includes a movable member disposed within a cylinder to define an enclosed pressure chamber, which has an inlet and an outlet. A pressure transducer senses the pressure level within the enclosed pressure chamber, and a valve communicates pressurized air to the inlet of the enclosed pressure chamber based on the pressure level. A displacement device coupled to the movable member extends and retracts the movable member within the enclosed pressure chamber, to respectively increase and decrease the pressure level of pressurized air communicated via the chamber outlet. The pressurized air is communicated to enclosed volume within a pneumatically activated vitrectomy probe, which includes a hollow inner cutting member disposed within the hollow outer member. Upon extension of the displacement member, the resulting increase in pressure level of the pressurized air in the enclosed volume acts against the biasing spring to move the hollow inner cutting member, to cut vitreous material extending within the hollow outer member.
