Cataracts

The lens of the eyes is filled with mostly water and proteins that focuses light onto the back of the eye (retina) to form an image.  It is essential this liquid is clear to produce a sharp, clear image.

What is a Cataract?:
A Cataract is the clouding of the liquid in the lens or the envelope holding the lens which obscures light passing efficiently to the retina.  The poteins in the lens build up and group together clouding sight.  As well as reducing vision a cataract may cause yellowing of the vision due to it preventing blue light to pass through the lens. 

Though if left untreated the Cataract can cause complete blindness by letting no light to the retina, they are relatively simple to treat with complete resoration of vision.  Cateracts usually occur in both eyes, sometimes at varying degrees, but cannot be "caught" from one eye to the other.

Over half of people over 65 have cateracts and even more common in the over 80s but for most it is not serious enough for treatment.  In the UK about 5.5% of blind and partially sighted people have cataracts.  Cataracts cause 48% of blindness around the world, mainly due to the lack of treatment readily available in the third and developing worlds.

Symptoms:
Initially the vision can become blurred around the edges, giving the impression of misty or scratched glasses.  If it effects more than one place double vision can occur.  As the cataract becomes more opaque and the lens more cloudy, bright light can make it more difficult to see properly as light is scattered and diffused.  As vision decreases contrast becomes less obvious and colours less vivid.

As the proteins in the lens become clumped together, the lens becomes more "milky".  Eventually the lens can swell, followed by shinkage, resulting in the complete loss of transparency.  As it advances, a notable milkiness to the lens can be observed.  (The name "cataract" comes from the appearance of fast flowing water turning white).

Causes:
The majority of cases of cataracts are in people over 65.  The proteins in the lens gather together over time so is more likely later in life.
 

There are a number of causes or contributory factors to developing cataracts including:

• age
• family history
• secondary effects of diseases such as diabetes
• secondary effects of other eye conditions
• long-term exposure to ultraviolet light
• exposure to radiations
• eye injury or physical trauma (often at a much earlier stage to development of cataracts)
• allergies can quicken the development of cataracts
• nutrition
• smoking
• dehydration

Treatment:
Treatment for cataracts is successful, very effective and relatively simple.  Once the cataract has formed suffiently surgery can be performed to remove the lens (and sometimes the capsule in which it sits) and replaced by a plastic lens.  This is a quick prodedure down under local anesthetic. Sometimes high frequency sound is used to break up the lens before removal.  Patients are normally allowed to go home on the same day.

Most patients get an immediate improvement in their sight.  Eye drops should be taken during the healing process for a couple of months. 

Due to the fact the replacement lens is plastic it doesn't have the same properties as the "natural" lens. Unable to flex and stretch to focus at different lengths the new lens has a fixed focal distance.  As they are usually set for distance vision (short-sightedness) the patient may need glasses for close vision (or have their precription glasses changed to suit).

A common complications may occur after cataract surgery is a thickening of the cases which holds the lens in they eye, giving similar symptoms to the catracts themselves. This is easily correctable with laser treatment to create a hole in the lens capsule to let light pass through to the retina unobstructed.

Links:
For a more detailed and expert opinion visit:

RNIB information on Cataracts
NHS site on Age Related Cataracts
SightSavers charity page on Cataracts