UPDATE ON GLAUCOMA SURGERY

     John Grigg
     Senior Lecturer
     University of Sydney
     Sydney Eye Hospital
     Children's Hospital at Westmead
     johng@eye.usyd.edu.au
 
Glaucoma Surgery - What's New?
 

  • Trabeculectomy

    • Antimetabolites
    • Releasable sutures
    • Wound healing

 
Role of post-operative wound healing
 

  • Patients requiring glaucoma surgery are often at high risk for failure
  • Post-operative healing is the main determinant of failure and final IOP
  • Early post-operative intervention to modulate wound healing is crucial
 
Modulation of wound healing
 

  • Pre-op

    • Identification of high risk
      - Youth, previous surgery, Afro-Caribbean, topical medications, rubeosis, uveitis, diabetes
    • Suppression of inflammation eg uveitis

  • Intraoperatively

    • Application of antimetabolites
    • Surgical technique

  • Post-op

    • Anti-inflammatory agents (steroids, NSAIDs)
    • Antimetabolites - 5FU
    • Releasable sutures / laser suture lysis
    • Needling

Post-operative healing is a major determinant of failure and final IOP

 
Mitomycin C
 

  • potent antifibrotic agent
  • antibiotic antimetabolite isolated from Streptomyces caespitosus
  • effects are irreversible
    - alkylating agent through irreversible covalent bonding with DNA

 
5-Fluorouracil
 

  • fluorinated pyrimidine analogue, mimics uracil
  • affects DNA synthesis phase (S-phase) of the cell cycle
  • 5-FU is a Competitive Inhibitor of Thymidylate Synthetase

 
Trabeculectomy: Starting
 

  • 7/O vicryl corneal traction sutures
    - prevents conj damage

  • Site selection
    - superior temporal or nasal
    - facilities large posterior dissection between the recti muscles in either quadrant
    - avoid 12 O'clock initially facilitates a repeat if required!

  • Conjunctival dissection
    - Fornix based flap
    - precise dissection conj from limbus
    - dissect tenons from its broad insertion
    - large dissection in the quadrant

 
Trabeculectomy - Traction sutures and Peritomy
 
 
Antimetabolite selection
 

  • Identification of high risk
    - Youth, previous surgery, Afro-Caribbean, topical medications, rubeosis, uveitis, diabetes

  • Mitomycin C for high risk

  • Dose MMC
    - 0.5mg/ml duration 3 mins
    - shorter application time if thin tenons

  • 5-Fluorouracil
    - use in medium risk in practice everyone else
    - 5mg/0.1 mls for 3 mins

 
Application of antimetabolite
 
  • Antimetabolite application

    • 5-Fluorouracil
      - 3 mins 5mg/0.1mls

    • Mitomycin C
      - 0.5mg/ml
      - 3 mins or titrate for response

  • Apply to large surface area and posteriorly

  • Avoid conjunctival cut edge

  • Conjunctival clamp to hold tissues


    • Antimetabolite Application     Play Video   Download Video

 
Scleral Flap Dissection
 
  • Triangular flap
  • Commence dissection posterior to limbus to reduce chance leak around "the edge of flap"
  • Crescent knife to undermine edges of flap and into cornea to create pentagon final shape → direct flow posteriorly


    • Trab Flap Dissection     Play Video   Download Video

 
Trabecular Block Removal
 
 
Peripheral Iridectomy
 
  • Perform with one cut if possible
  • Irrigate under flap into AC to wash away pigment and reform AC


    • Peripheral Iridectomy     Play Video   Download Video

 
Trabeculectomy Technique - Releasable Sutures
 
  • Releasable sutures gives control of post-op course to surgeon
  • Aim to close flap tightly
  • Number of sutures used depends on case. Children need more cf adults
  • Day 1 IOP is similar to pre-op level

     


    • Releasable Sutures 1     Play Video   Download Video
    • Releasable Sutures 2     Play Video   Download Video

 
Conjunctival Closure - Wing Anchor Sutures
 
  • 10/O nylon
  • Wing slip knots
  • Create tight tension line across limbus


    • Anchor Sutures     Play Video   Download Video

 
Conjunctival Closure
 
  • 2 horizontal mattress sutures to compress conjunctival to sclera

    • long intracorneal bite
    • bite between conjunctiva and sclera exiting through tension line
    • re-enter conj through tension line adjacent to origin of suture
    • tie with slip knot to achieve tension
    • suture passes under releasable suture loop


    • Conjunctival Closure 1     Play Video   Download Video

     

  • Another case showing closure


    • Conjunctival Closure 2     Play Video   Download Video

 
Post-op Care
 
  • Post-operative management in most cases will have a significant influence on the final result

  • Requires close monitoring of:

    • wound healing response
      • releasable sutures
      • antimetabolites
    • flat anterior chambers

 
Protocol for Post-operative Management of Trabeculectomy
 
  • Stepwise removal of sutures/massage of bleb depending on IOP

  • Releasable suture removal effective day 2 - 10

  • Maximum bleb wound healing Day 7-21
    - longer in children

  • Bleb function assessed to determine:
    - modulation of topical therapy
    - application of post-op 5-FU injections

 
Early Post-operative Intervention to Modulate Wound Healing
 
  • Assessment of bleb inflammation and function
  • Effect of early intervention to change day 4 (left) post-op into outcome (right) at day 30


 
Bleb Morphology Assessment - Vascularity
 


    0   No vessels (pale bleb)
    1   Vessels = surrounding conjunctiva

    2   Moderate, increased vascularity (congestion,
    numerous vessels - some corkscrew)
    3   Severe increased vascularity (congestion,
    numerous vessels, many corkscrews)

 
Bleb Morphology Assessment
 
  • Microcystic changes

    • 0 - No microcysts
    • 1 - Microcysts in 1/3 of the filtering bleb
    • 2 - Microcysts in 2/3 of the filtering bleb
    • 3 - Microcysts in 3/3 of the filtering bleb

  • Encapsulation and demarcation of the bleb
 
Supplemental Post-op Anti-inflammatory Protocol
 
  • Grade 2 vascularity or increased IOP

    • Steroids ↑ 8 times / day
    • 5 FU superior or adjacent to the bleb
      • Maximum 7 doses in 10 days

  • Bleb encapsulation - needling with 5-FU

 
Clinical Cases: Highlighting Effects of Timely Wound Healing Intervention

 
Oral and Topical steroids
 
  • 39 yo female: JCA & uveitic glaucoma


    IOP 32 → MMC Trab
    Grade 2 vascularity

    5FU * 4 (day 14 -21)
    Vascularity 1; IOP 10

 
Post-operative 5-FU and Topical Steroids
 
  • 14 yo male: congenital rubella, aphakic glaucoma


    IOP 27 → MMC Trab
    Grade 3 vascularity - 5FU * 7

    Grade 2 vascularity
    Grade 1 vascularity IOP 14

 
Post-operative Steroids
 
  • 68 yo female: End stage NTG


    12 mmHg → 5FU Trab
    Grade 2 vasc ↑ topical steroids

    Bleb now diffuse
    IOP @ 6 months 7 mmHg

 
Trabeculectomy Outcome
 
  • Success up to 90-95% but some long-term failure