What is a Cataract?

A cataract is a loss of transparency, or clouding, of the lens of the eye. The lens is normally crystal clear. As one ages, chemical changes occur in the lens that make it less transparent. The loss of transparency may be so mild vision is hardly affected or so severe that no shapes or movements are seen, only light and dark. When the lens gets cloudy enough to obstruct vision to any significant degree, it is called a cataract.

The top lens is translucent and normal. The bottom lens is not: this is a cataract.

A cataract will typically cause a slow, progressive, painless decrease in vision. Other possible changes include glare or haloes, particularly with night driving; trouble reading or making out fine details; frequent eyeglass prescription changes; a decrease in colour intensity and a yellowing of images. Glasses or contact lenses can help sharpen your vision somewhat if an early cataract is present, but as the clouding progresses, they will no longer be helpful. Your lifestyle and activities will also determine how soon the cataracts affect your lifestyle.


Blurry vision due to a cataract.

Ironically as the lens gets harder, farsighted or hyperopic people may initially experience improved distance vision and less dependence on glasses. However, nearsighted or myopic people may become more nearsighted or myopic, causing distance vision to be worse. Some types of cataracts affect distance vision more than reading vision. Others affect reading vision more than distance vision.

The most common cause of cataract is aging. Other causes include trauma, eye rubbing, medications such as steroids, systemic diseases such as diabetes and prolonged exposure to ultraviolet light. There are many different types of cataracts, and they can develop at any age. Babies can even be born with cataracts, requiring surgery.

Reducing the amount of ultraviolet light exposure by wearing a wide-brim hat and sunglasses may reduce your risk for developing a cataract but once developed there is no cure except to have the cataract surgically removed.

Outpatient surgical procedures can remove the cataract through either a small incision (phacoemulsification) or a large incision (extracapsular extraction). The time to have the surgical procedure is when your vision is affected enough to interfere with your lifestyle. It is no longer necessary, or desirable, to wait until the cataract is “ripe”. That was done years ago, when surgical techniques were very different from those that are used now.


Yellowing of vision due to a cataract.

Cataract surgery is, in general, a very successful operation. One and a half million people have this procedure every year and the vast majority report successful results. As with any surgical procedure, complications can occur during or after surgery and very rarely, some are severe enough to limit vision. But in most cases, vision, as well as quality of life, improves.