Vacuoles in the sperm head have been linked to failures in sperm chromatin condensation. Thus, this "unprotected" chromatin is more susceptible to DNA damage. In fact, some studies have linked vacuoles in spermatozoa to an increased rate of sperm DNA fragmentation.
If these vacuolated sperm are discarded in IMSI, it has been suggested that they may improve reproductive outcomes. However, the superiority of IMSI over conventional ICSI has not been demonstrated, so IMSI is not a routine procedure in assisted reproduction laboratories.