A vitreotomy device comprises a body (32) extendedby a cannula (36). The cannula has a closed distal end(36a)； it includes a window (38) in its side wall closeto said distal end. It houses a needle (40) driven withreciprocating motion and capable of periodically closingsaid window. The device further comprises suction meansconnected to the needle, and a double-acting cylinder(44) provided with a moving piston (50) for controllingthe movement of said needle. In said device, the needleis driven with reciprocating motion in translation insaid cannula； said piston of the double-acting cylinderis secured directly to said needle； as a result, itsmovements enable the needle to be moved into a firstposition in which said needle closes said window, and asecond position in which the needle leaves said windowopen. The device makes it possible to control veryaccurately the lengths of time for which the end of thecannula is open and closed.
