Cataract Surgery

Overview

Surgical Techniques

1. Intracapsular Cataract Extraction (ICCE) - Historical

2. Extracapsular Cataract Extraction (ECCE)

3. Manual Small-Incision Cataract Surgery (MSICS)

• Kanski's Clinical Ophthalmology, p. 308

4. Phacoemulsification (Standard Modern Technique)

Fig. 10.14C: Hydrodissection during phacoemulsification (Kanski's Clinical Ophthalmology)

Phacodynamics

• Bottle height: Controls infusion flow and intraocular pressure (IOP) stability; flow is proportional to bottle height
• Aspiration flow rate (AFR): Volume of fluid removed (ml/min); high AFR attracts lens material to the phaco tip faster but reduces effective power - trainee surgeons should use lower AFR
• Vacuum (mmHg): Generated when the pump attempts to aspirate during occlusion; determines how tightly material is held by the tip; lower vacuum slows events, reduces surge risk
• Post-occlusion surge: When tip occlusion breaks, pent-up energy causes a sudden outflow increase - can cause capsular rupture; suppressed by modern phaco machines

Pump Types

• Peristaltic (flow) pump: Pulls fluid by compressing tubing; vacuum builds only after tip occlusion, then stops at preset level
• Venturi (vacuum) pump: Driven by compressed gas, generating vacuum directly and immediately; faster vacuum response

Surgical Steps

1. Preparation: Topical anaesthetic, 5% povidone-iodine instilled into conjunctival sac (left for minimum 3 minutes), eyelid cleaning, draping to exclude lashes
2. Incisions: Side port ~60° from main incision (right-handed surgeon); viscoelastic injected into AC; main corneal incision sited on steepest corneal axis
3. Capsulorhexis: Continuous curvilinear capsulorhexis with cystotome or capsule forceps
4. Hydrodissection: Blunt cannula inserted under capsulorhexis edge; fluid injected to separate nucleus/cortex from capsule; a hydrodissection wave confirms success
5. Nucleus removal - three main techniques:
   • Divide and conquer: Two perpendicular grooves sculpted, nucleus cracked into quadrants, each emulsified and aspirated - safe, widely used
   • Phaco chop (horizontal): Blunt-tipped chopper passed under capsule to equator, nucleus split into pieces - faster, lower total phaco energy, longer learning curve
   • Phaco chop (vertical): Pointed-tip chopper, does not pass beyond capsulorhexis
   • Stop and chop: Combination technique
6. Cortex removal: Cortical segments aspirated using vacuum; automated coaxial, bimanual automated, or manual (Simcoe cannula) methods
7. IOL insertion: Capsular bag filled with cohesive viscoelastic; loaded injector cartridge introduced through main wound; IOL deployed into capsular bag

5. Femtosecond Laser-Assisted Cataract Surgery (FLACS)

Preoperative Evaluation

• Myocardial infarction within 30 days (uncomplicated) or 60 days (complicated)
• PCI within 14 days (no stent) or 30 days (with stent)
• Significant arrhythmias with haemodynamic compromise (VT, AF with rapid rates)
• Decompensated heart failure
• Active pneumonia, PE in past 3 months
• Stroke/TIA within 3 months, uncontrolled epilepsy, raised ICP
• Malignant hypertension
• DKA or HHS

• Elevated BP or hyperglycaemia on the day of surgery does NOT generally warrant delay
• Antiplatelet and anticoagulant medications should NOT be stopped - bleeding risk is very low (<0.4%)
• Routine preoperative medical testing (including cardiac risk assessment) is NOT recommended
• New-onset asymptomatic AF on day of surgery - surgery can proceed; refer for early outpatient management
• Miller's Anesthesia, p. 9724-9725

