Development of graphitic carbon nitride quantum dots-based oxygen self-sufficient platforms for enhanced corneal crosslinking.

Keratoconus, a disorder characterized by corneal thinning and weakening, results in vision loss. Corneal crosslinking (CXL) can halt the progression of keratoconus. The development of accelerated corneal crosslinking (A-CXL) protocols to shorten the treatment time has been hampered by the rapid depletion of stromal oxygen when higher UVA intensities are used, resulting in a reduced cross-linking effect.

An in vitro investigation into the impact of corneal rinsing on riboflavin/UVA corneal cross-linking.

Background: Corneal cross-linking (CXL) using riboflavin and ultraviolet-A light (UVA) is a treatment used to prevent progression of keratoconus. This ex vivo study assesses the impact on CXL effectiveness, as measured by tissue enzymatic resistance and confocal microscopy, of including a pre-UVA corneal surface rinse with balanced salt solution (BSS) as part of the epithelium-off treatment protocol.

Methods: Sixty-eight porcine eyes, after epithelial debridement, were assigned to six groups in three experimental runs.

Structural control of corneal transparency, refractive power and dynamics.

The cornea needs to be transparent to visible light and precisely curved to provide the correct refractive power. Both properties are governed by its structure. Corneal transparency arises from constructive interference of visible light due to the relatively ordered arrangement of collagen fibrils in the corneal stroma.

National survey of corneal cross-linking (CXL) practice patterns in the United Kingdom during 2019.

Objective: To provide an insight into trends in corneal cross-linking (CXL) practice in the UK, including criteria for progression of corneal ectasia, identification of patients for CXL, the CXL procedure itself and post-operative management.

Methods: All ophthalmologist members of the UK Cross-linking (UK-CXL) Consortium were invited to complete an online survey about CXL practice for the year 2019. The data collected was anonymised by site and analysed with descriptive statistics.

The Impact of Different Rose Bengal Formulations on Corneal Thickness and the Efficacy of Rose Bengal/Green Light Corneal Cross-linking in the Rabbit Eye.

Purpose: To examine central corneal thickness (CCT) changes during in vivo rose bengal-green light corneal cross-linking (RG-CXL) and compare the CXL efficacy of different rose bengal formulations.

Methods: After epithelium removal, the right eyes of rabbits were immersed in rose bengal solution prepared by different solvents (water, phosphate buffered saline, dextran, and hydroxypropyl methylcellulos [HPMC]) for 2 or 20 minutes, then the rose bengal distribution in the corneal stroma was analyzed by confocal fluorescence detection. During the RG-CXL process, the CCT was measured at seven time points.

Tropocollagen springs allow collagen fibrils to stretch elastically.

The mechanical properties of connective tissues are tailored to their specific function, and changes can lead to dysfunction and pathology. In most mammalian tissues the mechanical environment is governed by the micro- and nano-scale structure of collagen and its interaction with other tissue components, however these hierarchical properties remain poorly understood. In this study we use the human cornea as a model system to characterise and quantify the dominant deformation mechanisms of connective tissue in response to cyclic loads of physiological magnitude.

Keratoconus: cross-linking the window of the eye.

Unlabelled: Keratoconus is a condition in which the cornea progressively thins and weakens, leading to severe, irregular astigmatism and a significant reduction in quality of life. Although the precise cause of keratoconus is still not known, biochemical and structural studies indicate that overactive enzymes within the cornea break down the constituent proteins (collagen and proteoglycans) and cause the tissue to weaken. As the disease develops, collagen fibres slip past each other and are redistributed across the cornea, causing it to change shape.

Fibril density reduction in keratoconic corneas.

This study aims to estimate the reduction in collagen fibril density within the central 6 mm radius of keratoconic corneas through the processing of microstructure and videokeratography data. Collagen fibril distribution maps and topography maps were obtained for seven keratoconic and six healthy corneas, and topographic features were assessed to detect and calculate the area of the cone in each keratoconic eye. The reduction in collagen fibril density within the cone area was estimated with reference to the same region in the characteristic collagen fibril maps of healthy corneas.

X-Ray Diffraction Imaging of Corneal Ultrastructure.

X-ray scattering enables the structure of collagen-rich tissues, such as the cornea, to be examined at both the molecular and fibrillar level. The high-intensity X-rays available at synchrotron radiation sources, coupled with minimal sample preparation requirements, facilitates the rapid generation of high-quality X-ray scattering data from corneal tissue at a close-to-physiological state of hydration. Analysis of resulting X-ray scatter patterns allows one to quantify numerous structural parameters relating to the average diameter, lateral arrangement and alignment of collagen fibrils within the cornea, as well as the axial and lateral arrangements of collagen molecules within the fibrils.

Developmental abnormalities in the cornea of a mouse model for Marfan syndrome.

Elastic fibres provide tissues with elasticity and flexibility. In the healthy human cornea, elastic fibres are limited to the posterior region of the peripheral stroma, but their specific functional role remains elusive. Here, we examine the physical and structural characteristics of the cornea during development in the mgΔ dominant-negative mouse model for Marfan syndrome, in which the physiological extracellular matrix of its elastic-fibre rich tissues is disrupted by the presence of a dysfunctional fibrillin-1 glycoprotein.

