Overview
Cataract
1. Overview
A cataract is any opacity of the crystalline lens of the eye. It is the leading cause of blindness worldwide (though reversible).
Most cataracts are age-related ("senile"), but they can be congenital, traumatic, or secondary to drugs (steroids).
Classification by Location
- Nuclear Sclerotic: Center of lens yellows/hardens. Slow progression. Causes "Second Sight" (Myopic shift) - older people can suddenly read without glasses.
- Cortical: Spoke-like opacities from periphery. Glare is common.
- Posterior Subcapsular (PSC): Opacity at the back of the lens.
- Caused by Steroids and Diabetes.
- Progesses FAST.
- Causes devastating glare (e.g., driving at night).
Clinical Pearls
"Second Sight": Nuclear cataracts cause a myopic shift – elderly patients suddenly can read without glasses. But distance vision worsens.
"PSC = Steroids + Glare": Posterior Subcapsular Cataracts are classically steroid-induced and cause severe glare, especially at night.
"Red Reflex Matters": A reduced or absent red reflex is the key sign. In infants, absent red reflex = urgent referral (Retinoblastoma or Congenital Cataract).
2. Epidemiology
Prevalence
- Global Leading Cause of Blindness: ~50% of global blindness (Reversible).
- Age-Related: >50% of people >65 have some lens opacity.
- Prevalence by Age: 40-54 yo: ~2%. >75 yo: ~70%.
Risk Factors
| Factor | Mechanism |
|---|---|
| Age | Strongest risk factor. Protein denaturation over time. |
| UV Light Exposure | Accelerates oxidative damage. |
| Smoking | Oxidative stress. Doubles risk. |
| Diabetes | Sorbitol accumulates in lens. Osmotic hydration. "Snowflake" cataract. |
| Steroids | PSC cataracts. Both systemic and topical (Inhaled steroids too). |
| Trauma | Penetrating injury, Blunt trauma. Rosette-shaped cataract. |
| Radiation | Ionizing radiation (Radiotherapy). |
| Myotonic Dystrophy | "Christmas Tree" cataract. |
| Previous Eye Surgery | Vitrectomy accelerates cataract formation. |
3. Pathophysiology
The lens is made of proteins (crystallins) arranged in a precise lattice to be transparent. With age/oxidative stress/UV light:
- Proteins denature and clump together.
- The lens yellows (brunecense).
- Light is scattered (Glare) and blocked (Visual Loss).
2. Clinical Features
Symptoms
- Painless gradual loss of vision.
- Glare: Haloes around lights (driving at night).
- Change in Refraction: Frequent prescription changes.
- Washed out colours.
Physical Examination
- Red Reflex: Reduced or absent (dark shadow).
- Direct Ophthalmoscopy: Opacity seen against the red reflex.
- Slit Lamp: Defines the type (Nuclear vs Cortical).
3. Diagnosis
- Clinical Diagnosis: Slit lamp examination by Ophthalmologist/Optometrist.
- Biometry: Ultrasound/Laser measurement of eye length (Axial Length) to calculate the power of the replacement lens needed (IOL).
