Optical-flow Analysis of the Relationship Between Ooplasmic Fluidity and Oocyte Degeneration During...

To evaluate the predictive ability of ooplasmic fluidity assessment during piezo-intracytoplasmic sperm injection (ICSI) for unintentional membrane rupture (UMR) and oocyte degeneration.We established an optical-flow analysis method that detects ooplasm movement in piezo-ICSI videos. Videos of 104 oocytes recorded during piezo-ICSI at our institute between January 2020 and January 2024 were retrospectively analyzed.To evaluate the apparent velocities in the ooplasmic region, we analyzed the vertical velocity component of the obtained optical flow between the start of puncture and the rupture of the oolemma (1st period) and between sperm injection and pipette withdrawal (2nd period). The velocity distributions between groups were compared using the 95th, 99th, and 99.5th percentiles. The 95th, 99th, and 99.5th percentiles of the survival group (n = 76) were significantly higher than those of the degeneration group (n = 28) during the 1st period (P < 0.001). Similarly, the 95th, 99th, and 99.5th percentiles of the survival group were significantly higher than those of the degenerative group during the 2nd period (P < 0.05). The 95th, 99th, and 99.5th percentiles without UMR (n = 52) were significantly higher than those with UMR (n = 50) during the 1st period (P < 0.001). Similarly, the 95th, 99th, and 99.5th percentiles without UMR were significantly higher than those with UMR during the 2nd period (P < 0.001). Greater ooplasmic fluidity was correlated with lower incidence of UMR and oocyte degeneration. Elucidation of the mechanisms underlying this phenomenon may help reduce UMR and oocyte degeneration.