Cataracts
A cataract refers to opacification of the normally transparent lens, causing reduced transmission and scattering of light, which can impair vision.
This updated UKMLA guide to cataracts is based on NICE CKS, and NICE NG77, which covers: cataract types, risk factors, symptoms, diagnosis, and management.
This article focuses mainly on acquired cataracts in adults, especially age-related cataract, as this is the most common and most relevant form for general clinical practice and UKMLA-level learning. Congenital cataract is a separate paediatric topic and would be covered separately.
Epidemiology
Cataract surgery is the most common surgical procedure undertaken in the NHS
Cataract is the leading cause of blindness globally
Prevalence of visually-impairing cataracts increases with age:
- 71% is >85 y/o
- 42% is 75-79 y/o
- 16% is 65-69 y/o
Types
3 most common morphological types of cataracts:
| Type | Affected lens location |
|---|---|
| Nuclear cataract | Central nucleus of the lens |
| Cortical cataract | Lens cortex
Often with peripheral spoke-like opacities |
| Posterior subcapsular cataract | Posterior part of lens (just anterior to the capsule) |
Causes and Risk Factors
The cause for most cataracts is thought to be multifactorial. Ageing and oxidative stress are thought to be the primary causes.
General risk factors for acquired cataracts:
- Advancing age – most significant risk factor
- Female
- Smoking and excessive alcohol use
- UV exposure
- Corticosteroids
- Ocular conditions
- Severe myopia
- Uveitis
- Retinitis pigmentosa
- Trauma (most common cause of unilateral cataracts in young people)
- Blunt or penetrating injury to the eye
- Ionising radiation, electrical, or chemical burns
- Surgical eye operations (e.g. vitrectomies)
- Systemic diseases (e.g. diabetes, hypertension, obesity)
- Metabolic or hereditary conditions (e.g. Wilson’s disease, galactosaemia, myotonic dystrophy, Marfan syndrome, Down syndrome, neurofibromatosis type 2)
Certain risk factors are strongly associated with specific types of cataracts [Ref]
- Nuclear cataracts: primarily associated with age and diabetes
- Cortical cataracts: associated with age, diabetes and UV radiation
- Posterior subcapsular cataracts: associated with corticosteroid toxicity, uveitis, and inherited dystrophies
Clinical Features
Key presentation: gradual, painless reduction in visual clarity and sharpness, other symptoms:
- Reduced visual acuity (often described as cloudy / blurry / misty vision)
- Light-related symptoms
- Difficulty driving at night due to oncoming headlights
- Halos around lights (rings / glows seen around lights)
- Glare (visual discomfort or reduced visual clarity in bright light)
- Increased sensitivity to bright light
- Reduced colour perception (esp. blue)
- Diplopia (double vision) or polyopia (multiple images)
As a result, patients may report:
- Reduced ability to perform daily activities (e.g. reading, driving)
- Frequent changes in glasses prescription with limited improvement in vision
Specific cataract morphologies can produce slightly different symptom patterns: [Ref1][Ref2]
| Cataract type | Typical visual changes |
|---|---|
| Nuclear cataract |
|
| Cortical cataract |
|
| Posterior subcapsular cataract |
|
At a non-specialist level, detailed cataract morphology is less important than recognising the typical presentation of cataract: gradual, painless reduction in visual clarity. However, these patterns can help explain why different patients may report different symptoms.
Investigation and Diagnosis
Cataract is primarily a clinical diagnosis, based on typical symptoms (see above) and examination findings.
In the UK, many cataracts are first detected and monitored during routine optometrist appointments.
