Optometrists are vision care specialists who have four years of education after college and degrees from schools of optometry. You may identify their degree by the letters OD (Optometric Doctor) after their name. Their training is most intensely oriented to primary eye examinations, prescribing glasses and contacts and diagnosis and sometimes treatment of some of the more common and eye disorders depending on the state they practice in.
Without getting embroiled in the politics of vision care, I believe it is appropriate to say both disciplines have excellent training and benefit the patient. In my experience, the quality of care is frequently enhanced when optometrists and ophthalmologists maintain close working relationships for the betterment of care for the patient.