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AC to Lens

Cataract Surgery

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Phacoemulsification

  • Piezoelectric crystals in the handpiece vibrate at ultrasonic frequencies to breakup the lens by various mechanisms

    • Jackhammer effect: physical striking of probe against lens
    • Cavitation via vacuum creation: implosion of micro-bubbles generating energy
    • Acoustic shock wave
    • Fluid impact

  • Pumps facilitate aspiration/vacuum flow

    • Peristaltic: using rollers to compress phaco tubing. Vacuum formation requires occlusion of the outflow line (needle tip)
    • Venturi: negative pressure in a vessel by fluid flow (compressed air) allows preset vacuum without needle occlusion

  • Other phacodynamic effects

    • Surge: sudden increase in aspiration flow rate immediately after occlusion of the probe due to release of negative pressure which builds in the tubing during occlusion. If the tubing has high compliance, it collapses under this negative pressure and then rebounds to its original position when the occlusion is removed. This suddenly increases vacuum and causes rapid aspiration of fluid out of the AC. It is decreased by low compliance tubing and lower flow rates.

Viscoelastic agents

  • Dispersive: eg. viscoat. Better coating ability therefore protect the endothelium better and are harder to remove from the eye.

    • Low molecular weight therefore do not causes as great an IOP spike if left behind

  • Cohesive: eg. those made from hyaluronic acid (provisc). More easily removed with higher molecular weight (clog the TM more).

Intraoperative floppy iris syndrome

  • Triad

    • Iris prolapse
    • Iris billowing/floppiness
    • Progressive miosis

  • Increased risk of PC rupture, dropped nucleus, vitreous prolapse and iris trauma

  • Associated with alpha1-adrenergic antagonists eg tamsulosin, doxazosin, alfuzosin, silodosin (also labetalol) and some antipsychotics eg chlorpromazine

Posterior capsule rupture

  • Risk factors

    • Surgeon inexperience
    • Smaller pupil
    • Pseudoexfoliation
    • Dense lens
    • Previous IVT (possible lens touch)
    • Posterior polar cataract
    • Previous ocular trauma

  • Overview of management steps

    • Do not withdraw phaco tip: keep irrigation on

    • Fill AC with dispersive viscoelastic

    • Slowly withdraw phaco tip: assess how to remove remaining lens matter

      • Only use phaco on very low-flow low-vacuum settings
      • Instead consider using the anterior vitrector

    • Refill with viscoelastic

    • Remove cortical material: use the vitrector on I/A cut

    • Thorough anterior vitrectomy:

      • Consider using triamcinolone to visualise vitreous
      • Use the vitrector on cut I/A mode

    • Refill with viscoelastic

    • Insert an appropriate IOL

      • Very small PC tear (ideally also round): an IOL in the bag may be possible
      • Intact anterior capsule: 3-piece sulcus lens +/- optic capture
      • No capsular support: AC lens or leave aphakic for later implantation

    • Suture the main wound

    • Intracameral miochol: may reveal vitreous via a peaked pupil needing further vitrectomy

    • Intracameral antibiotics

    • Consider suturing sideports

    • Post-operative acetazolamide

  • Dropped nuclear fragments require surgical removal (cp cortical material which will resorb). Nuclear fragments can be left for up to 3 weeks before vitrectomy without increasing the risk of CMO

Posterior capsular opacification

  • The most common complication after uneventful cataract surgery

  • 12% at 1 year, 28% at 5 years (lower rates in modern lenses)

  • Due to residual lens epithelial cells migrating across the PC and secreting a collagen matrix which contracts causing wrinkling and PCO

  • Risk factors

    • Younger patient

    • Previous intraocular inflammation

    • Poor cortical removal

    • Pseudoexfoliation syndrome

    • Type of IOL material: lower rates in acrylic (lowest) and silicone IOLs compared to PMMA or hydrogel IOLs

    • Lens design: lower rates in sharp edge IOLs compared to rounded edge (but square-edged IOLs are more associated with pseudophakic dysphotopsias: subjective distortions in the temporal visual field)

      • Hydrophobic, posteriorly angulated IOLSs reduce the risk

    • Larger capsulorhexis

Refractive surprise

  • College guidelines suggest a benchmark of 85% within 1 dioptre of intended outcome

  • Hypermetropic surprise

    • Previous unrecognised myopic refractive surgery eg LASIK (keratometry overestimates corneal power and underestimates IOL power)
    • Unrecognised staphyloma: axial length measurement is inaccurate
    • Axial myopia: axial length may be falsely elevated due to the signal travelling through the eye/vitreous for longer. Third-generation formulas may tend to underestimate the IOL power needed in such cases

