In Canada, a person is legally blind if his or her best eye has less than 20/200 vision or less with the help of glasses or contact lenses. Having 20/200 vision means that a person cannot be more than 6 m (20 ft) away to see what a person with normal vision can see from 60 m (200 ft) away.
Canada also considers a person legally blind if his or her visual field is 20 degrees or less, even with the help of glasses or contact lenses. Having a visual field of 20 degrees means that a person has trouble seeing to his or her side when looking straight (peripheral vision). A vision test is used to measure a person's visual field.
Legal blindness does not mean that a person cannot see at all. People who are legally blind often have some vision, but their field of vision may be very narrow or blurry. Or they may have blind spots that glasses cannot correct.
Being diagnosed as legally blind restricts a person's ability to obtain a driver's licence. But a legally blind person is usually eligible for low visibility aids and other benefits to help improve daily functioning.
Adam Husney, MD - Family Medicine & Christopher Joseph Rudnisky, MD, MPH, FRCSC - Ophthalmology