Glaucoma Surgery

Trabeculectomy

Indications

• No absolute indications: care should be individualised
• Failure of maximal medical therapy: evidence of progressive optic neuropathy despite medical therapy or laser (eg. despite PIs in PACG)
• High risk of progression
• Patient intolerant of topical therapy due to side effects or compliance
• Other scenarios
  • Young patient with good visual potential
  • Only eye
  • Family history of severe disease

Technique

• Peribulbar plus traction suture
• Limbal vs fornix-based conjunctival flap: see table comparison
• Dissect Tenon’s with scissors
• Outline scleral flap with diathermy then cut with beaver blade and dissect with crescent blade to surgical limbus (2mm band between Bowman’s and scleral spur)
• Apply MMC under Tenon’s for 1-3 minutes
• Distant paracentesis
• Sclerostomy: enter AC through flap then excise portion of sclera with scissors
• Create peripheral iridectomy to prevent obstruction of sclerostomy
• Suture flap with 10.0 nylon
• Reform AC and check for leakage
• Suture conj with 10.0 nylon (or vicryl?)

Augmented or not?

• Risk factors for scarring

  • Age under 40
  • Ethnicity: afro-caribbean, Indian
  • Previous conjunctiva-involving surgery
  • Neovascular, aphakic, inflammatory or traumatic glaucoma
  • Chronic inflammation
  • Numerous topical therapies

• Standard trab

  • Low risk of scarring

• Augmented trabeculectomy

  • 5-FU: if moderate risk of scarring. Preferred if previous conjunctival surgery or planned combined phaco-trab
  • MMC: if higher risk of scarring, chronic inflammation, or previous failed trab

• Antifibrotics permit modulation of fibrosis and scarring which can close off a trab

  • Their use is titrated to the predicted risk of scarring as above
  • If VERY high risk of scarring, consider a seton procedure (eg. tube)

• 5-FU: inhibits DNA synthesis and RNA function

• MMC: alkylates DNA, inhibits DNA and RNA synthesis

• Complications of antifibrotics

  • Corneal erosions
  • Corneal decompensation
  • Limbal stem cell failure
  • Wound leak
  • Bleb leak
  • Hypotony
  • Scleritis
  • Cataract
  • Blebitis
  • Endophthalmitis

Complications

• Intraoperative

  • Conj/scleral flap damage eg. button-hole
  • Bleeding including suprachoroidal/subconjunctival haemorrhage and hyphaema
  • Vitreous loss
  • Wound leak

• Early post-operative

  • Shallow AC. Differential

    • Wound leak: Seidel’s positive, low IOP, flat bleb. Likely to resolve within 48 hours and a BCL can be used and topical steroids stopped temporarily. Surgical resuturing may be needed.
    • Ciliary body shutdown: low IOP, flat bleb, seidel negative. Managed with topical steroids and the AC may need reforming with viscoelastic
    • Overfiltration: low IOP, extensive bleb. May need to resuture flap
    • Pupillary block: high IOP, non-patent PI, flat bleb
    • Malignant glaucoma: high IOP, patent PI, flat bleb
    • Suprachoroidal haemorrhage: variable IOP, variable bleb

  • Hypotony

    • IOP <6 with a flat AC, choroidal detachment/suprachoroidal hemorrhage, hypotonous maculopathy, corneal oedema
    • Management: intensive topical steroids, cycloplegia/mydriasis, consider further surgery to re-form AC and drain choroidal effusions
    • Lens-corneal touch carries risk of corneal decompensation
    • Risk of hypotonous maculopathy is highest in young myopic patients undergoing first trabeculectomy (even higher is antifibrotics used)

  • High IOP

    • Pupillary block: incomplete or blocked PI
    • Malignant glaucoma aka aqueous misdirection
    • Filtration failure: obstruction of the sclerostomy

  • Infection

    • Blebitis: painful red eye with discharge. Milky bleb with pus. Requires swab and AC tap, intensive topical antibiotics, systemic ciprofloxacin +/- vitreous tap and inject.
    • Endophthalmitis

  • Visual loss, ‘wipe-out’ of remaining VF

    • Avoid adrenergics in local anaesthetic preparations and minimise periods of systemic hypotension in GA

  • Hyphaema

• Late postoperative complications

  • Filtration failure:

    • Early: blockage by ocular structure (eg. iris) or blood/viscoelastic
    • Late: subconjunctival fibrosis (increased risk with limbal based flaps) leads to a poorly filtering bleb
    • Needling revision with subconj antifibrotic: usually done at 6 weeks
    • Ocular compression/massage
    • Release of sutures eg. laser suture lysis usually done at 1-3 weeks

  • Leaky bleb: consider BCL, autologous blood injection, compression sutures or bleb revision

  • Infection: blebitis. Most common organisms (in order of frequency)

    • Streptococcus
    • Haemophilus influenzae
    • Staphylococcus epidermidis
    • Gram-negative species

  • Visual loss: eg. post-operative lens opacities

  • Ptosis

Indications for primary tube surgery (instead of trab)

• Uveitic glaucoma
• Aphakic glaucoma
• Neovascular glaucoma
• Scarred conjunctiva
• Those at risk of hypotonia eg. high myopes
• (but also an option after failed trab)

Drainage devices

• Divert aqueous from the AC to an external reservoir/fibrous capsule which forms after 4-6 weeks

• Non-valved

  • Molteno
  • Baerveldt

• Valved/flow-restricted: only unidirectional flow from AC to subconjunctival space

  • Ahmed
  • Krupin

• Patient selection (see indications above)

  • Complex glaucoma
  • Previous failed trabeculectomy
  • Assess for mobile conj
  • Assess for iris neovascularization: may need anti-VEGF
  • Assess AC depth: tube must be placed to avoid iris or cornea contact
  • Gonioscopy to locate PAS which may interfere with tube

Non-valved vs valved

• Non-valved

  • Easier to place with more predictable early post-op IOP
  • Valve is occluded with a stent or ligature so post-op IOP is unchanged (therefore pre-op meds need to continue until capsule forms)

• Valved

  • Require less post-op care ie. better for patients with poor compliance
  • Provide more immediate IOP control
  • Lower rate of hypotony

• Typically placed under peribulbar or retrobulbar local anaesthetic

Complications

• Early: similar to trabeculectomy

  • Flat AC
  • Hypotony: more common with non-valved devices. Due to inflammation, wound leak, incomplete occlusion of tube. Typically can be managed conservatively if the AC is formed. Choroidal effusions can be managed with topical steroids and cycloplegia
  • Suprachoroidal haemorrhage
  • Hyphaema, especially in neovascular glaucoma. Preoperative anti-VEGF reduces the risk

• Valve malfunction

  • Corneal decompensation: eg. from tube touch of the endothelium
  • Tube block
  • Tube erosion: can occur from overlying conjunctival melt near the limbus

• Endophthalmitis: more common in children

• Overhanging bleb: chronic Dellen may form

• Strabismus: more common with inferiorly placed implants

• Hypertensive phase: more common with valved implants. Can be managed with massage, topical therapy, bleb needling with 5-FU and surgical excision