A patient with keratoconus and a corneal thickness of 420 microns at the thinnest point is planned for corneal collagen cross-linking (CXL). The surgeon uses hypo-osmolar riboflavin. What is the purpose of hypo-osmolar riboflavin in this setting?
- A To sterilize the corneal surface before UV-A exposure
- B To reduce UV-A penetration and protect the endothelium
- C To swell the cornea to achieve adequate thickness above the 400-micron safety threshold ✓
- D To dissolve Bowman's layer for deeper riboflavin penetration
Correct answer: C. To swell the cornea to achieve adequate thickness above the 400-micron safety threshold
Explanation
The Dresden protocol requires minimum corneal thickness of 400 microns after epithelial removal to prevent UV-C damage to the endothelium. When the cornea is thinner than 400 microns, hypo-osmolar riboflavin drops are applied to swell the cornea and achieve adequate thickness. Hyperosmolar riboflavin would dehydrate the cornea further. Standard (iso-osmolar) riboflavin does not alter thickness significantly.
Reference: AAO BCSC Section 8: External Disease and Cornea, 2023-2024 ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.