Encapsulating curcumin in ethylene diamine-ß-cyclodextrin nanoparticle improves topical cornea delivery.

Curcumin is a powerful scavenger of reactive oxygen species and could prevent the corneal cells from oxidative damage. However, the clinical efficacy of curcumin is limited by its low aqueous solubility and stability, leading to poor bioavailability. ß-cyclodextrin, with a hydrophilic surface and a hydrophobic cavity and self-assembling properties, can form inclusion complexes with lipophilic drugs such as curcumin for ocular delivery. We synthesized ethylene diamine (EDA)-modified ß-cyclodextrin and prepared the curcumin complexation using the solvent evaporation method. The EDA-ß-cyclodextrin provided a better thermodynamic stability and higher complex yield for curcumin complexes, compared to ß-cyclodextrin, which were demonstrated on the analysis of their van't Hoff plots and phase solubility diagrams. We characterized EDA-ß-cyclodextrin curcumin nanoparticles and determined that the EDA modified ß-cyclodextrin is a more suitable carrier than parental ß-cyclodextrin, using FT-IR, XRD, TEM, and analyses of solubility and storage stability. In addition, the curcumin-EDA-ß-cyclodextrin nanoparticles had better in vitro corneal penetration and 3 -h cumulative flux in a porcine cornea experiment, and displayed an improved biocompatibility, confirmed by the histological examination of porcine corneas and cell viability of bovine corneal epithelial cells. These results together revealed a role of EDA modification in the ß-cyclodextrin carrier, including the improvement of curcumin complex formation, thermodynamic properties, cytotoxicity, and the in vitro corneal penetration. The EDA-ß-cyclodextrin inclusion can provide curcumin a higher degree of aqueous solubility and corneal permeability.

Effects of gamma radiation sterilization on the structural and biological properties of decellularized corneal xenografts.

To address the shortcomings associated with corneal transplants, substantial efforts have been focused on developing new modalities such as xenotransplantion. Xenogeneic corneas are anatomically and biomechanically similar to the human cornea, yet their applications require prior decellularization to remove the antigenic components to avoid rejection. In the context of bringing decellularized corneas into clinical use, sterilization is a crucial step that determines the success of the transplantation. Well-standardized sterilization methods, such as gamma irradiation (GI), have been applied to decellularized porcine corneas (DPC) to avoid graft-associated infections in human recipients. However, little is known about the effect of GI on decellularized corneal xenografts. Here, we evaluated the radiation effect on the ultrastructure, optical, mechanical and biological properties of DPC. Transmission electron microscopy revealed that gamma irradiated decellularized porcine cornea (G-DPC) preserved its structural integrity. Moreover, the radiation did not reduce the optical properties of the tissue. Neither DPC nor G-DPC led to further activation of complement system compared to native porcine cornea when exposed to plasma. Although, DPC were mechanically comparable to the native tissue, GI increased the mechanical strength, tissue hydrophobicity and resistance to enzymatic degradation. Despite these changes, human corneal epithelial, stromal, endothelial and hybrid neuroblastoma cells grew and differentiated on DPC and G-DPC. Thus, GI may achieve effective tissue sterilization without affecting critical properties that are essential for corneal transplant survival.

Gas-Permeable, Irritation-Free, Transparent Hydrogel Contact Lens Devices with Metal-Coated Nanofiber Mesh for Eye Interfacing.

An electronic "smart" contact lens device with high gas permeability and optical transparency, as well as mechanical compliance and robustness, offers daily wear capability in eye interfacing and can have broad applications ranging from ocular diagnosis to augmented reality. Most existing contact lens electronics utilize gas-impermeable substrates, electronic components, and interfacial adhesion layers, which impedes them from applications requiring continuous daily wear. Here we report on the design and fabrication of an eye interfacing device with a commercial ocular contact lens as the substrate, metal-coated nanofiber mesh as the conductor, and in situ electrochemically deposited poly(3,4-ethylenedioxythiophene) (PEDOT) /poly(styrene sulfonate) (PSS) as the adhesion material. This hydrogel contact lens device shows high gas permeability, wettability, and level of hydration, in addition to excellent optical transparency, mechanical compliance, and robustness. Using a rabbit model, we found that the animals wearing these hydrogel contact lens devices continuously for 12 hours showed a level of corneal fluorescein staining comparable to those wearing pure hydrogel contact lenses for same period of time, with no obvious corneal abrasion or irritation, indicating their high level of safety for continuous daily wear. Finally, full-field electroretinogram (ERG) recordings on rabbits were carried out to demonstrate the functionality of this device. We believe that the strategy of integrating nanofiber mesh-based electronic components demonstrated here can offer a general platform for hydrogel electronics with the advantages of preserving the physiological and mechanical properties of the hydrogel, thus enabling seamless integration with biological tissues and providing various wearable or implantable sensors with improved biocompatibility for health monitoring or medical treatment.

