What are cataracts?

A cataract is a progressive, painless clouding of the lens of the eye. Cataracts block light, making it difficult to see clearly. Over an extended period of time, cataracts can cause blindness. They're often related to growing older, but sometimes they can develop in younger people.

How cataracts affect your vision

In a normal eye, light enters and passes through the lens. The lens focuses that light into a sharp image on the retina, which relays messages through the optic nerve to the brain. If the lens is cloudy from a cataract, the image you see will be blurry. Other eye conditions, such as myopia, cause blurry vision too, but cataracts produce some distinctive signs and symptoms.

Cataract symptom: Blurry vision

Blurry vision at any distance is the most common symptom of cataracts. Your view may look foggy, filmy or cloudy. Over time, as the lenses become more clouded, less light reaches the retina. People with cataracts may have an especially hard time seeing and driving at night.

Cataract symptom: Glare

Another early symptom of cataracts is glare, or sensitivity to light. You may have trouble seeing in bright sunlight. Indoor lights that once didn’t bother you now may seem too bright or have halos. Driving at night may become a problem because of the glare caused by oncoming headlights.

Cataract symptom: Double vision

Sometimes, cataracts can cause double vision (also known as diplopia) when you look with one eye. As the cataract grows larger, the double vision may go away.

Cataract symptom: Colour changes

Cataracts can affect your colour vision, making some hues look faded. Your vision may gradually take on a brownish or yellowish tinge. At first, you may not notice this discolouration, but over time, it may make it harder to distinguish blues and purples.

Cataract symptom: Second sight

Sometimes, a cataract may temporarily improve a person’s ability to see close-up, because the cataract acts as a stronger lens. This phenomenon is called second sight, because people who may have once needed reading glasses find that they don’t need them any more. As the cataract worsens however, this goes away and vision worsens again.

Cataract symptom: New prescription

Frequent changes to your glasses or contact lens prescription can be a sign of cataracts. This is because cataracts are usually progressive, meaning they get worse over time.

Who gets cataracts?

The majority of cataracts are related to ageing. NHS figures show more than half of people in the UK over 65 have some cataract development in one or both eyes. Babies are sometimes born with cataracts, also called congenital cataracts, or children may develop them as a result of injury or illness. However, childhood cataracts are very rare, affecting about three in 10,000 children in the UK.

What causes cataracts?

The exact cause of cataracts is unknown. While the risk grows as you get older, these factors may also contribute:

• Diabetes
• Smoking
• Excess alcohol use
• Eye Injury
• Prolonged use of corticosteroids
• Prolonged exposure to sunlight or radiation

How are cataracts diagnosed?

Most cataracts can be diagnosed with an examination of the eye. Your optometrist or your eye doctor will test your vision and examine your eyes with a slit lamp microscope to look for problems with the lens and other parts of the eye. The pupils are dilated to better examine the back of the eye, where the retina and optic nerve lie.

Surgery for cataracts

If your vision loss can’t be corrected with glasses or contact lenses, you may need surgery to remove the cataracts. In cataract surgery, the cloudy lens is removed and replaced with an artificial lens. The surgery, which is done on an outpatient basis, is safe and extremely effective at improving vision. If cataracts are present in both eyes, surgery will be done on one eye at a time.

Types of cataract surgery

There are three types of cataract surgery. In phacoemulsification (phaco), the doctor makes a tiny incision in the eye and breaks up the lens using ultrasound waves. The lens is removed, and an intraocular lens (IOL) is put in its place. In extracapsular cataract surgery, the doctor makes a larger incision and removes the cloudy part of the lens in one piece. Rarely, intracapsular cataract surgery is performed, which involves removing the entire lens and lens capsule. In most modern cataract operations the IOL eliminates the need for thick glasses or a contact lens after surgery.

Cataract surgery innovations

Recent developments in cataract surgery include multifocal and accommodative cataract replacement implants, which can correct both near and distance vision. They minimise or eliminate the need for reading glasses after surgery. Conventional "monofocal" lenses only correct for distance vision, meaning reading glasses are still needed after surgery. "Toric" implants are available to correct astigmatism. A lens for better colour vision is in development (shown here next to a penny).

What to expect after surgery

For a few days, your eye may be itchy and sensitive to light. You may be prescribed eye drops to aid healing and asked to wear an eye shield or glasses for protection. It will take about eight weeks for your eye to heal completely, though your vision should begin to improve soon after surgery. You may still need glasses, at least occasionally, for distance or reading - as well as a new prescription after healing is complete.

Cataract surgery risks

Complications from cataract surgery are rare. The most common risks are bleeding, infection and changes in eye pressure, which are all treatable when caught early. Surgery slightly raises the risk of retinal detachment, which requires emergency treatment. Sometimes, the residual cataract tissue used to support the IOL can become cloudy, even years after surgery. This "after-cataract" is easily and permanently corrected by using a laser to make a tiny hole in the capsule to allow light to pass through.

Should you have cataract surgery?

Whether or not to have cataract surgery is up to you and your doctor. Rarely cataracts need to be removed right away, but this isn’t usually the case. Cataracts affect vision slowly over time, so many people wait to have surgery until glasses or contacts no longer improve their vision enough. If you don’t feel that your cataracts are causing problems in your day-to-day life, you may choose to wait.

Tips to prevent cataracts

Things you can do to lower your risk of developing cataracts:

• Don't smoke.
• Always wear a hat or sunglasses in the sun.
• Keep diabetes well controlled.
• Limit alcohol consumption.

Related reading

• Cataracts and your eyes
• 9 myths and facts about your eyes
• How to pick good sunglasses
• Eye pain? Causes and treatment
• Eye care and diabetes
• 5 ways to protect your eyes in summer
• Tips for buying specs
• Cataract surgery