Search

The most commonly used tissue substitute for ocular surface reconstruction is human amniotic membrane (AM). Because of its low biomechanical strength and intransparency there is a need to search for alternatives of consistent quality. This study, further explored the biocompatibility of Keratin Film (KF) and its ability to sustain corneal epithelial wound healing. In three equal groups of 5 New Zeeland white rabbits a 4 mm superficial keratectomy was created in the right eye. Five eyes received a KF, five a human AM graft and the remaining five no implant. All eyes were treated with ofloxacin and dexamethasone eye drops and followed up for 10 days. Corneal fluorescein staining, vascularization, and transparency were assessed using slit lamp biomicroscopy according to a standardized grading score during and at the end of follow-up. The corneal-scleral-button was excised and processed for histology. After 10 days all eyes which had received a KF showed complete epithelial healing and no signs of neovascularization. In the AM group 1 eye showed a persistent epithelial defect at day 10 and 2 eyes showed neovascularization at day 7 resolving at day 10. Transparency improved progressively both in the KF group as well as in the AM group towards the end of the follow. Histology showed a multilayer epithelium firmly adherent to the KF with no evidence of keratocyte migration or inflammatory reaction in the corneal stroma. In this study on rabbit eyes KF better supported corneal epithelial wound healing than amniotic membrane., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

The aim of the study was to investigate the effectiveness of exogenous recombinant human decoron and an accompanying penetration-enhancing solution in stiffening ex-vivo porcine corneas both transepithelially and after de-epithelialization. Eight porcine paired eyes were treated transepithelially: one eye with a pre-treatment solution (Pre-Tx), penetration enhancing solution (PE), and decoron while the fellow eye was treated by the same protocol but without decoron. A second group included 4 de-epithelialized pairs treated identically. The final group included 4 de-epithelialized pairs with one eye treated with Pre-Tx, PE, and decoron while the fellow eye was treated without PE. Uniaxial tensile testing was used to compare the corneal stiffness between the different treatment conditions. Residual tissue underwent immunohistochemistry analysis to evaluate the depth of penetration of decoron into the corneal stroma. There was no stiffening effect exhibited among corneas treated transepithelially with decoron compared to control (P > 0.05) and poor stromal penetration was exhibited on tissue analysis. Among de-epithelialized corneas, there was a significant stiffening effect seen in those treated with decoron at 3%, 4%, 5%, & 6% strain (P < 0.05) compared to control. Among de-epithelialized corneas there was also a significant stiffening effect seen in those treated with the PE and decoron at 4%, 5%, & 6% strain (P < 0.05) with improved stromal penetration confirmed by immunohistochemistry, versus without PE. De-epithelialization is necessary for effective stromal penetration of decoron. Depth of penetration and subsequent corneal stiffening may be improved with a penetration enhancing solution. Compared to riboflavin, decoron requires shorter treatment time and spares UV light exposure., (Copyright © 2021. Published by Elsevier Ltd.)

Secreted protein acidic and rich in cysteine (SPARC) shows a specific colocalization with limbal epithelial stem cells (LESCs) in vivo; however, the inherent relationship between SPARC and LESCs is still unclear. This study investigated the effects of SPARC on the maintenance of LESC stemness and corneal wound healing. To test the influence of different concentration of exogenous SPARC on the proliferation of LESCs, cell counting kit-8 assay and 5-ethynyl-2'-deoxyuridine staining were performed and the results indicated that 1 μg/mL SPARC was the optimum concentration for enhanced LESC proliferation. Compared with a control group, SPARC-treated group showed a higher expression of LESC-positive markers p63α, ABCG-2, and Bmi-1, and a lower level of differentiation marker cytokeratin-3 (CK3), thereby suggesting that SPARC could maintain LESC characteristic phenotype and suppress spontaneous epithelial differentiation in vitro. In vivo, exogenous SPARC accelerated the wound-healing process by both the enhancement of LESC proliferation and promoting the migration of the proliferating cells. However, the intact epithelium impaired this function of SPARC by contact inhibition.

Any significant loss of vision or blindness caused by corneal damages is referred to as corneal blindness. Corneal blindness is the fourth most common cause of blindness worldwide, representing more than 5% of the total blind population. Currently, corneal transplantation is used to treat many corneal diseases. In some cases, implantation of artificial cornea (keratoprosthesis) is suggested after a patient has had a donor corneal transplant failure. The shortage of donors and the side effects of keratoprosthesis are limiting these approaches. Recently, researchers have been actively pursuing new approaches for corneal regeneration because of these limitations. Nowadays, tissue engineering of different corneal layers (epithelium, stroma, endothelium, or full thickness tissue) is a promising approach that has attracted a great deal of interest from researchers and focuses on regenerative strategies using different cell sources and biomaterials. Various sources of corneal and non-corneal stem cells have shown significant advantages for corneal epithelium regeneration applications. Pluripotent stem cells (embryonic stem cells and iPS cells), epithelial stem cells (derived from oral mucus, amniotic membrane, epidermis and hair follicle), mesenchymal stem cells (bone marrow, adipose-derived, amniotic membrane, placenta, umbilical cord), and neural crest origin stem cells (dental pulp stem cells) are the most promising sources in this regard. These cells could also be used in combination with natural or synthetic scaffolds to improve the efficacy of the therapeutic approach. As the ocular surface is exposed to external damage, the number of studies on regeneration of the corneal epithelium is rising. In this paper, we reviewed the stem cell-based strategies for corneal epithelium regeneration., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

To compare the effectiveness of self- retained cryopreserved AM as an adjuvant therapy for infectious corneal ulcers. Retrospective, case-control study of 24 eyes of 24 consecutive patients with central and paracentral corneal infectious ulcers and initial visual acuity worse than 20/200. Among them, 11 eyes of 11 patients received additional placement of self-retained cryopreserved AM. Epithelialization and Best Corrected Snellen Visual Acuity (BCSVA) were compared between the two groups. At baseline, both groups had comparable age, gender, visual acuity (VA), size and location of corneal ulcer. Patients receiving additional placement of cryopreserved AM had significantly faster epithelialization within 3.56 ± 1.78 weeks vs 5.87 ± 2.20 weeks (p = 0.01) and achieved complete epithelialization in significantly more patients (72.7% vs 23.1% p = 0.04) despite overall larger baseline defect size (32.7 ± 19.5 mm 2 vs 21.5 ± 10.7 mm 2 , p = 0.11). Consequently, the AM group had clinically significant BCSVA (> 3 lines) (81.8% vs 38.4%, p = 0.047) and total VA improvement (log MAR 0.7 ± 0.6 vs 1.6 ± 0.9, p = 0.016) compared to the control group at the time of complete epithelialization. In-office sutureless AM may be an effective adjuvant therapy in treating sight-threatening infectious corneal ulcers by promoting faster corneal epithelialization and overall better recovery of the VA.

Aim: To compare the efficacy of cord blood and peripheral adult donor blood serum eyedrops, controlled for growth factor content, in the treatment of severe dry eye diseases (DED) resistant to conventional therapy., Methods: This was a multicentre randomised, double-masked, cross-over clinical trial. Sixty patients diagnosed as severe DED, associated to persistent corneal epithelial defects were randomised and equally assigned to group A (treated with cord blood serum (CBS)) or group B (treated with PBS), eyedrops administered eight times/day for 1 month. Primary outcome was the pretreatment and post-treatment change in corneal fluorescein staining. Secondary outcomes included the pretreatment and post-treatment change in Ocular Surface Disease Index (OSDI) questionnaire and Visual Analogue Score (VAS) of subjective symptoms, Schirmer I test, tear break-up time and conjunctival staining. Patients with relapse in signs or symptoms after further 2 months switched to the remaining group for one additional month. Data were statistically analysed (p<0.05)., Results: Corneal staining was more significantly reduced after the CBS treatment, both VAS and OSDI score reduction was observed in both groups, but group A reported significantly less grittiness and pain. Nineteen patients shifted in the crossover period, the within individual comparison confirmed a better recovery in the CBS treatment period. Reduction in epithelial damage was positively associated with epidermal growth factor, transforming growth factorα and platelet-derived growth factor content. Levels of interleukins (IL-13) were positively associated with symptom decrease., Conclusions: Overall, DED signs improved after both CBS and PBS treatments, with potential advantages of CBS for subjective symptoms and corneal damage reduction., Clinical Trial Registration: NCT03064984., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2019. No commercial re-use. See rights and permissions. Published by BMJ.)

