Update on Pterygium Therapy

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Update on Pterygium Therapy

• Jay C. Bradley, MD
• David L. McCartney, MD
• January Grand Rounds

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From the BCSC Basics

• Often bilateral
• Almost always situated at the nasal or temporal
  limbus within palpebral fissure
• Associated with prolonged UV exposure
• UV-B ? limbal stem cell p53 mutation ? ?
  apoptosis / ? TGF-? ? ? growth
• May be associated with dryness, inflammation, and
  exposure to wind and dust or other irritants
• Prevalence increases with proximity to equator
• Difficult to determine if race is independent
  risk factor due to confounding variables

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Albedo Hypothesis

• Researcher MT Coroneo (Australia)
• Pterygia occur secondary to albedo concentration
  in the anterior eye
• Light entering the temporal limbus at 90 degrees
  is concentrated onto the medial limbus
• Related to corneal curvature
• Explains predominance of medial pterygia
• Ophthalmic surg. 1990 Jan21(1)60-6.

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From BCSC Basics

• Encroaches on cornea in wing-like fashion
• Overlying epithelium often thinned, but can be
  hyperplastic or dysplastic
• Nearly always preceded by pingueculae
• Induces astigmatism (usually with-the-rule)
  proportional to size
• Excision indicated if persistent irritation,
  vision distortion, significant (gt 3-4 mm) and
  progressive growth toward visual axis, restricted
  ocular motility, and atypical appearance

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From the BCSC Basics

• Elastotic degeneration fragmentation and
  breakdown of stromal collagen
• Destruction of Bowmans layer by advancing
  fibrovascular tissue resulting in corneal scarring

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From BCSC Basics

• Recurrent pterygia lack elastotic degeneration
  and are more accurately classified as an
  exuberant granulation tissue response
• Stockers line a pigmented iron line in advance
  of pterygium

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Pterygium Excision

• Goal Achieve a normal, topographically smooth
  ocular surface
• Dissect a smooth plane toward the limbus
• Some surgeons prefer specialized blunt pterygium
  blades (Tooke or Gills) while others prefer sharp
  blades
• Preferable to dissect down to bare sclera at
  limbus
• Bare sclera remove loose Tenons layer and
  leave episcleral vessels intact

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• Some surgeons avoid medial dissection to avoid
  bleeding from trauma to adjacent muscle tissue
  while other remove excessive fibrovascular tissue
  medially
• Light thermal cautery is applied for hemostasis

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Pterygium Recurrence

• Growth of fibrovascular tissue across the limbus
  onto cornea after initial removal
• Excludes persistence of deeper corneal vessels
  and scarring which may remain even after adequate
  removal
• Bunching of conjunctiva and formation of parallel
  loops of vessels, which aim almost like an
  arrowhead at the limbus, usually denotes a
  conjunctival recurrence

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Proposed Recurrence Grading System

• Grade 1 normal appearing operative site
• Grade 2 fine episcleral vessels in the site
  extending to the limbus
• Grade 3 additional fibrous tissues in site
• Grade 4 actual corneal recurrence

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Wound Closure Options

• Bare sclera
• Simple closure
• Sliding flap
• Rotational flap
• Conjunctival graft

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Bare Sclera Closure

• No sutures or fine, absorbable sutures used to
  appose conjunctiva to superficial sclera in front
  of rectus tendon insertion
• Leaves area of bare sclera
• Relatively high recurrence rate with variable
  techniques of 5 68 with primary / 35 82
  with recurrent)

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Simple Closure

• Free edges of conjunctiva secured together
• Effective only if defect is very small
• Can be used for pingueculae removal
• Reported recurrence rates from 45 69 (one
  report of barest sclera, N800 of 2 )
• Few complications (dellen)

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Sliding Flap Closure

• An L-shaped incision is made adjacent to the
  wound to allow conjunctival flap to slide into
  place
• Reported recurrence rates from 0.75 5.6
  (poorly designed, retrospective)
• Few complications (flap retraction / cyst
  formation)

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Rotational Flap Closure

• A U-shaped incision is made adjacent to the wound
  to form tongue of conjunctiva that is rotated
  into place
• Reported recurrence of 4
• Few complications

