In keratoconus, corneal collagen cross-linking (CXL) with riboflavin and UVA light primarily works by:
- A Increasing corneal thickness by stimulating keratocyte proliferation
- B Reducing corneal irregular astigmatism by selectively ablating the cone apex
- C Forming new covalent bonds between collagen fibrils via reactive oxygen species, increasing stromal stiffness ✓
- D Inhibiting MMP-9 activity to prevent progressive stromal thinning
Explanation
CXL (Dresden protocol: riboflavin 0.1% with 30 minutes UVA at 3 mW/cm² for 30 minutes) generates reactive oxygen species that form new covalent bonds (pyridinium cross-links) between collagen fibers in the anterior stroma, increasing its biomechanical stiffness by 300-400%. This halts the progressive ectasia of keratoconus. The demarcation line at approximately 300 microns depth on OCT confirms adequate depth of treatment. Accelerated CXL uses higher fluence (9-45 mW/cm²) with shorter time to deliver equivalent total dose (5.4 J/cm²). Minimum corneal thickness of 400 microns pre-treatment is required to protect the endothelium.
Reference: Khurana Comprehensive Ophthalmology, 7th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.