What is Cataracts?

Cataracts

What are cataracts?

Normally, the lens of your eye is clear. But if you have a cataract, it means you have a cloudy spot in your lens.

As the cataract grows, your sight gets blurry or misty.

Source:
The Royal College of Ophthalmologists.
Understanding cataracts.
2001. http://www.rcophth.ac.uk/about/publications (accessed on 5 March 2009).

Source:
National Eye Institute.
Cataract: What you should know.
Available at http://www.nei.nih.gov/health/cataract/webcataract.pdf (accessed on 5 March 2009).

² You might feel as if you're looking through glasses that are dirty or scratched. It's just like a camera lens that's gotten scratched. The marks would show up on the pictures.

Cataracts are common. They can happen at any age, but most form as people get older.

If you have a cataract, you shouldn't worry. It might not bother you at first. And when it does, you can have an operation to take it out. You should be able to see much better afterward.

Key points for people with cataracts

One-third of people over the age of 65 have cataracts. And about half of people have them by the age of 75.
Most cataracts are caused by aging.
Your chances of getting cataracts as you get older can be higher because of the way you live. For example, your chances are higher if you smoke or you go out in the sun a lot.
But cataracts can be caused by other things. You can be born with them or get them because of health problems such as

diabetes
Diabetes is a condition that causes too much sugar to circulate in your blood. It happens when your body stops making a hormone called insulin (type 1 diabetes) or when insulin stops working (type 2 diabetes).

diabetes.
Surgery is the only treatment for cataracts that we know works.
You should be able to see much better and enjoy life more after surgery. But there are risks, and your eyesight probably won't be perfect.

How your eye works

The front of your eye has a thin film over it. This film is called the cornea. The cornea helps to stop your eye from getting damaged.

Your eyes turn light into pictures.

The hole in the center of your eye is the pupil. It lets light in.

The part of your eye that focuses light is the lens. It helps you see things clearly.

Source:
The Royal College of Ophthalmologists.
Understanding cataracts.
2001. http://www.rcophth.ac.uk/about/publications (accessed on 5 March 2009).

Source:
National Eye Institute.
Cataract: What you should know.
Available at http://www.nei.nih.gov/health/cataract/webcataract.pdf (accessed on 5 March 2009).

² Normally, your lens is clear.

The lens sits behind the colored part of your eye, called the iris. The lens is held in place by tissue known as the capsule.

The back of your eye is called the retina. It has nerve cells that pick up light.

This is what happens when you look at something.

Light comes into your eye through the hole in the center (your pupil).
The light goes through your lens.
The lens focuses the light onto the back of your eye (your retina), making a picture.
The nerve cells there pick up the picture and send signals to your brain.
Your brain tells you what you are seeing.

Your lens must be clear for your retina to get a sharp picture.

What goes wrong if you have cataracts

If you have a cataract, the lens in your eye has turned cloudy.

Source:
The Royal College of Ophthalmologists.
Understanding cataracts.
2001. http://www.rcophth.ac.uk/about/publications (accessed on 5 March 2009).

Source:
National Eye Institute.
Cataract: What you should know.
Available at http://www.nei.nih.gov/health/cataract/webcataract.pdf (accessed on 5 March 2009).

² This makes the picture on the back of your eye blurry. It's like looking through a dirty windshield or frosted glass.

The cataract is the cloudy part of your lens. It is not a layer of skin that grows over your eye and can be peeled off, as some people think.

Most cataracts are caused by aging. Doctors sometimes call these senile cataracts or age-related cataracts.

As you get older, your lens can change in two ways:

Source:
National Eye Institute.
Cataract: What you should know.
Available at http://www.nei.nih.gov/health/cataract/webcataract.pdf (accessed on 5 March 2009).

Your lens might get clumps in it. Your lens is made up mostly of water and

proteins
A lot of your body's tissues are made out of proteins. Proteins can be made in your cells. Proteins are also part of the food you eat, particularly meat and dairy products. Your body breaks down the protein you eat into amino acids. Your cells then use these amino acids to build new proteins, which make up muscles, joints, hair and other parts of your body.

protein. As you get older, the protein can clump up and cloud your lens. Then less light reaches the back of your eye. Your vision might get blurry.
Your lens might change color. When you are younger, your lens doesn't have any color. But as you get older, it slowly turns yellow-brown. You might find it harder to see some colors, such as blues and purples. But this change doesn't make your vision blurry.

Types of cataracts

Different parts of your lens can get cloudy, so you can get different types of cataract. To decide which type of cataract you have, your doctor will check where in your lens your cataract has started. Your symptoms will depend on the type of cataract you have.