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Conjunctival Graft Closure

• A free graft, usually from superior bulbar
  conjunctiva, is excised to correspond to wound
  and is then moved and sutured into place
• Can be performed with inferior conjunctiva to
  preserve superior conjunctiva

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Conjunctival Graft Closure

• Harvested tissue should be approximately 0.5 1
  mm larger than defect
• Most important aspect in harvesting is to
  procure conjunctival tissue with only minimal or
  no Tenons included
• Graft is transferred to recipient bed and secured
  with or without incorporating episclera
• Some surgeons harvest limbal stem cells along
  with graft and orient graft to place stem cells
  adjacent to site of corneal lesion excision

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Conjunctival Graft Closure

• Topical antibiotic-corticosteroid ointment used
  for 4 6 weeks post-operatively until
  inflammation subsides (compliance with this
  regimen decreases recurrence)
• Used when extensive damage or destruction of
  limbal epithelial stem cells is NOT present
• Reduces recurrence to 2 5 (up to 40 in some
  reports)
• Ameliorates the restriction of extraocular muscle
  function

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Limbal Conjunctival Autograft

• Reported recurrence rates are variable (between 0
  40 )
• Few complications
• Further prospective studies in primary and
  recurrent pterygia are needed

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Lamellar Corneal Transplant

• Wound closed with piece of lamellar sclera or
  cornea
• Reported recurrence rates of 6 30
• Not performed often
• Can be used in conjunction with AMT for multiply
  recurrent pterygia with corneal scarring and
  limited available conjunctiva
• Method involves increased surgical complexity,
  the requirement of donor tissue, and risk of
  infectious disease transmission

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Adjunctive Beta Irradiation

• Most common dosage is 15 Gy in single or divided
  doses
• Reasonably acceptable recurrence rates (from 0
  50 with bare sclera or simple conj closure)
• Risk of corneal or scleral necrosis and
  endophthalmitis

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Adjunctive Thiotepa

• Most common dose is 12000 thiotepa given up to
  every 3 hours for approx. 6 weeks
• Usually used with bare sclera method
• Low reported recurrence rates of 0 16 (poor
  study quality)
• Minimal complications (2 cases of scleral
  thinning)

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Adjunctive Mitomycin C

• Used with bare sclera or conj closure
• Most common dose is 0.02 applied for 3 min
  during surgery
• Risk of aseptic scleral necrosis / perforation
  and infectious sclerokeratitis
• Used more often for recurrent cases
• Rate of recurrence between 3 25 for intra-op
  / 5 54 for post-op with most studies showing
  lt 10 recurrence

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Amniotic Membrane Graft Closure

• Useful for very large conjunctival defects as in
  primary double-headed pterygium or to preserve
  superior conjunctiva for future glaucoma
  surgeries
• Requires costly donor tissue
• Reported recurrence rate between 3 64 for
  primary cases and 0 37.5 for recurrent cases

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Other Methods

• Pterygium head transplantation
• Split skin grafts
• Ruthenium adjunctive therapy
• Laser or thermal cautery
• Excimer laser treatment
• PDT (one report, N 10)
• Intraoperative doxorubicin / daunorubicin
• 5-FU
• Serum-free derived cultivated conjunctival graft
• Recombinant epidermal growth factor

Few studies with limited numbers of patients,
poor follow-up, and variable recurrence rates
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Primary Pterygium Metanalysis

• Includes 5 studies with N290 (BSMito257/CAG33)
  
• Comparison Odds Ratio 95 CI
• Bare sclera mito C 251 9.0 66.7
• Bare sclera CAG 61 1.8 18.8

Sanchez-Thorin JC et al. Br J Ophthalmol
82661-5, 1998.
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Conclusions

• There is no clear-cut superior single treatment
• Bare scleral and simple conjunctival closure
  without adjunctive therapy have relatively high
  but variable recurrence rates
• Use of beta irradiation and antimetabolites can
  be used with appropriate caution
• Conjunctival transplants and flaps appear to have
  overall lower rate of recurrence but require more
  surgical time and unnecessary conj destruction
• Other treatment options need further adequate
  study prior to widespread implementation

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Any Questions?