ABSTRACT
Backgroud EDTA is an important calcium chelator,commonly used as an ophthalmic additive,its role in promoting corneal penetration of drug may facilitate transepithelial corneal collagen crosslinking.However,there were few reports about the penetration of riboflavin to corneal stroma enhanced by EDTA both home and abroad.Objective To determine the concentrations of riboflavin in corneal intrastromal under different interventions using high-performance liquid chromatography (HPLC).To ensure the efficacy and safety of 0.5％ EDTA in riboflavin penetrating to corneal stroma by the transepithelial procedures.Methods Fifteen New Zealand white rabbits were randomized into three groups,corneal epithelium of 5 rabbits were debrided,corneal epithelium of another 5 rabbits were left in situ and 0.5％ EDTA-Na2 was topically applied for 1 hour,and the corneal epithelium of last 5 rabbits were just left in situ,after those procedures 0.1％ riboflavin + 20％ dextran was applied topically to the corneas for 30 minutes(1 drop every 3 minutes).Then,the epithelium in the corneas of EDTA and epi-situ group were carefully removed before all the corneas were punched with an 8.5 mm diameter blade and homogenized subsequently.Ultimately,the riboflavin concentrations were determined by HPLC.Results After treated with riboflavin for 30minutes,the mean concentration of riboflavin in the epi-removed group was (23.54± 1.61)μg/g tissue,the EDTA group was (2.04 ±0.25)μg/g tissue and the epi-situ group was (1.44 ±0.06)μg/g tissue,showing significant difference among them (F =1792.839,P =0.000).There were statistically significant differences between any two groups (t =41.780,7.484,43.408,all at P ＜ 0.05).However,the riboflavin concentration of other two groups were failed to meet the theoretical value 15 μg/g tissue,excepted for epi-removed group.Conclusions The diffusion of riboflavin to the corneal stroma can be fully enhanced by removing the epithelium preoperatively,penetration enhancer EDTA can effectively promote the penetration of riboflavin to the cornea,but it still can not replace the role of removing epithelium on the penetration of riboflavin to the cornea.