A cataract is a clouding of the normally clear and transparent lens of the eye. It is a fogging of the lens itself. When a cataract develops, the lens becomes cloudy like a frosted window and will cause a painless blurring of vision with a reduction in contrast.

The lens, located behind the pupil, focuses light on the retina at the back of the eye to produce a sharp image. When a cataract forms, instead of focusing all the light entering the eye, some of the light is scattered, causing blurred vision, a reduction of contrast and increase in glare. Often, however, a cataract affects only a small part of the lens and if sight is not greatly impaired, there is no need to remove the cataract. If a large portion of the lens becomes cloudy, sight can be partially or completely affected until the cataract is removed.

There are many misconceptions about cataracts. For instance, cataracts do not spread from eye to eye, though they often develop in both eyes about the same time. A cataract is not a film visible on the outside of the eye. Nor is it caused from overuse of the eyes or made worse by use of the eye. Cataracts rarely develop in a matter of months. Fortunately, vision can often be fully restored with a 15-minute procedure. Our referral surgeons use the latest techniques, without the use of needles or stitches and with recovery in about 24- 36 hours to full vision.

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There are many types of cataracts. Most are caused by a change in the chemical composition of the lens resulting in a loss of lens transparency. These changes can be caused by ageing, eye injuries, certain diseases and conditions of the eye and body, and hereditary or birth defects.

The normal process of ageing may cause the lens to harden and turn cloudy. These are are the most common type. They can occur as early as age 40.  The most common types of cataracts include nuclear sclerotic cataracts, cortical cataracts and posterior subcapsular cataracts.  Nuclear sclerotic cataracts are characterized by a centrally located lens discoloration (yellow-brown) caused by deterioration of the older fibre cells near the centre of the lens.  Posterior subcapsular cataracts are characterized by opacities at the posterior surface of the lens and tend to be the most visually debilitating due to their central location on the lens.  Cortical cataracts are caused by swelling and liquefaction of the younger, more exterior cortical fibre cells.  This type of cataract is characterized by radial linear opacities along the outer edge of the lens.

Children, as well as adults, can develop cataracts. When cataracts appear in children, they are sometimes inherited or they can be caused by an infection or inflammation during pregnancy which affects the unborn baby. This latter type of cataract is called congenital, meaning present at birth.

Eye injuries can cause cataracts in people of any age. A hard blow, puncture, cut, intense heat or chemical burn can damage the lens and result in what is called a traumatic cataract.

Certain infections, drugs, or diseases of the eye such as diabetes can also cause the lens to cloud and form a secondary cataract.

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Depending on the size and location of the cloudy areas in a lens, a person may or may not be aware that a cataract is developing. If the cataract is located on the outer edge of the lens, only a very slight in vision may be noticed. If the cloudiness is located near the center of the lens, it usually interferes with clear sight. Common symptoms experienced with developing cataracts include blurred or doubled vision, sensitivity to light and glare which may make driving difficult, less vivid perception of colour, and frequent eyeglass prescription changes.

As the cataract grows worse, stronger glasses no longer improve sight. It may help to hold objects nearer to the eye for reading and close-up work. The pupil, which normally appears black, may undergo noticeable colour changes and appear to be yellowish or white.


Usually, cataracts cannot be viewed from the outside of the eye without specialized instruments. If blurred vision or other symptoms are noticed, an eye doctor should be visited as soon as possible for a comprehensive medical eye examination.

An eye doctor examines the eye with a variety of instruments to determine the type, size and location of the cataract.

Other tests are also carried out in the interior of the eye after dilation to determine if there are any other eye disorders contributing to the blurred vision.


When cataracts cause enough loss of sight to interfere with a person’s usual activities or lifestyle, it is probably time to remove them. Depending on individual needs, the patient and the eye doctor decide together when removal is necessary.

Surgery, is usually performed under local anesthesia on an out-patient basis, is the only effective way to remove the cloudy lens from the eye. Laser can often be used to soften the cataract and make removal easier.

Fortunately, cataract surgery is highly successful and over 95% of patients who undergo surgery regain useful vision. It is important to understand that complications during or after surgery can occur. As with any surgery, a good result cannot be guaranteed, however having top doctors and surgeons manage your cataract surgery is the best guarantee for an optimal outcome.


If you notice any cataract symptoms, consult an eye doctor as soon as possible. Since cataracts most often form as a result of ageing, individuals over the age of 40 with a family history of cataracts should have their eyes checked periodically.

There is no known preventive measure for cataracts, but modern cataract surgery is highly effective and permanent vision loss is usually preventable. Once diagnosed, mild cataracts can be watched to see if they progress. If vision loss due to a cataract is interfering with your daily activities, there is usually no reason to delay surgical treatment. Fortunately, a cataract patient no longer needs to become nearly blind before cataracts can be removed.

If you have any additional questions or would like further information, call the Toronto Eye Clinic for a consultation with one of the doctors.