Key Examinations
| Examination | Typical findings in cataracts |
|---|---|
| Visual acuity assessment (e.g. Snellen chart) | Reduced visual acuity |
| Fundoscopy | Absent red reflex (or becomes absent / dull / shadowed)
Cataract may obscure visualisation of the fundus |
| Slit lamp examination | Lens opacity
Lens findings by cataract type: [Ref1][Ref2]
|
Additional Assessment
Additional examination is important to assess severity and exclude alternative or co-existing causes of visual impairment:
- External eye examination (including pupil size and function assessment)
- Glare testing (likely +ve in cataracts)
- Visual field assessment (normal in cataracts, visual defect may suggest alternative or co-existing pathology like glaucoma and retinal disease)
- IOP measurement (normal in cataracts, raised IOP suggest co-existing glaucoma)
Management
Surgery is the only definitive treatment for cataracts [Ref1][Ref2]
- Non-surgical management primarily involves optimising a patient’s prescription for eyeglasses or contact lenses [Ref1][Ref2]
There are currently NO approved pharmacological therapies to arrest or reverse cataract formation. [Ref1][Ref2]
Advise the person that all drivers must meet the following standards (they may be aided by prescribed glasses or contact lenses to reach these standards)
- In good daylight, be able to read a modern vehicle number plate at a distance of 20 m
- Visual acuity must be at least Snellen 6/12 with both eyes open or in the only eye if monocular
Indications For Cataract Surgery
In practice, cataract surgery is primarily indicated when: [Ref1][Ref2]
- Visual impairment affects the patient’s quality of life or activities of daily living (e.g. reading, driving, work), OR
- To correct a significant refractive imbalance between the 2 eyes (e.g. after cataract surgery in the other eye), OR
- Cataract prevents adequate visualisation or monitoring of underlying retinal pathology (e.g. diabetic retinopathy)
NICE does not provide a strict list of indications for cataract surgery. Instead, the decision to refer should be based on:
- Impact of cataracts on vision and quality of life
- How quality of life may be affected if chosen not to have surgery
- Whether one or both eyes are affected.
- Risk and benefits of surgery
- Whether the patient wants surgery
Access to cataract surgery should not be restricted based on visual acuity alone.
Information on Cataract Surgery
Standard surgical technique: phacoemulsification + artificial intraocular lens implantation
Key steps:
- Dilated eye drops + sub‑Tenon’s or topical (with or without intracameral) anaesthesia given pre-operatively
- Speculum is placed to keep the eye open
- Small incision made near the edge of the cornea
- Phacoemulsification is performed: ultrasound energy is used to break up and emulsify the cloudy lens
- The fragmented lens material is aspirated from the eye
- An artificial intraocular lens is inserted to replace the natural lens
Cataract surgery is usually performed under local anaesthesia. General anaesthesia is not routinely required in adults.
Benefits and Risks of Cataract Surgery
Benefits:
- 95% of patients (with no pre-existing ocular pathology) will achieve 6/12 vision – which meets the driving requirements in the UK
- Even in those with pre-existing ocular pathology, this is achievable in 86.2% patients
- Improvement in
- Vision clarity
- Colour vision
- Reduces risk of falls and fractures
- May reduce the risk of dementia and depression
Risks:
- Serious complications of cataract surgery are rare
- Most common intra-operative complication: posterior capsule rupture, which increases the risk of
- Acute intra-operative supra-choroidal haemorrhage (17x risk)
- Retinal detachment (20x risk in the year after surgery)
- Reduced acuity
- Post-operative endophthalmitis (7x risk)
- Most common late, post-operative complication: posterior capsular opacification
- Occurs gradually months or years after surgery
- Results in reduced visual acuity, blurred vision, glare (also known as secondary cataracts)
- Can be managed by laser treatment (capsulotomy)
- Other complications include:
- Corneal oedema (common, early post-operative complication causes blurred vision that improves with time)
- Cystoid macular oedema (important cause of reduced vision after surgery) – risk is reduced by post-operative topical corticosteroid +/- NSAID eye drops
- Endophthalmitis (sight-threatening emergency)
- Retinal detachment
- Floppy iris syndrome (mainly in those who take alpha blockers) – if at risk can be prevented with intra-operative phenylephrine
Endophthalmitis
Endophthalmitis is a severe intraocular infection and is a sight-threatening ophthalmic emergency.
It is prevented by routine intraoperative intracameral cefuroxime
Red flags: red, painful eye + vision loss following any recent eye surgery / infection
Key management principles:
- Immediate referral to ophthalmology
- Rapid vitreous sampling, followed by intravitreal antibiotics (typically vancomycin)
Avoid intraocular gentamicin due to the risk of retinal toxicity.
References
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