Cataract — Causes, Symptoms, Phacoemulsification & Treatment Guide — Symptoms, Causes & Treatment | MyMedicPlus

A cataract is a clouding of the normally clear crystalline lens of the eye, causing progressive loss of vision. Light passing through a cloudy lens scatters, producing blurry, foggy, or glare-affected vision rather than a sharp image on the retina. Cataracts are the leading cause of blindness worldwide, responsible for 51% of global blindness, affecting 94 million people. Most cataracts are age-related (nuclear sclerotic cataracts), but congenital, traumatic, metabolic (diabetic), and radiation-induced cataracts also occur. Cataract surgery is the most commonly performed elective surgical procedure in the world. Congenital cataracts present at birth and require urgent surgical management — they are the most common treatable cause of childhood visual impairment. Posterior subcapsular cataracts (PSC) develop characteristically in younger patients from corticosteroid use or diabetes and cause disproportionate glare and near vision difficulties due to their central location. Nuclear sclerotic cataracts — the most common age-related type — cause gradual yellowing, myopic shift, and progressive reduction in contrast sensitivity over years to decades. The cost-effectiveness of cataract surgery is among the highest of any medical intervention globally.

The primary risk factor is advancing age — over 95% of adults aged 65 and above have some degree of lens opacity. Other risk factors include ultraviolet (UV) light exposure (UVB accelerates lens protein oxidation), diabetes mellitus (10-25% increased risk — osmotic changes cause cortical cataracts), smoking (doubles cataract risk — antioxidant depletion), prolonged corticosteroid use (posterior subcapsular cataracts), previous eye trauma (traumatic cataracts — often unilateral), high myopia, previous eye surgery or inflammation (uveitis), and congenital cataracts (caused by maternal rubella infection or metabolic disorders in infants). Radiation cataracts from ionising radiation (nuclear workers, radiotherapy patients) and infrared radiation (glassblowers, steel workers) characteristically affect the posterior subcapsular region. Wilson's disease (copper deposition) and galactosaemia (galactitol accumulation) cause cataracts in children. Myotonic dystrophy causes a distinctive multicoloured 'Christmas tree' cataract. Atopic dermatitis is associated with anterior and posterior subcapsular cataracts in young adults.

Progressive painless blurring of vision (difficulty reading, recognising faces, watching television). Halos and glare around lights, particularly at night or oncoming headlights while driving. Faded or yellowed colours. Frequent changes in prescription spectacle strength. Double vision in one eye. Difficulty in bright light (light sensitivity) — especially with posterior subcapsular cataracts (PSC). 'Second sight' phenomenon in nuclear cataracts — early increased myopia temporarily improves near vision. Symptoms are usually bilateral but often asymmetric, with one eye affected more than the other. Visual acuity measured on Snellen chart shows reduced best-corrected vision. Monocular diplopia (double vision in one eye that disappears when the eye is covered) is a characteristic symptom of nuclear cataract from irregular refractive zones within the lens. Patients with PSC often report significantly worse vision in bright sunlight (photophobia) compared to dim light, as the pupil constricts in bright conditions and forces more light through the posterior central opacity.

Diagnosis is made by slit-lamp biomicroscopy — direct examination of the lens by an ophthalmologist using a bright light and magnification, allowing grading of cataract type (nuclear, cortical, posterior subcapsular) and density (Lens Opacities Classification System LOCS III). Assessment includes best-corrected visual acuity (BCVA), contrast sensitivity, and glare testing. Biometry (IOL Master or optical coherence tomography) measures axial length and corneal curvature to calculate the power of the intraocular lens (IOL) required for the patient's target refraction post-operatively. Fundus examination through the dilated pupil assesses retinal health. Potential acuity testing (PAM — potential acuity meter) estimates visual potential through the opaque lens, helping predict post-operative visual outcomes — particularly useful when there is coexisting macular degeneration or diabetic maculopathy that may limit post-operative vision. Corneal specular microscopy counts endothelial cells before surgery to identify patients at risk of post-operative corneal decompensation (Fuchs' endothelial dystrophy, previous eye surgery).

There is no effective pharmacological treatment — surgery is the only treatment for visually significant cataracts. Phacoemulsification (small-incision cataract surgery): a 2.2-2.4 mm self-sealing corneal incision is made; an ultrasonic probe emulsifies (liquefies) the cloudy lens; the lens fragments are aspirated; a foldable intraocular lens (IOL) is inserted into the lens capsule. Day-case procedure under topical (eyedrop) anaesthesia. Recovery is rapid — most patients achieve functional vision within 24-48 hours. IOL options include: monofocal IOLs (corrects distance or near); multifocal IOLs (corrects near and distance, reducing spectacle dependence); extended depth of focus (EDOF) IOLs; toric IOLs (corrects astigmatism). Femtosecond laser-assisted cataract surgery (FLACS) offers computer-precise incisions. Surgical outcomes: over 95% of patients achieve improved vision without complications. Preloaded IOL delivery systems have reduced surgical time and contamination risk. Cataract surgery in patients on tamsulosin (alpha-blocker for BPH) requires awareness of intraoperative floppy iris syndrome (IFIS) — pharmacological pupil dilation and iris hooks are used to prevent complications.

Untreated cataracts progress to complete loss of the red reflex and eventually to blindness. Hypermature (Morgagnian) cataracts can cause phacolytic or phacomorphic glaucoma — secondary raised intraocular pressure from lens protein leakage — a painful and sight-threatening complication. Dense cataracts also prevent the ophthalmologist from visualising the retina, potentially delaying diagnosis of diabetic retinopathy, macular degeneration, or retinal detachment. Globally, cataract blindness represents a massive preventable burden — particularly in low-income countries where surgical access is limited. Cataract blindness increases the risk of falls, hip fractures, depression, social isolation, and cognitive decline in older adults.

Wear UV-protective sunglasses (UVA and UVB 100% blocking) when outdoors — cumulative UV exposure significantly accelerates age-related cataracts. Stop smoking — smokers have twice the cataract risk of non-smokers; quitting reduces risk. Control blood sugar strictly in diabetes — hyperglycaemia accelerates lens opacification. Eat a diet rich in antioxidants (vitamins C and E, lutein, zeaxanthin from leafy green vegetables) — observational studies suggest modest protective effects. Avoid prolonged corticosteroid use where possible; if steroids are required, regular ophthalmology monitoring is advisable. Regular eye examinations (every 1-2 years from age 50) allow early detection and timely surgical referral before vision loss significantly impacts quality of life.

See a GP or optician if you notice any progressive blurring, glare around lights, difficulty driving at night, frequent spectacle prescription changes, or colours appearing faded or yellowed — these are typical cataract symptoms requiring slit-lamp assessment. Book an urgent same-day ophthalmology review or attend A&E for: sudden painless loss of vision, flashes of light, a shadow or curtain across vision (possible retinal detachment — requires urgent surgery), or a painful red eye with reduced vision (possible acute glaucoma). Children and infants need urgent paediatric ophthalmology review within days of any suspected cataract — a white reflex in the pupil in a photo ('red eye' absent) or failure to follow objects requires same-day emergency referral.