Epithelium-off corneal cross-linking in progressive keratoconus: 6- year outcomes.

PURPOSE: To evaluate the long-term results of corneal collagen cross-linking (CXL) with epithelium removal in patients with progressive keratoconus. METHODS: This retrospective study included 27 eyes of 18 patients who underwent CXL surgery for progressive keratoconus between April 2009 and March 2012. Best-corrected visual acuity (BCVA), manifest refraction spherical equivalent (SE), maximum keratometry reading (K max), mean of the minimum and maximum keratometry readings (mean-K), central corneal thickness (CCT), and anterior and posterior elevation at the apex preoperatively and year 1, 3 and 6 were evaluated and compared. P values<0.05 were considered to be statistically significant. RESULTS: Mean BCVA was 0.35±0.28 logMAR preoperatively and 0.23±0.20 logMAR 6 years after the procedure (P=0.01). Mean SE decreased from -4.3±2.45 diopters (D) to -3.91±2.12 D (P=0.03). Mean K max decreased from 49.6±3.2 D to 48.6±2.8 D (P=0.04), and mean-K decreased from 47.6±2.5D to 46.9±2.6 D (P=0.04). CCT decreased insignificantly from 466.5±32.1µm to 465.4±26.6µm (P=0.65). Mean anterior elevation at the apex decreased from 12.8±7.9 to 12±8.3µm (P=0.04), and posterior elevation decreased from 27.1±17.4µm to 26.8±18.5µm (P=0.27). Mean-K, max-K, BCVA and CCT showed no change over the last 5 years. After the first year, no significant change was observed in BCVA, SE, max-K, mean-K and CCT, which were therefore considered stable. On the other hand, anterior and posterior elevation readings continued to decrease up to 6 years after CXL. CONCLUSION: Based on our 6-year results, CXL can halt progression of keratoconus and reduce the need for keratoplasty.

Impact of environmental pollution on the ocular surface of Sjögren's syndrome patients / Impacto da poluição ambiental na superfície ocular de pacientes com síndrome de Sjögren

ABSTRACT Purpose: To evaluate the effect of air pollution on the ocular surface of patients with Sjögren's syndrome. Methods: We investigated the ocular surfaces of thirty patients with Sjögren's syndrome and thirty healthy volunteers (control group) living in the Metropolitan Area of Buenos Aires. We used nitrogen dioxide as an indicator of exposure to air pollution. An ocular symptoms questionnaire was answered by all subjects, who also underwent a complete ocular surface ophthalmic examination-including an Ocular Surface Disease Index questionnaire, biomicroscopy, tear breakup time, Schirmer 1 test, corneal and conjunctival vital staining with fluorescein and lissamine green, tear lysozyme concentration, and impression cytology. Results: In almost all ocular surface test findings, we found a positive and significant correlation between higher levels of exposure to air pollution and higher levels of ocular surface damage in both the control group and Sjögren's syndrome patients. In Sjögren's syndrome patients, the Ocular Surface Disease Index questionnaire, tear breakup time, vital staining and impression cytology showed a significant correlation between high levels of air pollution and ocular surface disease. In the control group, the Ocular Surface Disease Index questionnaire, tear breakup time, and impression cytology showed a significant correlation between high levels of air pollution and ocular surface disease. Conclusions: Here we demonstrated that in patients with dry eye syndrome associated with Sjögren, abnormalities of the ocular surface and eye irritation related to air pollution are more severe than those in the control group. We believe that measuring air quality should be not only an integral part of the evaluation of ocular surface disease but also a therapeutic consideration.

