Fig. 4From: Vitreoretinal instruments: vitrectomy cutters, endoillumination and wide-angle viewing systemsPneumatic spring return driven vitrectomy probe. An air pulse pushes down the diaphragm located inside the vitrectomy probe, leading the port to a closed position (the guillotine movement); at the same time, a spring is compressed and forces the diaphragm back to the open port position. Image provided by Alcon, USABack to article page