What is od, optician, ophthalmologist?

Neither. An o.D. Is neither an optician or an ophthalmologist. O.D. Is short for optometric doctor. An o.D. Is an optometrist. An ophthalmologist is an M.D. That stands for medical doctor. An ophthalmologist receives more training than any of the eye specialists. An ophthalmologist is trained in the entirety of the medical field prior to being trained in the specialty of eyes. An optician fits glasses.
Levels of qualificat. An ophthalmologist is a medical doctor specializing in eye care od is a person who can treat refractive errors and provide some other care depending on state rules optician helps you with making and fitting your eyeglasses.