| Backgrounds The possible risks of corneal infections, postoperative pain, long recovery, enough corneal thickness etc because of removing epithelium in classical corneal collagen cross-linking (CXL) make research about transepithelial CXL a hot topic in ophthalmology. A sufficient concentration of riboflavin in the corneal stroma is vital for efficacious and safe performance of transepithelial CXL.Objective To evaluate two kinds of different transepithelial CXL by intracameral injection and iontophoresis method with changed solvent, and investigate enrichment of riboflavin in the corneal stroma and mechanism, the efficacy and safety of transepithelial CXL were analyzed.Methods 1.30 rabbits (30 eyes) were divided into 3 groups and different concentrations riboflavin-balance salt solutions (BSS) were injected into the anterior chamber (0.5%,1%,2%).8 corneal buttons in every group were dissected at 30 minutes and riboflavin concentrations in corneal stroma were determined by high-performance liquid chromatography (HPLC). Another 2 rabbits in every group were observed for 24 hours and killed. As a comparison,16 corneal stromal riboflavin concentrations were determined by HPLC after 0.1% riboflavin-BSS solution instillation on corneal surface (8 without epithelium and 8 with intact epithelium).2. 20 rabbits (20 eyes) were randomly divided into four groups:0.1% riboflavin-balanced salt solution (BSS) by iontophoresis,0.1% riboflavin-saline solution by iontophoresis, 0.1% riboflavin-distilled water solution by iontophoresis, and classical riboflavin instillation after removing epithelium as the control group. The degree of yellowing of the de-epithelialized corneal stromal buttons was compared.3.15 eyes of 11 patients with progressive keratoconus were included. After 0.1% riboflavin-distilled water solution was transepithelial deliveried by iontophpresis, UVA irradiation was performed for 30min. The follow up were 6 months in all eyes.Results 1.The mean riboflavin concentrations were 11.19ug/g,18.97ug/g,25.08ug/g, 20.18ug/g,1.13ug/g respectively for 0.5%,1%,2%, de-epithelium, transepithelial groups. Enrichment of riboflavin similar with classical de-epithelium CXL could be achieved by intracameral 1% riboflavin-BSS solution 0.1ml at 30minutes and the effect looked continuous for at least 30 minutes.2. Iontophoretic delivery of a 0.1% riboflavin-distilled water solution did achieve similar yellow changes in stromal button compared with classical riboflavin instillation after de-epithelialization. However, the other two solvents were unsufficient at enhancing the permeability of the riboflavin.3. At 6 month postoperatively, mean uncorrected visual acuity and corrected visual acuity changed from 0.36 and 0.42 to 0.30 and 0.57, the maximum keratometry value (Kmax) and astigmatism decreased from 60.91 and 3.86 to 59.91 and 3.19 respectively; Central corneal thickness and thinnest corneal thickness showed a thinner trend from 460.93um and 450.87um to 455.40um and 440.60um but all these data had not statistical significance; Intraocular pressure statistically increased from 10.85mmHg to 12.62mmHg; No corneal haze occured. Mean corneal demarcation line depth emerged at 1 month postoperatively was 288.46um.Conclusions 1.Riboflavin can effectively penetrate into corneal stroma through endothelium after intracameral injection in vivo, so it possibly becomes an assistant enhance method improving corneal riboflavin concentration in transepithelial CXL.2. Riboflavin can effectively penetrate into the corneal stroma to saturation levels by iontophoresis using distilled water as the solvent.3. The stable pilot results confirmed transepithelial CXL by iontophoretic delivery of riboflavin- distilled water solution was effective and safe. |
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