Xiaosheng prescription (XSP) has been used for dry eye disease (DED) for more than 10 years in Eye Hospital of China Academy of Chinese Medicine Sciences. However, the effective ingredients involved have remained unclear, which was investigated in this study by the correlation of ingredient and therapeutic activity. Human corneal epithelial cells (HCEC) cultured with 110 mM NaCl solution in vitro and C57BL/6 mice injected subcutaneously with scopolamine hydrobromide were used to establish dry eye models, and the therapeutic effect of XSP extract 1 was better than that of XSP extract 2 significantly. Then, UPLC-Q-TOF/MS and data analysis program Progenesis QI and Makerlynx XS were used to analyze the potential effective ingredients of XSP, and 4 compounds were speculated and identified, in which Schisandrin and 1 μM of Schisantherin A could obviously increase the cell survival rate of injured cells on the cell model. It can be indicated that Schisandrin and Schisantherin A are probably the potential effective ingredients in XSP for DED., Competing Interests: Declaration of Competing Interest There are no conflicts to declare., (Copyright © 2020. Published by Elsevier Masson SAS.)

Diabetic keratopathy, a sight-threatening corneal disease, comprises several symptomatic conditions including delayed epithelial wound healing, recurrent erosions, and sensory nerve (SN) neuropathy. We investigated the role of neuropeptides in mediating corneal wound healing, including epithelial wound closure and SN regeneration. Denervation by resiniferatoxin severely impaired corneal wound healing and markedly upregulated proinflammatory gene expression. Exogenous neuropeptides calcitonin gene-related peptide (CGRP), substance P (SP), and vasoactive intestinal peptide (VIP) partially reversed resiniferatoxin's effects, with VIP specifically inducing interleukin-10 expression. Hence, we focused on VIP and observed that wounding induced VIP and VIP type 1 receptor (VIPR1) expression in normal (NL) corneas, but not corneas from mice with diabetes mellitus (DM). Targeting VIPR1 in NL corneas attenuated corneal wound healing, dampened wound-induced expression of neurotrophic factors, and exacerbated inflammatory responses, while exogenous VIP had the opposite effects in DM corneas. Remarkably, wounding and diabetes also affected the expression of Sonic Hedgehog (Shh) in a VIP-dependent manner. Downregulating Shh expression in NL corneas decreased while exogenous Shh in DM corneas increased the rates of corneal wound healing. Furthermore, inhibition of Shh signaling dampened VIP-promoted corneal wound healing. We conclude that VIP regulates epithelial wound healing, inflammatory response, and nerve regeneration in the corneas in an Shh-dependent manner, suggesting a therapeutic potential for these molecules in treating diabetic keratopathy., (© 2020 by the American Diabetes Association.)

Background: Healthy corneal epithelium acts as a barrier against damage to the deeper structures in the eye. Failure in the mechanisms of corneal epithelization can lead to persistent epithelial defects of the cornea (PEDs) and can compromise its function. Epidermal growth factor (EGF) promotes the proliferation, migration, and differentiation of epithelial cells, endothelial cells, and fibroblasts during wound healing and may be beneficial in treating patients with PEDs. We, therefore, investigated the effect of EGF ointment on patients with PEDs., Methods: Fifteen patients with PEDs refractory to conventional treatment were treated twice a day with EGF ointment. Patient demographics and comorbidities were noted. The epithelial healing time was determined along with the primary outcome measures in the areas of the epithelial defects, visual acuity, visual analog scale (VAS) scores, and esthesiometer scores 1 month and 2 months after treatment., Results: Five eyes of herpetic keratitis (33.3%), 3 eyes of dry eye disease (20.0%), 3 eyes of bacterial keratitis (20.0%), 2 eyes of limbal stem cell deficiency (13.3%), 1 eye of diabetic neurotrophic keratitis (6.7%), and 1 eye of filamentary keratitis (6.7%) were associated with PEDs, respectively. Two months following treatment with EGF ointment, there was a reduction in the area of the epithelial defects (5.7 ± 3.9 to 0.1 ± 0.3 mm 2 ) as well as a significant improvement in best-corrected visual acuity (0.9 ± 0.8 to 0.6 ± 0.5 LogMAR) and VAS scores (4.5 ± 1.2 to 2.5 ± 0.7) in 12 eyes (80%). Among these cases, the mean epithelial healing time was 5.5 ± 1.8 weeks. Amniotic membrane transplantation was performed on the remaining 3 (20.0%) patients that did not respond to EGF treatment., Conclusions: EGF ointment could reduce symptoms and promotes corneal epithelialization of refractory PEDs. It may, therefore, be well-tolerated and a potentially beneficial addition in the management of refractory PEDs.

Purpose: To determine the association of corneal sensitivity and tear functions on the prognosis of eyes after posttraumatic recurrent corneal erosion syndrome (RCES)., Methods: Patients were enrolled retrospectively and had unilateral RCES and a history of ocular surface trauma. A corneal sensitivity test and tear function test (tear break-up time and Schirmer test) were performed at three time points (month 1 to month 3, month 3 to month 6, and month 6 to month 12). Depending on the number of recurrences during the follow-up, patients were divided into group A (n > 2) or group B (n = 2). A comparison between diseased and normal fellow eyes in each patient was performed., Results: A total of 31 patients were enrolled and divided into group A (n = 14) and group B (n = 17). The mean age was 40.3 ± 12.2 years, whereas the mean follow-up was 28.0 ± 3.6 months. During the study period, corneal sensitivity, tear break-up time, and the Schirmer test results were all lower in diseased eyes than in normal fellow eyes in both groups. Compared to the first time point, recovery of corneal sensitivity and the Schirmer test values were observed in diseased eyes in group B at the second and third time points., Conclusions: Poor corneal sensitivity and tear function are associated with posttraumatic RCES. Recovery of corneal sensitivity and tear function may be associated with a reduction of recurrence in eyes with posttraumatic RCES.

Purpose of Review: To review the updated literature regarding eye rubbing complications and its association with ocular allergy disorders., Recent Findings: Atopy and ocular allergy disorders, mainly vernal keratoconjunctivitis (VKC), are strongly associated with rubbing-related complications, most probably via itching and watery eye sensations that trigger the habit of chronic eye rubbing. Vigorous and prolonged rubbing may lead to establishment of corneal remodeling and ectatic disorders, such as keratoconus. Keratoconus development in rubbed eyes can be caused by mechanical mechanisms of corneal thinning and its loss of rigidity, by elevated temperature of the epithelium during rubbing, by increased intraocular pressure (IOP) because of distending forces, and by inflammatory molecules that may serve as a causal mediator between eye rubbing and keratoconus. Other eye rubbing complications include acute hydrops and perforation, IOP spikes, iris prolapse and iridoschisis rupture of lens capsule and IOL dislocation, and even posterior segment disorders, such as glaucomatous optic neuropathy, retinal detachment and extrusion of implanted silicone oil in the eye., Summary: Chronic eye rubbing in allergic eye diseases can lead to progression of keratoconus, and to other rare anterior and posterior segment complications. Strategies eliminating eye rubbing and its consequences are vital, mainly among at-risk populations, such as young children and individuals with allergic ocular disorders or corneal transplants.

Purpose: To evaluate changes in corneal higher-order aberrations (HOAs) on the anterior and posterior corneal surfaces after 1.8 mm microincision cataract surgery (MICS) and 2.8 mm small-incision cataract surgery (SICS)., Setting: Eye Department, First Affiliated Hospital, School of Medicine, Zhejiang University, China., Design: Prospective case series., Methods: Right eyes of patients had MICS or SICS. The preoperative and 1-week and 3-month postoperative distance visual acuity (CDVA) and dry eye-related indices were determined. The corneal total HOAs and Zernike coefficients (3rd and 4th order) over 4.0 and 6.0 mm zones, corneal volume, central corneal thickness (CCT), and anterior and posterior corneal astigmatism were measured using a Pentacam HR analyzer., Results: The MICS group comprised 126 eyes and the SICS group 70 eyes. The MICS and SICS groups had similar postoperative CDVA; however, the MICS group had quicker recovery of CCT, corneal volume, and corneal astigmatism. Significantly increased anterior corneal total HOAs were observed in the SICS group over a 6.0 mm zone (P < .001). Both groups showed significantly increased posterior corneal total HOAs over both zones (P < .001). Similar changing patterns in individual Zernike terms were observed. The MICS group had quicker recovery of posterior corneal surface coma and trefoil than the SICS group, especially over the 6.0 mm zone. Changes in posterior corneal surface total HOAs were correlated with corneal volume changes (P < .01)., Conclusions: The data suggest quicker corneal recovery and less change in total and anterior corneal surface corneal HOAs after MICS. Changes in posterior corneal surface HOAs were more pronounced in both surgical groups., (Copyright © 2019 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.)

