Cataract is the word used to describe an area of increasing cloudiness in the lens of the eye — the lens of the eye is located behind the iris -the coloured part of the eye. A cataract may begin as a white spot at the edge of the lens or as a haze at the centre of the lens and gradually worsens until the vision is badly blurred.

Clouded vision can make it more difficult to read, drive a car or see the expression on a friend's face. Cataracts commonly affect distance vision and cause problems with glare. They generally don't cause pain, double vision with both eyes open or abnormal tearing.

Most cataracts develop slowly and don't disturb your eyesight early on. But as the clouding progresses, the cataract eventually interferes with your vision.

In the early stages, stronger lighting and eyeglasses can help you deal with the vision problems. But at some point, if impaired vision jeopardizes your normal lifestyle, you might need surgery. Fortunately, cataract removal is one of the safest, most effective and most common surgical procedures.

When to seek medical advice

An eye specialist can detect and track the development of cataracts during routine eye exams. Have your eyes examined:

• At least every two years beginning at age 60

• Any time you develop new eye symptoms

If you experience any signs and symptoms of cataracts, see your eye doctor. An eye doctor can diagnose cataracts with the help of a careful eye exam.

The only way to know for sure if you have a cataract is to have an eye examination that includes several tests:

• Visual acuity test. Acuity refers to the sharpness of your vision or how clearly you see an object. In this test, your eye doctor checks to see how well you read letters from across the room. Your eyes are tested one at a time, while the other eye is covered. Using the chart with progressively smaller letters from top to bottom, your eye doctor determines if you have 20/20 vision or less acute vision.

• Slit-lamp examination. A slit lamp allows your eye doctor to see the structures at the front of your eye under magnification. The microscope is called a slit lamp because it uses an intense line of light — a slit — to illuminate your cornea, iris, lens and the space between your iris and cornea. The slit allows your doctor to view these structures in small sections, which makes it easier to detect any small abnormalities.

• Retinal examination. In this procedure, your eye doctor puts dilating drops in your eyes to open your pupils wide and provide a bigger window to the back of your eyes. Using a slit lamp or a special device called an ophthalmoscope, he or she can examine your lens for signs of a cataract and, if needed, determine how dense the clouding is. Your eye doctor will also check for glaucoma and, if you have blurred vision or discomfort, for other problems involving the retina and the optic nerve. Dilating drops usually keep your pupils open for a few hours before their effect gradually wears off. Until then, you'll probably have difficulty focusing on close objects, while your distance vision is generally less affected. With your pupils open this wide, you'll probably want sunglasses for your trip home, especially if it's a bright day. Also, it's safer to let someone else do the driving.

If you have a cataract, you can discuss treatment options with your eye doctor.