RESUMO Objetivo: Avaliar o efeito da poluição do ar na superfície ocular de pacientes com síndrome de Sjögren. Métodos: Foram investigadas as superfícies oculares de trinta pacientes com síndrome de Sjögren e trinta voluntários saudáveis (grupo controle) residentes na Região Metropolitana de Buenos Aires. Usamos o dióxido de nitrogênio como um indicador de exposição à poluição do ar. Um questionário de sintomas oculares foi respondido por todos os indivíduos, que também foram submetidos a um exame oftalmológico completo da superfície ocular - incluindo um questionário do Índice da Doença da Superfície Ocular, biomicroscopia, tempo de ruptura do filme lacrimal, teste de Schirmer 1, coloração da córnea e conjuntiva com fluoresceína e lissamina verde, concentração de lisozima lacrimal e citologia de impressão. Resultados: Em quase todos os achados do teste de superfície ocular, encontramos uma correlação positiva e significativa entre níveis mais altos de exposição à poluição do ar e níveis mais elevados de danos na superfície ocular tanto no grupo controle quanto nos pacientes com síndrome de Sjögren. Em pacientes com síndrome de Sjögren, o questionário do Índice da Doença da Superfície Ocular, tempo de ruptura do filme lacrimal, coloração vital e citologia de impressão mostraram uma correlação significativa entre altos níveis de poluição do ar e doença da superfície ocular. No grupo controle, o questionário do Índice de Doenças da Superfície Ocular, tempo de ruptura do filme lacrimal e citologia de impressão mostraram uma correlação significativa entre altos níveis de poluição do ar e doença da superfície ocular. Conclusões: Aqui demonstramos que, pacientes com síndrome de olho seco associada a Sjögren, as anormalidades da superfície ocular e a irritação ocular relacionadas à poluição do ar são mais graves do que aquelas no grupo controle. Acreditamos que a medição da qualidade do ar não deve ser apenas uma parte integral da avaliação da doença da superfície ocular, mas também uma consideração terapêutica.

Membrane permeation of giant unilamellar vesicles and corneal epithelial cells with lipophilic vitamin nanoemulsions.

Nanoemulsions of a lipophilic vitamin, retinol palmitate (vitamin A; VA), have a therapeutic effect on corneal damage. The nanoemulsion based on a triblock-type polymer surfactant with polyoxyethylene and polypropylene, EO100PO70EO100 (EOPO) showed superior efficacy, as compared with a nanoemulsion based on polyoxyethylene (60) hydrogenated castor oil (HCO). We studied the mechanism of VA nanoemulsions related to efficacy from the viewpoint of the interaction with plasma membrane-mimicking giant unilamellar vesicles (GUVs) and the plasma membrane permeation in corneal epithelial cells. When nanoemulsions and GUVs doped with fluorescent compounds were mixed each other, and observed by confocal laser microscopy, EOPO nanoemulsions induced endocytic morphological changes like strings and vesicles of the bilayer drawn inside a GUV by budding. Judging by isothermal titration calorimetry and ζ potential measurements, the EOPO nanoemulsions seemed to have stronger hydrophobic interactions with the lipid bilayer because of lower coverage of the core interface. Next, when the nanoemulsions prepared with a pyrene derivative of retinol (VApyr) were applied to corneal epithelial cells, the EOPO nanoemulsions greatly permeated the cells and gathered around the cell nucleus, as compared with HCO nanoemulsions. Furthermore, according to the three-dimensional images of the cell, it was found that the vesicles that absorbed nanoemulsions formed from the plasma membrane as real endocytosis, and were transported to the area around the nucleus. Consequently, it is likely that EOPO nanoemulsions entered the cell by membrane-mediated transport, delivering VA to the cell nucleus effectively and enhancing the effects of VA.

Rebamipide suppresses TNF-α production and macrophage infiltration in the conjunctiva.

PURPOSE: To evaluate the anti-inflammatory effect of rebamipide during corneal epithelial wound healing using a mouse wound repair model. METHODS: A 2-mm circular disc of the central cornea was demarcated in the right eye of C57BL/6 mice and the epithelium removed. Rebamipide 2% eyedrop was instilled onto the wounded eye 5 times a day (n = 26). Phosphate-buffered saline (PBS) was used in the control group (n = 26). Corneal and conjunctival IL-1ß and TNF-α levels were measured at 6 h and 24 h postinjury by ELISA. The wounded area was evaluated by fluorescein staining at 24 h postinjury. Macrophage infiltration was assessed immunohistochemically, and TNF-α secretion from macrophages was examined in vitro. RESULTS: Conjunctival IL-1ß and corneal IL-1ß levels were not significantly different between PBS-treated and rebamipide-treated groups. However, conjunctival TNF-α level was significantly lower in the rebamipide-treated group compared with the PBS-treated group. Macrophage migration into the conjunctiva, but not into the cornea, was suppressed by rebamipide treatment. In addition, TNF-α secretion from cultured macrophages was suppressed by rebamipide in a concentration-dependent manner. Rebamipide treatment significantly accelerated corneal epithelial wound healing at 24 h postinjury. CONCLUSIONS: In a mouse corneal epithelial wound model, rebamipide suppressed TNF-α secretion and macrophage infiltration in the conjunctiva, which might have contributed to accelerated corneal epithelial wound healing in the first 24 h following injury.