The aim of the present study was to investigate the effects of an amniotic membrane lacrimal stent in the treatment of dry eye syndrome in a perimenopausal rabbit model. In total, 48 healthy female rabbits were randomly divided into four groups (12 rabbits/group): Group A, sham‑operated group; group B, negative control group; group C, sham‑implantation group; and group D, implantation with amniotic membrane lacrimal stents. A Schirmer I test (SIT), corneal fluorescein staining, optical coherence tomography angiography and corneal confocal microscopy were conducted and the biomechanical properties of the amniotic membrane were measured prior to and 2, 4 and 6 weeks after the operations. There were marked differences in the amount of tear secretion and the SIT following the operation compared with prior to the operation. The amount of tear secretion of group B and C was significantly reduced (F=8.894; P=0.0017). Compared with groups A, B and C, group D demonstrated a significant increase in the amount of tear secretion and a significant reduction in SIT (P<0.05). However, there was no statistical difference between the tear secretion of the A, B and C groups (P>0.05). The cornea epithelial of groups A and D was significantly thinner compared with groups B and C. The superior part [superior temporal (ST)5, superior (S)5, superior nasal (SN)5, ST6, S6 and SN6] was significantly thinner compared with the central part of the cornea epithelium. The corneal epithelia of all groups were thin in the center and thick at the edge. At 6 weeks after the operation, group D exhibited a markedly decreased number of anterior stromal luminescent cells, compared with groups A, B and C. Furthermore, the bending degree of corneal stromal neural trunks was significantly improved, and the density, branches and curvature of corneal epithelium sub‑basal nerves ameliorated to a certain extent (P<0.05). Amniotic membrane lacrimal stents demonstrated specific therapeutic effects on dry eye in perimenopausal female rabbits.

Diabetes mellitus is an epidemic in the US and abroad. With the advent of new contact lens technology, the use of contact lenses as glucose sensors in lieu of the traditional finger stick is quickly becoming realized. This has the potential to rapidly expand the contact lens market into this growing patient population. The independent cellular and physiological effects of contact lens wear and diabetes on the corneal epithelium have been described. However, little evidence exists to date to support whether there is increased risk associated with contact lens wear in diabetes. The focus of this review is to discuss what is known about the cellular effects of contact lenses on the corneal epithelium, the pathophysiological changes in the corneal epithelium that occur in diabetes, and whether an increased risk for corneal epithelial damage and/or infection may negatively impact safety in diabetic contact lens wearers. Available data indicates that there are inherent risks associated with contact lens wear in diabetics. Importantly, eye care practitioners fitting contact lenses in the diabetic patient need to carefully consider the duration of disease, the level of glycemic control, the presence of retinopathy, and the patient's overall health., (Copyright © 2018 Elsevier Inc. All rights reserved.)

The limbus is the anatomical and functional barrier between corneal and conjunctival epithelia. It is characterized by presence of the limbal stem cell niche which allows corneal homeostasis to be maintained. Limbal stem cell deficiency is characterized by a dual process: insufficient regeneration of corneal epithelium, which cannot therefore assure its function of physiological support, associated with corneal invasion by conjunctival proliferation. Diagnosis is currently made via routine clinical examination, corneal impression cytology and in vivo confocal microscopy (IVCM). Slit lamp examination shows abnormal limbal anatomy, thin and irregular epithelium with late fluorescein staining, and superficial vascularization. With its high resolution, IVCM allows identification of limbal and corneal epithelial changes at a cellular level in en face views, parallel to the corneal surface, but with a restricted viewing field of the corneal surface. It shows a poor transition between the corneal and conjunctival epithelia, associated with a loss of the normal corneal epithelial stratification, low basal cell and sub-basal nerve plexus densities, even with sub-epithelial fibrosis. Optical coherence tomography in central cornea and at the limbus, with scans in different orientations, allows a quick, global and non-invasive analysis of normal eyes and those with limbal stem cell deficiency. It shows a thin limbal epithelium, lacking normal thickening, featuring absence of stromal undulations and limbal crypts in cross-sections and sections parallel to the limbus, lack of visible limbal crypts in en face sections, loss of clear transition between the hyporeflective corneal epithelium and the hyperreflective conjunctival epithelium, and hyperreflective sub-epithelial fibrosis., (Copyright © 2018. Published by Elsevier Masson SAS.)

Dry Eye disease causes discomfort and pain in millions of patients. Using a mouse acute desiccating stress (DS) model we show that DS induces a reduction in intraepithelial corneal nerve (ICN) density, corneal sensitivity, and apical extension of the intraepithelial nerve terminals (INTs) that branch from the subbasal nerves (SBNs). Topical application of 0.02% Mitomycin C (MMC) or vehicle alone has no impact on the overall loss of axon density due to acute DS. Chronic dry eye, which develops progressively as C57BL/6 mice age, is accompanied by significant loss of the ICNs and corneal sensitivity between 2 and 24 months of age. QPCR studies show that mRNAs for several proteins that regulate axon growth and extension are reduced in corneal epithelial cells by 24 months of age but those that regulate phagocytosis and autophagy are not altered. Taken together, these data demonstrate that dry eye disease is accompanied by alterations in intraepithelial sensory nerve morphology and function and by reduced expression in corneal epithelial cells of mRNAs encoding genes mediating axon extension. Précis: Acute and chronic mouse models of dry eye disease are used to evaluate the pathologic effects of dry eye on the intraepithelial corneal nerves (ICNs) and corneal epithelial cells. Data show reduced numbers of sensory nerves and alterations in nerve morphology, sensitivity, corneal epithelial cell proliferation, and expression of mRNAs for proteins mediating axon extension accompany the pathology induced by dry eye., (Copyright © 2018 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Purpose: To evaluate the epithelial erosion incidence and refractive results in myopic eyes undergoing single-step transepithelial photorefractive keratectomy (TransPRK) compared with alcohol-assisted photorefractive keratectomy (PRK)., Methods: This was a retrospective nonrandomized comparative study conducted at the American University of Beirut Medical Center. A total of 189 eyes that had undergone single-step transepithelial PRK (TransPRK) were compared with 189 matched eyes that had undergone alcohol-assisted PRK over a follow-up of 1 year. The incidence and symptoms of epithelial erosion were evaluated in both treatment groups using a post hoc questionnaire administered to patients selected in the study. Visual and refractive outcomes, including vector analysis of astigmatism, and corneal higher-order aberrations were also compared at 1-year postoperatively., Results: Baseline characteristics were similar between 2 groups (P > 0.05). A slight difference was detected at 12-month follow-up in the refractive cylinder (P = 0.02) and difference vector (P = 0.01) between eyes that had undergone TransPRK versus alcohol-assisted PRK. All other visual and refractive outcomes were similar at 12-month follow-up between both groups. Of note, 9.9% of patients with alcohol-assisted PRK (10/101) reported to the clinic because of tearing and stabbing sensation within 1 week after contact lens removal as opposed to 1% (1/100) of the TransPRK group (P = 0.0097). Subclinical recurrent epithelial erosion symptoms occurred more frequently in alcohol-assisted PRK: soreness to touch, sharp pains, and eyelid sticking occurred in 26.0% versus 6.6%, 32.5% versus 7.9%, and 26.0% versus 6.6% among the patients who were treated with alcohol-assisted PRK versus those who were treated with TransPRK, respectively (P ≤ 0.002)., Conclusions: Single-step TransPRK for myopic eyes yields refractive results similar to those of alcohol-assisted PRK but shows a lesser incidence of early postoperative epithelial erosions and subsequent subclinical recurrent erosions.

