[Controlled suction in vitrectomy (author's transl)]

Abstract

A peristaltic pump (type "Perpex", J. H. Guldener, Zürich, Switzerland) was modified for controlled aspiration in vitrectomy (fig. 1). The surgeon operates start, instantaneous stop and back flush with a single foot pedal. Suction and cutting device are controlled independently. Suction flow can continuously be varied between 0 and 16 ml/min (fig. 2). This less critical function is operated by the assistent. The upper limit of suction flow depends on infusion resistance and preselected differential pressure (fig. 3). The infusion resistance and its reciprocal, the inflow rate, vary considerably with different instruments. In four devices infusion resistance was measured and found to vary by a factor of up to 4.6. Low infusion resistance allows high suction flow and thus shorter operation time for certain conditions such as "ochre membranes" or intrasurgical bleedings. Further aids which we use in combination with a Zeiss OPMI-8 are an intense external xenon light source for variable slit illumination which makes the use of intravitreal fiber optics unnecessary, and a mirror combination to achieve an 11 degrees semi-coaxial stereoscopic view of the operation field for the assistent.