[Extracapsular fluid dynamics and suction-irrigation cannulas. A model observation].

The ECCE technique often requires additional removal of lens residues remaining attached to the capsular bag after lens nucleus extraction. These residual lens substances in the form of a visco-elastic fluid are detached and removed by means of various types of irrigation-aspiration cannulas. During the aspiration process the elastic properties of the fluid are utilized. The aim of the investigations presented was modification and optimization of the geometric design of the irrigation-aspiration cannulas to improve the flow efficiency, facilitate the detachment and reduce the amount of rinsing fluid required. The fluid mechanic properties of various type of irrigation-aspiration cannulas were investigated and compared in an eye model. Some of the commercially available irrigation-aspiration cannulas give good results, being convenient to handle and functional. Our experimental data indicate that canalization of the rinsing fluids and the special location of the irrigation-aspiration openings will improve the flow-field. An adjustable valve has been developed, which enables safe aspiration/irrigation changeover if it should be necessary. Two models of the newly designed irrigation-aspiration probes are presented and discussed.