Although the wound healing effects of nitric oxide (NO) are known, the mechanism by which NO modulates corneal wound healing remains unclear. In this study, we investigated the effect of exogenous NO donor (NaNO 2 ) on corneal wound healing. We found that NaNO 2 (0.1 μM to 100 μM) increased human corneal epithelial cell (HCEC) viability and migration. It also modulated the phosphorylation of mitogen-activated protein kinases (MAPKs) in a time- dependent manner in those HCECs. Further, p38 MAPK phosphorylation increased at 6 h and normalized at 24 h, while the phosphorylation of extracellular signal regulated kinase (ERK) was increased both at 6 h and 24 h. Topical treatment with NaNO 2 (10 μM) enhanced corneal epithelial healing and decreased corneal opacity in murine corneal alkali burn model by modulating inflammatory cytokines. Our findings suggest that NO increased HCEC proliferation and migration via time-dependent MAPK activation and eventually enhanced corneal recovery from the alkali burn.

Purpose: To evaluate the treatment of autologous serum eye drops (ASED) on dry eyes in patients with graft-versus-host disease (GVHD)., Methods: A retrospective chart review of 35 patients with a history of ocular GVHD following hematopoietic stem cell transplantation that used ASED to alleviate dry eye symptoms was performed. Patients were categorized into three different groups. If patients had available ophthalmic data before and after starting treatment was group 1 (n = 14), had available ophthalmic data after starting treatment in group 2 (n = 10) and had available ophthalmic data before treatment or did not have any data after starting treatment in group 3 (n = 11). Data were collected on patient's age, gender, primary diagnosis, visual acuity and fluorescein corneal staining were collected on individual eyes in order to evaluate the efficacy of the ASED on alleviating dry eye-related signs and symptoms., Results: No adverse ocular effect from the ASED was found in our series (except one fungal keratitis). All patients reported either improvement (55%) or stability (45%) in their ocular symptoms upon the use of ASED. In patients with available data before and after starting treatment, the corneal staining score improved by a median of 1 (p = 0.003) and the LogMAR visual acuity had a non-significant improvement., Conclusion: In our study, ASED used by patients with ocular GVHD were both safe and effective. ASED should be considered in patients with GVHD who suffer from dry eyes.

The eye is innervated by neurons derived from both the central nervous system and peripheral nervous system (PNS). While much is known about retinal neurobiology and phototransduction, less attention has been paid to the innervation of the eye by the PNS and the roles it plays in maintaining a functioning visual system. The ophthalmic branch of the trigeminal ganglion contains somas of neurons that innervate the cornea. These nerves provide sensory functions for the cornea and are referred to as intraepithelial corneal nerves (ICNs) consisting of subbasal nerves and their associated intraepithelial nerve terminals. ICNs project for several millimeters within the corneal epithelium without Schwann cell support. Here, we present evidence for the hypothesis that corneal epithelial cells function as glial cells to support the ICNs. Much of the data supporting this hypothesis is derived from studies of corneal development and the reinnervation of the ICNs in the rodent and rabbit cornea after superficial wounds. Corneal epithelial cells activate in response to injury via mechanisms similar to those induced in Schwann cells during Wallerian Degeneration. Corneal epithelial cells phagocytize distal axon fragments within hours of ICN crush wounds. During aging, the proteins, lipids, and mitochondria within the ICNs become damaged in a process exacerbated by UV light. We propose that ICNs shed their aged and damaged termini and continuously elongate to maintain their density. Available evidence points to new unexpected roles for corneal epithelial cells functioning as surrogate Schwann cells for the ICNs during homeostasis and in response to injury. GLIA 2017;65:851-863., (© 2016 Wiley Periodicals, Inc.)

Vascular endothelial growth factor (VEGF)-B possesses the capacity of promoting injured peripheral nerve regeneration and restore their sensory and trophic functions. However, the contribution and mechanism of VEGF-B in diabetic peripheral neuropathy remains unclear. In the present study, we investigated the expression and role of VEGF-B in diabetic corneal neuropathy by using type 1 diabetic mice and cultured trigeminal ganglion (TG) neurons. Hyperglycemia attenuated the endogenous expression of VEGF-B in regenerated diabetic corneal epithelium, but not that of VEGF receptors in diabetic TG neurons and axons. Exogenous VEGF-B promoted diabetic corneal nerve fiber regeneration through the reactivation of PI-3K/Akt-GSK3β-mTOR signaling and the attenuation of neuronal mitochondria dysfunction via the VEGF receptor-1 and neuropilin-1. Moreover, VEGF-B improved corneal sensation and epithelial regeneration in both normal and diabetic mice, accompanied with the elevated corneal content of pigment epithelial-derived factor (PEDF). PEDF blockade partially abolished trophic function of VEGF-B in diabetic corneal re-innervation. In conclusion, hyperglycemia suppressed endogenous VEGF-B expression in regenerated corneal epithelium of diabetic mice, while exogenous VEGF-B promoted recovery of corneal innervations and trophic functions through reactivating PI-3K/Akt-GSK-3β-mTOR signaling, attenuating neuronal oxidative stress and elevating PEDF expression.

Purpose: The purpose of this study was to investigate the biomechanical stiffening effect induced by nanoplatform-based transepithelial riboflavin/UV-A cross-linking protocol using atomic force microscopy (AFM)., Methods: Twelve eye bank donor human sclerocorneal tissues were investigated using a commercial atomic force microscope operated in force spectroscopy mode. Four specimens underwent transepithelial corneal cross-linking using a hypotonic solution of 0.1% riboflavin with biodegradable polymeric nanoparticles of 2-hydroxypropyl-β-cyclodextrin plus enhancers (trometamol and ethylenediaminetetraacetic acid) and UV-A irradiation with a 10 mW/cm2 device for 9 minutes. After treatment, the corneal epithelium was removed using the Amoils brush, and the Young's modulus of the most anterior stroma was quantified as a function of scan rate by AFM. The results were compared with those collected from four specimens that underwent conventional riboflavin/UV-A corneal cross-linking and four untreated specimens., Results: The average Young's modulus of the most anterior stroma after the nanoplatform-based transepithelial and conventional riboflavin/UV-A corneal cross-linking treatments was 2.5 times (P < 0.001) and 1.7 times (P < 0.001) greater than untreated controls respectively. The anterior stromal stiffness was significantly different between the two corneal cross-linking procedures (P < 0.001). The indentation depth decreased after corneal cross-linking treatments, ranging from an average of 2.4 ± 0.3 μm in untreated samples to an average of 1.2 ± 0.1 μm and 1.8 ± 0.1 μm after nanoplatform-based transepithelial and conventional cross-linking, respectively., Conclusions: The present nanotechnology-based transepithelial riboflavin/UV-A corneal cross-linking was effective to improve the biomechanical strength of the most anterior stroma of the human cornea.

Analysis of abnormal phenotypes produced by different types of mutations has been crucial for our understanding of gene function. Some floxed alleles that retain a neomycin-resistance selection cassette (neo cassette) are not equivalent to wild-type alleles and provide useful experimental resources. Pax6 is an important developmental gene and the aim of this study was to determine whether the floxed Pax6 (tm1Ued) (Pax6 (fl) ) allele, which has a retained neo cassette, produced any abnormal eye phenotypes that would imply that it differs from the wild-type allele. Homozygous Pax6 (fl/fl) and heterozygous Pax6 (fl/+) mice had no overt qualitative eye abnormalities but morphometric analysis showed that Pax6 (fl/fl) corneas tended be thicker and smaller in diameter. To aid identification of weak effects, we produced compound heterozygotes with the Pax6 (Sey-Neu) (Pax6 (-)) null allele. Pax6 (fl/-) compound heterozygotes had more severe eye abnormalities than Pax6 (+/-) heterozygotes, implying that Pax6 (fl) differs from the wild-type Pax6 (+) allele. Immunohistochemistry showed that the Pax6 (fl/-) corneal epithelium was positive for keratin 19 and negative for keratin 12, indicating that it was abnormally differentiated. This Pax6 (fl) allele provides a useful addition to the existing Pax6 allelic series and this study demonstrates the utility of using compound heterozygotes with null alleles to unmask cryptic effects of floxed alleles.

