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Lasers were initially used for the treatment of male subfertility. The aim was to overcome fertilization failures in patients with severe oligoasthenoteratozoospermia (OAT). In these patients, the zona pellucida was found to be an obstacle which the low number of slowly moving spermatozoa present in OAT patients were unable to overcome. One approach was to create an artificial opening into the zona pellucida which should allow sperm cells to gain access to the perivitelline space and to fertilize the oocyte. Several methods for opening the zona pellucida have been proposed, based on mechanical or chemical methods. Mechanical zona opening involves the use of a sharp glass capillary mainly to cut or dissect the zona (zona cutting, Tsunoda et al. 1986; partial zona dissection, Malter and Cohen 1989). The chemical opening of the zona is achieved with acidic Tyrode’s solution (Gordon and Talansky 1987). The use of these techniques have been described in detail in the literature (Depypere et al. 1988, Cohen 1992). |
