ULTRASTRUCTURAL OBSERVATIONS IN HUMAN OOCYTES AND PREIMPLANTATION EMBRYOS AFTER ZONA OPENING USING AN ERBIUM-YTTRIUM-ALUMINUM-GARNET (ER-YAG) LASER

For more than 3 years we have performed laser-assisted hatching prior to embryo transfer in patients with recurrent implantation failure usi ng an erbium-yttrium-aluminium-garnet (Er:YAG) laser system that opera tes in the infrared region of the light spectrum. The laser beam is gu ided through a quartz fibre and is brought into direct contact with th e zona pellucida, This study was undertaken to evaluate the ultrastruc tural effects of this laser on the zona pellucida and underlying cell membrane of unfertilized human oocytes and pathologically fertilized p reimplantation embryos using light and scanning electron microscopy. T he Er:YAG laser produces an almost circular zona opening in the shape of a truncated cone tapering off towards the inside, with a mean diame ter of IS mm. The exact diameter of the drilled site depends on the di ameter of the fibre tip and the total number of pulses applied. After laser interaction, the zona matrix and the surface of the underlying o oplasm membrane showed no degenerative alterations, We conclude that t he Er:YAG laser is an effective microsurgical tool for achieving repro ducible, precise zona openings particularly suitable for purposes of a ssisted hatching because of their characteristic shape.