# Cataracts: symptoms, causes and treatment > Source: World Aid Network — https://worldaidnetwork.org/eye-health/cataracts > Last reviewed: 2026-06-19 ## In short A cataract is a clouding of the eye's natural lens, which sits behind the pupil. As it clouds, vision becomes blurry, dim and faded — like looking through a frosted window. Cataracts are extremely common with age and are the single biggest cause of blindness in the world. The remarkable thing is that they are almost always curable: a short, safe operation replaces the cloudy lens with a clear artificial one, often restoring sight in well under an hour. In the UK this is routine; in low-income countries, millions stay needlessly blind simply because they cannot reach or afford that one operation. Cataracts are the leading cause of blindness in the world. The World Health Organization estimates that cataracts account for around 51% of global blindness — affecting approximately 65 million people. Yet cataracts are entirely curable. A 20-minute operation to remove the clouded lens and replace it with an artificial intraocular lens (IOL) restores sight in the vast majority of patients. In the United Kingdom, cataract surgery is one of the most commonly performed NHS operations, with around 400,000 procedures carried out each year. Outcomes are excellent — over 95% of patients achieve improved vision. In low-income countries, the same surgery that is routine in the UK remains out of reach for millions of people, leaving them unnecessarily blind. This guide answers the twenty most commonly searched questions about cataracts in the UK, drawing on NHS and WHO sources. ## At a glance - Global rank: #1 cause of blindness - Most common in: Older adults - Cure: A short lens-replacement op - Surgery time: Often under an hour ## When to see a doctor - Cloudy, blurry or misty vision that is slowly getting worse - Glare or haloes around bright lights, especially when driving at night - Colours looking faded or yellowed - Difficulty seeing in dim light - Needing brighter light to read, or changing your glasses more often ## What are cataracts? A cataract is a clouding of the crystalline lens inside the eye. The lens — normally clear — sits behind the iris and pupil and focuses light onto the retina, producing sharp images. When the proteins that make up the lens begin to break down and clump together, they scatter and block light passing through the lens, causing progressive blurring, glare and eventual loss of functional vision. The most common type is age-related cataract, which affects virtually everyone to some degree over the age of 65. Other types include: congenital cataract (present at birth); secondary cataracts (caused by diabetes, steroid medication or eye disease); traumatic cataracts (following eye injury); and radiation cataracts. ## Symptoms and when to seek help Cataracts develop slowly and painlessly. Early symptoms include: blurred, cloudy or misty vision; dazzle and glare from lights, particularly when driving at night; colours appearing faded or washed out; a 'halo' effect around lights; double vision in one eye; and frequent changes in glasses prescription. People sometimes notice they can read better in dim light than bright light (because the pupil dilates, avoiding the central denser part of the cataract). The NHS advises seeing your optician if any of these symptoms affect your daily activities — driving, reading, recognising faces or watching television. Your optician can detect cataracts during a routine eye examination and will refer you to an ophthalmologist when your cataracts are affecting your quality of life sufficiently to warrant surgery. ## Cataract surgery Modern cataract surgery (phacoemulsification) is a day-case procedure performed under local anaesthetic — typically an eye drop anaesthetic, with no injection or general anaesthetic required. A small incision is made at the edge of the cornea; an ultrasound probe breaks up the cloudy lens; the fragments are removed by suction; and an artificial intraocular lens (IOL) is inserted into the natural lens capsule. The incision is usually self-sealing. The whole procedure takes approximately 15–20 minutes. NHS cataract surgery is funded when your cataract significantly affects your ability to carry out everyday activities. Most patients are treated within 18 weeks of referral, though this varies. Visual recovery is rapid — many patients notice improved vision within 24–48 hours, with full recovery over two to six weeks. ## Cataracts and global blindness Cataract blindness is almost entirely an inequality issue. The surgery to restore sight costs approximately £25–£50 in high-volume developing-country settings — yet it remains inaccessible to the rural poor in many countries. The WHO estimates that 80% of global visual impairment is avoidable or preventable. World Aid Network funds sight-restoring eye surgery — including cataract operations — for poor patients through locally-licensed ophthalmologists. A single donation can fund the procedure that gives someone their sight back, transforming their ability to work, care for their family and live independently. ## Key takeaways - Cataracts — clouding of the crystalline lens — are the world's leading cause of blindness, affecting around 65 million people globally and accounting for 51% of all blindness. - Symptoms include blurred or cloudy vision, glare, faded colours, halos around lights and frequent prescription changes. Cataracts develop slowly and are painlessly progressive. - Cataract surgery (phacoemulsification) is a 15–20-minute day-case procedure with an excellent safety record. The NHS performs around 400,000 procedures per year with over 95% of patients achieving improved vision. - Different intraocular lens (IOL) types are available — monofocal (standard NHS), toric (for astigmatism), extended depth of focus and multifocal — the latter two reducing spectacle dependence but available only privately. - Cataract blindness is almost entirely preventable at the global level. The surgery that is routine in the UK costs approximately £25–£50 in developing countries but remains inaccessible to millions of poor patients. ## Frequently asked questions ### What are cataracts? A cataract is a clouding of the crystalline lens inside the eye that causes progressive visual impairment. The lens — normally transparent — becomes opaque as proteins within it break down and clump together, scattering light and preventing a clear image from reaching the retina. Cataracts are the leading cause of blindness worldwide, affecting an estimated 65 million people, and the most common cause of correctable visual impairment in the UK. ### What are the symptoms of cataracts? Symptoms include: blurred, cloudy or misty vision (as if looking through frosted glass); increased glare and dazzle from lights — particularly car headlights at night; colours appearing faded or yellowish; halos around lights; double vision in one eye; and a frequent need to change glasses prescription. Cataracts are painless and develop gradually over months to years. Sight loss caused by a cataract is not sudden. See your optician if any symptoms interfere with daily activities. ### What causes cataracts? Age-related breakdown of proteins within the crystalline lens is the most common cause. Other causes include: long-term exposure to ultraviolet (UV) radiation; smoking (significantly increases cataract risk); diabetes (causes earlier and more aggressive cataracts); long-term corticosteroid medication (systemic or eye drops); eye injury or previous eye surgery; and certain medications. Congenital cataracts can be caused by infections during pregnancy (rubella, toxoplasmosis) or metabolic disorders in newborns. ### Who is at risk of developing cataracts? Age is the main risk factor — virtually everyone will develop some degree of lens clouding by their seventies. Additional risk factors include: smoking; diabetes; prolonged sun exposure without UV-protective sunglasses; long-term steroid use; a previous eye injury or inflammation; previous eye surgery; and a family history of early cataracts. People who have undergone radiotherapy near the eye and those with myopia also have higher risk. ### How are cataracts diagnosed? Your optician can diagnose cataracts during a routine eye examination using a slit-lamp (a specialised biomicroscope that illuminates the eye). Visual acuity testing measures the impact on your sight. If cataracts are found, your optician will refer you to an ophthalmologist (eye doctor) when they are affecting your quality of life significantly enough to consider surgery. No special tests beyond a clinical eye examination are needed to diagnose a cataract. ### How are cataracts treated? The only effective treatment for cataracts is surgery to remove the cloudy lens and replace it with an artificial intraocular lens (IOL). No eye drops, dietary supplements or glasses can reverse or significantly slow cataract formation. In the early stages, an updated glasses prescription may help compensate for mild blurring. NHS surgery is offered when the cataract significantly affects daily activities such as driving, reading or working. ### What happens during cataract surgery? Modern cataract surgery (phacoemulsification) is a day-case procedure under local anaesthetic eye drops — no injection or general anaesthetic is needed. A tiny incision (approximately 2.2–2.8 mm) is made at the edge of the cornea. An ultrasound probe is inserted to break up (emulsify) the cloudy lens; the fragments are suctioned away; and a foldable artificial intraocular lens (IOL) is placed inside the remaining lens capsule. The incision is usually self-sealing. The procedure takes approximately 15–20 minutes. ### Are cataracts dangerous if left untreated? Cataracts are not dangerous in the early stages but will progressively worsen over time without surgery. Severely advanced cataracts (hypermature or Morgagnian cataracts) can eventually cause complications including raised eye pressure (phacolytic or phacomorphic glaucoma) and inflammation inside the eye — both of which can permanently damage the optic nerve. More practically, untreated cataracts impair safe driving, increase the risk of falls in older people and significantly reduce quality of life. ### How long does cataract surgery take? The surgical procedure itself typically takes 15–20 minutes per eye. Your overall time at the hospital or day-surgery unit will be longer — usually two to three hours — to allow for pre-operative assessment, anaesthetic preparation (eye drops to dilate the pupil and numb the eye) and post-operative monitoring. Cataracts in both eyes are almost always treated as two separate procedures several weeks apart. ### What is recovery like after cataract surgery? Most patients notice improved vision within 24–48 hours of surgery. Full visual recovery and stabilisation typically takes four to six weeks. You will be given antibiotic and anti-inflammatory eye drops to use for up to four weeks. The NHS advises: avoiding rubbing or pressing on your eye; protecting the eye with a shield at night for the first week; not swimming for four weeks; and avoiding heavy lifting and strenuous activity for the first two weeks. A follow-up appointment is arranged to check progress. ### What are the risks of cataract surgery? Cataract surgery has an excellent safety record — it is one of the safest surgical procedures in the UK. Serious complications are rare. The most common significant complication is posterior capsule rupture (tear in the lens bag), occurring in approximately 