A liquid crystal medium has stability to heat, light and so forth, and significantly high dielectric anisotropy, and develops an optically isotropic liquid crystal phase. Moreover, various kinds of optical devices can be used in a wide temperature range and have a short response time, a large contrast ratio and low driving voltage.A liquid crystal composition contains achiral component T containing at least one compound 1 represented by formula (1) and a chiral agent, and develops the optically isotropic liquid crystal phase. In formula (1), for examples, R1 is alkyl, L1 and L2 are each independently fluorine or hydrogen, and X1 is halogen.