How does it work?
Spindles are composed of microtubules that show birefringence, which cytoplasm does not. Polarized light microscopy has the potential to visualize and measure birefringent structures such as spindles.
Spindle observation has two main merits.
The first is the detection of the spindle location during ICSI. The visualization of the metaphase II (MII) spindle in oocytes by polarized light microscopy can be used to avoid damaging the spindle and chromosomes when inserting the ICSI needle into the ooplasma.
In the basic technique of human ICSI, the injection is usually made at the 3 or 9 o’clock position with the first polar body (PB) at the 12 or 6 o’clock position, because it is postulated that the MII spindle is located adjacent to the first PB.
When the spindle is intentionally damaged by cytoplasm aspiration, the normal fertilization rate decreases and the multi-pronuclear formation rate increases. Therefore, for safe ICSI, it is thought that the injection should be made at the 3 or 9 o’clock position with the MII spindle visualized using a polarized light microscope at the 12 or 6 o’clock position to avoid damaging the spindle.
The second merit of spindle observation is that the spindle image provides an indication of the optimal timing of ICSI.
There are results showing that we should not estimate the oocyte maturity by the presence of the first PB alone. Rather, observation of the MII spindle in oocytes by polarized light microscopy gives us more information on oocyte quality and provides the best estimate of the optimal timing for ICSI.
Whom Spindle imaging is for?
- Advanced maternal age
- Low anti-mullerian hormone (AMH)
- Previous poor IVF embryos with normal male
- Morphologically poor-looking oocytes in previous IVF
- Previous poor fertilization with ICSI
- Assessment of oocyte optimization therapy
- Frozen and thawed oocyte assessment