  • Myopic surprise

    • Previous hyperopic refractive surgery
    • Higher than intended A constant for IOL
    • Steep corneas: eg. if average K value is >46
    • Flat corneas: eg. average K <42

Anterior chamber IOLs

  • Used after unintentional disruption of capsular support

  • Can be angle or iris supported

  • Angle supported: measured based on ‘white-to-white’

    • Take the horizontal W-W measurement and add 1mm (an insert the IOL horizontally)
    • Pupil distortion suggests the IOL is too large
    • Excess movement of the IOL suggests it is too small

  • A surgical PI should be performed

Brown McLean syndrome

  • Peripheral corneal oedema after cataract extraction
  • Spares the central cornea
  • Brown pigmentation and guttae of the underlying endothelium
  • No neovascularisation
  • Associated with long-term aphakia
  • Typically asymptomatic

Zonular insufficiency

  • Complicates multiple steps of cataract surgery

  • Phacodonesis may only be evident intraoperatively

  • Causes

    • Trauma
    • Prior intraocular surgery or IVT
    • Dense cataracts
    • High myopia: high AL and globe volume stretches and loosens zonules
    • Ectopia lentils
    • Coloboma
    • Pseudoexfoliation
    • Retinitis pigmentosa
    • Uveitis

  • Postoperatively can lead to lens decentration or subluxation: consider use of a capsular tension ring

Risk factors for post-op cystoid macular oedema

  • AC or sulcus IOL
  • Age
  • Diabetes mellitus
  • Topical latanoprost
  • uveitis

Risk factors for anterior capsular phimosis

  • Pseudoexfoliation
  • Loose zonules: trauma, Marfan’s
  • Small capsulorrhexis
  • Silicone IOLs
  • Plate haptic IOLs (cp. Three piece IOLs)

Risk factors for post-op corneal oedema

  • Prolonged phaco time
  • Phaco energy too close to the endothelium (or mechanical trauma to the endothelium)
  • Inflammation eg. from retained nuclear/cortical material
  • High IOP
  • Toxic anterior segment syndrome
  • Generally, if the peripheral cornea is clear then the oedema will settle as peripheral cell migrate to replace the central ones
    • If it persists at 3 months, then it is likely to be permanent

Lens-iris diaphragm retropulsion syndrome (LIDRS)

  • Reverse pupillary block

  • Iris bows posteriorly blocking flow to the posterior chamber, leading to iris stretch, high IOP and pain

  • Risk factors

    • High myopia
    • Deep AC
    • Floppy iris
    • Loss of vitreous support eg. post-vitrectomy

  • Management: lift the iris to relieve the block and equalise the pressure between the AC and PC. if noted post-operatively, a PI can be performed.

Capsular block syndrome

  • Capsular bag distension due to relatively opaque fluid accumulation between the IOL and the PC
  • Can occur intraoperatively, early post-op and late post-op.
  • Can cause myopic shift
  • Yag capsulotomy can allow egress of fluid
  • If any inflammation present, one should always consider late chronic endophthalmitis

Risk factors for post-occlusion surge

  • Increased tubing compliance
  • Decreased bottle height
  • Increased aspiration rate
  • Wound leaks

Risk factors for expulsive haemorrhage

  • Rupture of the short posterior ciliary arteries with suprachoroidal hemorrhage
  • Hypertension
  • Atherosclerosis
  • Tachycardia
  • Glaucoma
  • High myopia
  • Sudden decompression of the globe eg in large incision surgery such as ECCE

NICE guidelines on cataract surgery

  • Do not restrict access to cataract surgery on the basis of visual acuity

  • Use optical biometry

    • Use ultrasound biometry if optical not possible or inaccurate

  • Consider corneal topography if: abnormally flat/steep corneas, significant astigmatism, previous refractive surgery

  • Use Haigis or Hoffer Q if AL <22

  • Use Barrett Universal II if installed or SRK/T if AL 22-26

  • Use Haigis or SRK/T if AL >26

  • Do not offer multifocal IOLs

  • Offer monovision if patients already have it or anisometropia pre-op and would like to keep it

  • Record discussion about refractive outcome in patients notes

  • At least two members of team in theatre should have checked appropriateness of IOL choice

  • Only use femtosecond laser as part of an RCT

  • Consider bilateral simultaneous surgery if: low risk for ocular complications or GA needed but carries additional risks

  • Offer sub-Tenon’s or topical anaesthesia, or peribulbar if these are contraindicated

    • Do not use retrobulbar block (higher risk of complications)

  • Do not offer in-person first-day post-op review to patients after uncomplicated surgery

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