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This outstanding volume in the Essentials in Ophthalmology series presents recent developments in the diagnosis and treatment of corneal disease. Its intention is not to replace the relevant textbooks, but to serve as a bridge between primary and tertiary literature. This well-structured volume covers the following main topics: Herpes simplex keratitis.-Amniotic membrane transplantation for the treatment of corneal ulceration in infectious keratitis.-Chlamydial infection.-Chronic blepharitis.-New aspects on the pathogenesis of conjunctival melanoma.-Confocal microscopy of malignant tumors.

The permeability through the cornea determines the ability of a drug or any topically applied compound to cross the tissue and reach the intraocular area. Most of the permeability values found in the literature are obtained considering topical drug formulations, and therefore, refer to the drug permeability inward the eye. However, due to the asymmetry of the corneal tissue, outward drug permeability constitutes a more meaningful parameter when dealing with intraocular drug-delivery systems (i.e., drug-loaded intraocular lenses, intraocular implants or injections). Herein, the permeability coefficients of two commonly administered anti-inflammatory drugs (i.e., bromfenac sodium and dexamethasone sodium) were determined ex vivo using Franz diffusion cells and porcine corneas in both inward and outward configurations. A significantly higher drug accumulation in the cornea was detected in the outward direction, which is consistent with the different characteristics of the corneal layers. Coherently, a higher permeability coefficient was obtained for bromfenac sodium in the outward direction, but no differences were detected for dexamethasone sodium in the two directions. Drug accumulation in the cornea can prolong the therapeutic effect of intraocular drug-release system ; This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement N° 813440 (ORBITAL—Ocular Research by Integrated Training And Learning) and is also supported by the Fundação para a Ciência e Tecnologia (FCT) [UID/QUI/00100/2019, UIDB/00100/2020 and UID/BIM/04585/2020] ; SI

Abstract
The cornea is a protective and refractive barrier in the eye crucial for vision. Understanding the human cornea in health, disease, and cell-based treatments can be greatly advanced with cornea organoids developed in culture from induced pluripotent stem cells. While a limited number of studies have investigated the single-cell transcriptomic composition of the human cornea, its organoids have not been examined similarly. Here, we elucidated the transcriptomic cell fate map of 4-month-old human cornea organoids and human donor corneas. The organoids harbor cell clusters that resemble cells of the corneal epithelium, stroma, and endothelium, with subpopulations that capture signatures of early developmental states. Unlike the adult cornea where the largest cell population is stromal, the organoids contain large proportions of epithelial and endothelial-like cells. These corneal organoids offer a 3D model to study corneal diseases and integrated responses of different cell types.

Mammalian Piezo2 channels are essential for transduction of innocuous mechanical forces by proprioceptors and cutaneous touch receptors. In contrast, mechanical responses of somatosensory nociceptor neurons evoking pain, remain intact or are only partially reduced in Piezo2-deficient mice. In the eye cornea, comparatively low mechanical forces are detected by polymodal and pure mechanosensory trigeminal ganglion neurons. Their activation always evokes ocular discomfort or pain and protective reflexes, thus being a unique model to study mechanotransduction mechanisms in this particular class of nociceptive neurons. Cultured male and female mouse mechano- and polymodal nociceptor corneal neurons display rapidly, intermediately and slowly adapting mechanically activated currents. Immunostaining of the somas and peripheral axons of corneal neurons responding only to mechanical force (pure mechano-nociceptor) or also exhibiting TRPV1 (transient receptor potential cation channel subfamily V member 1) immunoreactivity (polymodal nociceptor) revealed that they express Piezo2. In sensory-specific Piezo2-deficient mice, the distribution of corneal neurons displaying the three types of mechanically evoked currents is similar to the wild type; however, the proportions of rapidly adapting neurons, and of intermediately and slowly adapting neurons were significantly reduced. Recordings of mechano- and polymodal-nociceptor nerve terminals in the corneal surface of Piezo2 conditional knock-out mice revealed a reduced number of mechano-sensitive terminals and lower frequency of nerve terminal impulse discharges under mechanical stimulation. Eye blinks evoked by von Frey filaments applied on the cornea were lower in Piezo2-deficient mice compared with wild type. Together, our results provide direct evidence that Piezo2 channels support mechanically activated currents of different kinetics in corneal trigeminal neurons and contributes to transduction of mechanical forces by corneal nociceptors. ; The authors gratefully acknowledge the financial support received by the Spanish Government projects: SAF2016-77233R (A.Gomis and F.V.) and the "Severo Ochoa" Program for Centers of Excellence in R&D (SEV-2017-0723); A.I.-P and O. GG., were supported by the project SAF2017-83674-C2-1-R and C2-2R. ; Peer reviewed

