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Background Repeated surgery excisions could induce obvious irregular astigmatism in patients with recurrent pterygium. Our study is aimed to illustrate the effect of adjunct excimer laser phototherapeutic keratectomy (PTK) in limbal-conjunctival autograft transplantation on visual quality for patients with recurrent pterygium. Methods Retrospective case-control study. Eyes that underwent pterygium excision with (PTK group) or without (control group) PTK from 2006 to 2017 were retrospectively included. Recurrence rate, preoperative and postoperative surface regularity index (SRI), surface asymmetry index (SAI), cylinder and LogMAR vision were collected. Postoperative anterior segment optical coherence topography and in vivo confocal microscopy were performed to monitor the cornea epithelium healing and cellular recovery process respectively. Results A total of 99 eyes of 99 patients were collected, of which 39 were treated with PTK and 60 without PTK. The mean follow-up time was 50.4 ± 38.1 months. The recurrence rate was 10.3% (4 eyes) in the PTK group and 13.3% (8 eyes) in the control group (p = 0.759). The SRI decreased 0.53 (range: − 0.88, 2.81), SAI decreased 0.53 (range: − 0.64, 2.94), and the cylinder decreased 2.08 (range:-0.16, 9.40) D in the PTK group, and the corresponding values were 0.48 (range:-0.45, 2.27), 0.27 (range:-1.06, 2.21) and 0.71 (range:-1.75, 3.55) D in the control group, respectively (Z = 1.76, 2.15, and 3.97, p = 0.005, 0.016, and 0.000 respectively). LogMAR vision improved in both groups after surgery, with an improvement of 0.18 (range: 0.00, 0.70) in the PTK group and 0.06 (range: − 0.12, 0.50) in the control group (Z = 4.08, p = 0.000). Besides, the eyes treated with PTK showed faster re-epithelization and better cellular recovery. Conclusions For recurrent pterygium, surgical excision with adjunct PTK might be a better option with improved corneal surface and vision outcomes.

AIM: To observe the efficacy of different artificial eye drops on corneal epithelium healing in rabbit. METHODS: Thirty-five rabbits with 6 mm diameter central corneal epithelium removed were randomly assigned to six groups: 0.9% normal saline (NS) group, 0.1% hyaluronate (HA) group, 0.3% HA group, Tears Naturale Free® (TNF) group, 0.4% polyethylene glycol (PEG) group, 0.5% carboxymethyl cellulose (CMC) group and blank control group. Treatments were administered topically four times daily. Corneal epithelium healing was evaluated by the percentage reduction in wound area at 24, 36, 48, 60, and 72h after removal of the corneal epithelium. Cornea re-epithelialization was also assessed by histological analysis and electron microscopy. RESULTS: All corneal wounds completely re-epithelialized in less than 72h. The average re-epithelialization time was 47.61±4.25h in the 0.3% HA group and 49.72±1.05h in the 0.9% NS group, followed by 0.1% HA, TNF, 0.4% PEG, 0.5% CMC, and lastly by the control group. Compared to the control group, there were significant differences among 0.3% HA, 0.9% NS, PEG, and TNF (P

Purpose: Our aim was to examine the associations between the cornea morphological parameters, endothelial cell density, and anterior chamber measurements. Methods: This observational study included 50 eyes of 50 healthy volunteers. The thicknesses of corneal epithelium, Bowman’s layer, stroma, Descemet’s membrane–endothelium complex, and pre-ocular tear film were measured by means of anterior segment optical coherence tomography. The keratometry (K), corneal volume (CV), corneal optical densitometry (COD), iridocorneal angle (ICA), anterior chamber depth (ACD), and anterior chamber volume (ACV) measurements were taken by the Scheimpflug anterior segment imaging. The corneal endothelial cell density and percentage of hexagonality were measured by specular microscopy. Results: The COD was only correlated with the thickness of Bowman’s layer (r = -0.30, p = 0.035). The hexagonal endothelial cell percentage was correlated with the thickness of the pre-ocular tear film (r = -0.50, p

