Effect of Epithelial Retention and Removal on Riboflavin Absorption in Porcine Corneas (original) (raw)
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Effect of corneal epithelium on ultraviolet-A and riboflavin absorption
Arquivos Brasileiros de Oftalmologia, 2011
apenas observada nos olhos que receberam riboflavina intracameral. Conclusão: Foi demonstrado, através de microscopia por imunofluorescência em córneas de porcos, que o epitélio corneano íntegro diminui a efetividade do CXL por reduzir a penetração da riboflavina, e não por impedir a penetração dos raios UVA. Uma concentração intraestromal inadequada de riboflavina limita o efeito do tratamento.
BioMed research international, 2013
To evaluate the role of corneal epithelium in riboflavin/ultraviolet-A (UVA) mediated corneal collagen cross-linking treatment. Fifty New Zealand rabbits were divided into 5 groups: UVA treatment with or without corneal epithelium, UVA+riboflavin treatment with or without corneal epithelium, and control without any treatment. All rabbits were sacrificed after irradiation and subsequently 4 mm × 10 mm corneal strips were harvested for biomechanical evaluation. UVA irradiation alone did not enhance the maximal stress and Young's modulus of corneal specimens with (3.15 ± 0.56 mpa, 1.00 ± 0.09 mpa) or without (3.53 ± 0.85 mpa, 0.94 ± 0.21 mpa) the corneal epithelium, compared to specimens in the control group (4.30 ± 0.68 mpa, 1.03 ± 0.24 mpa). However, UVA irradiation combined with riboflavin significantly increased the maximal stress and Young's modulus of corneal specimens with (5.27 ± 1.09 mpa, 1.23 ± 0.23 mpa, P < 0.05) or without (7.16 ± 1.88 mpa, 1.42 ± 0.16 mpa, P <...
Clinical Ophthalmology (Auckland, N.Z.), 2021
Purpose To evaluate effects of sodium iodide (NaI) on riboflavin concentration in corneal stroma before and during ultraviolet A (UVA) light exposure using a novel transepithelial corneal collagen crosslinking (CXL) procedure (EpiSmart CXL system, CXL Ophthalmics, Encinitas CA). Methods Riboflavin solutions with NaI (Ribostat, CXL Ophthalmics, Encinitas CA) and without NaI were used for CXL in rabbits using EpiSmart. A pilot study determined sufficient riboflavin loading time. Four rabbits were dosed and monitored. Riboflavin fluorescence intensity was assessed from masked slit-lamp photos. A 12 min loading time was selected. Sixteen additional rabbits received the two formulae in contralateral eyes for CXL. Riboflavin uptake was assessed at 0, 10, 15, 20, 25, and 30 min of UVA exposure using a scale for riboflavin fluorescence previously validated against stromal concentration. Post sacrifice, corneal stromal samples were analyzed for concentrations of riboflavin and riboflavin 5ʹ-...
2009
Methods: 14 keratoconic patients enrolled for penetrating keratoplasty were selectioned as in vivo samples donors and 16 warm-stored ex vivo sclerocorneal rings unsuitable for transplant were used. In vivo samples were immediately exposed to sterile 0.1% riboflavin solution. 7 of the 14 specimens were debrided and the other 7 were left with the epithelium in situ. One of the latter and one of the debrided samples were not exposed with riboflavin (control groups). In 7 sclerocorneal rings epithelium was removed and in 9 was left in situ. Debrided and not debrided samples were soaked with 0.1% riboflavin solution, instilled every 2 minutes for 5 min, 15 min and 30 min in both in vivo and ex vivo groups. Riboflavin concentrations were determined by HPLC.
Investigative Opthalmology & Visual Science, 2016
PURPOSE. We investigated the concentration of riboflavin in human donor corneas during corneal cross-linking using two-photon optical microscopy and spectrophotometry. METHODS. Eight corneal tissues were de-epithelialized and soaked with 20% dextran-enriched 0.1% riboflavin solution for 30 minutes. After stromal soaking, three tissues were irradiated using a 3 mW/cm 2 UV-A device for 30 minutes and three tissues irradiated using a 10 mW/cm 2 device for 9 minutes. Two additional tissues were used as positive controls. A Ti:sapphire laser at 810 nm was used to perform two-photon emission fluorescence (TPEF) and second harmonic generation axial scanning measurements in all specimens before and after stromal soaking and after UV-A irradiation. In addition, spectrophotometry was used to collect the absorbance spectra of each tissue at the same time intervals. Analysis of the absorbance spectra and TPEF signals provided measures of the concentration depth profile of riboflavin in corneal stroma. RESULTS. After stromal soaking, the average peak concentration of riboflavin (0.020% 6 0.001%) was found between a stromal depth of 100 and 250 lm; the concentration of riboflavin was almost constant up to 320 6 53 lm depth, then decreased toward the endothelium, though riboflavin was still enriched in the posterior stroma (0.016%% 6 0.001%). After conventional and accelerated UV-A irradiation, the concentration of riboflavin decreased uniformly 87% 6 2% and 67% 6 3% (P < 0.001), respectively. CONCLUSIONS. The combined use of two-photon optical microscopy and spectrophotometry provides relevant information for investigating the concentration of riboflavin in corneal stroma. The method can assist with the assessment of novel riboflavin formulations and different UV-A irradiation protocols.
PLoS ONE, 2013
Purpose: To examine the effect of riboflavin/UVA corneal crosslinking on stromal ultrastructure and hydrodynamic behaviour. Methods: One hundred and seventeen enucleated ungulate eyes (112 pig and 5 sheep) and 3 pairs of rabbit eyes, with corneal epithelium removed, were divided into four treatment groups: Group 1 (28 pig, 2 sheep and 3 rabbits) were untreated; Group 2 (24 pig) were exposed to UVA light (3.04 mW/cm 2) for 30 minutes and Group 3 (29 pig) and Group 4 (31 pig, 3 sheep and 3 rabbits) had riboflavin eye drops applied to the corneal surface every 5 minutes for 35 minutes. Five minutes after the initial riboflavin instillation, the corneas in Group 4 experienced a 30 minute exposure to UVA light (3.04 mW/cm 2). X-ray scattering was used to obtain measurements of collagen interfibrillar spacing, spatial order, fibril diameter, D-periodicity and intermolecular spacing throughout the whole tissue thickness and as a function of tissue depth in the treated and untreated corneas. The effect of each treatment on the hydrodynamic behaviour of the cornea (its ability to swell in saline solution) and its resistance to enzymatic digestion were assessed using in vitro laboratory techniques. Results: Corneal thickness decreased significantly following riboflavin application (p,0.01) and also to a lesser extent after UVA exposure (p,0.05). With the exception of the spatial order factor, which was higher in Group 4 than Group 1 (p,0.01), all other measured collagen parameters were unaltered by cross-linking, even within the most anterior 300 microns of the cornea. The cross-linking treatment had no effect on the hydrodynamic behaviour of the cornea but did cause a significant increase in its resistance to enzymatic digestion. Conclusions: It seems likely that cross-links formed during riboflavin/UVA therapy occur predominantly at the collagen fibril surface and in the protein network surrounding the collagen.