4. Management Algorithm
┌─────────────────────────────────────────────────────────────────────────────┐
│ CATARACT MANAGEMENT │
├─────────────────────────────────────────────────────────────────────────────┤
│ │
│ IS SURGERY INDICATED? │
│ • NO: If symptoms are mild or managed with glasses. │
│ • YES: If visual loss affects ACTIVITY OF DAILY LIVING (Driving/Reading). │
│ • NOTE: Visual acuity number (e.g., 6/9) is NOT the only criterion. │
│ └─────────────────────────────────────────────────────────────────────┘ │
│ ↓ │
│ ┌─────────────────────────────────────────────────────────────────────┐ │
│ │ SURGICAL TECHNIQUE (Phacoemulsification) │ │
│ │ • The Gold Standard worldwide. │ │
│ │ • Day Case procedure. Local Anesthetic (Drops or Sub-tenon). │ │
│ │ • Steps: │ │
│ │ 1. Tiny incision (2mm) in cornea. │ │
│ │ 2. Capsulorhexis (Circular tear in front of lens bag). │ │
│ │ 3. Phaco (Ultrasound probe) breaks up old lens. │ │
│ │ 4. Aspiration of fragments. │ │
│ │ 5. Insertion of Artificial Lens (IOL) into the empty bag. │ │
│ │ 6. No stitches usually needed. │ │
│ └─────────────────────────────────────────────────────────────────────┘ │
│ ↓ │
│ ┌─────────────────────────────────────────────────────────────────────┐ │
│ │ POST-OP CARE │ │
│ │ • Eye drops for 4 weeks (Antibiotic + Steroid). │ │
│ │ • Avoid rubbing eye or swimming. │ │
│ │ • Vision improves within days. │ │
│ └─────────────────────────────────────────────────────────────────────┘ │
│ │
└─────────────────────────────────────────────────────────────────────────────┘
5. Complications
Intra-operative:
- Posterior Capsule Rupture (PCR): "Breaking the bag". The vitreous jelly prolapses forward. Risk of retinal detachment. (Rate: 1-2%).
Post-operative:
- Endophthalmitis:
- Red Flag Emergency.
- Infection inside the eye (e.g., Staph epidermidis).
- Pain + Loss of Vision + Hypopyon (pus level).
- Needs Intravitreal Antibiotics immediately ("Tap and Inject").
- PCO (Posterior Capsular Opacification):
- "After-cataract".
- Occurs in 20% of patients months/years later.
- Cells grow over the back of the bag causing blurry vision.
- Treatment: YAG Laser Capsulotomy (takes 5 mins, curative).
6. Prognosis
- Success rate >95% achieve driving vision (if retina is healthy).
- Quality of life improvement is immense (falls reduction).
7. Special Considerations
Congenital Cataract
- Causes: Rubella, Galactosemia, Lowe syndrome.
- Leukocoria (White pupil).
- Must be removed urgently (weeks) to prevent Amblyopia (Lazy eye) - brain ignores the eye permanently.
Refractive Aims
- Usually, we aim for "Plano" (Emmetropia) - perfect distance vision. Patient needs reading glasses.
- "Monovision": One eye for distance, one for near.
- Multifocal Lenses: Premium option (NHS usually only funds Monofocal).
8. Key Clinical Pearls
Exam-Focused Points
- Steroids: Cause Posterior Subcapsular Cataract.
- Diabetes: Causes Snowflake cataract (osmotic hydration) or accelerates senile cataract.
- Endophthalmitis: The nightmare complication. Painful red eye post-op = Emergency.
- Marfan's Syndrome: Lens dislocation (Ectopia Lentis) - lens floats UP. (Homocystinuria = Down).
- Myotonic Dystrophy: "Christmas Tree" cataract.
Common Exam Scenarios
- Patient post-cataract surgery (3 days ago) presents with severe pain and reduced vision. (Endophthalmitis).
- Patient had surgery 2 years ago, vision blurry again. Dx? (PCO - treat with YAG laser).
- Baby with no red reflex. (Refer urgently - Retinoblastoma or Congenital Cataract).
9. Patient Explanation
What is a cataract?
"Inside your eye, there is a lens, like the lens in a camera or spectacles. Over time, this lens becomes cloudy and yellow, like a frosted bathroom window. This stops light getting in clearly."
How do you fix it?
"We cannot clean the lens. We have to replace it. Through a tiny keyhole cut, we use sound waves to break up the cloudy lens, suck it out, and slide a new clear plastic lens into its place. It stays there forever and you won't feel it."
