Cataract surgerys short note elaborative 5 mark
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Cataract Surgery - Short Note (5 Marks)
Definition
Cataract surgery is the surgical removal of the opacified crystalline lens of the eye, usually followed by implantation of an artificial intraocular lens (IOL) to restore vision.
Indications
- Visual impairment - when the cataract significantly reduces best-corrected visual acuity
- Glare and contrast sensitivity loss - especially troublesome in night driving
- Lens-induced complications - phacomorphic glaucoma, phacolytic glaucoma, lens-induced uveitis
- Anisometropia - unequal refraction causing amblyopia in children
- Retinal disease monitoring - when the cataract prevents adequate fundus examination
Pre-operative Evaluation
- Ocular assessment: Visual acuity, slit-lamp examination, IOP, dilated fundus examination
- Biometry: Axial length measurement (by A-scan ultrasound or optical biometry) and keratometry for IOL power calculation
- Pupil dilation: Ensure adequate mydriasis (> 6 mm) for good visualization
- Systemic assessment: Blood pressure, blood sugar; anticoagulants reviewed
Anaesthesia
| Type | Details |
|---|---|
| Topical | Proxymetacaine 0.5%, tetracaine 1% drops, or lidocaine 2% gel; most widely used today |
| Intracameral | Preservative-free lidocaine 0.2-1% (often combined as Mydrane - tropicamide 0.02% + phenylephrine 0.31% + lidocaine 1%) |
| Sub-Tenon | Blunt cannula injection; provides akinesia and analgesia |
| Peribulbar / Retrobulbar | Injections around/behind the globe; less commonly used now |
| General anaesthesia | Reserved for children, uncooperative patients |
Types of Cataract Surgery
1. Intracapsular Cataract Extraction (ICCE) - Obsolete
- Entire lens including its capsule is removed using a cryoprobe
- Requires large incision (~12 mm), no IOL in capsular bag possible
- Abandoned due to high complication rates
2. Extracapsular Cataract Extraction (ECCE)
- Large-incision ECCE: 8-10 mm limbal incision; anterior capsulotomy created, nucleus expressed after hydrodissection, cortex aspirated; posterior capsule retained to support IOL
- Requires suturing, can induce significant corneal astigmatism
- Manual Small-Incision Cataract Surgery (MSICS): Variant of ECCE; used in high-volume settings for dense cataracts, especially in developing countries; sutureless
3. Phacoemulsification (PHACO) - Current Gold Standard
Uses ultrasound energy (27-40 kHz) to emulsify the lens nucleus through a small incision (2.2-3.2 mm). Steps include:
- Preparation: Povidone-iodine 5% instillation, sterile draping, speculum placement
- Corneal incision: Main clear corneal incision (2.2-3.2 mm) + 1-2 side port incisions
- Continuous Curvilinear Capsulorhexis (CCC): Circular tear in the anterior capsule, performed with cystotome or capsule forceps
- Hydrodissection: Fluid injected under capsule to separate nucleus from cortex; a "hydrodissection wave" confirms success
- Nuclear emulsification techniques:
- Divide and conquer: Two perpendicular grooves sculpted, nucleus cracked into quadrants and emulsified one by one
- Phaco chop: Uses a chopper to mechanically divide nucleus; less ultrasound energy needed
- Stop and chop: Combination technique
- Cortex aspiration: Cortical matter engaged by vacuum, peeled centrally, and aspirated (automated or manual Simcoe cannula)
- IOL insertion: Capsular bag filled with viscoelastic; foldable IOL loaded in injector and unrolled inside the bag
- Wound closure: Hydro-sealing with saline; prophylactic intracameral antibiotic (e.g., cefuroxime) instilled
4. Femtosecond Laser-Assisted Cataract Surgery (FLACS)
- Laser performs corneal incisions, capsulorhexis, and lens fragmentation with extreme precision
- Reduces ultrasound energy use and may improve refractive outcomes
- Higher cost; no proven superiority in final visual outcomes over standard phaco
Intraocular Lenses (IOLs)
| Type | Feature |
|---|---|
| Monofocal | Fixed focus at one distance (usually distance); most commonly implanted |
| Multifocal / EDOF | Extended depth of focus; reduces spectacle dependence |
| Toric | Corrects pre-existing corneal astigmatism; must be aligned to correct axis |
| Accommodating | Attempt to mimic natural accommodation |
| Phakic IOL | Implanted without removing the natural lens (for refractive correction) |
IOL power is calculated using formulae (SRK/T, Holladay, Barrett Universal II) based on axial length and corneal curvature.
Complications
Intraoperative
| Complication | Notes |
|---|---|
| Posterior capsule rupture (PCR) | Most feared intraoperative complication; ~0.5-2% rate; may require anterior vitrectomy |
| Vitreous loss | Follows PCR; raises risk of endophthalmitis, CMO, retinal detachment |
| Zonular dehiscence | Especially in pseudoexfoliation, trauma, Marfan syndrome |
| Suprachoroidal haemorrhage | Rare (0.04% with phaco); expulsive if severe; stop surgery immediately and suture wound |
| Posterior dislocation of nucleus | Fragments fall into vitreous; requires pars plana vitrectomy |
Postoperative
| Complication | Notes |
|---|---|
| Endophthalmitis | ~0.03-0.05%; presents as severe pain, hypopyon, reduced vision; emergency - intravitreal antibiotics |
| Posterior Capsule Opacification (PCO) | Most common late complication ("after-cataract"); treated with Nd:YAG laser posterior capsulotomy |
| Corneal oedema | Endothelial cell loss; risk increased in Fuchs dystrophy |
| Cystoid Macular Oedema (CMO/Irvine-Gass syndrome) | Peaks at 4-6 weeks post-op; treated with topical NSAIDs/steroids |
| Retinal detachment | Risk ~0.5-1%; higher in myopes, vitreous loss cases |
| IOL dislocation | Into vitreous cavity; requires vitrectomy with repositioning or exchange |
| Refractive surprise | Biometry error; managed with spectacles, contact lenses, or IOL exchange |
Post-operative Care
- Topical antibiotics (e.g., moxifloxacin) and steroids (prednisolone 1%) for 4-6 weeks
- NSAIDs (ketorolac, diclofenac) to prevent CMO
- Avoid eye rubbing, swimming for 4 weeks
- Final spectacle prescription after 4-6 weeks (when refraction stabilises)
- Visual recovery typically within 24-48 hours for uncomplicated phacoemulsification
Visual Outcomes
Phacoemulsification delivers excellent results:
-
95% of patients achieve visual acuity of 6/12 or better
- Outcome depends on pre-existing ocular co-morbidities (glaucoma, AMD, diabetic retinopathy)
Sources: Kanski's Clinical Ophthalmology: A Systematic Approach, 10th Edition; Goldman-Cecil Medicine; Bailey & Love's Short Practice of Surgery, 28th Edition
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