I should start by specifying, this is about the three EYE Os. You won't find Obstetrician, Osteopath, or Orthopedist here. So, now that we're clear, what's the difference between an Optometrist, an Ophthalmologist and an Optician.
First of all, we are Optometrists. An Optometrist goes to four years of college and then much like dentists and podiatrists, four more years of professional school on a very specific area of the body. For Optometry, as you know, that's eyes, specifically improving vision with glasses and contact lenses and diagnosing and treating eye disease. Where that treatment line is drawn is surgery inside the eyes. We do treat glaucoma, eye infections, etc., but we don't do cataract surgery or LASIK. Some optometrists, like us, do an additional Residency. They can vary from pediatrics to specialty contact lenses to ocular disease. Our Residency was in Hospital Based Optometry where we did a high volume of ocular disease diagnosis and treatment.
Ophthalmologists go to four years of college, followed by four years of medical school that is non-focused, but gives broad exposure to all things health. Following that they do a Residency in a specific area. An Ophthalmology Residency is three years. An Ophthalmologist technically can do anything that an Optometrist can do in addition to eye surgery. In practice, it doesn't quite work that way for most offices. Ophthalmology residents get very little training in refraction (determining glasses prescription), glasses and contact lenses and most often delegate that function to technicians as soon as they can. They are great for surgery, but not the best option for many other things.
Opticians fit and fabricate glasses and sometimes contact lenses. In Oregon, Opticianry is not regulated, so they can be very experienced and competent or they might have just been hired from a fast food restaurant. Nowhere will your mileage vary more. A top notch Optician who understands not only frame style, but modern lens design, materials, coatings and modern position of wear measurements is critical for realizing your best possible vision.