A novel riboflavin soak-and-rinse protocol for transepithelial corneal collagen crosslinking

Abstract

Purpose : To enrich stromal riboflavin concentration and reduce epithelial riboflavin in transepithelial corneal collagen crosslinking (CXL).

Methods : Ex-vivo experiments on rabbit corneas were performed. The active control group consisted of 30-min epi-off application of isotonic 0.1% riboflavin solution with 20% dextran according to the standard Dresden CXL protocol. The experimental transepithelial riboflavin solutions comprised various riboflavin concentrations in a carrier of 1% hydroxypropyl methylcellulose (HPMC) in 0.45% saline. Some also contained 0.01% benzalkonium chloride (BAK) to enhance diffusion. Optical coherence tomography was used to check epithelial and stromal thickness. The novel soak-and-rinse protocol consists of a 20-min riboflavin application immediately followed by 10-min rinsing with normal saline. A spectrophotometer measured the riboflavin concentration on 3-mm stromal buttons. The epithelial riboflavin was also measured with the spectrophotometer after elution in a standardized volume of solution. Linear regression and one-tailed unpaired t-tests were used for comparisons.

Results : The 20-min soaking increased stromal riboflavin compared to 10-min (Figure 1). A 76% increase in stromal concentration was seen by adding BAK to the transepithelial 0.8% riboflavin solution (p<0.05). The 10-min additional rinsing achieved Dresden equivalent stromal riboflavin and dramatically reduced epithelial riboflavin (-83%, p<0.0001, Figure 2).

Conclusions : Stromal riboflavin concentration equivalent to the epi-off Dresden protocol can be achieved by transepithelial application of a novel high-concentration riboflavin formulation. The addition of a 10-minute rinsing effectively reduced the epithelial riboflavin to facilitate delivery of ultraviolet light and oxygen during CXL.

This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.

 

Comparison of stromal riboflavin concentrations achieved with various riboflavin soaking protocols. All protocols were transepithelial except for the rightmost bar (green) representing epi-off soaking with the Dresden protocol (6 corneas). The effect of BAK and rinsing were tested using the 0.8% riboflavin solution (second group from right). Each protocol in the transepithelial groups of with and without BAK were tested on 6 and 2 corneas, respectively.

 

Epithelial riboflavin concentration after extended 10-minute rinse vs. standard immediate 10-sec rinse. Total 8 corneas were tested for each rinsing duration.