Optometrists examine and test eyes for disease, general health problems and defects in eyesight. They used to be called ophthalmic optician.
Opticians specialise in the design, fitting, and dispensing of eyeglasses, contact lenses, low vision aids, and prosthetic ocular devices, using the initial prescription from an Ophthalmologist.
They probably changed because more and more of these �opticians� started to employ optometrists who did the eye tests and general eye health checks �in house�.