Background
Corneal collagen cross-linking with riboflavin (Vitamin B2) and long-wave ultraviolet A (UV-A) is a surgical treatment for corneal ectasia. Cross-linking (also called C3-R, CXL, CCL, and KXL) is performed to make the cornea more rigid.
The most common corneal ectasia is keratoconus. Keratoconus has the following characteristics:
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Generally believed to be non-inflammatory, although there are numerous recent papers published suggesting there may be an inflammatory component
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Progressive corneal ectasia
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Increasing irregular astigmatism
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Loss of best-corrected visual acuity (BCVA) and may lead to surgery
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Possible scarring and hydrops (acute disruption of Descemet's membrane in the setting of corneal ectasia)
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Genetic and environmental causes
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No curative treatment
Indications
The main benefit of corneal cross-linking is to halt the progression of corneal ectasia (also known as 'kerectasia' or 'keratectasia').
Medical indications
Accepted medical indications for corneal cross-linking include the following:
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Individuals with keratoconus, with documented progression of corneal ectasia
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Children with keratoconus, who are eye rubbers
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Individuals with LASIK-induced corneal ectasia
In post-refractive surgery (LASIK or Radial Keratotomy) ectasia, there are no definitive criteria for progression. Parameters considered include changes in refraction, uncorrected and best-corrected visual acuity, and corneal shape.
Other indications
Other indications for corneal cross-linking include the following:
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Terrien marginal degeneration
Contraindications
There are numerous contraindications to corneal cross-linking, and they include the following:
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Corneal thickness lesser than 400 microns (may cause irreversible damage to the corneal endothelium)
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Prior herpetic infection (may result in viral reactivation)
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Concurrent infection (although there now are more scientific papers attesting to the efficacy of cross-linking in sterilizing bacterial and fungal corneal ulcers)
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Severe corneal scarring or opacification (the results are uneven and unpredictable)
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History of poor epithelial wound healing
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Severe ocular surface disease (eg, dry eye)
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Autoimmune disorders
Poorer results are noted in the following:
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Aged > 35 years (the cornea is naturally cross-linked by the UVA from sunlight)
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< 400-micron cornea (possible irreversible endothelial damage)
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Keratoconus stage III or IV (scarring and opacification)
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Keratometry > 57 D
Technical Considerations
The commonly used and currenty investigated procedures in clinical practice include the following:
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Conventional dresden protocol
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Accelerated corneal cross-linking
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Transepithelial cross-linking using chemical enhancers
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Iontophoresis cross-linking
Outcomes
The most consistent results of observational and randomized controlled studies have been that corneal cross-linking induces a small decrease in keratometry values that appears to be maintained over at least a year. This is a significant finding since progressive keratoconus keratometry typically increases over time. Important corneal cross-linking studies include the following:
Complications
Complications of corneal collagen cross-linking include the following:
Controversies
Epithelium off or on?
Should we do transepithelial crosslinking or not?
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Shallower demarcation
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Reduced efficacy
Is it good for children?
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Centration issues
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Sedation issues
Higher UV fluence is better?
A shorter operation time may be achieved by means of UV-fluences between 10 to 15 mW/cm2 and riboflavin in HPMC solution.
Shorter operation time results in a shallower demarcation line.
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Corneal cross-linking treatment aims to prevent the progression of keratoconus. Courtesy of Optimed (www.optimed.co.uk).
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Once the eye is numbed with drops, further drops of riboflavin are added to the eye. Riboflavin is instilled until the cornea is saturated. Courtesy of Optimed (www.optimed.co.uk).
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A small dose of UV-A light is used to activate the riboflavin. Courtesy of Optimed (www.optimed.co.uk).
Tables
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- Overview
- Periprocedural Care
- Technique
- Approach Considerations
- Standard cross-linking (CXL)
- Transepithelial cross-linking (TCXL)
- Iontophoresis-assisted Transepithelial Cross-Linking
- Pocket cross-linking (PCXL)
- Contact lens-assisted collagen cross-linking (CACXL)
- Accelerated cross-linking
- Combined with other refractive eye procedures
- Photorefractive Intrastromal corneal cross-linking (PiXL)
- Show All
- Medication
- Laboratory Medicine
- Media Gallery
- References