Cataracts
Cataracts are the most common cause of treatable blindness worldwide, caused by opacification of the lens, presenting with gradual painless visual loss and managed surgically with phacoemulsification and intraocular lens implantation.
Key Facts
Cataracts are the most common cause of treatable blindness worldwide; affect approximately 30% of people >65 in the UK Types: nuclear sclerotic (most common age-related), cortical, posterior subcapsular (steroid-related, younger patients) Symptoms: gradual painless blurred vision, glare (especially driving at night), faded colours, frequent spectacle prescription changes Nuclear sclerotic cataract causes myopic shift ("second sight" — temporary improvement in near vision as refractive index increases) Surgery (phacoemulsification + IOL): the only effective treatment; most common elective surgery performed in the UK (~400,000/year) NICE NG77: refer when visual impairment affects daily activities; surgery improves quality of life and reduces falls by 34% Risk factors: age (most important), UV exposure, smoking, diabetes, corticosteroids, trauma, high myopia Complications of surgery: posterior capsule opacification (most common; 20-30% at 5 years; treated with YAG laser capsulotomy), endophthalmitis (rare but serious; 1 in 1,000)
Overview
Key Facts
Cataract surgery is one of the most cost-effective interventions in healthcare. Modern phacoemulsification has excellent outcomes with >95% of patients achieving improved vision.
Epidemiology
- ~30% of >65s have visually significant cataracts
- ~400,000 cataract operations/year in the UK (most common elective surgery)
- Prevalence increases with age: 50% by age 80
- Leading cause of blindness globally (mostly in developing world where surgical access is limited)
Aetiology
- Age-related (most common): nuclear sclerosis, cortical, posterior subcapsular
- Metabolic: diabetes mellitus (sorbitol accumulation → osmotic damage), galactosaemia
- Drug-induced: systemic corticosteroids (posterior subcapsular), amiodarone
- Traumatic: blunt or penetrating injury, radiation
- Congenital: genetic, intrauterine infection (rubella — TORCH)
- Secondary to ocular disease: uveitis, retinal detachment surgery, high myopia
Pathophysiology
- Lens opacification due to: protein denaturation and aggregation, oxidative damage, osmotic imbalance, UV-induced cross-linking
- Nuclear sclerotic: lens nucleus becomes yellow-brown → increased refractive index (myopic shift)
- Cortical: spoke-like opacities from cortex
- Posterior subcapsular: granular opacity on posterior lens capsule → early visual symptoms (affects near vision and causes glare)
Clinical Presentation
Symptoms
- Gradual painless blurred vision (bilateral but often asymmetric)
- Glare (especially with oncoming headlights at night)
- Faded or yellowed colours
- Frequent spectacle changes (myopic shift with nuclear cataract)
- "Second sight" — temporary improvement in near vision (nuclear sclerosis increases refractive index)
- Monocular diplopia (rare)
Signs
- Reduced visual acuity (Snellen)
- Red reflex: absent or diminished on direct ophthalmoscopy
- Lens opacity visible on slit lamp examination
- Fundal view may be obscured
Red Flags
- Sudden visual loss (NOT cataract — consider retinal detachment, CRVO, CRAO, vitreous haemorrhage)
- Pain (NOT cataract — consider AACG, uveitis, keratitis)
- Young patient with cataract (consider secondary cause: diabetes, steroid, trauma, uveitis)
- Congenital cataract (urgent paediatric ophthalmology referral — amblyopia risk)
Differential Diagnosis
| Diagnosis | Key Features | Investigation |
|---|---|---|
| Age-related macular degeneration | Central visual loss, metamorphopsia | OCT, Amsler grid |
| Glaucoma | Peripheral field loss, disc changes | IOP, visual fields, OCT |
| Diabetic retinopathy | Diabetic, retinal changes | Fundoscopy, OCT |
| Refractive error | Correctable with glasses | Refraction |
| Corneal opacity | Corneal haze/scar | Slit lamp |
Diagnosis / Investigation
Bedside
- Visual acuity (Snellen chart): document for each eye
- Red reflex: using direct ophthalmoscope (absent = dense cataract)
- Slit lamp examination: cataract type and density
- Fundoscopy: assess retina (if visible through cataract)
Bloods
- Blood glucose/HbA1c: if diabetes suspected
- Not routinely needed for cataract assessment
Imaging
- Biometry (IOLMaster): measurement of axial length and corneal curvature for IOL power calculation (pre-operative)
- OCT: if macular pathology suspected (may limit visual outcome despite successful surgery)
- B-scan ultrasound: if fundal view obscured by dense cataract
Special Tests
- Pre-operative assessment: biometry, refraction, assessment of coexisting eye disease
- Check for amblyopia (may limit post-surgical visual improvement)
Management
Non-pharmacological
- Updated spectacles: may temporarily improve vision in early cataract
- Brighter reading light: helpful in early stages
- Driving assessment: inform DVLA if cannot meet visual standards
Pharmacological
- No medical treatment effectively treats or prevents cataracts
- Pre-operative: topical chloramphenicol or povidone-iodine (infection prevention)
- Post-operative: topical steroid (dexamethasone 0.1% drops QDS for 4 weeks, taper) + topical NSAID (ketorolac/nepafenac)
Surgical/Interventional
- Phacoemulsification + IOL implantation: gold standard surgery
- Day case under local anaesthetic (topical or sub-Tenon's)
- Ultrasound breaks up cataractous lens → aspiration → foldable IOL inserted
- Operating time: 15-30 minutes
- Visual recovery: days to weeks
- IOL options: monofocal (most common; glasses for near), multifocal/toric (corrects astigmatism)
- Second eye surgery: typically 1-3 months after first eye
- YAG laser capsulotomy: for posterior capsule opacification (outpatient, quick, painless)
Referral Criteria
- NICE NG77: refer when visual impairment affects quality of life/daily activities
- No specific visual acuity threshold required for referral
- Second eye surgery: if impaired binocular vision
- Congenital cataract: urgent paediatric ophthalmology (within days of detection)
Prognosis
- >95% of patients achieve improved vision after uncomplicated surgery
- Posterior capsule opacification: 20-30% at 5 years; easily treated with YAG capsulotomy
- Endophthalmitis: rare (1 in 1,000); sight-threatening; requires urgent intravitreal antibiotics
- Cystoid macular oedema: 1-2%; usually resolves with topical NSAIDs/steroids
- Retinal detachment: 1 in 1,000 (higher in high myopes)
- Cataract surgery reduces falls by 34% in older adults (Harwood 2005)
- Driving: most patients meet driving standards after surgery
Other Relevant Information
Cataract Types and Associations
| Type | Association | Key Feature |
|---|---|---|
| Nuclear sclerotic | Age | Myopic shift, "second sight" |
| Cortical | Age, diabetes | Spoke-like opacities |
| Posterior subcapsular | Steroids, diabetes, uveitis | Glare, near vision affected first |
| Congenital | Rubella, Down syndrome, galactosaemia | White pupil, amblyopia risk |
Complications of Cataract Surgery
| Complication | Incidence | Management |
|---|---|---|
| Posterior capsule opacification | 20-30% (5yr) | YAG laser capsulotomy |
| Cystoid macular oedema | 1-2% | Topical NSAID/steroid |
| Endophthalmitis | 0.1% | Intravitreal antibiotics (emergency) |
| Retinal detachment | 0.1% | Vitrectomy |
| Posterior capsule rupture (intra-op) | 1-2% | May affect IOL placement |