It is a statistically remote risk and is limited almost exclusively to the possibility of developing a post-operative infection. Published statistics range between 1/3000 and 1/1000 infections. Our own unpublished statistics estimate 1 infection in every 4000 LASIK surgeries.
If infection does occur, this does not mean it will end with loss of vision. A microbiological study to identify the germ responsible and early treatment with antibiotics should resolve the infection with minimal visual sequelae.