Rose Bengal Penetration Depth with Iontophoresis in Human Cornea Tissue

Abstract

Purpose : Rose bengal photodynamic antimicrobial therapy (RB-PDAT) is a novel treatment against superficial infectious keratitis; however, efficacy for infections deep in the cornea is limited by rose bengal’s penetration into the stroma. Iontophoresis is a non-invasive procedure that improves corneal permeation of charged topical ophthalmic pharmacologic agents by electrorepulsion and electroosmosis. By using RB disodium’s negatively charged properties, this study investigated the effects of iontophoresis on the corneal penetration of RB in ex vivo human corneas.

Methods : Corneal epitheliums of human donor eyes (n=11) were surgically removed. Five eyes were subjected to 0.1% RB with iontophoresis at 2500 μA for 15 minutes. Three eyes were soaked with 0.1% RB disodium epithelial side down without iontophoresis for 30 minutes. Three eyes were soaked in NaCl under identical conditions as controls. After treatment, the corneal tissues were harvested, and the endothelium of all corneas were stained with DAPI for one hour. Corneas were then imaged with confocal microscopy. Z-stacks were analyzed to find the cornea thickness and maximum RB penetration depth. All experiments were performed on eyes with intact stromas.

Results : The average corneal thickness of the eyes treated with iontophoresis, soak, and control were 460±78μm, 426±69μm and 498±50μm respectively. There were no significant differences found in the corneal thicknesses between the eyes that underwent iontophoresis and soak (p=0.935). The average corneal penetration of RB of the eyes that underwent with iontophoresis and soak were 177±9.5μm and 100±5.7μm, respectively. A significant difference was found in the penetration depth of RB between the two treatment groups (p < 0.001). No rose bengal signal was detected among the control group, as expected.

Conclusions : Corneal penetration of RB disodium is significantly improved by utilizing iontophoresis. These findings support the investigation of combining RB-PDAT with iontophoresis as a novel therapy for deep infectious keratitis that fail to be treated by conventional topical agents alone. However, further studies would be needed to confirm this inference.

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

 

Figure 1: Average Corneal Thickness and RB Penetration Depth of Iontophoresis (n=5) and Soak (n=3).

 

Figure 2: Z-stack of Soak (left) and Iontophoresis (right) treated corneas. Blue signal is DAPI and indicates corneal thickness, green signal is RB.