The IDENT Fluorescence option is used as a method of determining sperm motility and concentration without the interference of detritus.
By staining the cells with the IDENT Stain (DNA-specific dye, based on Hoechst bisbenzimide), all DNA-containing objects will fluoresce under the appropriate illumination. Cytoplasmic detritus, which does not contain DNA, will not fluoresce and will not be visible. Somatic cells that are not sperm (diploid cells such as leukocytes, spermatogonia, epithelial cells, etc.) can be eliminated since they will generally possess a larger size and lower degree of fluorescent intensity than the haploid sperm (although sperm have only half the DNA complement of a somatic cell, it is highly condensed, resulting in a higher degree of fluorescent intensity.)
For added convenience, Hamilton Thorne sells prepackaged IDENT Stain tubes. Sold in quantities of 200 tubes per bag, each tube contains 40 µg of stain, which is readily dissolved in sperm suspension medium.