Corneal collagen cross-linking (CXL) for progressive keratoconus uses riboflavin and UV-A light. The Dresden protocol specifies the UV-A irradiance and total energy dose as:
- A 9 mW/cm² for 10 minutes = 5.4 J/cm²
- B 3 mW/cm² for 30 minutes = 5.4 J/cm² ✓
- C 45 mW/cm² for 2 minutes = 5.4 J/cm²
- D 3 mW/cm² for 60 minutes = 10.8 J/cm²
Explanation
The original Dresden protocol for CXL specifies UV-A irradiance of 3 mW/cm² applied for 30 minutes, delivering a total energy of 5.4 J/cm² to the corneal stroma. Riboflavin (0.1% in 20% dextran) acts as a photosensitizer, generating reactive oxygen species that cross-link collagen fibers via covalent bonds, increasing corneal rigidity. Epithelium-off (de-epithelialized) technique ensures riboflavin penetration. Minimum stromal thickness of 400 microns is required to prevent endothelial damage. Accelerated protocols use higher irradiance for shorter times to deliver the same 5.4 J/cm².
Reference: Khurana Comprehensive Ophthalmology, 7th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.