The sperm are visualised using a high magnification microscope, which is almost 6000x more powerful than a normal ICSI microscope, to choose the sperm that appear to be the healthiest. The rationale is that the sperm that meet the criteria should have a superior genetic quality. Specifically, the sperm that are selected are those with the correct shape and size and with minimal vacuolisation (spaces) in the head. Vacuolisation in the sperm head relates to an increased incidence of poor DNA arrangement.
Once the sperm is selected they are injected into the egg using the ICSI procedure.
The IMSI selection will not increase the fertilization rate by ICSI or the outcome, but is intended to decrease the subsequent miscarriage rate.