The mechanisms of corneal epithelial lesions and delayed wound repair, as well as their association with diabetes mellitus, are critical issues for clinical ophthalmologists. To test whether the diabetic condition alters the circadian rhythm in a mouse cornea and whether insulin can synchronise the corneal clock, we studied the effects of streptozotocin-induced diabetes on the mitosis of epithelial cells, the recruitment of leukocytes to the cornea, and the expression of main core clock genes (Clock, Bmal1, Per2, Cry1, and Rev-erbα) in the corneal epithelium. We also assessed the possible effect of insulin on these modifications. Diabetes downregulated Clock, Bmal1, and Per2 expression, upregulated Cry1 and Rev-erbα expression, reduced corneal epithelial mitosis, and increased leukocyte (neutrophils and γδ T-cells) recruitment to the cornea. Early treatments with insulin partially restored the altered rhythmicity in the diabetic cornea. In conclusion, insulin-dependent diabetes altered the normal rhythmicity of the cornea, and insulin administration had a beneficial effect on restoring normal rhythmicity in the diabetic cornea.

Some recent research has resulted in a hypothesis that there is a common 'lid wiper' region that is apposite to the ocular surface or anterior lens surface (where contact lenses are worn), responsible for spreading tears during blinking. In the upper eyelid, it extends about 0.6 mm from the crest of the sharp posterior (inner) lid border (i.e. the mucocutaneous junction, or line of Marx) to the subtarsal fold superiorly and from the medial upper punctum to the lateral canthus horizontally. Histologically, it is seen as an epithelial elevation comprising of stratified epithelium with a transitional conjunctival structure of (moving posteriorly) squamous cells then cuboidal cells, with some parakeratinised cells and goblet cells. Lid wiper epitheliopathy (LWE) denotes staining of the lid wiper observed after instillation of dyes such as fluorescein, rose bengal or lissamine green. There have been some reports of higher rates of LWE in dry eye patients and contact lens wearers, but others have failed to find such associations. The primary cause of LWE is thought to be increased friction between the lid wiper and ocular or anterior contact lens surface due to inadequate lubrication, which could be caused by dry eye and may be exacerbated by factors such as abnormal blinking patterns, poor contact lens surface lubricity and adverse environmental influences. Recent evidence suggests that LWE is associated with sub-clinical inflammation. LWE has the potential to provide the missing mechanistic link between clinical observation and symptoms associated with dry eye and contact lens wear. Clinical and fundamental research into LWE is still in its infancy and in many instances equivocal; however, it is an idea that provides a potentially important new avenue for further investigation of anterior eye discomfort associated with ocular dryness and contact lens wear., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Protection of corneal endothelium from apoptosis using gene and cell therapy is in a translational phase. This approach offers advantages for eye banking and after transplantation. Safe vehicles for gene or cell therapeutic transduction of corneal endothelium with nucleic acids are available. This strategy will be further developed in consultation with the Paul Ehrlich Institute and European regulatory authorities.

Dry eye is an allegedly autoimmune disorder for which the initiating mechanisms and the targeted antigens in the ocular surface are not known, yet there is extensive evidence that a localized T helper type 1 (Th1)/Th17 effector T cell response is responsible for its pathogenesis. In this work, we explore the reconciling hypothesis that desiccating stress, which is usually considered an exacerbating factor, could actually be sufficient to skew the ocular surface's mucosal response to any antigen and therefore drive the disease. Using a mouse model of dry eye, we found that desiccating stress causes a nuclear factor kappa B (NF-κB)- and time-dependent disruption of the ocular surface's immune tolerance to exogenous ovalbumin. This pathogenic event is mediated by increased Th1 and Th17 T cells and reduced regulatory T cells in the draining lymph nodes. Conversely, topical NF-κB inhibitors reduced corneal epithelial damage and interleukin (IL)-1β and IL-6 levels in the ocular surface of mice under desiccating stress. The observed effect was mediated by an augmented regulatory T cell response, a finding that highlights the role of mucosal tolerance disruption in dry eye pathogenesis. Remarkably, the NF-κB pathway is also involved in mucosal tolerance disruption in other ocular surface disorders. Together, these results suggest that targeting of mucosal NF-κB activation could have therapeutic potential in dry eye., (© 2016 British Society for Immunology.)

The aim of this study is to describe factors that influence the measured intraocular pressure (IOP) change and to develop a predictive model after myopic laser in situ keratomileusis (LASIK) with a femtosecond (FS) laser or a microkeratome (MK). We retrospectively reviewed preoperative, intraoperative, and 12-month postoperative medical records in 2485 eyes of 1309 patients who underwent LASIK with an FS laser or an MK for myopia and myopic astigmatism. Data were extracted, such as preoperative age, sex, IOP, manifest spherical equivalent (MSE), central corneal keratometry (CCK), central corneal thickness (CCT), and intended flap thickness and postoperative IOP (postIOP) at 1, 6 and 12 months. Linear mixed model (LMM) and multivariate linear regression (MLR) method were used for data analysis. In both models, the preoperative CCT and ablation depth had significant effects on predicting IOP changes in the FS and MK groups. The intended flap thickness was a significant predictor only in the FS laser group (P < .0001 in both models). In the FS group, LMM and MLR could respectively explain 47.00% and 18.91% of the variation of postoperative IOP underestimation (R2 = 0.47 and R(2) = 0.1891). In the MK group, LMM and MLR could explain 37.79% and 19.13% of the variation of IOP underestimation (R(2) = 0.3779 and 0.1913 respectively). The best-fit model for prediction of IOP changes was the LMM in LASIK with an FS laser.

Purpose: To evaluate acute corneal permeability changes after instillation of benzalkonium chloride (BAC) using a newly developed in vivo less invasive corneal transepithelial electrical resistance (TER) measurement method in animals and humans., Methods: We previously developed an in vivo method for measuring corneal TER using intraocular electrodes in animals. This method can be used to precisely measure the decline of the corneal barrier function after instillation of BAC. To lessen the invasiveness of that procedure, we further refined the method for measuring the corneal TER by developing electrodes that could be placed on the surface of the cornea and in the conjunctival sac instead of inserting them into the anterior chamber. Corneal TER changes before and after exposure to 0.02% BAC were determined in this study using the new device in both rabbits and humans., Results: There was a significant decrease in the corneal TER after exposure of the cornea to 0.02% BAC solution in both rabbits and humans (P<.01). The results of this new less invasive method agreed with those of formerly established anterior chamber methods in rabbit experiments., Conclusion: This new less invasive corneal TER measurement method enables us for the first time to measure TER of the human cornea, allowing safe and reliable investigation of the direct effect of different eye drop treatments on the corneal epithelium., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Purpose: To determine the efficacy of epithelial debridement and diamond burr polishing (ED + DBP) in managing recurrent corneal erosion (RCE) and visually significant epithelial irregularity associated with epithelial basement membrane dystrophy (VS-EBMD)., Methods: Retrospective, interventional, consecutive case series of all ED + DBP procedures performed between December 1, 2002, and December 1, 2014., Results: ED + DBP was performed in 91 eyes (66 patients) for the management of RCE and VS-EBMD. Sixty percent (55/91) of the procedures were performed for RCE, of which 65% (36/55) were associated with EBMD and 22% (12/55) with previous corneal trauma. Forty-six percent (42/91) of the procedures were performed for VS-EBMD, including 6 eyes with RCE. RCE resolved after treatment in 97% of eyes with >3 months of follow-up (mean, 33.2 months; range, 3.5-137.6 months). Corrected distance visual acuity (CDVA) and mean topographic astigmatism improved significantly in the 36 eyes treated for VS-EBMD with >1 month of follow-up. In none of the 22 eyes treated for VS-EBMD with >3 months of follow-up did EBMD recur (mean, 31.7 months; range, 3.2-137.6 months). Surgically induced subepithelial haze was present on last follow-up in 9.4% (8/85) of eyes with >1 month of follow-up, but was not associated with decreased final CDVA in any patient., Conclusions: ED + DBP is effective in producing long-term resolution of RCE in 95% of treated eyes and significant improvement in CDVA, decreased topographic astigmatism, and long-term resolution of VS-EBMD in 100% of treated eyes.

