ENHANCED RESISTANCE TO ENZYMATIC DIGESTION VIA SAME SESSION HIGH-FLUENCE ACCELERATED CORNEAL CROSS-LINKING UTILIZING RIBOFLAVIN/UV-A AND ROSE BENGAL/GREEN LIGHT

To evaluate enzymatic resistance in ex vivo porcine corneas by combining Riboflavin (RI)/UV-A and Rose Bengal (RB)/Green Light CX), and assess oxygen-dependency of enzymatic resistance in RB-mediated photoactivated chromophore for infectious keratitis- CXL (PACK-CXL).

ELZA Institute, Dietikon/Zurich, Switzerland & Laboratory for Ocular Cell Biology, CABMM, University of Zurich, Switzerland.

In Setting 1, 58 corneas were assigned to three groups with different PACK-CXL protocols.

• Group 1: RI/UV-A irradiation (10 J/cm², 9'15" @ 18 mW/cm²)
• Group 2: RB/green light (10 J/cm², 11'07" @ 15 mW/cm²)
• Group 3: RI and UV-A irradiation, then RB/green light irradiation (UV settings as above).
  
  

In Setting 2, 106 corneas were segmented into 5 groups:

• In 21% atmospheric oxygen:
• Group 1: control (abrasion/RB application).
• Group 2: RB/green (10 J/cm², 11'7" @ 15mW/cm²)
• Group 3: RB/green (15 J/cm², 8' @ 30 mW/cm²)
• In oxygen-sparse nitrogen chamber:
• Group 4: Per Group 2
• Group 5: Per Group 3

In both studies, all corneas were digested in 0.3% collagenase A solution. Time until complete dissolution was assessed.

Setting 1: Mean digestion time was significantly prolonged in Group 3 (combined RI/UV-A and RB/Green light) at 39.82 ± 2.16 hours compared to Group 1 (30.61 ± 1.79 hours) and Group 2 (33.7 ± 2.38 hours) (both P < 0.001).

Setting 2: All treated groups displayed significantly increased resistance to enzymatic digestion compared with control (P ≤ 0.017), irrespective of oxygen presence or fluence.

Combining RI/UV-A and RB/Green light PACK-CXL in the same session significantly boosts corneal resistance to enzymatic digestion over single chromophore/light combinations. Rose Bengal-mediated enzymatic resistance appears to be oxygen-independent, suggesting broader application for various PACK-CXL protocols.