RES-loaded pegylated CS NPs: for efficient ocular delivery.

The objective of this study is to develop resveratrol (RES) loaded polyethylene glycols (PEGs) modified chitosan (CS) nanoparticles (NPs) by ionic gelation method for the treatment of glaucoma. While increasing the concentration of PEG, the particle size and polydispersity index of the formulations increased. Entrapment efficiency and RES loading (RL) of NPs decreased while increasing PEG concentration. The in vitro release of NPs showed an initial burst release of RES (45%) followed by controlled release. Osmolality of formulations revealed that the prepared NPs were iso-osmolar with the tear. Ocular tolerance of the NPs was evaluated using hen's egg test on the chorioallantoic membrane and it showed that the NPs were non-irritant. RES-loaded PEG-modified CS NPs shows an improved corneal permeation compared with RES dispersion. Fluorescein isothiocyanate loaded CS NPs accumulated on the surface of the cornea but the PEG-modified CS NPs crossed the cornea and reached retinal choroid. RES-loaded PEG-modified CS NPs reduced the intra-ocular pressure (IOP) by 4.3 ± 0.5 mmHg up to 8 h in normotensive rabbits. These results indicate that the developed NPs have efficient delivery of RES to the ocular tissues and reduce the IOP for the treatment of glaucoma.

Nonlinear optical corneal collagen crosslinking of ex vivo rabbit eyes.

PURPOSE: To determine whether riboflavin-induced collagen crosslinking (CXL) could be precisely achieved in the corneal stroma of ex vivo rabbit eyes using nonlinear optical excitation with a low numerical aperture lens and enlarged focal volume. SETTING: Gavin Herbert Eye Institute, University of California Irvine, Irvine, California, USA. DESIGN: Experimental study. METHODS: The corneal epithelium was removed and the corneas were soaked in 0.5% riboflavin solution. Using a 0.1 numerical aperture objective, a theoretical excitation volume of 150 µm × 3 µm was generated using 1 W of 760 nm femtosecond laser light and raster scanned with 4.4 µm line separation at varying effective speeds over a 4.50 mm × 2.25 mm area. Corneal sections were examined for collagen autofluorescence. RESULTS: Collagen autofluorescence was enhanced 2.9 times compared with ultraviolet-A (UVA) CXL. Also, increasing speed was linearly associated with decreasing autofluorescence intensity. The slowest speed of 2.69 mm/s showed a mean of 182.97 µm ± 52.35 (SD) long autofluorescent scan lines axially in the central cornea compared with 147.84 ± 4.35 µm for UVA CXL. CONCLUSIONS: Decreasing dwell time was linearly associated with decreasing autofluorescence intensity, approaching that of UVA CXL at a speed of 8.9 mm/s. Using an effective speed of 8.9 mm/s, nonlinear optical CXL could be achieved over a 3.0 mm diameter area in fewer than 4 minutes. Further development of nonlinear optical CXL might result in safer, faster, and more effective CXL treatments. FINANCIAL DISCLOSURE: None of the authors has a financial or proprietary interest in any material or method mentioned.

Effects of genipin corneal crosslinking in rabbit corneas.