The condition of the corneal epithelium is a critical determinant of corneal transparency and clear vision. The corneal epithelium serves as a barrier to protect the eye from external insults, with its smooth surface being essential for its optical properties. Disorders of the corneal epithelium include superficial punctate keratopathy, corneal erosion, and persistent epithelial defects (PEDs). The prompt resolution of these disorders is important for minimization of further damage to the cornea. Currently available treatment modalities for corneal epithelial disorders are based on protection of the ocular surface in order to allow natural healing to proceed. PEDs remain among the most difficult corneal conditions to treat, however. On the basis of characterization of the pathobiology of PEDs at the cell and molecular biological levels, we have strived to develop new modes of treatment for these defects. These treatments rely on two key concepts: provision of a substrate, such as the adhesive glycoprotein fibronectin, for the attachment and migration of corneal epithelial cells, and activation of these cells by biological agents such as the combination of substance P and insulin-like growth factor-1 (IGF-1). Central to both approaches is the role of the fibronectin-integrin system in corneal epithelial wound healing. Determination of the minimum amino acid sequences required for the promotion of corneal epithelial wound closure by fibronectin (PHSRN) and by substance P (FGLM-amide) plus IGF-1 (SSSR) has led to the development of peptide eyedrops for the treatment of PEDs that are free of adverse effects of the parent molecules., (Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Purpose: To compare the efficacy of epithelium-off corneal collagen crosslinking (CXL) with transepithelial CXL in patients with progressive keratoconus., Setting: Department of Ophthalmology, Marmara University School of Medicine, Istanbul, Turkey., Design: Retrospective cohort study., Methods: Eyes that had transepithelial CXL were compared with eyes treated with epithelium-off CXL. All patients with a follow-up of 18 months were evaluated for uncorrected (UDVA) and corrected (CDVA) distance visual acuities, corneal topography, aberrometry, and pachymetry (Pentacam)., Results: The mean patient age was 22.8 years ± 4.7 (SD) (range 18 to 31 years) in the transepithelial group (30 eyes) and 23.7 ± 3.9 years (range 18 to 30 years) in the epithelium-off group (30 eyes). The mean UDVA and CDVA significantly improved in both groups (P < .001). There was no significant difference in the CDVA gain between the 2 groups. In the epithelium-off group, significant improvements occurred in spherical error (P = .002), spherical equivalent (P = .004), maximum keratometry (K), flat K (P = .036), and steep K (P < .001). The reductions in flat K, steep K, and maximum K were greater in the epithelium-off group (P = .004 for flat K; P < .001 for steep K and maximum K). In the transepithelial group, significant improvements occurred in the cylindrical error (P = .009) and in the index of surface variance and index of surface asymmetry (both P < .001)., Conclusion: Although transepithelial CXL seemed to have reduced effectiveness in inducing improvement in topographic indices, its effect on visual acuity is likely to be similar to that of epithelium-off CXL., Financial Disclosure: No author has a financial or proprietary interest in any material or method mentioned., (Copyright © 2015 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.)

The epithelial barrier is critical in the maintenance of the homeostasis of the cornea. A number of eye disorders are associated with the corneal epithelial barrier dysfunction. Viral infection is one common eye disease type. This study aims to elucidate the mechanism by which the activation of toll like receptor 3 (TLR3) in the disruption of the corneal epithelial barrier. In this study, HCE cells (a human corneal epithelial cell line) were cultured into epithelial layers using as an in vitro model of the corneal epithelial barrier. PolyI:C was used as a ligand of TLR3. The transepithelial electric resistance (TER) and permeability of the HCE epithelial layer were assessed using as the parameters to evaluate the corneal epithelial barrier integrity. The results showed that exposure to PolyI:C markedly decreased the TER and increased the permeability of the HCE epithelial layers; the levels of cell junction protein, E-cadherin, were repressed by PolyI:C via increasing histone deacetylase-1 (HDAC1), the latter binding to the promoter of E-cadherin and repressed the transcription of E-cadherin. The addition of butyrate (an inhibitor of HDAC1) to the culture blocked the corneal epithelial barrier dysfunction caused by PolyI:C. In conclusion, activation of TLR3 can disrupt the corneal epithelial barrier, which can be blocked by the inhibitor of HDAC1., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Purpose: We investigated how the microRNA (miRNA) modifies the expression of silent mating type information regulation 2 homolog 1 (SIRT1) in diabetic corneas., Methods: The bioinformatic assay was used to predict which miRNAs might regulate the expression of SIRT1. A lipid transfection protocol was used to upregulate or knockdown the miRNA expression in TKE2 cells. Adenovirus-expressing short interfering RNA was used to knockdown the expression of SIRT1 in TKE2 cells and Ins2(Akita/+) mice were used to evaluate how miRNA promotes diabetic corneal epithelial wound healing. Cell cycle status was determined by flow cytometry assay and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay was used to analyze the cell viability., Results: Nine miRNAs were selected for quantitative PCR (qPCR) detection after bioinformatics analysis. The miR-204-5p merited further investigation, because it was increased almost 5-fold in diabetic corneal epithelia compared to nondiabetic control corneal epithelia. Using luciferase activity assay, we identified SIRT1 was a direct target of miR-204-5p. The results of flow cytometry and MTT assay demonstrated that downregulation of miR-204-5p increased TKE2 cell growth and restored cell cycle progression in high glucose (HG) conditions by the regulation of Cyclin D1 and p16. Furthermore, we showed downregulation of miR-204-5p promoted HG attenuation of corneal epithelial wound healing via upregulation of SIRT1 in Ins2(Akita/+) mice., Conclusions: Our data provide firm evidence of a role for miR-204-5p in the direct regulation of SIRT1 in diabetic corneas and identified the miR-204-5p-mediated regulation of SIRT1 contributes to the delay of epithelial cell cycle traversal in diabetic keratopathy. : Chinese Abstract., (Copyright 2015 The Association for Research in Vision and Ophthalmology, Inc.)

Heme oxygenase (HO)-2 deficiency impairs wound healing and exacerbates inflammation following injury. We examine the impact of HO-2 deficiency on macrophage function and the contribution of macrophage HO-2 to inflammatory and repair responses to injury. Corneal epithelial debridement was performed in control and macrophage-depleted HO-2(-/-) and wild-type (WT) mice and in bone marrow chimeras. Peritoneal macrophages were collected for determination of phagocytic activity and classically activated macrophage (M1)-alternatively activated macrophage (M2) polarization. Depletion of macrophages delayed corneal healing (13.2%) and increased neutrophil infiltration (54.1%) by day 4 in WT mice, whereas in HO-2(-/-) mice, it did not worsen the already impaired wound healing and exacerbated inflammation. HO-2(-/-) macrophages displayed an altered M1 phenotype with no significant expression of M2 or M2-like activated cells and a 31.3% reduction in phagocytic capacity that was restored by inducing HO-1 activity or supplementing biliverdin. Macrophage depletion had no effect, whereas adoptive transfer of WT bone marrow improved wound healing (34% on day 4) but did not resolve the exaggerated inflammatory response in HO-2(-/-) mice. These findings indicate that HO-2-deficient macrophages are dysfunctional and that macrophage HO-2 is required for proper macrophage function but is insufficient to correct the impaired healing of the HO-2(-/-) cornea, suggesting that corneal epithelial expression of HO-2 is a key to resolution and repair in wound healing., (© FASEB.)

Diabetic corneal neuropathy can result in chronic, sight-threatening corneal pathology. Although the exact etiology is unknown, it is believed that a reduction in corneal sensitivity and loss of neurotrophic support contributes to corneal disease. Information regarding the relationship between nerve loss and effects on the corneal epithelium is limited. We investigated changes in the corneal epithelium and nerve morphology using three-dimensional imaging in vivo and in situ in a streptozotocin-induced diabetic mouse model. Streptozotocin-treated mice showed increased levels of serum glucose and growth retardation consistent with a severe diabetic state. A reduction in the length of the subbasal nerve plexus was evident after 6 weeks of disease. Loss of the subbasal nerve plexus was associated with corneal epithelial thinning and a reduction in basal epithelial cell density. In contrast, loss of the terminal epithelial nerves was associated with animal age. Importantly, this is the first rodent model of type 1 diabetes that shows characteristics of corneal epithelial thinning and a reduction in basal epithelial cell density, both previously have been documented in humans with diabetic corneal neuropathy. These findings indicate that in type 1 diabetes, nerve fiber damage is evident in the subbasal nerve plexus before terminal epithelial nerve loss and that neurotrophic support from both the subbasal nerve plexus and terminal epithelial nerves is essential for the maintenance of corneal epithelial homeostasis., (Copyright © 2014 American Society for Investigative Pathology. Published by Elsevier Inc. All rights reserved.)

