Cataracts are cloudy patches that develop in the lens of your eye and can cause blurred or misty vision. They are very common.

The lens is the transparent structure that sits just behind your pupil (the black dot in the centre of your eye). It allows light to get to the back of your eye (retina).

In some people, cataracts develop in the lens as they get older, stopping some of the light from reaching the back of the eye.

Over time, the cataracts become worse and start affecting vision. Many people with cataracts will eventually need surgery to remove and replace the affected lens.

Symptoms of cataracts

Cataracts develop over many years and problems may at first be unnoticeable. They often develop in both eyes, although each eye may be affected differently.

You will usually have blurred, cloudy or misty vision, or you may have small spots or patches where your vision is less clear.

Cataracts may also affect your sight in the following ways:

• you may find it more difficult to see in dim or very bright light
• the glare from bright lights may be dazzling or uncomfortable to look at
• colours may look faded or less clear
• everything may have a yellow or brown tinge
• you may have double vision
• you may see a halo (a circle of light) around bright lights, such as car headlights or street lights
• if you wear glasses, you may find that they become less effective over time

Cataracts are not painful and don’t make your eyes red or irritated.

When to see an optician

If you have problems with your vision, make an appointment to see your optician (also known as an optometrist). An optician can examine your eyes and test your sight.

The optician may look at your eyes with an instrument called a slit lamp or an ophthalmoscope. These magnify your eye and produce a bright light that allows the optician to look inside and check for any cataracts.

If it is thought you have cataracts, you may be referred to an ophthalmologist or an ophthalmic surgeon, who can confirm the diagnosis and plan your treatment. These are doctors who specialise in eye conditions and their treatment.

Who is affected

Cataracts are the main cause of impaired vision worldwide.

Although rare types of cataracts affect babies and young children (childhood cataracts), the problem is much more common in older people. Cataracts that develop with age are known as age-related cataracts.

In England and Wales, it is estimated that around 2.5 million people aged 65 or older have some degree of visual impairment caused by cataracts.

What causes age-related cataracts?

The exact cause of age-related cataracts is unknown, although some experts have suggested they may be the result of changes in the structure of the lens over time.

It is thought that the cloudy areas in the lens may be the result of changes in the proteins that make up the lens. However, it’s not clear how or why getting older could cause these changes to happen.

As well as your age, several other factors may increase your risk of developing cataracts, including:

• a history of cataracts in your family
• smoking
• regularly drinking excessive amounts of alcohol
• a poor diet lacking in vitamins
• lifelong exposure of your eyes to sunlight
• taking corticosteroid medication at a high dose or for a long time
• previous eye surgery or injury
• certain health conditions, such as diabetes or long-term uveitis (inflammation of the middle layer of the eye)

As the exact cause of age-related cataracts is not clear, there is no known way to prevent them.

Treating age-related cataracts

If your cataracts are mild, stronger glasses and brighter reading lights may be helpful for some time. However, cataracts get worse over time so it’s likely you will eventually need treatment.

The only treatment that is proven to be effective for cataracts is surgery. This will usually be recommended if your loss of vision has a significant effect on your daily activities, such as driving or reading.

Cataract surgery involves removing the cloudy lens through a small incision (cut) in your eye and replacing it with a clear plastic one. In most cases, this will be carried out under local anaesthetic (where you are awake, but the eye is numbed) and you can usually go home the same day.

Almost everyone who has cataract surgery experiences an improvement in their vision, although it can sometimes take a few days or weeks for your vision to settle. You can usually return to most of your normal activities within about two weeks.

After the operation, your plastic lens will be set up for a certain level of vision, so you may need to wear glasses in order to see objects that are either far away or close to you. If you wore glasses previously, your prescription will probably change. However, your optometrist will need to wait until your vision has settled before they can give you a new prescription.

Read more about cataract surgery.

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Map of Medicine: cataract