This document discusses corneal crosslinking, a procedure proposed in 2000 by Dr. Theo Seiler to strengthen the cornea. It involves applying riboflavin drops to the cornea, then exposing it to UVA light, which causes photopolymerization of corneal fibers. This increases the rigidity of collagen and resistance to deformation by creating new covalent bonds between collagen fibers. The procedure is used to treat keratoconus and keratectasia following LASIK to stabilize the cornea. It may also help treat resistant bacterial ulcers and reduce edema and hyperopia. Potential disadvantages include lack of long-term data and minimal improvement in vision, with risks of infiltrates, scarring and endothelial damage in rare cases

1. Corneal
Crosslinking
Dr. David Edmison
14th, 2012

2. Corneal Crosslinking
• CXL proposed by Dr. Theo Seiler (Dresden) in 2000.
• Combination of riboflavin & UVA (3mw/cm2 at
370nm) to strengthen the cornea.
• Involves photopolymerization of stromal fibers
which increases the rigidity of corneal collagen and
its resistance to deformation.
• After UVA exposition the riboflavin is excited into a
triplet state and generates singlet oxygen. These
induce the formation of new covalent bonds between
the amino acids of neighbouring collagen fibres and
results in a stiffening of the cornea.

3. Corneal Crosslinking

4. Corneal Crosslinking
Keratoconus: less crosslinking After CXL: more crosslinking
Creates chemical bonds between collagen fibers

5. Corneal Crosslinking

6. Keratectasia
 Keratoconus
 Post LASIK ectasia
 Pellucid Marginal
Degenaration
 Therapeutic treatment – variable Rx and K’s
during post-op period (1-6 mths)

7. Keratectasia
Keratoconus
 1/2000: usually in adolescence, peaks at age 20-35
 Thinning of corneal stroma
 Clinically:
 irregular scissor reflex on retinoscopy
 Vertical striae (Vogt)
 Fleischer’s ring (hemosiderin)
 Stromal edema with breaks in Descemet’s → hydrops
 Munson’s sign
 Path: defects in Bowman’s
 Etiology: genetic, atopic disease, asthma, exzema, eye rubbing
 10-25% require transplant or lamellar Sx.

8. Corneal Crosslinking
 Intrastormal ring segments + CXL
Intrastromal ring segments + CXL

9. Keratectasia
Post LASIK ectasia
 Variable degrees of corneal thinning in stromal bed and flap
 Macrostriae in stromal bed
 Steepening of central cornea +/- iron ring around steepening.
 Thinning of stromal collagen lamellae
 Occasional scarring at flap-stromal bed interface

10. Keratectasia
Pellucid Marginal Degenaration
 Thinning in periphery of cornea
 Usually high against the rule astigmatism.

11. Corneal Crosslinking
Other indications for CXL
 Recalcitrant corneal ulcers
 Reduces pathogen load
 Increases resistance to collagenases
 Reducing corneal edema in Bullous keratopathy & Fuch’s
 Reducing hyperopic shift following RK
 Prophylactic for all patients treated with PRK with high
myopia or Forme Fruste K

12. Corneal Crosslinking
 Bacteria can be eliminated using the
combination of UV-A and riboflavin

13. Corneal Crosslinking
85-year-old woman with an
advanced infectious ulcer,
including presence of hypopyon.

14. Corneal Crosslinking
Advantages
 Stabilizes (slows or stops) progression of keratectasia.
 Some flattening of the cornea
 Studies show results last at least 3 years
 Synergistic effect with PRK as seen in Athens protocol.
 Helps treat resistant bacterial ulcers.

15. Corneal Crosslinking
Disadvantages
 No long term data
 Stabilizing effect shown but minimal improvement in
VA for patients.
 Of 200 reported studies only 10 are prospective,
randomized and controlled.
 No titration of dose to degree of keratectasia.
 Sterile infiltrates and stromal scars reported.
 Rare corneal melt and damage to endothelium.
 Estimated that CXL has same stiffening impact on
cornea as 30 years of aging.

16. Corneal Crosslinking

17. Corneal Crosslinking
 Riboflavin (0.1%) and UVA (365nm) 3-45 mW/cm2
 Corneal epithelium off or on
 Treatment for corneal disorders & infections
 Adjunct therapy for LVC
Indications:
 Keratoconus
 Ectasia (post LVC)
 Resistant bacterial infections

18. Corneal Crosslinking
Crosslinked cornea
Used for years in dentistry
to harden polymers. Normal cornea

19. Corneal Crosslinking
 Athens Protocol
 Combined partial PRK and CXL
 Not a refractive procedure

20. Corneal Crosslinking
Provide extra corneal strengthening preventing ectasia

21. Focus Eye Centre
Thank you!