PURPOSE: To evaluate the effect of genipin, a natural crosslinking agent, in rabbit eyes. SETTING: Department of Ophthalmology, Universidad Nacional de Colombia Centro de Tecnologia Oftalmica, Bogotá, Colombia. DESIGN: Experimental study. METHODS: Ex vivo rabbit eyes (16; 8 rabbits) were treated with genipin 1.00%, 0.50%, and 0.25% for 5 minutes with a vacuum device to increase corneal permeability. Penetration was evaluated using Scheimpflug pachymetry (Pentacam). In the in vivo model (20 rabbits; 1 eye treated, 1 eye with vehicle), corneas were crosslinked with genipin as described. Corneal curvature, corneal pachymetry, and intraocular pressure (IOP) assessments as well as slitlamp examinations were performed 0, 7, 30, and 60 days after treatment. RESULTS: In the ex vivo model, Scheimpflug pachymetry showed deep penetration in the rabbit corneas with an increase in corneal density and a dose-dependent relationship. Corneal flattening was observed in treated eyes (mean 4.4 diopters ± 0.5 [SD]) compared with the control eyes. Pachymetry and IOP were stable in all evaluations. No eye showed toxicity in the anterior chamber or in the lens. CONCLUSIONS: Corneal crosslinking induced by genipin produced significant flattening of the cornea with no toxicity in rabbit eyes. This crosslinking could be useful in the treatment of corneal ectasia and in the modification of corneal curvature. FINANCIAL DISCLOSURE: None of the authors has a financial or proprietary interest in any material or method mentioned.

Quantitative proteomic analysis of mice corneal tissues reveals angiogenesis-related proteins involved in corneal neovascularization.

Corneal neovascularization (CNV) was induced in Balb/c mice by alkali burns in the central area of the cornea with a diameter of 2.5mm. After fourteen days, the cornea from one eye was collected for histological staining for CNV examination, while the cornea from the other eye of the same mouse was harvested for proteomic analysis. The label-free quantitative proteomic approach was applied to analyze five normal corneal tissues (normal group mice n=5) and five corresponding neovascularized corneal tissues (model group mice n=5). A total of 2124 proteins were identified, and 1682 proteins were quantified from these corneal tissues. Among these quantified proteins, 290 proteins were significantly changed between normal and alkali burned corneal tissues. Of these significantly changed proteins, 35 were reported or predicted as angiogenesis-related proteins. Then, these 35 proteins were analyzed using Ingenuity Pathway Analysis Software, resulting in 26 proteins enriched and connected to each other in the protein-protein interaction network, such as Lcn-2, αB-crystallin and Serpinf1 (PEDF). These three significantly changed proteins were selected for further Western blotting validation. Consistent with the quantitative proteomic results, Western blotting showed that Lcn-2 and αB-crystallin were significantly up-regulated in CNV model, while PEDF was down-regulated. This study provided increased understanding of angiogenesis-related proteins involved in corneal vascular development, which will be useful in the ophthalmic clinic of specifically target angiogenesis.

[The correlations between corneal sensation, tear meniscus volume, and tear film osmolarity after femtosecond laser-assisted LASIK].

OBJECTIVE: To investigate the correlations between corneal sensation, tear meniscus volume, and tear film osmolarity after femtosecond laser-assisted LASIK (FS-LASIK) surgery. METHODS: In this prospective clinical study, 31 patients undergoing FS-LASIK for myopia were recruited. The upper and lower tear meniscus volumes (UTMV and LTMV) were measured by customized anterior segment optical coherence tomography, tear film osmolarity was measured by a TearLab Osmolarity test device, central corneal sensation was measured by a Cochet-Bonner esthesiometer preoperatively, at 1 week, 1 and 3 months postoperatively. Repeated measures analysis of variance was used to evaluate whether the tear film osmolarity, tear meniscus volume, and corneal sensation were changed after surgery. The correlations between these variables were analyzed by the Pearson correlation analysis. RESULTS: The tear film osmolarity was (310.03 ± 16.48) mOsms/L preoperatively, (323.51 ± 15.92) mOsms/L at 1 week, (319.93 ± 14.27) mOsms/L at 1 month, and (314.97±12.91) mOsms/L at 3 months. The UTMV was (0.42±0.15), (0.25± 0.09), (0.30±0.11), and (0.35±0.09) µL, respectively; the LTMV was (0.60±0.21),(0.37±0.08), (0.44± 0.14), and (0.52±0.17) µL, respectively. The tear film osmolarity was significantly higher at 1 week and 1 month postoperatively compared with the baseline (P=0.001, 0.004), and reduced to the preoperative level at 3 months (P=0.573). The UTMV, LTMV, and corneal sensation values presented significant decreases at all postoperative time points (all P<0.05). The Pearson correlation analysis showed the postoperative UTMV had a weak relationship with corneal sensation at 1 week after surgery (r=0.356,P=0.005). There were significant correlations between the preoperative LTMV and corneal sensation at 1 week, 1 and 3 months (respectively, r=0.422, 0.366, 0.352;P=0.001, 0.004, 0.006). No significant correlations were found between the tear film osmolarity, tear meniscus volume, and corneal sensation after surgery (all P>0.05). CONCLUSION: The tear film osmolarity, tear meniscus volume, and corneal sensation became aggravated due to the FS-LASIK surgery procedures. There were significant correlations between the preoperative tear meniscus volume and recovery of corneal sensation early after surgery. A higher tear meniscus volume before surgery may contribute to a faster corneal sensation recovery.

