Light intensity and wavelength during embryo manipulation are important factors for maintaining viability of preimplantation embryos in vitro.

Objective: To optimize embryo culture system by evaluating lighting effect during in vitro manipulation.
Design: Randomized prospective study using an animal model.
Setting: Gamete and Stem Cell Biotechnology Laboratory at Seoul National University in Korea.
Animal(s): Twelve- to 15-week-old hamsters (Mesocricetus auratus).
Intervention(s): Two-cell embryos were manipulated in vitro under lighting of different intensities and wavelengths.
Main Outcome Measure(s): Preimplantation development, Hsp70 expression, reactive oxygen species (ROS) generation, and blastomere apoptosis.
Result(s): A significant increase in morula and blastocyst formation was detected at 200 lux compared with 900 lux visible ray lighting, but not compared with 500 lux. At 200-lux lighting, red (620-750 nm) ray yielded the best development, whereas blue (445-500 nm) decreased blastocyst formation. Compared with the visible ray, Hsp70 expression and ROS generation in morula were increased in the blue ray but decreased in the red ray lighting. The blue ray also reduced blastocyst quality with increasing blastomere apoptosis.
Conclusion(s): Specific wavelength of visible ray increases Hsp70 expression, ROS generation, and blastomere apoptosis. Therefore, removing this stress factor improves embryo development.