Purpose We have observed noticably weak epithelial attachment in vitamin D receptor knockout mice (VDR KO) undergoing epithelial debridement. We hypothesized that VDR KO negatively affects corneal epithelial cell desmosomes and/or hemidesmosomes. Methods Transcript levels of desmosome and hemidesmosome proteins in VDR KO corneas were assessed by qPCR. Western blotting and immunochemistry were used to detect proteins in cultured cells exposed to 1,25(OH)2D3 and 24R,25(OH)2D3. Results VDR KO resulted in decreased corneal desmosomal desmoglein 1 (DSG1) and desmocollin 2 (DSC2) mRNA, and hemidesmosomal plectin mRNA. DSG1 and plectin protein expression were reduced in VDR KO corneas. DSG1 protein expression increased in VDR wild types (VDR WT) and VDR KO mouse primary epithelial cells (MPCEC) treated with 1,25(OH)2D3 and 24R,25(OH)2D3. 24R,25(OH)2D3 treatment resulted in increased plectin and integrin β4 levels in VDR WT MPCEC, and decreased levels in VDR KO MPCEC. Treatment of human corneal epithelial cells (HCEC) with 1,25(OH)2D3 and 24R,25(OH)2D3 resulted in increased DSC2 and DSG1 protein expression. Plectin and integrin β4 were only increased in 24R,25(OH)2D3 treated HCEC. Conclusions VDR KO results in reduced desmosomal and hemidesmosomal mRNA and protein levels. 1,25(OH)2D3 and 24R,25(OH)2D3 increased DSG1 protein in all cells tested. For hemidesmosome proteins, 24R,25(OH)2D3 increased plectin and integrin β4 protein expression in VDR WT and HCEC, with decreased expression in VDR KO MPCEC. Thus, vitamin D3 is involved in desmosome and hemidesmosome junction formation/regulation, and their decreased expression likely contributes to the loosely adherent corneal epithelium in VDR KO mice. Our data indicate the presence of a VDR-independent pathway.

Keeping the integrity and transparency of the cornea is the most important issue to ensure normal vision. There are more than 10 million patients going blind due to the cornea diseases worldwide. One of the effective ways to cure corneal diseases is corneal transplantation. Currently, donations are the main source of corneas for transplantation, but immune rejection and a shortage of donor corneas are still serious problems. Graft rejection could cause transplanted cornea opacity to fail. Therefore, bioengineer-based corneas become a new source for corneal transplantation. Limbal stem cells (LSCs) are located at the basal layer in the epithelial palisades of Vogt, which serve a homeostatic function for the cornea epithelium and repair the damaged cornea. LSC-based transplantation is one of the hot topics currently. Clinical data showed that the ratio of LSCs to total candidate cells for a transplantation has a significant impact on the effectiveness of the transplantation. It indicates that it is very important to accurately identify the LSCs. To date, several putative biomarkers of LSCs have been widely reported, whereas their specificity is controversial. As reported, the identification of LSCs is based on the characteristics of stem cells, such as a nuclear-to-cytoplasm ratio (N/C) ≥ 0.7, label-retaining, and side population (SP) phenotype. Here, we review recently published data to provide an insight into the circumstances in the study of LSC biomarkers. The particularities of limbus anatomy and histochemistry, the limits of the current technology level for LSC isolation, the heterogeneity of LSCs and the influence of enzyme digestion are discussed. Practical approaches are proposed in order to overcome the difficulties in basic and applied research for LSC-specific biomarkers.

Background To study basal epithelial cell (BEC), sub-basal nerve plexus (SBN) and Langerhans cell (LC) density in patients with type 2 diabetes mellitus (T2DM) with corneal punctate epitheliopathy (CPE) and to assess their association with time to healing of CPE. Methods Retrospective study of in vivo confocal microscopy (IVCM) in 160 eyes from 160 patients with T2DM diagnosed with CPE due to a single cause. Key exclusion criteria included multiple-causes for CPE or treatment with autologous serum. A total of 149 eyes from 149 gender- age- and aetiolgy-matched patients with CPE without T2DM comprised the control group. Electronic records were reviewed for demographic features, history of T2DM and aetiology of CPE. Density of BEC, SBN and LC were compared between the two groups. Results The healing time in days for CPE with different aetiologies in the T2DM and control groups were as follows: dry eye (21.56 ± 2.41; 7.00 ± 2.19; P = 0.001); meibomian gland dysfunction (26.42 ± 6.04; 9.21 ± 2.55; P = 0.001); cataract extraction (38.00 ± 19.62; 25.83 ± 11.49; P = 0.043); drug induced (53.19 ± 18.83; 41.86 ± 23.87; P = 0.018) and exposure (38.25 ± 14.13; 29.00 ± 13.67; P = 0.026). LC density was 38.70 ± 9.65 cells/mm2 in the T2DM group comparedwith 25.53 ± 3.54 cells/mm2 in the controls (P = 0.001). SBN density was 11.76 ± 1.69 mm/mm2 in the T2DM group compared with 20.92 ± 1.43 mm/mm2 in the controls (P = 0.001). BEC density in the T2DM group was 4982 ± 1178 cells/mm2 compared with 5739 ± 394 cells/mm2 in the control group (P = 0.018). Age and duration of T2DM had no relationship with healing time (multiple linear regression, P = 0.618; P = 0.787). The density of LC in the T2DM group showed a negative correlation with SBN density (r = 0.350; R2 = 0.1225; P = 0.034). The density of SBN in the T2DM group showed a positive correlation with BEC density (r = 0.427; R2 = 0.1823; P = 0.008). The density of BEC in the T2DM group showed a negative correlation with healing time (r = 0.931; R2 = 0.8668; P = 0.001). Conclusions Utilising IVCM, we have demonstrated increased LC and decreased SBN in patients with T2DM and CPE. Both may be related to lower BEC density and nuclei enhanced reflection. Furthermore, decreased BEC density may lead to delay in cornea epithelium healing in the T2DM group comparedwith controls. An immune-mediated response may play a role in delayed wound closure in patients with T2DM.

