Posters

Long-term results of corneal stiffening by WST11-D and near infra-red (NIR) illumination: biomechanical efficacy and keratocyte repopulation in rabbits 1, 4 and 8 months after treatment

Poster Details

First Author: J. Brekelmans NETHERLANDS

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

Abstract Details

Purpose:

Previously we reported on the safety and efficacy of WST11-D/NIR treatment for corneal stiffening one month after treatment, and its efficacy in vivo after only five minutes of illumination. In the current study we set out to determine the safety and efficacy at a longer follow-up. We compared biomechanical strength and histological sections of corneas of New Zealand White rabbits treated with WST11-D and NIR, according to parameters comparable to the Dresden protocol, 1, 4, and 8 months after treatment.

Setting:

Academic research institute. In-vivo laboratory study.

Methods:

The left cornea of 19 New Zealand White rabbits was de-epithelialized mechanically and treated topically with WST11 (Steba-Biotech, France) 2.5mg/ml combined with dextran-500 (WST11-D) for 20 minutes. Next, illumination with NIR (755nm) at 10mW/cm2 was applied for 30 minutes. Untreated fellow eyes served as controls. One (n=6), 4 (n=9), or 8 (n=4) months after treatment 4±0.2mm wide corneal strips were harvested for stress-strain measurements. Remaining corneal tissue was fixed in 4% formaldehyde for histological examination. Keratocyte distribution was evaluated at a 200x magnification in 4µm thick hematoxylin and eosin stained sections.

Results:

Two rabbits (4 and 8 months) were excluded due to problems during sample handling. The elastic modulus in the treated eyes significantly increased compared to their paired controls at 1- (16.1±2.1 MPa vs. 9.6±3.2 MPa, p=0.002), 4- (17.1±5.0 MPa vs. 12.8±2.1 MPa, p=0.025) and 8- (18.6±3.6 MPa vs. 14.2±3.6 MPa, p=0.01) months after treatment. Contralateral eyes showed an increase in elastic modulus over time. A decrease in keratocyte count at the anterior part of the cornea was seen after treatment. Eight months after treatment repopulation had occurred.

Conclusions:

WST11-D/NIR treatment with illumination of 10 mW/cm2 at 755 nm results in a significant and persistant increase in corneal stiffness. The gradual increase over time in both treated and control group may be due to ageing-related natural occurring cross-linking. WST11-D/NIR treatment induces keratocyte apoptosis in the anterior stroma, however repopulation of keratocytes is seen at 8 months. The safe nature of NIR light allows treatment of corneas of any thickness, making WST11-D/NIR treatment a safe and effective alternative for Riboflavin/UVA cross-linking.

Financial Disclosure:

One or more of the authors research is funded, fully or partially, by a company producing, developing or supplying the product or procedure presented