A known disposable per use surgical primary cassette is modified to avoid contamination thereof during use by aspirated fluid from a vitreous cutter connected thereto by bypassing the aspirated fluid into a receiving chamber of a relatively less expensive disposable secondary cassette, whereby during use a vacuum produced in a chamber of the primary cassette connected to the receiving chamber of the secondary cassette in turn produces a vacuum in the receiving chamber of the latter for drawing aspirated fluid from the vitreous cutter directly into the receiving chamber.