Cataracts

The lens is a transparent disc that sits behind the coloured part of your eye (iris). It adjusts its shape to allow light entering your eye to be focused onto the back of your eye (retina). This results in clear, sharp vision.

The lens is usually clear but as you age it changes, becoming more opaque, rigid and thicker. It becomes less transparent as you get older because proteins inside the lens break down and clump together to form cloudy patches. These are called cataracts. Cataracts scatter light as it passes through your lens, which prevents the light from properly focusing on the back of your eye, causing misty, blurred vision. 

At first, you may only notice small blurry areas in your vision. However, over time, less and less light will be able to reach the back of your eye. As your lens becomes more opaque, your vision will become increasingly blurred. You may struggle to read, drive a car or pick up the expressions on people’s faces. Eventually, if left untreated, cataracts cause vision loss.

Cataracts are most common in people over 65 but they can begin earlier than this.

There are three main types of cataracts: 

Nuclear cataracts 

Also known as nuclear sclerotic cataracts, these are the most common type of cataract. They occur in the centre of the lens, which is called the nucleus. As the lens hardens you may temporarily see an improvement in your near vision (eg when reading) — this is called second sight but is fleeting. As the centre of your lens continues to harden, it turns yellow and sometimes brown. Symptoms of nuclear sclerotic cataracts include: 

• Colours appearing washed out
• Difficulty seeing details eg reading text
• Seeing halos around bright lights at night eg street lights

Cortical cataracts

These cataracts occur on the outer edge of your lens. They initially form white wedge shapes pointing towards the centre of your lens. As the white wedges grow, light passing through your eye scatters more, causing glare. Symptoms include: 

• Difficulty driving at night
• Difficulty judging how far away objects are 
• Difficulty telling the difference between similar colours, particularly blues and purples
• Hazy vision — it is often described as looking at objects through a fog

Cortical cataracts are usually removed at an early stage of their development as they impair both near and distance vision. 

Posterior subcapsular cataracts

These cataracts occur at the back of the lens, right next to the back of the lens capsule — a thin sac that holds the lens in place.

Other types of cataracts

There are several other types of cataracts, which are less common. These include: 

• Anterior subcapsular cataracts — occur at the front of the lens, right next to the front of the lens capsule and can be caused by an eye injury or swelling, or the skin condition, atopic dermatitis 
• Anterior or posterior polar cataracts — occur either on the front centre (anterior) or back centre (posterior) of your lens; posterior polar cataracts usually run in families; anterior polar cataracts cause small white dots, which don't usually affect your vision
• Brunescent cataracts — caused by leaving a nuclear cataract untreated so it becomes very hard and brown
• Congenital cataracts — occur from birth or develop in childhood and can be caused by genetics or by the mother becoming infected with rubella during pregnancy
• Radiation cataracts — sunlight contains damaging ultraviolet (UV) radiation and too much exposure without wearing sunglasses with 100% UVA and UVB protection can cause radiation cataracts; you are at greater risk if you work outdoors (eg farming, fishing, gardening)
• Traumatic cataracts — develop after an eye injury (eg an impact, burn, chemical spill or splinter) but can occur soon after or years later 

Cataracts can also be caused by another medical condition or treatment — these are called secondary cataracts and include: 

• Christmas tree cataracts — also known as polychromatic cataracts and most commonly occur in people with the muscle disorder myotonic dystrophy; shiny, coloured crystals form in the lens
• Diabetic snowflake cataracts — this is rare and occurs in people with diabetes; it worsens quickly, forming grey-white snowflake patterns
• Post-vitrectomy cataracts — vitrectomy is a type of eye surgery to remove the clear gel (vitreous) that fills the space between your lens and the back of your eye and is used to treat certain eye conditions

In young children, lamellar or zonular cataracts can occur in both eyes. 

Cataracts develop slowly over many years so you may not notice them at first — if you wear glasses, you may just think your lenses are dirty. However, the first signs are:

• Blurred vision
• Misty or cloudy vision
• Sensitivity to bright lights

As symptoms get worse over time, your impaired vision will eventually affect everyday activities. Even if you wear glasses, you may find that reading and driving become increasingly difficult — driving at night, in particular, may become challenging due to extra glare and halos around bright lights. Sometimes one eye is worse than the other and occasionally only one eye is affected. Other symptoms of worsening cataracts include:

• Colours appearing washed out or tinged yellow
• Difficulty seeing at night
• Double vision in one eye — this is different from double vision caused by both eyes not working together correctly (amblyopia)
• Needing a bright light for reading
• Needing to more frequently change your glasses or contact lens prescription — in older people, you may find it harder to see objects in the distance (short-sightedness)
• Seeing halos around bright lights

Cataracts are usually painless and do not cause redness or irritation. However, if you have cataracts alongside another eye condition or have very advanced cataracts, you may experience some pain. 

If you think you have cataracts, go for an eye check-up with an optician who can refer you to an ophthalmologist (a doctor who specialises in treating the eyes) for treatment. Treatment is usually cataract surgery.

Cataracts are usually diagnosed with the following:

• Retinal exam — your ophthalmologist will apply drops to your eyes to dilate them (ie to widen the opening at the centre of your iris (pupil)) so they can better see the back of your eye (retina) and your cataract
• Slit-lamp examination — a special microscope with a bright light is used to check the health of different parts of your eye, including your cornea (clear outer layer on the front of your eye) and iris (the coloured part of your eye)
• Visual acuity test — this measures how well you see at different distances and involves reading letters of different sizes on an eye chart

By far the most common cause of cataracts is ageing of the proteins in the lens of the eye. One in three people over 65 have cataracts or have had cataracts removed by surgery but sometimes people can get them in their 40s or 50s.

Lifestyle factors, such as smoking and alcohol, can contribute, as well as a family history of cataracts.

Some medical conditions can also mean you’re more likely to develop cataracts. These include:

• Diabetes
• Eye conditions, such as retinitis pigmentosa, glaucoma or uveitis
• High blood pressure
• Previous eye injury, eye inflammation or eye surgery
• Radiotherapy
• Severe short-sightedness (myopia)

Taking certain medications, such as long-term use of steroids, also increases your risk of cataracts, as does too much exposure to sunlight.

Cataracts can only be effectively treated with surgery.

In the early stages of cataracts, it may help to wear glasses and avoid bright lights, but eventually, surgery will be necessary to restore failing vision. 

You don’t have to wait for your eyesight to become really bad before you have surgery. For most people, the sooner they have cataract surgery the better their quality of life and ability to continue everyday activities. Cataract surgery is generally considered a safe and effective procedure. 

Cataracts may affect your ability to drive. If you still meet the visual standards set by the DVLA for driving, you do not need to tell them if you have cataracts or have had cataracts. 

This is also true if you drive a bus, coach or lorry, but with the added requirement that you should not have any increased sensitivity to glare caused by your cataracts. 

There are no guaranteed ways to prevent or slow down cataracts. However, doctors do recommend:

• Eating a healthy diet
• Keeping up with your regular eye examinations
• Managing any other health problems you may have
• Quitting smoking
• Reducing how much alcohol you drink
• Wearing sunglasses when outside in the daytime