Biomechanical Response After Corneal Cross-linking With Riboflavin Dissolved in Dextran Solution Versus Hydroxypropyl Methylcellulose

Abstract

PURPOSE: To evaluate corneal stiffening in porcine eyes induced by corneal cross-linking (CXL) using riboflavin dissolved in either aqueous dextran or hydroxypropyl methylcellulose (HPMC) solution. METHODS: Fifty-one porcine corneas were divided into three groups of 17 each. After deepithelialization, the first (Dresden) group was treated for 30 minutes with 0.1% riboflavin (riboflavin-5-monophosphate in 0.9% NaCl) dissolved in hypertonic 20% dextran and the second (HPMC) group for 30 minutes with isotonic solution containing 0.1% riboflavin and 1.1% HPMC. Thereafter, corneas of both groups were irradiated using 5.4 J/cm 2 (irradiance of 9 mW/cm 2 for 10 minutes; 10*9). After CXL, all corneas were kept in an isotonic 16% dextran bath for 2 hours to obtain an equal hydration state. The third group served as the control group. Stress-strain measurements were performed on 5-mm–wide strips. Corneal thickness was monitored throughout the entire course of the experiments. RESULTS: The required stress for a 10% strain was increased by 83% in the Dresden group and 35% in the HPMC group compared to the control group. Resultant Young's modulus (at 10% strain) was 2.53 ± 0.73, 1.87 ± 0.50, and 1.47 ± 0.44 Pa for the Dresden, HPMC, and control groups, respectively. The differences between the Dresden and HPMC groups ( P = .006), the Dresden and control groups ( P < .001), and the HPMC and control groups ( P = .014) were statistically significant. Pachymetry measurements showed a significantly increased corneal thickness after application of HPMC compared with the Dresden group ( P = .002) and control group ( P = .041). CONCLUSIONS: The biomechanical stiffening of the cornea by CXL can be achieved using dextran- and HPMC-based riboflavin solutions in porcine corneas with an application time of 30 minutes. Dextran-based riboflavin solutions seem to induce a slightly stronger biomechanical response in this setting. HPMC solutions induce less thinning than dextran solutions. [ J Refract Surg . 2021;37(9):631–635.]

An in vitro investigation into the impact of corneal rinsing on riboflavin/UVA corneal cross-linking

“…Indeed, clinical studies have shown that the application of riboflavin/HPMC solution has little effect on corneal hydration, producing a small increase [ 23 ] or decrease [ 14 ] in corneal thickness during treatment. In tandem with the clinical findings of Zaheer et al [ 23 ] and the laboratory studies of Fischinger et al [ 28 ] on porcine corneas, this study revealed a significant increase in CCT (9%) following a 16-min application of riboflavin/HPMC to the de-epithelialised cornea. Furthermore, we showed that the post-treatment thickness of corneas that underwent CXL without a BSS rinse prior to UVA exposure, was similar to that of untreated (epithelium-removed) corneas.…”

Photophysical and photodynamic analysis of different formulations of riboflavin

“…Oxygen depletion has been proposed as a reason for the formation of new covalent junctions [26,27]. Many authors argue that the medium in which Rb is delivered is essential to shorten the exposure time and improve the cost-effectiveness of CXL [28,29]. In the current study, the performance of VibeX Rapid® was superior to that of the other formulations.…”

Recent advances in medicinal compounds related to corneal crosslinking

“…Compared with dextran riboflavin, HPMC riboflavin might present improved CXL effect resulted from enhanced concentration of riboflavin in the cornea and a deeper demarcation line (Malhotra et al, 2017;Thorsrud et al, 2019). Nevertheless, dextran riboflavin might result in slightly stronger biomechanical properties and better visual outcomes (demonstrated by visual acuity) (Rapuano et al, 2018;Fischinger et al, 2021). As for safety, HPMC riboflavin performed as well as dextran riboflavin (De Paula et al, 2020).…”