These three occupations are often used interchangeably and can be difficult to differentiate. Aside from other similar root words, the different tasks that each individual is responsible for is very different and each provides an important component of your eye health and vision.
The first of the three occupations is the optician. The primary focus of opticians is to facilitate the measurement and sale of glasses. Licensed opticians will go to 2 years of schooling, during which they study the various aspects of ordering and dispensing glasses and sometimes contact lenses (depending on their state or country of practice). However, opticians are not licensed to determine the prescription that is to be ordered into the lenses, as that is the job of the optometrist or ophthalmologist.
Optometrists are required to complete a minimum of 3 years in an undergraduate program before being admitted into a 4 year optometry program. After this, they have the option of completing an extra year in residency but are not required to in order to practice, as their practicum is built into the four year program. Most optometrists can prescribe topical pharmaceuticals (ie:eye drops) as well as pertinent oral medications, provide patients with prescriptions for glasses or contact lenses, and order specific laboratory testing. Optometrists are also able to manage ocular diseases and, in certain states, perform basic laser procedures and external surgical procedures.
The ophthalmologist performs intraocular surgery, laser treatment, and certain neurology assessments. Ophthalmologists are required to attend a minimum of 3 years in an undergraduate program and then a 4 year degree program to become a medical doctor. After this, it is an additional 5 years of residency to become an ophthalmologist. Extra fellowship training can be pursued after this for subspecialization. The longer the fellowship, the more specific the training. For example, 2 year fellowship programs include specialties in glaucoma, neuro-ophthalmology, retinal disease, oculoplastics, and more.