The cornea is a very particular tissue due to its transparency and its barrier function as it has to resist against the daily insults of the external environment. In addition, maintenance of this barrier function is of crucial importance to ensure a correct corneal homeostasis. Here, the corneal epithelial permeability has been assessed in vivo by means of non-invasive tetrapolar impedance measurements, taking advantage of the huge impact of the ion fluxes in the passive electrical properties of living tissues. This has been possible by using a flexible sensor based in SU-8 photoresist. In this work, a further analysis focused on the validation of the presented sensor is performed by monitoring the healing process of corneas that were previously wounded. The obtained impedance measurements have been compared with the damaged area observed in corneal fluorescein staining images. The successful results confirm the feasibility of this novel method, as it represents a more sensitive in vivo and non-invasive test to assess low alterations of the epithelial permeability. Then, it could be used as an excellent complement to the fluorescein staining image evaluation.

Purpose: To evaluate the effect of tobacco smoking on healing of corneal abrasions and keratitis in humans., Methods: A retrospective chart review of patients diagnosed with corneal abrasions and corneal ulcers from 1990 to 2010 at the Dean McGee Eye Institute was performed. The primary outcome measured was time from initial examination to epithelial closure; tobacco smoking was the primary exposure variable. Comorbidity variables were also examined as potential confounding factors. The data were analyzed using Kaplan-Meier curves and Cox proportional hazards models., Results: Eighty-seven patients met the inclusion criteria for corneal abrasion and 52 for keratitis. The mean healing time was 4.8 days in nonsmokers and 5.9 days in smokers in the abrasion arm, and 15.5 days in nonsmokers and 39.4 days in smokers in the keratitis arm. After controlling for comorbidities, treatment, and demographic variables, the healing time in both arms was significantly delayed in smokers when compared with nonsmokers (P = 0.01 and P = 0.03, respectively). The comorbidities were also studied after adjusting for smoking. A statistically significant delay was seen with previous keratoplasty and steroid treatment for the abrasion arm. In the keratitis arm, neurotrophic corneas and fungal infections were associated with a delay in healing after correcting for smoking., Conclusions: Epithelial healing is delayed by 1.1 days on average in smokers when compared with nonsmokers with corneal abrasions. Patients who had undergone a previous keratoplasty had delayed healing from corneal abrasions regardless of the smoking status. Epithelial healing is delayed by 23.9 days on average in patients with keratitis who report smoking. Neurotrophic corneas and fungal infections also had prolonged time to healing.

Purpose: The aim of this study was to evaluate the balance and changes of corneal higher order aberrations (HOAs) after photorefractive keratectomy (PRK)., Methods: Myopic and myopic-astigmatic patients (89 eyes of 48 patients) were enrolled in this study. A PRK was performed using an Asclepion Meditec MEL 80 G flying-spot excimer laser. The mean ablation depth and diameter were 76.78 μm (±19.40 μm) and 6.0 mm (±0.06 mm), respectively. Before and 1 year after the surgery, uncorrected and best spectacle-corrected visual acuities were determined. Wavefront aberrations of the anterior [root mean square (RMS)-HOA anterior], posterior (RMS-HOA posterior), and total cornea (RMS-HOA total) were measured using a Scheimpflug Camera. Linear piecewise regression analysis was used for correlations between the ablation depth and aberration of the anterior corneal surface. The follow-up time was 1 year., Results: At baseline, RMS-HOA anterior proved to be significantly higher compared with RMS-HOA total (P < 0.001). After the PRK was performed, the RMS-HOA anterior (P < 0.001) and RMS-HOA total values (P < 0.001) increased significantly; however, RMS-HOA posterior values (P = 0.12) remained stable. Above an ablation depth of 76.78 μm, the RMS-HOA anterior increased 2.4-fold. Uncorrected and best spectacle-corrected visual acuities were 1.0 (20/20) in 95.5% and 98.8% of the patients 1 year postoperatively., Conclusions: Aberrations of the posterior corneal surface seem to compensate for wavefront alterations of the anterior cornea, decreasing the amount of wavefront error regarding the total cornea in myopic patients. PRK induced increased HOAs with respect to the anterior corneal surface; however, the posterior surface remained stable. The increase in the HOAs was measured to be significantly larger above 76.78 μm photoablation depth.

Purpose: Our main purpose was to compare safety and efficacy in the treatment of progressive keratoconus with "epithelium-on" and "epithelium-off" corneal collagen cross-linking (CXL). Our secondary purpose was to evaluate efficacy of CXL when hypotonic 0.5% riboflavin is used as photosensitizer., Methods: One eye of 20 patients with bilateral progressive keratoconus was randomly treated for "epithelium-on" CXL (group 1) while the fellow eye underwent "epithelium-off" CXL (group 2). Hypotonic 0.5% riboflavin was used in both groups. Visual acuity, refraction, corneal topography, and wavefront aberrometry were evaluated at baseline and after 1, 6, and 12 months. Specular microscopy was performed on 10 patients preoperatively and after 12 months. Postoperative pain was evaluated using a patient questionnaire., Results: Uncorrected and corrected distance visual acuity improved significantly in both groups. Refraction, topography, and aberrometry showed nonsignificant changes from the preoperative status throughout the 12-month follow-up in both groups. Moreover, the outcomes between the groups were comparable at all follow-up points. Endothelial cell-count was stable. Postoperative pain length was shorter in group 1 (P < 0.001)., Conclusion: "Epithelium-on" and "epithelium-off" CXL using hypotonic 0.5% riboflavin were equally safe and effective in stabilization of keratoconus. Topography and aberrometry outcomes in both groups failed to show any significant improvements. This study is registered at ClinicalTrials.gov: NCT01181219.

A series of 10 patients at Armed Forces Institute of Ophthalmology, Rawalpindi, from September 2009 to August 2010 is reported. Follow-up of patients were done till February 2012. Patients with persistent corneal epithelial defects (PED) of minimum 2 weeks duration, in whom conventional therapy had failed, were included in the study. They were prescribed 100% autologous serum eye drops on hourly basis. When PED healed within 02 weeks, it was labeled as effective and when it healed within one month, it was labeled as partially effective. Six weekly follow-up was done for 18 months for all patients to document any recurrence of PED. Eight out of 10 patients had successful outcome i.e. 80% of PED healed within one month, out of which 7 patients had 'effective' outcome. Autologous serum eye drops are safe, effective and minimally invasive modality in treating PED.

The corneal epithelium is the outermost layer of the cornea that directly faces the outside environment, hence it plays a critical barrier function. Previously, conditional loss of Notch1 on the ocular surface was found to cause inflammation and keratinization of the corneal epithelium. This was in part attributed to impaired vitamin A metabolism, loss of the meibomian glands and recurrent eyelid trauma. We hypothesized that Notch1 plays an essential role in the corneal epithelial barrier function and is a contributing factor in the pathologic changes in these mice. Notch1 was conditionally deleted in adult Notch1(flox/flox), K14-Cre-ERT(+/-) mice using hydroxy-tamoxifen. The results indicated that conditional deletion of Notch1 on the ocular surface leads to progressive impairment of the epithelial barrier function before the onset of corneal opacification and keratinization. Loss of the barrier was demonstrated both by an increase in in vivo corneal fluorescein staining and by enhanced penetration of a small molecule through the epithelium. Corneal epithelial wounding resulted in significant delay in recovery of the barrier function in conditional Notch1(-/-) mice compared to wild type. Mice with conditional deletion of Notch1 did not demonstrate any evidence of dry eyes based on aqueous tear production and had normal conjunctival goblet cells. In a calcium switch experiment in vitro, Notch1(-/-) cells demonstrated delayed membrane localization of the tight junction protein ZO-1 consistent with a defect in the epithelial tight junction formation. These findings highlight the role of Notch1 in epithelial differentiation and suggest that intrinsic defects in the corneal epithelial barrier recovery after wounding is an important contributing factor to the development of inflammatory keratinization in Notch1(-/-) mice.