Biometry and IOL Power Calculation

• Keratometry: Measures anterior corneal curvature (steepest and flattest meridians, in dioptres or mm)
• Optical coherence biometry (preferred): Non-contact axial length measurement using partial coherence interferometry (e.g. IOLMaster); also measures keratometry, anterior chamber depth, lens thickness, white-to-white diameter
• Ultrasound biometry (A-scan): Used when OCB is not possible (e.g. dense cataract blocking the signal)
• IOL formulas: Haigis, SRK/T, Barrett Universal II, Kane formula - selection depends on axial length

IOL Types

Anesthesia

• Topical anaesthesia: Most common; drops only; no block; suitable for cooperative patients
• Peribulbar block: Local anaesthetic injected outside the muscle cone; good akinesia and analgesia
• Retrobulbar block: Injected inside the muscle cone; more complete akinesia but higher risk (globe perforation, retrobulbar haemorrhage, brainstem anaesthesia)
• Sub-Tenon block: Low-pressure cannula technique; relatively safe
• MAC (Monitored Anaesthesia Care): Sedation with local/topical; avoids GA risks
• General anaesthesia: Reserved for uncooperative or paediatric patients; avoid succinylcholine (raises IOP transiently)

Informed Consent: Risk Discussion

• ~1 in 1,000 operations: eye left with little or no sight
• ~1 in 10,000: loss of the eye

• Periocular ecchymosis
• Allergy to eye drops
• IOP spike
• Iridocyclitis
• Posterior capsular opacification (PCO)

• Posterior capsular rupture with vitreous loss: <1% experienced surgeons, higher for trainees
• Zonular dehiscence
• Dropped nucleus (~0.2%)
• Cystoid macular oedema (CMO/Irvine-Gass syndrome)
• Corneal decompensation
• Unexpected refractive outcome
• Retinal detachment (<1%)
• IOL dislocation
• Persistent ptosis or diplopia

• Endophthalmitis (0.1%)
• Suprachoroidal haemorrhage (0.04%)

Complications in Detail

Posterior Capsular Rupture (Intraoperative)

Acute Postoperative Endophthalmitis

• Incidence: ~0.1%
• Pathogens: ~90% Gram-positive (most commonly S. epidermidis), ~10% Gram-negative
• Risk factors: posterior capsule rupture, prolonged surgery, clear corneal sutureless incision, temporal incision, wound leak, delayed postoperative antibiotics, diabetes, adnexal disease
• Prophylaxis: Intracameral cefuroxime 1 mg in 0.1 ml at end of surgery (or moxifloxacin 0.5 mg/0.1 ml if unavailable); avoid intracameral vancomycin (risk of haemorrhagic occlusive retinal vasculitis)
• Treatment: Intravitreal ceftazidime 2 mg/0.1 ml + vancomycin 2 mg/0.1 ml immediately after obtaining culture specimens; oral moxifloxacin 400 mg/day x10 days; oral prednisolone 1 mg/kg/day (after 12-24 hours, once fungal infection excluded)

Posterior Capsular Opacification (PCO)

• Most common late complication
• Caused by migration and proliferation of residual lens epithelial cells
• Presents as gradual visual decline weeks to months postoperatively
• Types: vacuolated/pearl type (Elschnig pearls), fibrotic
• Treatment: Nd:YAG laser posterior capsulotomy - creates a clear central opening in the opacified capsule; outpatient, quick, effective

Cystoid Macular Oedema (Irvine-Gass Syndrome)

• Peak incidence 6-10 weeks post-surgery
• Incidence increases with surgical complications
• Treated with topical NSAIDs ± steroids

Immediate Sequential vs. Delayed Sequential Bilateral Cataract Surgery (ISBCS vs. DSBCS)

Postoperative Care

• Pain is usually short-lived; persistent pain may indicate choroidal effusion, suprachoroidal haemorrhage, or aqueous misdirection syndrome
• Topical antibiotics and steroids in the first weeks
• IOP monitored on day 1 (risk of acute IOP spike from retained viscoelastic)
• Watch for signs of endophthalmitis: pain, redness, reduced vision, hypopyon within 2-7 days postoperatively