Nanoparticle cross-linked collagen shields for sustained delivery of pilocarpine hydrochloride.

Glaucoma is a common progressive eye disorder which remains the second leading cause of blindness worldwide. Current therapy involves frequent administration of eye drops which often results in poor patient adherence and therapeutic outcomes. The aim of this study was to overcome these limitations by developing a novel nanoparticle cross-linked collagen shield for sustained delivery of pilocarpine hydrochloride (PHCl). Three metal oxide nanoparticles (NPs); titanium dioxide (TiO2), zinc oxide (ZnO) and polyvinylpyrrolidone (PVP) capped zinc oxide (ZnO/PVP), were evaluated for their cytotoxicity as well as shield transparency before selecting ZnO/PVP NPs as the ideal candidate. Cross-linked collagen shields were then characterized for their mechanical strength, swelling capacity and bioadhesive properties, with ZnO/PVP NP cross-linked shields showing the most favorable characteristics compared to plain films. The shield with the best properties was then loaded with PHCl and in vitro release of zinc ions as well as PHCl was measured without and with further cross-linking by ultraviolet irradiation. The concentration of zinc ions released was well below the IC50 rendering them safe for ocular use. Moreover, collagen shields cross-linked with ZnO/PVP NPs released PHCl over a period of 14 days offering a promising sustained release treatment option for glaucoma.

Uptake and bioconversion of stereoisomeric dipeptide prodrugs of ganciclovir by nanoparticulate carriers in corneal epithelial cells.

PURPOSE: The objective of this study is to investigate cellular uptake of prodrug-loaded nanoparticle (NP). Another objective is to study bioconversion of stereoisomeric dipeptide prodrugs of ganciclovir (GCV) including L-Val-L-Val-GCV (LLGCV), L-Val-D-Val-GCV (LDGCV) and d-Val-l-Val-GCV (DLGCV) in human corneal epithelial cell (HCEC) model. METHODS: Poly(D,L-lactic-co-glycolic acid) (PLGA) NP encapsulating prodrugs of GCV were formulated under a double emulsion method. Fluorescein isothiocyanate isomer-PLGA conjugates were synthesized to fabricate biocompatible fluorescent PLGA NP. Intracellular uptake of FITC-labeled NP was visualized by a fluorescent microscope in HCEC cells. RESULTS: Fluorescent PLGA NP and non-fluorescent NP display similar hydrodynamic diameter in the range of 115-145 nm with a narrow particle size distribution and zeta potentials around -13 mV. Both NP types showed identical intracellular accumulation in HCEC cells. Maximum uptake (around 60%) was noted at 3 h for NP. Cellular uptake and intracellular accumulation of prodrugs are significantly different among three stereoisomeric dipeptide prodrugs. The microscopic images show that NPs are avidly internalized by HCEC cells and distributed throughout the cytoplasm instead of being localized on the cell surface. Following cellular uptake, prodrugs released from NP gradually bioreversed into parent drug GCV. LLGCV showed the highest degradation rate, followed by LDGCV and DLGCV. CONCLUSION: LLGCV, LDGCV and DLGCV released from NP exhibited superior uptake and bioreversion in corneal cells.

[Predictive factors for visual outcome after corneal collagen crosslinking treatment in progressive keratoconus: One-year refractive and topographic results]. / Facteurs prédictifs de bonne réponse au crosslinking d'un kératocône évolutif : résultats réfractifs et topographiques à un an postopératoire.