PubMed: 18035754, We investigated whether the addition of Gingko Biloba extract (EGb 761) to rabbit corneal epithelial medium before cell freezing improved cell viability after freezing then thawing. After removal of corneas, they were treated with enzymes and the corneal epithelium was prepared as a single cell suspension in freezing media with or without EGb 761. After freezing for two weeks then thawing, a higher cell viability was found in the cornea cell suspensions which had been frozen pretreated with EGb 761 in the media. The improvement with corneal cell viability with EGb 761 pretreatment is postulated to be based on the antioxidant capacity of the plant extract.

Descemet’s stripping endothelial keratoplasty is an emerging technique finalized to treat endothelial dysfunction replacing only the pathological portion of cornea. The advent of any new technique puts us in front of new complications. The epithelial ingrowth is a well-known complication already studied in case of ocular trauma and more recently in refractive surgery. This job analyzed the potential etiopathogenesis of epithelial ingrowth after DSAEK, reviewing the cases described in literature, and suggests the potential therapy.

Biomedical engineering is a unique area that allows fusion between two distinct fields of engineering and medicine. The integration of efforts from both fields promises progress through acquisition of information from tissues, cells, and organs through non-invasive methods of assessment. Here we investigate the ability of a hyperspectral device in extracting data from tissues through the wavelength spectrum, in foreseeing its potential in clinical diagnostics by simplifying methods of examination by clinicians in detecting corneal injuries. Hyperspectral imaging using 400 to 1000nm visible wavelength was used to scan five porcine eyes (injured and non-injured). Images were saved in three dimensional images of rows, columns, and depth slices at 1200 to 1300×804×604 and were processed. All laboratory works were performed in accordance with the general risk assessment of University of Strathclyde. In our results, analysis of the images reveals significant cue between 500 to 800nm bands in differentiating between injured and non-injured parts of the eye.

Background/Aim. Pterygium internum presents a significant epidemiological problem. Its etiopathogenesis is still unclear. After surgical removal it shows great tendency to recidives. The aim of this paper was to investigate connection between histopathological characteristics (inflammation presence, vascularization degree and fibrinoid changes) of pterygium and its clinical characteristics (duration, size, pterygium grade, presence of Fuchs' spots and recidives) and determine indicators for recidives prediction. Metods. We analyzed the material taken from 55 patients operated by Arlthi's method. The samples were colored by using standard histochemical methods: hematoxylin-eosin (HE), trichrome Masson painting, Gomora reticulin and PAS technique. Results. Pterygium was mostly covered by epithelium resembling conjunctival, while in the frontal cap region it showed the morphology of plate-layer cornea epithelium. The structural basis of the epithelium was composed of continuous basal lamina and continuous adhesive fibres underneath. This adhesive basis showed fibrinoid changes in the form of oval islands of various size, parallel to convexity of pterygium, or in the form of unified focus. The number, caliber and type of blood vessels showed a pronounced variability. Duration of pterygium and its size were in negative correlation with intensity of inflammation, without statistical significance. Pterygium with a longer period of develepment had negative correlation with the degree of vascularization (p > 0.05). The presence of Fuchs' spots showed a statitistically significant positive correlation with the degree of vascularization (p < 0.05). The intensity of fibrinoid changes was higher in pterygium with Fuchs' spots and in those which recurred (p > 0.05). Conclusion. Histopathological analysis of pterygium morphological shapes is a good basis for the prediction of recidives, which present the greatest problem in the treatment of this widely spread disease.

