Posters

Comparison of WST-D/near infrared and riboflavin/ultraviolet: cross-linking treatments on corneal resistance to collagenase digestion

Poster Details

First Author: J.Brekelmans THE NETHERLANDS

Co Author(s):    K. Rieff   M. Dickman   A. Brandis   A. Marcovich   A. Scherz   R. Nuijts     

Abstract Details

Purpose:

In ectatic and infectious corneal disorders, biomechanical instability and loss of structural integrity may occur due to an increased activity of proteolytic enzymes. Photosensitizing cross-linkers, such as Riboflavin/Ultraviolet A (RF/UVA) and WST11/Near infrared (WST11/NIR), have been shown to increase corneal biomechanical stiffness by the formation of additional bonds within the corneal extracellular matrix. This study sets out to experimentally determine and compare the ability of clinically available RF/UVA and experimental WST-D/NIR cross linking treatments to preserve structural integrity during collagenase digestion.

Setting:

Academic research institute. Ex vivo study, porcine eyes.

Methods:

Eighty-eight porcine corneas were de-epithelialized ex vivo. Per pair, one eye was treated with(hypo- or hyperosmolar) RF/UVA or WST11/NIR, while the paired eye served as control. Central corneal thickness (CCT) was measured in between steps. A central 8.0mm button of each cornea was placed in 2mL of 3% collagenase solution (420u/mL) and put on a shaker (170rpm) at 37°C. At 30-minute intervals sample survival was assessed visually. After 6 hours, sample remains were lyophilized for 72 hours, and dry sample weight was measured. Sample survival and weight were measured by a blinded examiner. Statistical analysis was done with SPSS.

Results:

All control samples had been completely digested after 6 hours. For RF, RF-D, WST11, and WST-D treated samples, dry sample weight measurement read 1.68±0.6 (n=10), 2.19±0.50 (n=8), 1.17±0.36 (n=9), and 1.54±0.60 (n=9) milligram. All four cross-linking modalities showed a highly significant treatment effect (within-subject effect, F1,30=321.1, p<0.001). Furthermore, a significant difference was seen between chromophores (between-subject effect, F3,30=6.194, p=0.002). Post hoc comparison using Bonferroni correction indicated a significant difference in treatment effect between WST11 and RF-D only (p=0.001). The addition of Dextran achieved a greater resistance against proteolytic degradation (F1,34=4.171, p=0.049, R2=0.109).

Conclusions:

Our results show both RF and WST11 formulations increase resistance against collagenase digestion and may provide new treatment modalities for infectious keratitis. Clinically, hypotonic RF is applied in thin corneas to induce swelling and assure treatment safety. However, our results indicate hypotonic solutions are less effective than Dextran enriched formulations, which may limit the application of RF in (thin) melting corneas. Particularly in these more severely affected corneas, WST-D/NIR may provide an effective alternative to RF/UVA cross-linking.

Financial Disclosure:

receives consulting fees, retainer, or contract payments from a company producing, developing or supplying the product or procedure presented