Source:
Elliott DB.
Assessment of patients with age-related cataract.
Ophthalmic Physiology and Optometry. 1998; 18 (supplement): 51-61.

Source:
Ford JG, Karp CL (editors).
Cataract classification.
In: Cataract surgery and intraocular lenses. 2nd edition. American Academy of Ophthalmology, San Francisco, USA; 2001.

⁴

Some cataracts begin around the edges of your lens and grow in a pattern like the spokes of a wheel. Doctors call these cortical cataracts. When you look at bright lights, you get a lot of glare or see a ring around the light. Or you might have these symptoms when the sun is low in the sky. If you drive, you might find that headlights coming at you bother you more than before.
Other cataracts happen when the middle of your lens turns yellow-brown and gets harder. Doctors call these nuclear cataracts. Your vision might get blurry.
Some cataracts happen when grainy cells get between the back of your lens and the capsule. This can cause bad glare from lights. Doctors call these posterior subcapsular cataracts. They can develop when you are younger.

You can have a combination of any of these three kinds of cataracts. This is known as a mixed cataract. Almost one-third of eyes with cataracts have a mixture of types.

Source:
Elliott DB.
Assessment of patients with age-related cataract.
Ophthalmic Physiology and Optometry. 1998; 18 (supplement): 51-61.

Source:
Ford JG, Karp CL (editors).
Cataract classification.
In: Cataract surgery and intraocular lenses. 2nd edition. American Academy of Ophthalmology, San Francisco, USA; 2001.

⁴

You can get a cataract in just one eye, although most people get them in both eyes. But cataracts don't spread from one eye to the other. You don't catch them like an

infection
You get an infection when viruses, bacteria, fungi or other tiny organisms get into your body. These bugs are so tiny that you can't see them without a microscope. For example, an infection in your airways causes the common cold. And an infection in your skin can cause rashes such as athlete's foot.

infection.

Most cataracts are caused by aging. But other things can cause them.

Source:
National Eye Institute.
Cataract: What you should know.
Available at http://www.nei.nih.gov/health/cataract/webcataract.pdf (accessed on 5 March 2009).

² To read more, see Other causes of cataracts.

Why me?

We don't know exactly why some people get cataracts as they age and others don't. And we don't know why some people's cataracts get worse faster. There are probably many reasons.

We do know there are some things that make it more likely that you will get cataracts as you age. Doctors call these risk factors. Risk factors for cataracts include:

Smoking a lot
Having cataracts run in your family
Getting very

dehydrated
When you're dehydrated, you don't have enough fluid in your blood. This could be because you're not drinking enough or because you're losing water by sweating or having diarrhea.

dehydrated at some point in your life (for example, having severe

diarrhoea
Diarrhoea is when you have loose, watery stools and you need to go to the toilet far more often than usual. Doctors say you have diarrhoea if you need to go to the toilet more than three times a day.

diarrhea can make you dehydrated)
Taking drugs called

steroids
Steroids are a type of chemical. Your body naturally produces steroids, which play a part in many of its processes. For example, steroids are involved in how your immune system, reproductive system and metabolism work. Steroids can also be given as medicines and are used for a number of different conditions: including asthma, rheumatoid arthritis and eczema. Corticosteroids are not the same as the steroids used by some body builders and athletes. Those steroids are called 'anabolic steroids'.

steroids for a long time
Being in the sun a lot
Having

high blood pressure
Your blood pressure is considered to be high when it is above the accepted normal range. The usual limit for normal blood pressure is 140/90. If either the first (systolic) number is above 140 or the lower (diastolic) number is above 90, a person is considered to have high blood pressure. Doctors sometimes call high blood pressure "hypertension."

high blood pressure or

heart disease
You get heart disease when your heart isn't able to pump blood as well as it should. This can happen for a variety of reasons.

heart disease.

To read more, see Risk factors for cataracts.

Sources for the information on this page:

The Royal College of Ophthalmologists.Understanding cataracts.2001. http://www.rcophth.ac.uk/about/publications (accessed on 5 March 2009).

National Eye Institute.Cataract: What you should know.Available at http://www.nei.nih.gov/health/cataract/webcataract.pdf (accessed on 5 March 2009).

Elliott DB.Assessment of patients with age-related cataract.Ophthalmic Physiology and Optometry. 1998; 18 (supplement): 51-61.

Ford JG, Karp CL (editors).Cataract classification.In: Cataract surgery and intraocular lenses. 2nd edition. American Academy of Ophthalmology, San Francisco, USA; 2001.

This information was last updated on Mar 06, 2009

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