Use of a laser to detect viable but immotile spermatozoa

Summary.  A prerequisite for the success of intracytoplasmic sperm injection (ICSI) is the use of viable sperm that will support oocyte activation and embryo development. Usually, spermatozoa are selected according to motility, which is a clear indication for viability. However, in cases with complete asthenozoospermia, it is impossible to select viable sperm by morphological means. Here we report for the first time on the use of a laser to discriminate between viable and dead immotile spermatozoa. The application of a single laser shot to the far end of the sperm tail causes a curling of the sperm tail only in viable sperm, similar to the reaction observed in the hypo-osmotic swelling test. Using this method for sperm selection prior to ICSI we achieved high fertilization and cleavage rates in cases with immotile sperm in fresh testicular biopsy material as well in cases with ejaculated immotile sperm. It is concluded that laser sperm interaction allows for the identification of viable but immotile spermatozoa.