10. Evidence & Guidelines
Key Guidelines
| Guideline | Organization | Year | Key Points |
|---|---|---|---|
| Cataract Surgery | NICE (NG77) | 2017 | Second eye surgery rec. |
| PCO Management | RCOphth | 2019 | YAG laser protocols. |
Evidence-Based Recommendations
| Recommendation | Evidence Level |
|---|---|
| Phacoemulsification | High |
| Bilateral sequential surgery | High |
| Intracameral Antibiotics | High (Reduces endophthalmitis) |
12. Triage: When to Refer
| Scenario | Urgency | Action |
|---|---|---|
| Gradual visual decline, cataract suspected | Routine | Optometry/Ophthalmology. Assess need for surgery. |
| Visual impairment affecting daily activities | Routine | Ophthalmology. Surgery indicated. |
| Post-Op Pain + Vision Loss (Suspected Endophthalmitis) | Emergency | Immediate Ophthalmology. Intravitreal Antibiotics. |
| Absent Red Reflex in Infant | Emergency | Urgent Ophthalmology. Exclude Retinoblastoma. |
| Traumatic Cataract | Urgent | Ophthalmology. Exclude Globe Rupture. |
14. Quality Markers: Audit Standards
| Standard | Target |
|---|---|
| PCR Rate (Posterior Capsule Rupture) | <2% |
| Endophthalmitis Rate | <0.1% |
| Achieving Target Refraction (Within 1D) | >5% |
| Same-Day or Next-Day Post-Op Review if Symptomatic | 100% |
15. Intraocular Lens (IOL) Types
| IOL Type | Description | Notes |
|---|---|---|
| Monofocal | Single focus (Usually distance). | Standard. Patient needs reading glasses. NHS funded. |
| Monovision | One eye for distance, One for near. | Compromise. Brain adapts. |
| Multifocal | Multiple focal points (Distance + Near). | Premium. Can have glare/haloes. |
| Toric | Corrects astigmatism. | Precise positioning required. |
| Extended Depth of Focus (EDOF) | Smooth range of vision. | Less haloes than Multifocal. |
Choosing an IOL
| Patient Factor | IOL Consideration |
|---|---|
| Standard Expectations | Monofocal for distance. Reading glasses for near. |
| High Astigmatism | Toric IOL. |
| Desire for Spectacle Independence | Multifocal or EDOF (Premium – Private). |
| Night Driving Concerns | Avoid Multifocal (Haloes). Monofocal safer. |
16. Historical Context
- Jacques Daviel (1747): First successful extracapsular cataract extraction.
- Harold Ridley (1949): Invented the first IOL (Acrylic lens). Inspired by observing perspex from WW2 aircraft canopies was tolerated in pilots' eyes.
- Phacoemulsification (Kelman, 1967): Charles Kelman developed ultrasound-based lens fragmentation. Revolutionised cataract surgery – small incision, faster recovery.
17. Common Clinical Pitfalls
| Pitfall | Consequence | Prevention |
|---|---|---|
| Ignoring Glare Symptoms | Delayed surgery. Falls. MVA. | Ask about night driving, reading. |
| Missing Endophthalmitis | Permanent vision loss. | Any pain + vision drop post-op = Emergency. |
| Not Checking Red Reflex in Infants | Missed Retinoblastoma/Congenital Cataract. | Routine newborn and 6-8 week check. |
| Operating on Wrong Eye | Serious harm. | Surgical Safety Checklist. Mark eye pre-op. |
18. Patient FAQs
| Question | Answer |
|---|---|
| "Will I feel the operation?" | No. We numb the eye with drops or an injection. You may see lights and colours but no pain. |
| "How long does the operation take?" | About 15-30 minutes for each eye. |
| "Can I have both eyes done at once?" | Usually we do one eye first, then the second a few weeks later. Bilateral same-day surgery is sometimes offered. |
| "Will I need glasses after?" | Most people need reading glasses. Some premium lenses reduce this. |
| "When can I drive?" | Usually a few days to a week after surgery, if your vision meets the legal standard. |
| "What if my vision gets worse years later?" | This may be PCO ("after-cataract"). A quick YAG laser treatment fixes it. |
19. References
- NICE Guideline [NG77]. Cataract in adults: management. 2017.
- Day AC, et al. The Royal College of Ophthalmologists' National Ophthalmology Database study of cataract surgery. Eye. 2015.
- Ridley H. Intraocular acrylic lenses. Trans Ophthalmol Soc U K. 1951. PMID: 14893013
Medical Disclaimer: MedVellum content is for educational purposes and clinical reference. If you have vision problems, please consult an eye care professional.