Cataracts
A cataract is an acquired or congenital opacification of the crystalline lens that scatters and absorbs light, degrades retinal image quality and produces a painless, usually bilateral, progressive loss of visual acuity. It remains the leading cause of reversible blindness worldwide, responsible for an estimated 17 % of distance‐vision impairment and more than 50 % of blindness in low- and middle-income countries despite the existence of a highly effective surgical cure.
Symptoms
Patients describe painless, slowly progressive blurring or dimming of distance and near vision, increased glare and halos around lights, decreased contrast sensitivity, difficulty with night driving, frequent spectacle-prescription changes, monocular diplopia or a shift toward myopia (“second sight”) in nuclear cataract. Posterior subcapsular cataracts disproportionately reduce near vision and cause disabling photophobia in bright light.
Risk Factors
Advancing age is the dominant determinant, but early cataractogenesis is accelerated by ultraviolet-B and ionising radiation, cigarette smoking and biomass-fuel exposure, chronic hyperglycaemia in diabetes mellitus, metabolic syndrome, systemic corticosteroids, topical ocular steroids, statin or phenothiazine use, high myopia, ocular trauma, uveitis, pseudoexfoliation syndrome, prolonged miotic therapy, atopic dermatitis, retinitis pigmentosa, congenital rubella, hypocalcaemia, malnutrition, dehydration crises, low serum vitamin C, and genetic syndromes such as galactosaemia or Down syndrome. Female sex, African or South-Asian ancestry, low educational attainment and poor access to surgical services increase lifetime visual burden.
Diagnosis
Diagnosis is confirmed by slit-lamp biomicroscopy after mydriasis: opacities are graded by the Lens Opacities Classification System III. Visual-acuity charting, pinhole testing, contrast sensitivity and glare testing quantify functional impact. Direct and indirect ophthalmoscopy evaluate posterior-segment comorbidity; optical coherence tomography of the macula is routinely obtained in patients with diminished potential acuity or diabetes. Biometry with partial-coherence interferometry calculates intra-ocular-lens (IOL) power, and keratometry or corneal topography identifies astigmatism amenable to toric correction. Laboratory investigations exclude hyperglycaemia, hyperparathyroidism or infectious causes when history dictates.
Treatment
No pharmacologic therapy reverses lens opacity; definitive management is surgical extraction when vision loss impairs activities of daily living. Modern phacoemulsification through a clear-corneal micro-incision removes the nucleus and cortex, preserves the posterior capsule and implants a foldable acrylic IOL—monofocal, toric, multifocal, extended-depth-of-focus or accommodating—selected to meet refractive goals. Small-incision manual cataract surgery is preferred in resource-constrained settings and dense brunescent cataracts. Peri-operative intracameral moxifloxacin and posterior-capsule polishing reduce endophthalmitis and posterior-capsule-opacification risks. Post-operative topical fluoroquinolone and tapering steroid–NSAID combination for three to four weeks control inflammation. Nd:YAG capsulotomy treats visually significant posterior-capsule opacification in 10–20 % of cases. Aphakic or pseudophakic corrected visual acuity of 20/25 or better is achieved in over 90 % of uncomplicated surgeries in high-income settings, though outcomes lag in underserved regions, prompting WHO targets of a 30 % increase in effective cataract-surgical coverage by 2030.
Outlook
Prognosis after timely surgery is excellent; complication rates for phacoemulsification are under 2 % in experienced hands. Delay allows progression to hypermature cataract with lens-induced phacolytic or phacomorphic glaucoma, zonular weakness and capsular rupture risks, making early referral essential. Global cataract burden will rise with population ageing; expanding cost-effective surgical services and postoperative optical correction are key to meeting WHO vision targets.
Complications
Untreated cataract can progress to lens-induced glaucoma, uveitis and dislocation; surgical risks include posterior-capsule rupture, zonular dialysis, retained lens material, endophthalmitis, cystoid macular edema, suprachoroidal hemorrhage, refractive surprise, posterior-capsule opacification, dry-eye exacerbation and dysphotopsias such as negative glare arcs.
Prevention
No proven medical prophylaxis exists, but epidemiologic evidence suggests that smoking cessation, ultraviolet-blocking eyewear, glycaemic and blood-pressure control, maintenance of healthy body weight, regular consumption of carotenoid- and vitamin C-rich fruits and vegetables, and avoidance of chronic systemic or topical steroid overuse may delay cataractogenesis. Occupational eye protection reduces traumatic cataracts, and rigorous measles and rubella immunisation prevents congenital varieties.
Support
Patients awaiting surgery should optimise lighting, use anti-glare sunglasses, magnifiers and updated spectacles, control systemic disorders such as diabetes and hypertension, cease smoking, and ensure adequate dietary antioxidants. Postoperatively they must instil drops as prescribed, avoid eye rubbing, heavy lifting and swimming for two weeks, wear protective shields while sleeping and sunglasses outdoors, and attend follow-up visits to detect raised intra-ocular pressure, infection or cystoid macular edema.
Sources
The information presented above is supported by reputable medical sources and research publications. These references provide additional clinical insights and evidence-based findings for healthcare professionals and individuals seeking comprehensive understanding of this medical condition.
