VITRECTOMY MACHINE CHOICE

Didier Ducourneau (Nantes)

Like a good car is one that allows the driver to perfectly control its speed and braking, a good vitrectomy machine will allow the operator to have under precise control all the parameters he or she will need, parameters which first obey the laws of physics and particularly, the laws of fluid dynamics. We then analyse all the parameters that we need to control, recalling the physics base lines, regarding the J.C. Badet MD and B. Collin PhD experimental work and the surgical consequences.
We need:

• The infusion opening control with the foot pedal, as in phaco.
• The precise control of the aspirating flow. A pressiometric pump, like Venturi pump doesn't allow this aspi-rating flow control. Only a debitmetric pump, like peristaltic one permits this precise control at high level (15 to 20 cc/mn) for central vitrectomy, as well as at low level (2 to 4 cc/mn) for peripheral work. We will then choice a debitmetric pump.
• An aspiration system without compliant forces: airtight handpieces, depression panels without air bubbles, and tubing as rigid as possible.
• An handpiece with 0.5 mm internal diameter as a minimum; this handpiece must give the possibility of decreasing the opening of the port - A bilinear foot pedal permitting the simultaneous control of aspiration flow and cutting frequency ( at low frequency, as well as at high speed frequency).
• A cutting with short duration occlusion of the port by the blade. In fact, with classical cutting system, the gradient of pressure which have the time to increase during the duration of the port occlusion, induces movements of the retina.