Regular eye examinations are important for identifying conditions that could eventually rob someone of their sight.

People tend to assume that if their eyesight is OK, then their eyes are healthy — but that's not necessarily the case, says John Rafferty, president of the CNIB.

The reasons people lose their sight have to do with the health of the retina, optic nerves, the viscous fluid and various other factors.

"You need someone who's going to take a look into your eye, understand the health of your eyes," Rafferty says.

"If they see indicators of one of the major eye diseases then they will be able to start a course of treatment early enough — not necessarily be able to cure or prevent it but can significantly slow things down so that you don't lose functional vision."

Genetics play a big role in certain eye diseases, he said. Practising good heart health — exercise, not smoking, proper eating — can also contribute to good eye health.

Some of the major eye diseases:

Age-related macular degeneration: the leading cause of vision loss in Canada, affecting nearly one million people. Occurs mostly as a result of aging. For some types, no treatment is available and people lose their entire vision very quickly. Other types have treatments available to slow or stop the loss of sight.

Glaucoma: second most common cause of irreversible vision loss in seniors in Canada, affecting 250,000 people. It involves damage to the optic nerve, usually caused by high pressure in the eye. Usually painless, with no symptoms. "There are quite a few treatment options if people find out about it early enough," Rafferty said.

Diabetic retinopathy: caused by changes in the blood vessels that feed the retina, which in its early stages can cause swelling and blurred vision. In advanced stages, it can lead to blindness. It's the leading cause of vision loss in Canadians under 50 and affects 7.2 per cent of people who come to the CNIB.

Cataracts: lenses naturally harden and may also turn cloudy. A cloudy lens blocks light from reaching the retina and interferes with vision. Surgery is highly successful in correcting the problem. "There are a surprising number of people who have cataracts that don't know that they have them and don't know that they can have a simple procedure ... to be able to restore sight," Rafferty said.