Rabbit cornea epithelium was exposed to UV-radiation for 15 min from a distance of 50 cm, and specimens were studied after 1/2, 1, and 3 h, respectively. The following changes occurred: 1) Reduced number of the large impressions or the full-thickness holes of the superficial cells. 2) Partly rejected cells. 3) Numerous small plasma membrane defects. This investigation shows plasma membrane defects at an early stage after the exposure, and this may be the locus for the initial damage.

The keratoprosthesis (KPro; “artificial cornea”) offers patients with cornea blindness, the hope of visual recovery. The first KPro designs entailed placing an optically clear material through an opaque cornea. Although introduced over 200 years ago, the basic concept is retained in many of the modern KPro designs. The Boston KPro, employs a polymethylmethacrylate (PMMA) (inert plastic) optic stabilized between a front and back plate. With over 2000 implanted world-wide to date, the Boston KPro has an excellent retention rate in patients who have failed prior penetrating keratoplasties, but lack chemical injuries or auto-immune cicatricial diseases, such as Stevens-Johnson syndrome or pemphigoid. From the Boston KPro multicenter study, the patient population who had a primary diagnosis of graft rejection retained the KPro in 97% of the eyes with a mean follow-up of 8.5 months.1 However, patients with cicatricial autoimmune disease had a retention rate of 83% and those with chemical injuries as a primary diagnosis had an 89% retention rate. Over a longer follow-up period, the retention rate decreases further for patients with autoimmune diseases and chemical injuries.2,3 For this subset of desperate patients, we continue to search for methods of increasing the retention rate of a KPro. Some KPro models differ from early designs by surrounding a central optic with a carrier or haptic that is intended to “biointegrate” with the cornea. In theory, the KPro could potentially integrate with the cornea epithelium, stroma, endothelium, or a combination of the corneal layers. Most of the “biointegratable” KPro research has focused on integration with either the cornea epithelium or the stomal keratocytes. Integration with the cornea epithelium may offer the advantage of a barrier to infection, but it would offer little structural support. Given that the stroma comprises about 90% of the cornea thickness, a type of stromal adhesion may increase the structural integrity of a KPro. Bio-integratable KPro designs can be separated into autologous biologic models and other models derived from biologic materials. These models include biologic haptics, coatings, and scaffolds. This paper will review both the clinical use of and the research on biologic KPro models.

AIM:To investigate the effect of amniotic membrane covering (AMC) on the healing of cornea epithelium and visual acuity for fungal keratitis after debridement.METHODS:Twenty fungal keratitis patients were divided into two groups randomly, the AMC group and the control group, ten patients each group. Both debridement of the infected cornea tissue and standard anti-fungus drugs treatments were given to every patients, monolayer amniotic membrane were sutured to the surface of the entire cornea and bulbar conjunctiva with 10-0 nylon suture for patients in the AMC group. The diameter of the ulcer was determined with slit lamp microscope and the depth of the infiltration was determined with anterior segment optical coherence tomography. Uncorrected visual acuity (UCVA) was tested before surgery and three month after healing of the epithelial layer. The healing time of the cornea epithelium, visual acuity (VA) was compared between the two groups using t-test.RESULTS:There was no statistical difference of the diameter of the ulcer, depth of the infiltration, height of the hypopyon and VA between the two groups before surgery (P＞0.05). The average healing time of the AMC group was 6.89±2.98d, which was statistically shorter than that of the control group (10.23±2.78d) (P＜0.05). The average UCVA of the AMC group was 0.138±0.083, which was statistically better than that of the control group (0.053±0.068) (P＜0.05).CONCLUSION:AMC surgery could promote healing of cornea epithelium after debridement for fungal keratitis and lead to better VA outcome.