1–2% of cases, which may require additional treatment. Other rare complications include endophthalmitis (serious infection inside the eye, less than 1 in 1,000), retinal detachment and persistent corneal oedema. The risk of serious sight-threatening complication is approximately 1 in 1,000. ### What types of intraocular lens are available? Standard NHS IOLs are monofocal lenses — corrected for a single focal distance (usually distance vision), meaning glasses are still needed for reading. Private options include: toric IOLs (correcting astigmatism simultaneously); extended depth of focus (EDOF) IOLs (providing a range of distances with some spectacle independence); and multifocal IOLs (designed to provide both distance and near vision without glasses, though some patients experience halos and glare). The ophthalmologist will discuss which IOL is appropriate for your lifestyle and optical needs. ### Can cataracts come back after surgery? The replaced artificial lens cannot develop a cataract. However, a common late complication is posterior capsule opacification (PCO) — sometimes called a 'secondary cataract' — which occurs when cells on the back of the lens capsule multiply and cause the capsule to cloud over. This affects approximately 20–40% of patients within five years of surgery and causes blurring similar to the original cataract. It is treated simply and effectively in clinic using a YAG laser capsulotomy — a painless, five-minute procedure requiring no incision. ### Are cataracts hereditary? Age-related cataracts are not directly inherited, but a family history of early-onset cataracts (before age 60) may slightly increase your risk. Some rare types of cataracts are strongly genetic — congenital cataracts (present at birth) are often caused by specific gene mutations and can be inherited in an autosomal dominant or recessive pattern. If you have a family history of congenital cataracts, genetic counselling may be appropriate when planning a family. ### Can cataracts be prevented? Age-related cataracts cannot be entirely prevented, but several modifiable factors can delay their onset. The NHS advises: wearing UV400-rated sunglasses in bright sunlight; stopping smoking; eating a diet rich in antioxidants (leafy greens, colourful fruits and vegetables); managing diabetes well to control blood sugar; and avoiding unnecessary steroid use. Regular eye tests (every two years) ensure cataracts are detected early and managed appropriately. ### At what point does the NHS operate on cataracts? NHS clinical guidance states that cataract surgery is appropriate when the cataract significantly impacts a patient's ability to carry out everyday activities — driving, reading, recognising faces, working or maintaining independence. There is no objective threshold based on visual acuity alone. Your ophthalmologist will assess how much your cataracts are affecting your daily life and discuss the risks and benefits of surgery. Some NHS trusts have specific referral criteria, but access should not be refused solely on the basis of driving vision thresholds. ### Can cataracts cause blindness? Yes. Untreated cataracts are the single leading cause of blindness worldwide, accounting for approximately 51% of global blindness — around 65 million people. In the UK, blindness from cataracts is rare because surgery is readily available on the NHS. Globally, cataract blindness is overwhelmingly concentrated in low- and middle-income countries where surgery is unaffordable or unavailable. The WHO estimates that 80% of global visual impairment — including cataract blindness — is avoidable. ### Do cataracts affect children? Yes. Congenital cataracts are present at birth or develop in early childhood. They are a leading cause of visual impairment in children and require urgent treatment to prevent amblyopia ('lazy eye') — the permanent loss of visual development that occurs when a child's developing brain does not receive clear images during the critical early years. Congenital cataracts are managed by paediatric ophthalmologists, and treatment — surgery plus intensive patching therapy — must begin as early as possible to maximise visual outcome. ### Are cataracts the same as macular degeneration? No. Cataracts and macular degeneration (age-related macular degeneration, AMD) are different conditions. Cataracts affect the lens — the transparent structure that focuses light — and cause overall blurring and glare. AMD affects the macula — the central part of the retina — and causes loss of central (detail) vision. A person can have both conditions simultaneously. Cataracts are treatable by surgery; AMD currently has no cure, though progression of wet AMD can be slowed with anti-VEGF injections. Having cataracts can make AMD more difficult to diagnose. ### How does cataract blindness affect people in developing countries? Globally, cataracts cause unnecessary blindness in approximately 65 million people — almost entirely in low- and middle-income countries. The operation that takes 20 minutes in the UK and is available free on the NHS costs approximately £25–£50 in developing-country high-volume settings, yet remains inaccessible to the rural poor due to lack of specialist facilities, distance from services and out-of-pocket costs. World Aid Network funds sight-restoring cataract surgery for poor patients through locally-licensed ophthalmologists, giving people back their independence, livelihood and quality of life. ## How you can help World Aid Network funds sight-restoring eye care for poor patients in Pakistan, Indonesia and Malaysia through locally-licensed surgeons. Donate at https://worldaidnetwork.org/donate --- This is general information, not medical advice, published by World Aid Network. Always consult a qualified clinician about your own health.