Program list

Advantages of peristaltic + short occlusion duration cutting
for dislocated lens removal

Didier Ducournau

Nantes, France

Two functionning properties are helpfull when removing a dislocated lens with the vitrectomy machine hand piece.
- the pump system: when the lens is soft, it can be aspirated by only using the aspiration power of the machine. After occlusion of the hand piece port by the lens, the depression mesured at the tip level, increases and permits the lens to be aspirated. With a peristaltic pump, when the occlusion occurs, the pump continues to turn and the depression at the tip level can reach up to -500 mm Hg without risk of accident (because of the aspiration flow control). This is not possible with a Venturi pump.
- the cutting system: when the cataract is harder, cutting must be used to facilitate the aspiration. With a classical cutting system, at 1 Hz, the occlusion duration of the port by the knife is 0.5 second. During this duration, the lens is not still attracted by the gradient of pressure; it may separate from the hand piece tip and can fall under gravity effect. With a 0.02 second occlusion duration cutting system, the lens fragments remain attached even durinf the occlusion time.