Optical coherence tomography (OCT) is a non-invasive depth resolved optical imaging modality, that enables high resolution, cross-sectional imaging in biological tissues and materials at clinically relevant depths. Though OCT offers high resolution imaging, the best ultra-high-resolution OCT systems are limited to imaging structural changes with a resolution of one micron on a single B-scan within very limited depth. Nanosensitive OCT (nsOCT) is a recently developed technique that is capable of providing enhanced sensitivity of OCT to structural changes. Improving the sensitivity of OCT to detect structural changes at the nanoscale level, to a depth typical for conventional OCT, could potentially improve the diagnostic capability of OCT in medical applications. In this paper, we demonstrate the capability of nsOCT to detect structural changes deep in the rat cornea following superficial corneal injury. (C) 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement ; The authors acknowledge the help provided by Dr Hrebesh Molly Subhash during the experiments. This project has received funding from the European Union's Horizon 2020 research and innovation program under grant agreements No 761214 (STARSTEM) and 779960 (IMCUSTOMEYE). The materials presented and views expressed here are the responsibility of the authors(s) only. The EU Commission takes no responsibility for any use made of the information set out. ; peer-reviewed

Objective: summarizing the scientific content produced about the risk factors for corneal injury in critically
ill patients in intensive care. Method: this is an integrative review of the literature conducted by question:
"Which risk factors are involved in the development of corneal injury in critically ill patients in intensive
care?" We searched the banks of BDENF, LILACS, SciELO and MEDLINE. The collection was performed
according to the research protocol from January to April 2014. Results: the risk factors found are related to
impairment of defense mechanisms, ventilation, and level of consciousness, severity and hemodynamic
instability and use of specific medications. Conclusion: there was noted the scarcity of scientific papers
about the subject in our country, which makes it imperative to urgent investigation into our reality, in order
to demonstrate the problems of this disease.

Corneal mechanical changes are believed to occur before any visible structural alterations observed during routine clinical evaluation. This study proposed developing an elastography technique based on torsional waves (TWE) adapted to the specificities of the cornea. By measuring the displacements in the propagation plane perpendicular to the axis of the emitter, the effect of guided waves in platelike media was proven negligible. Ex vivo experiments were carried out on porcine corneal samples considering a group of control and one group of alkali burn treatment ( NH 4OH) that modified the mechanical properties. Phase speed was recovered as a function of intraocular pressure (IOP), and a Kelvin-Voigt rheological model was fitted to the dispersion curves to estimate viscoelastic parameters. A comparison with uniaxial tensile testing with thin-walled assumptions was also performed. Both shear elasticity and viscosity correlated positively with IOP, being the elasticity lower and the viscosity higher for the treated group. The viscoelastic parameters ranged from 21.33 to 63.17 kPa, and from 2.82 to 5.30 Pa s, for shear elasticity and viscosity, respectively. As far as the authors know, no other investigations have studied this mechanical plane under low strain ratios, typical of dynamic elastography in corneal tissue. TWE reflected mechanical properties changes after treatment, showing a high potential for clinical diagnosis due to its rapid performance time and paving the way for future in vivo studies. ; Ministerio de Educacion, Cultura y Deporte Grant DPI2017-83859-R DPI2014-51870-R UNGR15-CE-3664 EQC2018-004508-P ; Spanish Government DTS15/00093 PI16/00339 ; Instituto de Salud Carlos III y Fondos Feder ; Junta de Andalucia PI-0107-2017 PIN-0030-2017 IE2017-5537 ; MCIN/AEI - European Social Fund "Investing in your future" PRE2018-086085 ; Consejeria de economia, conocimiento, empresas y universidad SOMM17/6109/UGR B-TEP-026- IE2017-5537 P18-RT-1653 ; European Commission SOMM17/6109/UGR B-TEP-026- IE2017-5537 ...