Testing Near and Far Vision

Part 1: Distance (Far) Visual Acuity

What it measures

The Snellen Chart

Fig 1.1 Snellen visual acuity chart (Kanski's Clinical Ophthalmology)

1. Place the patient 6 metres (20 feet) from the chart (or use a mirror system to simulate this in a smaller room)
2. The room should be well lit
3. Test the worse eye first, with the other eye firmly occluded
4. The patient should wear their usual distance glasses or contact lenses if they have them
5. Push the patient to read every letter possible, even if uncertain
6. Record the smallest line the patient can read correctly

• Written as a fraction: distance tested / distance at which a person with normal vision reads that line
• Example: 6/6 (20/20) = normal. Patient reads at 6 m what a normal person reads at 6 m
• 6/12 (20/40) = patient reads at 6 m what a normal person reads at 12 m (reduced vision)
• 6/60 (20/200) = only the top letter visible - significantly reduced

• Unaided (uncorrected) VA - without glasses
• Best-corrected VA (BCVA) - with optimal spectacle correction

Pinhole Test

Fig 1.2 Pinhole occluder (Kanski's Clinical Ophthalmology)

• VA improves with pinhole → vision loss is due to uncorrected refractive error (myopia, hyperopia, astigmatism) or media opacity (e.g. cataract)
• VA does not improve (or worsens) with pinhole → vision loss is likely due to a retinal, macular, or neurological cause
• Note: In macular disease and posterior lens opacities, pinhole VA may actually be worse than with spectacle correction
• Kanski's Clinical Ophthalmology, p. 16

When vision is too poor for the Snellen chart

Alternative Distance Charts

• Tumbling E / Illiterate E chart: Patient indicates the direction the letter "E" is pointing (up/down/left/right) - used for illiterate patients or children >3.5 years
• Landolt C chart: Patient identifies the gap position in a broken ring - used internationally
• Numbers chart: For patients who know numbers but not letters
• HOTV chart (children): Wall chart with only H, O, T, V; child matches to a handheld board - suitable for ages 3-5 years
• Allen card test (very young children): Flashcards with 7 simple pictures; tested at varying distances; recorded as e.g. 15/30 (equivalent to 20/40)
• Textbook of Family Medicine, 9th ed.

LogMAR and ETDRS Charts (Research/Clinical Standard)

Figure 12-1A/B: Snellen chart and Jaeger card (Adams & Victor's Principles of Neurology)

• ETDRS chart (Early Treatment Diabetic Retinopathy Study): Uses balanced rows of Sloan optotypes, equal numbers of letters per row (controls for "crowding"), more accurate and reproducible than Snellen
• Tested at 4 metres

• Kanski's Clinical Ophthalmology, p. 17

Part 2: Near Vision Testing

Purpose

Jaeger Near Vision Card

1. Hold the Jaeger card at 14-16 inches (35-40 cm) from the eyes - a comfortable reading distance - or ask the patient to hold it where they normally read
2. Measure and record the exact distance used
3. Test each eye separately with the other occluded
4. Patient wears reading glasses if they have them
5. Record the smallest print size the patient can read

• Adams & Victor's Principles of Neurology, 12th ed., p. 251

Other Near Vision Charts

• LogMAR near charts: More standardised; text size described in M-notation (e.g. 1M = standard newspaper print at 40 cm)
• ETDRS near version: Same optotypes as distance ETDRS chart, used at a fixed distance
• Reading test types (test-type book): Book held at comfortable reading distance; actual distance measured and recorded
• Kanski's Clinical Ophthalmology, p. 17

Summary: Key Differences

General Rules for All Visual Acuity Testing

1. Always test each eye separately - occlude the other eye completely
2. Test worse eye first so the better eye result doesn't bias the patient's confidence
3. Wear the appropriate correction (distance glasses for far, reading glasses for near)
4. Encourage the patient to read every letter even if uncertain - guessing correctly still counts
5. Record precisely: note whether VA is unaided, with correction, or with pinhole
6. Binocular VA (both eyes open) is usually slightly better than the better monocular VA and is sometimes recorded separately