A cataract is a condition that causes decreased vision due to clouding of the lens behind the iris. It typically occurs as a result of aging and can occur in one or both eyes. More than 2.5 million Canadians have cataracts.
The lens is mainly composed of protein and water. A cataract is caused by the coalescence of natural proteins in the lens. Normally, these proteins are organized in such a way that the lens remains clear, and light is not blocked from entering the eye. However, as we age, the protein components of the lens tend to fuse together forming a cloudy area.
Although, most cataracts are due to aging, there are other types of cataracts. Traumatic cataracts are cataracts that have developed due to injury; congenital cataracts are present at birth and may or may not affect vision, while a radiation cataract is caused by exposure to certain types of radiation.
Certain lifestyle changes may help to prevent cataract formation, such as maintaining a healthy, antioxidant-rich diet, protecting the eyes from ultraviolet radiation by wearing sunglasses and hats, and refraining from smoking.
The lens is responsible for focussing light on the retina, the light-receptive tissue that lines the back of the eye. In a normal healthy eye with a clear lens, light passes unobstructed through the lens to the retina. The retina then converts the light into neural signals that are sent to the brain. In order for the brain to receive a sharp image, the lens must be clear. Consequently, people with cataracts often experience blurry vision over time as their lens gets cloudier. Additionally, cataracts due to age can cause discolouration of the lens from clear to a yellowish or brownish hue. This change in colour may result in a change in colour perception. Other symptoms of cataracts include glare, difficulty with night vision and vision in low lighting conditions, and double vision occurring in one eye.
A cataract can be detected during a routine comprehensive eye examination. Routine eye exams are also helpful in monitoring cataract progression.
Although cataracts are irreversible, there are methods of managing the symptoms, such as prescription glasses with anti-reflective coating, prescription polarized sunglasses, magnifying lenses, and brighter lighting. If these options are ineffective, cataract surgery may be advised to remove the cloudy lens and replace it with an artificial intraocular lens.