PURPOSE: To assess the effects of preoperative patient characteristics on clinical outcomes of corneal collagen crosslinking (CXL) in patients with progressive keratoconus. PATIENTS AND METHODS: Fifty-four eyes of 41 patients underwent CXL for progressive keratoconus between June 2011 and December 2012. Corneal topography (Orbscan(®)) was assessed at 1, 3, and 6 months and 1 year after CXL treatment and compared with preoperative data. RESULTS: A significant improvement in 1-year postoperative best-corrected visual acuity (BCVA) (0.16±0.21 LogMar preoperatively versus 0.09±0.16 LogMar postoperatively, P=0.007) and in 3mm topographic central irregular astigmatism (P=0.04) was demonstrated with CXL. No significant change was noted for refractive astigmatism (P=0.69), or for 1-year postoperative Kmax (48.4 D±4.1 at baseline versus 48.5 D±4.1 postoperatively, P=0.46). Predictive factors for BVCA improvement were low preoperative BCVA, high refractive astigmatism and advanced keratoconus. Predictive factors for stability of postoperative Kmax values were early keratoconus, and central cone ("nipple" morphology of the cone mainly located in the central 3mm of the cornea). CONCLUSION: This retrospective study confirms the efficacy of CXL for progressive keratoconus, from a refractive as well as topographic standpoint. While cone localization or its eccentricity seems to explain the variability of CXL efficacy reported in the literature, cone severity appears to be the main predictive factor for a lack of topographic stability after CXL treatment but must be weighted by the preferential localization of the cone (3 or 5mm central corneal zone).

AFM characterization of chemically treated corneal cells.

We present a characterization of chemically treated cells using atomic force microscopy (AFM) which can observe changes in morphology and elasticity of cells. Since AFM has the significant advantage that it does not require fixation of samples, the method is simple and can capture various properties of living cells. In this study, corneal epithelial and endothelial cells were examined. The topography images of the corneal cells without glutaraldehyde (GA) fixation were successfully obtained. The images showed a natural three-dimensional shape of these cells, which scanning electron microscope (SEM) images could not provide. The AFM images of GA-fixed cells were taken and compared with a SEM image reported in the literature. Our results show that longer time for GA fixation makes the surface of the corneal endothelial tissue stiffer. Also, longer treatment results in relatively large structural variation in samples. Combined with conventional histochemical methods, this approach helps us gain an overall understanding of the influence of such chemical treatment.

Polarization-sensitive sum-frequency generation microscopy of collagen fibers.

Point-scanning sum-frequency generation (SFG) microscopy enables the generation of images of collagen I fibers in tissues by tuning into specific vibrational resonances of the polypeptide. It is shown that when collagen-rich tissues are visualized near the 2954 cm(-1) stretching vibration of methylene groups, the SFG image contrast is higher compared to the contrast seen in nonresonant second-harmonic generation (SHG) imaging. Polarization and spectrally resolved analysis of the SFG signal as a function of fiber orientation in the CH-stretching range of the vibrational spectrum enabled a comparative characterization of the achiral tensor elements of collagen's second-order susceptibility. This analysis reveals that selected on-resonance tensor elements are enhanced over other elements, giving rise to a much stronger anisotropy ρ of the signal for SFG (ρ ≈ 15) compared to SHG (ρ ≈ 3). The improved anisotropy of the vibrationally resonant signal contributes to the higher contrast seen in the SFG tissue images.

Evaluation of ABCG2 and p63 expression in canine cornea and cultivated corneal epithelial cells.

OBJECTIVE: To examine the expressions of ABCG2 and p63 in canine corneal epithelia and to evaluate their significance in corneal regeneration. PROCEDURES: Canine corneal and limbal epithelial cells were obtained from five healthy beagle dogs. We analyzed the morphological properties of cultivated limbal and corneal epithelial cells. We compared the expressions of ABCG2 and p63 in the limbus and central cornea by immunohistochemistry and real-time quantitative PCR. We analyzed the expression of these markers in cultivated cells by immunocytochemistry and real-time quantitative PCR. RESULTS: The limbal epithelial cells were smaller and proliferated more rapidly than the corneal epithelial cells in primary cultures. The corneal cells failed to be subcultured, whereas the limbal cells could be subcultured with increasing cell size. ABCG2 was localized in the basal layer of the limbal epithelium, and p63 was widely detected in the entire corneal epithelia. ABCG2 expression was significantly higher, and p63 was slightly higher in the limbus compared with the central cornea. ABCG2 was detected only in limbal cells in primary culture, not in corneal cells or passaged limbal cells. p63 was detected in both limbal and corneal cells and decreased gradually in the limbal cells with the cell passages. CONCLUSIONS: ABCG2 was localized in canine limbal epithelial cells, and p63 was widely expressed in canine corneal epithelia. ABCG2 and p63 could prove to be useful markers in dogs for putative corneal epithelial stem cells and for corneal epithelial cell proliferation, respectively.