Safety and efficacy of a novel topical eye drops against chronic corneal toxicity up to 4-months after mustard gas exposure to rabbit eyes in vivo

Abstract

Purpose : Sulfur mustard (SM) gas exposure to the eye causes severe toxicity to the cornea called mustard gas keratopathy (MGK). This study investigated the safety and efficacy of a novel topical eye drops (TED) and evaluated the clinical manifestations up to 4 months in rabbit eyes in vivo exposed to SM.

Methods : The study was approved by the IACUC and followed ARVO guidelines. Eyes of New Zealand White Rabbits were exposed to SM vapor (200 mg-min/m³ for 8 minutes). Study has 6 groups: Naïve, TED, SM, 3 groups/regimens of SM+TED (2 drops twice a day for 7, 14, and 28 days). Clinical eye examinations in live rabbits were performed with the slit-lamp microscope, confocal HRT3 microscope, Fante's grading system, fluorescein staining, Schirmer’s tests, pachymetry, applanation tonometry, specular microscope, and optical coherence tomography. At the 4-month endpoint, rabbits were humanely euthanized, and corneas were collected for histological, molecular, and cellular analyses.

Results : SM-exposed rabbit corneas showed a significant corneal haze (Fante’s scores 2-2.5; p<0.0001), central corneal thickness (596 ± 30.7; p<0.0001), tear flow (18-22 ± 2.4 p<0.0001), and corneal edema, decreased in keratocyte density, loss of endothelium cell density (2213 ± 205/mm² p<0.01) and corneal neovascularization (NV) compared to naïve untreated control corneas up to 4-month post-SM exposure. TED regimen-2 significantly reduced the corneal haze (Fante’s scores 1-1.5; p<0.0001), central corneal thickness (466± 30.7; p<0.001), tear flow (11-16 ± 2.4 p<0.001), and corneal neovascularization increased keratocyte density, restored endothelium cell density (2823 ± 250/mm² p<0.001) and hexagonality. The beneficial effects of regimen-1 were weaker than regimen-2, while regimen-3 appeared strong clinically. The H&E staining revealed epithelium-stroma separation after SM exposure, while TED showed mitigation. TED-alone treated eyes showed structural, cellular, or functional responses similar to Naïve eyes.

Conclusions : Mustard gas exposure to eyes causes chronic corneal toxicity, and topical TED therapy reduces MGK symptoms in rabbits in vivo. Additional studies are ongoing.

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