Corneal Collagen Crosslinking Using The New Rose Bengal Formulations

To explore central corneal thickness (CCT) changes during in vivo rose bengal-green light corneal cross-linking (RGX) and compare the cross-linking efficacy of new rose bengal (Rb) formulations.

School of Ophthalmology and Optometry and Eye Hospital, Wenzhou Medical University, Wenzhou, Zhejiang, China. Structural Biophysics Research Group, School of Optometry and Vision Sciences, Cardiff University, Cardiff, UK. Eye Institute and Department of Ophthalmology, Eye & ENT Hospital, Fudan University; Key Laboratory of Myopia, Chinese Academy of Medical Sciences, Shanghai, China.

After epithelium removal, the right eyes of rabbits were immersed in Rb solution for 2 or 20 minutes, then the Rb distribution in the corneal stroma was analyzed by confocal fluorescence detection. During the RGX process, the CCT was measured at 7 time points. The left eyes served as untreated control group. Corneal enzymatic resistance and corneal biomechanics were tested to compare the RGX efficacy. 

The Rb infiltration depths were about 100 μm and 200 μm for the 2-minute and the 20-minute groups, respectively. CCT increased significantly after infiltration, then decreased significantly in the first 200 seconds of irradiation and decreased slowly for the next 400 seconds. The CCT of the 20 min groups was significantly higher than that of the 2 min groups (P < 0.0001). All the RGX treatments improved the corneal enzymatic resistance and corneal biomechanics, with the effects being greater in the 20 min groups. The inclusion of 1.1% hydroxypropyl methylcellulose (HPMC) in the Rb formulation helped to maintain CCT during irradiation, whilst not affecting either the infiltration of Rb or the efficacy of RGX.

Within the range studied, RGX effectiveness increase with instillation time. The incorporation of a 20-minute instillation of 0.1% Rb-1.1% HPMC into the RGX procedure may further improve the safety of the treatment and its prospects for clinical use.