Purpose: To investigate the effects of gene ablation of epiplakin on the homeostasis of corneal epithelium in mice., Methods: Light and transmission electron microscopic histology, immunohistochemistry, and real-time RT-PCR were carried out to evaluate the effects of the loss of epiplakin on structure and gene expression of cell-cell adhesion-related components in mice. Integrity against mechanical intervention and wound-healing response of corneal epithelium were also tested., Results: Epiplakin protein was detected in the cells of the basal layer of corneal epithelium. Morphologically basal-like cells were observed in the suprabasal layer of adult epiplakin-null corneal epithelium, suggesting an impaired intraepithelial cell differentiation. Such abnormality was not detected in mice before the age of postnatal day 14. Epiplakin-deficient epithelium exhibits fragility against mechanical intervention as compared with wild-type epithelium. Although cell proliferation is suppressed, migration-dependent wound healing is promoted in epiplakin-null epithelium. E-cadherin expression was suppressed by the loss of epiplakin in the epithelium., Conclusions: Lacking epiplakin affects cell differentiation of the corneal epithelium, as well as its proliferation activity and its structural integrity. The mechanism of acceleration of cell migration in the epiplakin-null corneal epithelium is to be further investigated, although suppression of expression of E-cadherin might be included.

Background/aim: Corneal epithelial defects may heal slowly in patients with diabetes, limbal stem cell deficiency, extensive chemical burns or anesthetized corneas. Studies have shown that erythropoietin, a glycoprotein hormone that promotes red blood cell proliferation and inhibits apoptosis of erythroid progenitors, may also exert a cytoprotective, antiapoptotic effect on nonhematopoietic cells. The aim of the study was to examine the effect of erythropoietin on the healing process of corneal epithelial erosions in rabbit eyes., Methods: Fifteen New Zealand albino rabbits were divided into 3 groups following induction of unilateral uniform corneal epithelial erosions. The first group received local treatment with erythropoietin-containing cellulose-based gel 4 times daily; the second group received treatment with cellulose-based gel without erythropoietin 4 times daily, and the third group received no treatment. The healing process was monitored twice daily using cobalt-blue-filtered slit lamp photography and digital images of fluorescein-stained corneas until complete re-epithelization was achieved. Following re-epithelization, corneas were removed for histologic processing. One-way analysis of variance and Mann-Whitney tests were used for statistical analysis., Results: Mean ± SD time to complete re-epithelization was 55 ± 2.19 h in the group treated with erythropoietin-containing cellulose-based gel, 66.5 ± 14.25 h in the group treated with gel only and 62.2 ± 9.09 h in the untreated group (p = 0.16, not significant). There was no significant difference among the groups in the time to complete re-epithelization or the rate of epithelial healing. Histologic corneal evaluation revealed stromal vascularization in 2 of the 6 erythropoietin-treated rabbits and in neither of the control groups., Conclusion: Erythropoietin has no beneficial effect on the rate of healing of corneal epithelial erosions in rabbit eyes, and corneal stroma neovascularization seems to be a significant adverse effect., (© 2013 S. Karger AG, Basel.)

Purpose: Cornea confocal microscopy is emerging as a clinical tool to evaluate the development and progression of diabetic neuropathy. The purpose of these studies was to characterize the early changes in corneal sensitivity and innervation in a rat model of type 1 diabetes in relation to standard peripheral neuropathy endpoints and to assess the effect of Ilepatril, a vasopeptidase inhibitor which blocks angiotensin converting enzyme and neutral endopeptidase, on these endpoints., Methods: Streptozotocin-diabetic rats 8 weeks duration were treated with or without Ilepatril for the last 6 weeks of the experimental period. Afterwards, standard diabetic neuropathy endpoints, subbasal corneal nerves and innervation of the epithelium, corneal sensitivity using a Cochet-Bonnet esthesiometer, and vascular reactivity of the posterior ciliary artery were examined., Results: Diabetes caused a decrease in nerve conduction velocity, thermal hypoalgesia, and a reduction in intraepidermal nerve fiber profiles. In the cornea there was a decrease in corneal nerve fibers innervating the epithelium and corneal sensitivity, but subbasal corneal nerve fibers was not changed. Vascular relaxation in response to acetylcholine was decreased in the posterior ciliary artery. These defects were partially to completely prevented by Ilepatril treatment., Conclusions: These studies suggest that in type 1 diabetic rats decreased innervation of the cornea epithelium occurs early in diabetes and prior to a detectable decrease in subbasal corneal nerves and that these and other diabetic neuropathy-related defects can be partially to completely prevented by a vasopeptidase inhibitor.

Limbal stem cell deficiency results from the loss of tissue regenerating stem and progenitor cells. Corneal epithelial regeneration is maintained by stem and progenitor cells which reside in the schlerocorneal limbus. They possess stem cell characteristics and can be stimulated to proliferate by external signals. The limbus is the stem cell niche for corneal epithelial stem cells and forms a unique microenvironment in which stem cell characteristics are conserved. Regulation of limbal epithelial stem cells is produced by a network of signals within the niche which governs cell fate decisions with regards to proliferation, differentiation or maintenance of a quiescent status.

Background: To compare the corneal high-order aberrations (HOAs), asphericity and regularity after Q-value guided laser in situ keratomileusis (LASIK) and laser epithelial keratomileusis (LASEK) in high myopic astigmatism., Methods: In this retrospectively comparative study, we measured the corneal HOAs, asphericity indices (Q values) and corneal regularity indices preoperatively and 36 months postoperatively in 70 eyes (35 patients) with Q-value guided surgeries. All the patients with high myopic astigmatism were divided into two groups which included 34 eyes underwent LASIK and 36 eyes underwent LASEK procedures. The main impact factors of the high-order aberrations were also analyzed., Results: In the two groups, the efficacy index was more than 1.00 and safety index approached 1.00 at year 3 postoperatively. Statistically significant (P < 0.05) increased in Q values and main corneal HOAs (spherical aberrations and coma) following Q-value guided LASIK and LASEK procedures. Spherical aberrations increased more in the LASEK group and there was statistically difference compared to the LASIK group (P < 0.05). LASEK had better effects in correcting corneal astigmatism (P < 0.05). All the corneal regularity indices after surgeries increased and there was no significant difference (P = 0.707, P = 0.8 and P = 0.224, respectively) between the two groups. The main impact factors of spherical aberration included the optic zone size, changes of Q value, surgical procedure and the corrected refraction., Conclusions: In high myopic astigmatism, Q-value guided ablation showed good safety, efficacy and predictability. Q value, regularity indices, spherical aberration and coma increased in both LASIK and LASEK procedures. Astigmatism could be corrected more effectively by LASEK but greater spherical aberration could be created. The difference might be related to the different healing mechanisms. Optic zone size and the corrected refraction might be the main influence factors on the anterior corneal high order aberrations.

Purpose: To define the contribution of the corneal epithelium in corneal topography in keratoconus and discuss the implications regarding combined topography-guided photorefractive keratectomy and corneal collagen crosslinking (CXL)., Setting: French National Reference Center for Keratoconus, Bordeaux, France., Design: Case series., Methods: Specular topographies were performed before and immediately after epithelial removal during conventional CXL surgery in patients with keratoconus., Results: The study included 1 eye with forme fruste keratoconus, 4 eyes in Krumeich stage I, and 3 eyes in stage II. The mean simulated maximum keratometry (K) increased by 2.87 diopters (D) after epithelial removal. The mean effective refractive power increased by a mean of 4.01 D and the astigmatic refractive power, by a mean of 2.17 D. The difference in mean axis deviation was not significant. The mean inferior-superior ratio irregularity index increased 1.51 units. All K and refractive readings except astigmatic refractive axis were significantly increased after epithelial removal. All regularity indices increased significantly without the epithelium. The amplitude of variations in K readings made it difficult to predict the refractive changes after custom laser photoablation based on epithelial-based topography., Conclusions: The astigmatism refractive axis did not change significantly; therefore, this axis could be useful for astigmatic corrections, whereas the spherical component would not be useful. Topographic changes after epithelial removal can be important but not intuitive in keratoconus eyes. This should be considered in custom topography-guided photoablation strategies when attempting to correct refractive errors at the time of CXL., (Copyright © 2012 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.)