World Council of Optometry (WCO) define optometry as: 
“Optometry is a healthcare profession that is autonomous, educated, and regulated (licensed/registered), and optometrists are the primary healthcare practitioners of the eye and visual system who provide comprehensive eye and vision care, which includes refraction and dispensing, detection/diagnosis and management of disease in the eye, and the rehabilitation of conditions of the visual system.”
Optometrists are trained to examine the eyes to detect defects in vision, signs of injury, ocular diseases or abnormality and problems with general health, such as high blood pressure or diabetes. They make a health assessment, offer clinical advice, prescribe spectacles or contact lenses and refer patients for further treatment, when necessary.

What is the difference between an Optometrist, an Ophthalmologist, and an Optician?

Optometrist

An optometrist is a primary health care provider (OD) that specializes in eye care and visual health.

Ophthalmologist

An ophthalmologist is a medical doctor (MD) specializing in eye disease who may perform ocular surgery. 

​Optician 

An optician is a professional who fits and grinds lenses and dispenses glasses.