Corneal Iron Ring After Hyperopic LASIK

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Corneal Iron Ring After Hyperopic LASIK

• Grand Rounds April 2005
• Jay C. Bradley, MD
• David L. McCartney, MD

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Report of Case

• 56 year old male
• Pre-operative refraction
• 6.00 2.50 x 7
• 6.00 1.75 x 165
• Pre-operative pachymetry
• OD 516 µm
• OS 525 µm

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Operative Summary (2001)

• LADARVision 4000
• Laser-assisted in situ keratomileusis
• Blend Radius 1.50 mm
• Zone Size 6.00 mm
• Ablation depth OD 91.0 microns
• OS 90.8 microns
• No flap or ablation complications

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Follow-up (2004)

• Returns to clinic with complaints of decreased
  near vision OU
• Does not use distance Rx
• Normal exam except for trace NSC OU and prominent
  corneal iron ring OU ( 5 mm diameter)
• Patient given Rx for reading glasses

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Corneal Iron Ring Photo
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Prior Reports of Corneal Iron Ring After
Hyperopic LASIK

• Ozdamar A et al. Cornea. 1999 Mar 18(2)243-5.
• 3 patients with pre-op spherical equivalent
  refraction of 3.37 to 6.50
• Paracentral iron ring OU at 6 7 months after
  surgery
• Localized to outside border of central steep zone
• No change in ring at 1 year follow-up

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Prior Reports of Corneal Iron Ring After
Hyperopic LASIK

• Probst LE et al. JCRS. 1999 May 25868-870.
• 1 patient with pre-op Rx of 7.00 1.50 x 153 OD
  and 7.50 1.50 x 165 OS
• Paracentral corneal iron ring OU at 6 months
  after surgery (5 mm diameter)
• 6.0 mm optical zone with 9.5 mm blend zone
• Ring corresponded to base of hyperopic ablation
  on corneal topography
• Increased mean pre-operative SE and ablation
  depth associated with deposition

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Histology

• Hemosiderin deposition in basal corneal
  epithelial cells
• Iron deposits when there is an abrupt change in
  corneal surface curvature in area of diminished
  tear flow and hydrodynamic stasis

(Hyperopic PRK)
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Pathogenesis Tear-pool hypothesis

• Proposed by Gass (1964)
• Sequestered iron in the tear film is
  preferentially deposited in areas of the cornea
  with pooling of the tear film
• Explains Hudson-Stahli lines corresponding to the
  lid position at rest
• Low iron in tears, protective effect of mucus,
  and occurrence of iron lines in eyes without
  tears question this theory

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Pathogenesis Basal-Cell-Migration Theory

• Proposed by Rose and Lavin (1987)
• Abrasive lid action on corneal surface induces
  enhanced mitotic activity
• Dividing, nonmigrating, basal cells become mature
  and accumulate iron

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Pathogenesis Tear Desiccation Hypothesis

• Proposed by Assil (1993)
• Iron deposits occur in areas of initial tear
  breakup

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Pathogenesis Senescent Basal Cell Hypothesis

• Proposed by Assil (1993)
• Iron accumulates in the epithelial cells where
  there are diminished rates of cell turnover

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Iron Lines Associated with Rx / Tx Corneal
Procedures

• Arcuate along anterior suture border after PK
• Lamellar keratoplasty
• Ring adjacent to margin of donor lenticule after
  epikeratophakia
• Central stellate pattern after RK ( 80 )
• Inferior line or midperipheral arcuate after
  intrastromal corneal ring segment (ICRS)
  placement
• Central line after uneventful PRK (myopic and
  hyperopic)
• Small central ring associated with steep central
  islands after PRK
• Myopic and hyperopic LASIK
• Overnight orthokeratology
• Conductive keratoplasty

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Iron ring associated with overnight ortho-K
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Other Corneal Iron Lines

• Fleischer ring
• Associated with keratoconus
• First reported in 1906
• Partial or complete ring encircling base of cone
• Yellowish to dark brown
• Best seen with cobalt blue light

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Other Corneal Iron Lines

• Hudson-Stähli
• Iron line along lower third of cornea in
  otherwise normal eyes
• Associated with age
• Area of tear pooling when eye lids at rest

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Other Corneal Iron Lines

• Stocker-Busacca line
• Associated with pterygia
• Anterior to leading edge
• Yellow to golden brown

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Other Corneal Iron Lines

• Ferrys line
• Associated with filtering blebs
• First reported in 1968

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Other Corneal Iron Lines

• Elevated corneal scars
• Salzmanns nodular degeneration
• Corneal foreign body
• Coats white ring
• Juvenile corneal arcus lipoides

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Coats White Ring
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Salzmanns Nodular Degeneration
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Importance of Corneal Iron Lines

• Diagnosis of associated ocular condition
• Identification of corneal donor tissue with prior
  refractive surgery (ie LASIK flap)
• Possible estimation of optical size and
  centration of ablation with hyperopic LASIK

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• Any Questions?