What Causes Cataracts
Ageing accounts for most cataracts. Other risk factors can bring one on sooner, and some can be changed.
- Age is the dominant factor, by a wide margin
- Diabetes, smoking and steroids raise the risk
- No supplement has been shown to prevent them
Camden (Orchard)Joo ChiatClementiBedokToa PayohJurong
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Why cataracts form
Ageing causes most cataracts. The lens adds protein layers throughout life and never sheds them. Over decades it thickens and the proteins clump together, so it scatters light instead of passing it cleanly.
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Clear lens
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Clouded lens — a cataract
Every eye that lives long enough develops some clouding of the lens, which is why cataract is described as a normal part of ageing. Risk factors change the pace, and where in the lens the clumping starts decides the type of cataract.
Concerned about cataracts or vision loss? Talk to our friendly staff for a same-day appointment (subject to availability).
What raises the risk
Each is an association from published studies, not a certainty about any one eye. Changing one does not clear a cataract that is already there.
- Age
- By far the main factor: about 3.9% of people aged 55 to 64 have a cataract, against 92.6% of those aged 80 and over.
- Diabetes
- Associated with cataract of every type.
- Smoking
- Linked most to nuclear cataract, in the centre of the lens. Across 21 studies, people who had ever smoked were about 1.7 times as likely to have one.
- Long-term steroids
- Linked mainly to posterior subcapsular cataract, at the back of the lens. The risk rises with the total dose and how long it is taken, whether as tablets, eye drops, injections around the eye, inhalers or nasal sprays.
- Sunlight
- Ultraviolet light is linked more to cortical cataract, at the edge of the lens, though the measured effect is small.
- Severe short-sightedness
- Highly short-sighted eyes tend to develop cataract earlier.
- Eye injury, inflammation or surgery
- A blow to the eye, uveitis, surgery inside the eye or radiotherapy involving it can each be followed by a cataract, sometimes years later.
Do not stop a prescribed steroid on your own. Talk to the doctor who prescribed it, or bring the prescription to your eye appointment.
Cataracts in younger eyes
A cataract in your thirties or forties usually has a specific cause, and finding it is part of the examination.
- The cause is usually one of the risk factors above: diabetes · long-term steroids · an eye injury · uveitis · previous eye surgery · radiotherapy · severe short-sightedness.
- It usually forms at the back of the lens, as a posterior subcapsular cataract, and tends to affect reading and bright light before it shows on a distance chart.
- In babies and young children, cataract is a separate condition, often genetic, and managed differently.
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Posterior subcapsular — clouding at the back
Can cataracts be prevented?
Not reliably. Nothing has been shown to stop a cataract forming, because the main driver is ageing.
9randomised trials
117,272people
Antioxidant supplements were tested and did not work. Taken together, the trials found no effect of beta-carotene, vitamin C or vitamin E on developing a cataract, needing surgery for it, or how fast it progressed.
No treatment slows a cataract down, including the eye drops sold for it.
The general advice is worth following for its own sake:
- Do not smoke — it has the strongest link of any risk you can change.
- Keep diabetes well controlled.
- Wear sunglasses that block ultraviolet light, though the effect on cataract is small.
- Review any long-term steroid with the doctor who prescribed it; do not stop it yourself.
- Have your eyes examined, so any change can be followed from a baseline.
What does not cause cataracts
Four things get blamed regularly, and none of them is supported.
Screens and blue light
Screens are not a meaningful source of ultraviolet, and their blue light has not been shown to damage the eye. Long screen sessions cause tired, dry eyes, which is a different problem.
Reading, or using your eyes too much
Reading in dim light, reading a lot, watching television and close work do not cloud the lens. It is the other way round: an early cataract makes you need more light, so reading in dim light gets harder, and gets the blame.
Laser vision correction
LASIK and similar procedures reshape the cornea, at the front of the eye. A cataract forms in the lens, behind the pupil, which they do not touch. Mention any past laser correction before cataract surgery: a reshaped cornea changes the calculation for the replacement lens.
Catching it from someone
A cataract is not an infection and does not spread, between people or from one eye to the other. Both eyes often get one simply because they are the same age.
If you are at higher risk
A risk factor is a reason to have your eyes examined, not to assume anything — every symptom of a cataract has other causes too.
At our Clementi, Bedok, Toa Payoh and Jurong clinics:
- A cataract screening looks at the lens.
- If you have diabetes, a diabetic retinal screening also checks the back of the eye, where diabetes does its other damage.
Both are senior optometrist-led, and the report is reviewed by an ophthalmologist.
Finding a cataract does not commit you to surgery on any timetable. What you would notice and how it is treated are covered separately.
Common questions
What causes cataracts?
Ageing, in most cases. The lens is built from proteins laid down in layers throughout life, none of which is ever shed, and over decades those proteins clump together and the lens thickens — so it scatters light instead of passing it cleanly. Diabetes, smoking, long-term steroid treatment, ultraviolet light, severe short-sightedness and injury to the eye all make it happen earlier or worse.
Can cataracts be prevented?
No, not reliably. Nothing has been shown to stop a cataract forming, because the main driver is ageing. What is worth doing is what reduces the associations that can be changed: not smoking, keeping diabetes well controlled, wearing sunglasses that block ultraviolet light, and reviewing any long-term steroid with the doctor who prescribed it.
Do eye vitamins or supplements prevent cataracts?
The evidence says no. A review pooling nine randomised trials in 117,272 people found no effect of antioxidant vitamin supplementation — beta-carotene, vitamin C or vitamin E — on the risk of developing a cataract, on needing it removed, or on how fast it progressed. The doses tested were above the recommended daily allowance.
Why do some people get cataracts young?
Usually there is a reason behind it. Diabetes, long-term steroid treatment, an injury to the eye, inflammation inside the eye, previous eye surgery, radiotherapy involving the eye and severe short-sightedness are the common ones. Cataract present from birth or early childhood is a separate matter and is often genetic.
Are cataracts hereditary?
Age-related cataract runs in families to some degree, but it is common enough in old age that a family history adds little to what age already tells you. Congenital cataract — present at birth or appearing in early childhood — is a different condition and does have clear genetic causes.
Does using screens or blue light cause cataracts?
There is no evidence that it does. The light that cataract research has actually examined is ultraviolet from sunlight, and even there the measured association is small. Device screens are not a meaningful source of ultraviolet. Long screen sessions do cause tired, dry eyes, which is a different problem with a different answer.
Can LASIK cause cataracts?
Laser vision correction reshapes the cornea, at the front of the eye; a cataract forms in the lens, behind the pupil. The procedure does not touch the lens. It does matter later on, though — a cornea that has been reshaped changes the calculation used to choose the replacement lens, so any previous laser vision correction should be mentioned before cataract surgery.
Can an eye injury cause a cataract?
Yes. A blunt or penetrating injury can cloud the lens, sometimes immediately and sometimes years afterwards. That is a traumatic cataract, and it is one reason cataract turns up in people far younger than the usual age range.
Does reading in dim light cause cataracts?
No. Neither does reading a lot, watching television, or using your eyes closely for work. Poor light makes reading harder and more tiring, and someone with an early cataract will notice that sooner than they used to — which is the reverse of the cause people assume.
Ask about your eyes
Send us a message and we will answer. If you have diabetes, or have been on steroids for a long time, say so in the message.