Submitted by Vitor Silverio Rodrigues (vitorsrodrigues@reitoria.unesp.br) on 2014-05-27T11:28:49Z No. of bitstreams: 0Bitstream added on 2014-05-27T14:48:19Z : No. of bitstreams: 1 2-s2.0-84876059594.pdf: 325470 bytes, checksum: 793db00f101b8990f7ce3b874b80b0b7 (MD5) Made available in DSpace on 2014-05-27T11:28:49Z (GMT). No. of bitstreams: 0 Previous issue date: 2013-04-01 A exemplo do que ocorre com outros fármacos, a biodisponibilidade da anfotericina B (AmB) através da via ocular repreesenta um grande desafio para a pesquisa científica. Na verdade, a baixa biodisponibilidade apresentada por tal molécula é devido, principalmente, a presença das barreiras oculares que impedem a absorção deste fármaco para os tecidos internos. A toxicidade associada a este fármaco, assim como a sua baixa capacidade em permear a córnea íntegra também consiste em um problema associado ao seu uso clínico. Novos veículos seguros e eficazes para a liberação ocular da AmB são, portanto, necessários. As microemulsões (MEs) aparecem como um interessante sistema devido à sua transparência, estabilidade termodinâmica e favorável viscosidade. O conhecimento do processo de formação das MEs contendo AmB, assim como a compreensão de toda a sua caracterização físico- química correspondem a aspectos importantes para se determinar as condições favoráveis para que estes sistemas venham a ser empregados como colírios. Esta revisão tem como objetivo, portanto, abordar este tema enfatizando os principais aspectos relacionados com a utilização de MEs como sistemas de liberação para a AmB através da via tópica oftálmica. As occurs with a number of drugs, the bioavailability of amphotericin B (AmB) used to treat fungal infections by the ocular route remains a great challenge to research scientists. In fact, the poor bioavailability of AmB is due mainly to the corneal barrier, which leads to a precorneal loss and consequent decrease in the absorption of this drug into the intraocular tissues. The toxicity associated with this molecule, together with its poor ability to penetrate the intact corneal epithelium, also represents a major drawback to its clinical use. New effective and safe drug vehicles for ocular delivery of AmB are therefore urgently needed. Microemulsions (MEs) seem to be an interesting system, owing to their transparent appearance, thermodynamic stability and favorable viscosity. Knowledge of the process of formation of AmB-containing MEs, as well as a good understanding of the physical chemistry of such systems, would provide reliable information on the best conditions for the use of these systems as eye drops. The goal of this research was thus to make an approach to this subject by reviewing the main studies on the use of MEs as delivery systems for AmB in topical eye treatment. Centro de Ciências da Saúde (CCS) Programa de Pós-Graduação em Ciências da Saúde (PPGCSa) Laboratório de Sistemas Dispersos (LaSiD), Natal-RN Centro de Ciências Biológicas e da Saúde (CCBS) Departamento de Farmácia, Campina Grande-PB Grupo de Sistemas Biomiméticos Fármacos Universidade Estadual Paulista (UNESP), Araraquara-SP Centro de Ciências da Saúde (CCS) Programa de Pós-Graduação em Ciências da Saúde (PPGCSa) Laboratorio de Sistemas Dispersos, (LASID), Universidade Federal do Rio Grande do Norte (UFRN), Natal-RN Departamento de Medicamentos Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro, RJ Grupo de Sistemas Biomiméticos Fármacos Universidade Estadual Paulista (UNESP), Araraquara-SP

Submitted by Vitor Silverio Rodrigues (vitorsrodrigues@reitoria.unesp.br) on 2014-05-27T11:22:27Z No. of bitstreams: 0Bitstream added on 2014-05-27T14:43:54Z : No. of bitstreams: 1 2-s2.0-34248579599.pdf: 604626 bytes, checksum: 1957b4bfbf6c652cb41fa86d4a6aa46d (MD5) Made available in DSpace on 2014-05-27T11:22:27Z (GMT). No. of bitstreams: 0 Previous issue date: 2007-04-01 • Aim: To observe the effects of topical application of 5-fluorouracil (5-FU) on the rabbits corneal limbus. • Methods: 5-FU was applied topically to the corneoscleral region of rabbits eyes. The animals were sacrificed immediately or 7, 15, 30 and 60 days later, and tissues were submitted to histological examination. • Results: All animals presented corneoscleral deepithelization close to the site of application during the immediate post-operative period, whereas on the 4th postoperative day ulceration was no longer present. Histological examination showed absence of epithelium and slight edema. After one week (G2), 2 animals presented epithelial defects, thickened epithelium with larger basal cells and loose chromatin, and slight subepithelial edema. The remaining groups showed no alterations. • Conclusion: The 5-FU topically on the corneoscleral limbus postpone the epitelization. Department of Ophthalmology Faculdade de Medicina de Botucatu, 18618-000-Botucatu-Sao, Paulo State Department of Pathology Faculdade de Medicina de Botucatu, 18618-000-Botucatu-Sao, Paulo State Department of Ophthalmology Faculdade de Medicina de Botucatu, 18618-000-Botucatu-Sao, Paulo State Department of Pathology Faculdade de Medicina de Botucatu, 18618-000-Botucatu-Sao, Paulo State

The corneal endothelium is essential for the maintenance of the corneal transparency. The aim of this study was to examine the morphology of the endothelial surface and perform morphometric analysis of the normal corneal endothelial cells of the Magellanic penguin (Spheniscus magellanicus) using scanning electron microscopy. The present work demonstrates that the corneal endothelium of the Magellanic penguin is similar to those described in other vertebrates.

