Cataracts: A cataract is a clouding of the normally clear and transparent lens of the eye. It is not a tumour or a new growth of skin or tissue over the eye, but rather a fogging of the lens itself. When a cataract develops, the lens becomes as cloudy as a frosted window and light cannot be properly focused on the retina resulting in an unclear image. Cataracts are the number one cause of blindness in the world, ahead of all other eye diseases. Of the estimated 45 million people in the world who are blind, approximately half are blind because of cataracts. Eighty-five percent of the world's cataract blind people live in developing countries. Field hospitals in developing countries restore sight to the cataract blind by means of a relatively simple eye operation, taking only minutes and costing less than CDN $30. Until recently, field-hospital patients had to be provided with thick eyeglasses to perform the function of the lens removed from their eyes. Now, field surgeons are beginning to place low-cost intraocular lens implants right inside the eye.

Cornea: The clear, transparent front portion of the eye’s fibrous coat, through which light passes to be focussed on the retina. With a curvature greater than the rest of the eye, it also acts somewhat as a lens.

Diabetic Retinopathy: A condition in which changes occur in the tiny blood vessels that nourish the retina (the light-sensitive tissue that lines the back of the eye and changes the light into nerve messages to be transmitted to the brain). In the early stages of diabetic retinopathy, called nonproliferative or background retinopathy, small blood vessels weaken and leak fluid or tiny amounts of blood, which distort the retina. At this stage the person may have normal vision or may note blurred or changing vision.

Glaucoma: Glaucoma is a disease affecting one of every one hundred Canadians over 40 years of age. It is one of the most common causes of blindness. Although associated with increased age, glaucoma may develop at any age-even in infancy. Visual loss in glaucoma is thought to be caused by raised intraocular pressure and other influences on the optic nerve, located at the back of the eye. The gradual loss of nerve function causes loss of peripheral, or side, vision painlessly and without notice.

Intraocular: Meaning within the eyeball, e.g., artificial intraocular lenses can be implanted during cataract surgery to replace a patient’s own clouded or opaque lens; the alternative to this is the patient must wear thick glasses to enable focusing of light on the retina.

Macular degeneration: Macular degeneration is the leading cause of blindness in Canada, accounting for one-third of all cases of vision loss. The most common form of macular degeneration occurs in people over age 55 years and is known as age-related macular degeneration, or AMD. Macular degeneration causes loss of central vision, leaving only peripheral, or side vision intact.

Onchocerciasis. The medical/scientific term for River Blindness.

River Blindness. Called onchocerciasis within the medical community, River blindness is a disease caused by a parasitic worm transmitted by black flies that breed along fast flowing rivers. The disease is rampant in countries throughout West and Central Africa and in a few regions of Latin America (a total of 37 countries). Destroying the optic nerve, the disease causes irreversible blindness. An estimated 17 million people are infected with onchocerciasis, with 500,000 gone blind already. MectizanÔ , a donated tablet from Merck, can treat the infection and prevent blindness if taken once every year.

Trachoma: An infectious disease of the eye caused by the microorganism chlamydia trachomatis, thriving in dry, poverty-stricken areas of the world where water is scarce and washing is difficult. After years of repeated infection, scarring gradually builds up on the underside of the eyelid, causing the eyelid to turn inward. This pulls the eyelashes into contact with the cornea; the eyelashes break off into bristles that scratch the cornea, causing pain, opaque scarring and ultimately irreversible blindness.

Six million people in the world have already been irreversibly blinded by trachoma. An additional 146 million people, 75 per cent of them children, have the active disease and are in need of antibiotic treatment to treat the infection. At least 10.5 million adults in the world are in urgent need of surgery to rotate the eyelid back to its original position to prevent further laceration of the cornea.

Vitamin A Deficiency: Vitamin A deficiency and malnutrition is the number one cause of blindness among children throughout the developing world. It is responsible for irreversibly blinding an estimated 350,000 children and killing two million children each year. Two hundred and fifty million pre-school children in the world are currently vitamin A deficient. More than 1.5 million children in the world are blind ¾ of these, more than 50 per cent are irreversibly blind because of vitamin A deficiency.

In developing countries vitamin-A-rich foods, such as fruits and green vegetables, liver and milk, are not always available. When young vitamin-deficient children then contract diseases that further reduce their intake of vitamin A (diarrhea) or diseases that use up a large amount of vitamin A (measles), their vitamin A supplies drop to dangerous levels. Such clinical cases of vitamin A deficiency, left untreated, cause irreparable damage to the cornea, and will almost always lead to blindness and often to death.

For those children whose supply of vitamin A is critically low, as well as for those children who have contracted measles or severe diarrhea, capsules containing high concentrations of vitamin A (200,000 IU) can stop the blinding effects of vitamin A deficiency in their tracks. Three vitamin A can save a child's sight ¾ and very often his or her life.