In terms of what the law says and technical terms, there is nothing that an optometrist can do that an ophthalmologist can't. However, in reality, optometrists can do many things that ophthalmologists won't touch because they don't know how and it would be unethical for them to attempt these things that they're not really trained at. Optometrists are good at stereoacuity, depth perception and binocular vision, low vision, sports vision, contact lens fittings of odd shaped corneas etc., diagnosis, treatment of eye diseases and they are the BEST at what they do. Ophthalmologists are good at LASIK, surgical procedures, treatment of diseases that require surgery, diagnosing common/rare diseases in their area of specialty (whether that be the retina, optic nerve, etc.) and they are the BEST at what they do. Believe it or not, it is usually best to see an optometrist first, because ophthalmologists are usually the best diagnosing their specific area of specialization whereas optometrists are better at a general diagnosis. People go to an ophthalmologist first and end up being referred from one ophthalmologist to the other because each one is very proficient at their area of specialty of the eye and don't really deal with other areas on a daily basis. An optometrist usually has a more general understanding of the eye and can usually tell you what you have right away (since they do general eye exams as their profession). Sometimes they might not necessarily be able to tell you what you have exactly, but will know where the problem in your eyes lie and can refer you to the right ophthalmologist that will be able to diagnose your disease. So in summary, regardless what the law says, an ophthalmologist (generally) can't be a good optometrist without receiving a lot of experience and training from an optometrist. Not to mention that optometrists do residencies in areas that ophthalmologists are completely clueless about (i.e. contact lenses, low vision, etc.). But like I said, optometrists are good at what they do and they are the best at what they do. Ophthalmologists are good at what they do and they are the best at what they do.