*Contrast Sensitivity>>>ophthalmologist

What's the difference between an optician, optometrist, ophthalmologist, and an obstinate person?

optician -
an expert in the art and science of making and fitting glasses and may also dispense contact lenses.

optometrist -
a primary eye care provider who diagnoses, manages, and treats disorders of the visual system and eye diseases.

ophthalmologist -
Physician (MD) specializing in diagnosis and treatment of refractive, medical and surgical problems related to eye diseases and disorders.

obstinate -
stubborn: tenaciously unwilling or marked by tenacious unwillingness to yield

The first 3 deal with eyes, the last one is just a pain...................
some have a M.D. and others don't what a stupid question ! wasting our time with a question like that! I would call you a jackassologist!
What git_sum said............it looks like sdw_46 needs a nap though.
Git_Sum is almost correct, except for the definition of an optometrist. The "...metrist" part of this title refers to "measuring". An optometrist is an expert in measuring the focusing function of your eyes. By his tests and measurements he can calculate the precise curvature of lenses for eyeglasses or contacts that are needed to accurately compensate for the focusing ability of your eyes. Poor vision is the result of distortions in the natural lenses of your eyes that cause the focal point of light passing through your eyes to be displaced on your retina so you can't see clearly. The optometrist can determine what the degree of displacement is and the measurement of correcting lenses you need to wear so light passing through both your eyeglass lenses and your natural eye lense focus in the proper location on your retina.