In summary, we found that AMT can be helpful for the treatment of epithelial defects and stromal ulcers. We came to learn that cases with total limbal deficiency or extensive ocular surface inflammation may not be cured with AMT alone. AMT provides improvement of corneal sensitivity, tear film stability and impression cytology parameters. However, the entire mechanism of the healing effect of amniotic membrane is still unknown. A recent experimental study revealed that amniotic membrane transplantation vs tarsorraphy in murine HSV-1 stromal keratitis resulted in improvements in substance-P-related corneal nerve fibres in eyes treated with amniotic membrane, but not in eyes treated with tarsorraphy. We think that prospective, controlled, comparative studies of corneal ulcers treated by, for instance, tarsorraphy or other modalities should be performed to investigate whether the beneficial changes of amniotic membrane transplantation are greater or lesser than the changes that might have been observed by an alternative treatment. In this study, we tried to point to the effects of amniotic membrane transplantation on the ocular surface together with the problematic and unresolved issues. Thus, it is our sincere belief that further studies should be carried out along these lines.

Submitted by Vitor Silverio Rodrigues (vitorsrodrigues@reitoria.unesp.br) on 2014-05-27T11:29:40Z No. of bitstreams: 0Bitstream added on 2014-05-27T14:43:14Z : No. of bitstreams: 1 2-s2.0-84879942078.pdf: 528802 bytes, checksum: 81a8810f0e9a6d7b82ac2c651e0fc456 (MD5) Made available in DSpace on 2014-05-27T11:29:40Z (GMT). No. of bitstreams: 0 Previous issue date: 2013-06-13 Corneal collagen cross-linking (CXL) has been described as a promising therapy for keratoconus. According to standard CXL protocol, epithelium should be debrided before treatment to allow penetration of riboflavin into the corneal stroma. However, removal of the epithelium can increase procedure risks. In this study we aim to evaluate stromal penetration of a biocompatible riboflavin-based nanoemulsion system (riboflavin-5-phosphate and riboflavin-base) in rabbit corneas with intact epithelium. Two riboflavin nanoemulsions were developed. Transmittance and absorption coefficient were measured on corneas with intact epithelia after 30, 60, 120, 180, and 240 minutes following exposure to either the nanoemulsions or standard 0.1% or 1% riboflavin-dextran solutions. For the nanoemulsions, the epithelium was removed after measurements to assure that the riboflavin had passed through the hydrophobic epithelium and retained within the stroma. Results were compared to de-epithelialized corneas exposed to 0.1% riboflavin solution and to the same riboflavin nanoemulsions for 30 minutes (standard protocol). Mean transmittance and absorption measured in epithelialized corneas receiving the standard 0.1% riboflavin solution did not reach the levels found on the debrided corneas using the standard technique. Neither increasing the time of exposure nor the concentration of the riboflavin solution from 0.1% to 1% improved riboflavin penetration through the epithelium. When using riboflavin-5-phosphate nanoemulsion for 240 minutes, we found no difference between the mean absorption coefficients to the standard cross-linking protocol (p = 0.54). Riboflavin nanoemulsion was able to penetrate the corneal epithelium, achieving, after 240 minutes, greater stromal concentration when compared to debrided corneas with the standard protocol (p = 0.002). The riboflavin-5-phosphate nanoemulsion diffused better into the stroma than the riboflavin-base nanoemulsion. © 2013 Bottos et al. Department of Ophthalmology Paulista School of Medicine Federal University of Sao Paulo - UNIFESP, Sao Paulo, SP Department of Pharmaceutics School of Pharmaceutical Sciences Sao Paulo State University, UNESP, Araraquara, SP Department of Informatics in Health Paulista School of Medicine Federal University of Sao Paulo - UNIFESP, Sao Paulo, SP Department of Pharmaceutics School of Pharmaceutical Sciences Sao Paulo State University, UNESP, Araraquara, SP