In Ontario, optometrists are licensed by the College of Optometrists of Ontario. The College of Optometrists (UK) has specified guidelines for optometrists who use the colorimeter system. Prescribing of contact lenses is usually restricted to various combinations of ophthalmologists, optometrists and opticians. Ophthalmologists and optometrists are able to provide this service. It is typically performed by orthoptists, ophthalmologists and optometrists during eye examinations. Instructors may be optometrists, ophthalmologists, or professors (Ph.D.). Among its products are the most common tools used by ophthalmologists and optometrists. For several years he worked for various optometrists and ophthalmologists. Optometrists and/or orthoptists are eyecare professionals who fix binocular vision problems. Specialists such as Chiropractors, Optometrists, Dentists, and Hygienists travels in every two-three months. The station also has visiting specialists including optometrists and dentists. There is a handful of pharmacies, dental offices, chiropractic clinics and optometrists in town. Among other things, the changes to the Act name optometrists as authorised prescribers. Like most healthcare professions, the education and certification of optometrists are regulated in most countries.