as·tig·mat·ic [àstig máttik], adjective – 1. cause of blurred vision: an unequal curving of one or more of the refractive surfaces of the eye, usually the cornea. It prevents light rays lying in specific planes from coming to a focus on the retina, thus producing blurred vision. 2. optical lens defect: a defect in a lens or mirror that prevents light rays from meeting at a single point, producing an imperfect image