Microwave treatment of the cornea leads to localised disruption of the extracellular matrix.

Microwave keratoplasty is a thermo-refractive surgical procedure that can correct myopia (short-sightedness) and pathologic corneal steepening by using microwave energy to cause localised shrinkage around an annulus of the cornea leading to its flattening and vision correction. The effects on the corneal extracellular matrix, however, have not yet been evaluated, thus the current study to assess post-procedure ultrastructural changes in an in-vivo rabbit model. To achieve this a series of small-angle x-ray scattering (SAXS) experiments were carried out across whole transects of treated and untreated rabbit corneas at 0.

An Investigation of the Effects of Riboflavin Concentration on the Efficacy of Corneal Cross-Linking Using an Enzymatic Resistance Model in Porcine Corneas.

Purpose: To investigate riboflavin concentration on enzymatic resistance following corneal cross-linking (CXL).

Methods: Ninety-six porcine eyes were divided into five groups in two treatment runs. Group 1 remained untreated.

Biomaterials-enabled cornea regeneration in patients at high risk for rejection of donor tissue transplantation.

The severe worldwide shortage of donor organs, and severe pathologies placing patients at high risk for rejecting conventional cornea transplantation, have left many corneal blind patients untreated. Following successful pre-clinical evaluation in mini-pigs, we tested a biomaterials-enabled pro-regeneration strategy to restore corneal integrity in an open-label observational study of six patients. Cell-free corneal implants comprising recombinant human collagen and phosphorylcholine were grafted by anterior lamellar keratoplasty into corneas of unilaterally blind patients diagnosed at high-risk for rejecting donor allografts.

: an integrated software tool for analysing fibrous collagen-based tissues.

This article provides an overview of a new integrated software tool for reduction and analysis of small-angle X-ray scattering (SAXS) data from fibrous collagen tissues, with some wider applicability to other cylindrically symmetric scattering systems. combines interactive features for data pre-processing, bespoke background subtraction, semi-automated peak detection and calibration. Both equatorial and meridional SAXS peak parameters can be measured, and the former can be deconstructed into cylinder and lattice contributions.

Why self-care is key to providing high-quality care to others.

Jo McCormick, Consultant Nurse and Associate Director of Nursing, Belfast Health and Social Care Trust, Joanna.McCormick@belfasttrust.hscni.

The structural response of the cornea to changes in stromal hydration.

The primary aim of this study was to quantify the relationship between corneal structure and hydration in humans and pigs. X-ray scattering data were collected from human and porcine corneas equilibrated with polyethylene glycol (PEG) to varying levels of hydration, to obtain measurements of collagen fibril diameter, interfibrillar spacing (IFS) and intermolecular spacing. Both species showed a strong positive linear correlation between hydration and IFS and a nonlinear, bi-phasic relationship between hydration and fibril diameter, whereby fibril diameter increased up to approximately physiological hydration, = 3.

The Structural Role of Elastic Fibers in the Cornea Investigated Using a Mouse Model for Marfan Syndrome.

Purpose: The presence of fibrillin-rich elastic fibers in the cornea has been overlooked in recent years. The aim of the current study was to elucidate their functional role using a mouse model for Marfan syndrome, defective in fibrillin-1, the major structural component of the microfibril bundles that constitute most of the elastic fibers.

Methods: Mouse corneas were obtained from animals with a heterozygous fibrillin-1 mutation (Fbn1+/-) and compared to wild type controls.

An investigation into corneal enzymatic resistance following epithelium-off and epithelium-on corneal cross-linking protocols.

The aim of this study was to investigate corneal enzymatic resistance following epithelium off and on riboflavin/UVA cross-linking (CXL). One hundred and fourteen porcine eyes were divided into four non-irradiated control groups and seven CXL groups. The latter comprised; (i) epithelium-off, 0.

Enzymatic Resistance of Corneas Crosslinked Using Riboflavin in Conjunction With Low Energy, High Energy, and Pulsed UVA Irradiation Modes.

Purpose: To investigate the effect of various riboflavin/ultraviolet light (UVA) crosslinking (CXL) protocols on corneal enzymatic resistance.

Methods: A total of 66 enucleated porcine eyes, with the corneal epithelium removed, were divided into 6 groups. Group 1 remained untreated.

Standard versus accelerated riboflavin-ultraviolet corneal collagen crosslinking: Resistance against enzymatic digestion.

Purpose: To examine the effect of standard and accelerated corneal collagen crosslinking (CXL) on corneal enzymatic resistance.

Setting: School of Optometry and Vision Sciences, Cardiff University, Cardiff, United Kingdom.

Design: Experimental study.

A study of stromal riboflavin absorption in ex vivo porcine corneas using new and existing delivery protocols for corneal cross-linking.

Purpose: To indirectly measure stromal riboflavin penetration using commercially available riboflavin solutions and new and existing epithelium-off, trans-epithelial and iontophoresis-assisted delivery protocols.

Methods: Forty porcine eyes were divided into eight groups. Group 1: Ricrolin applied to the de-epithelialised cornea for 30 min; Group 2: epithelium-intact, no treatment; Groups 3-5: epithelium-intact, 30-min application of Ricrolin TE, Mediocross TE or ParaCel/Vibex, respectively.

Donor cross-linking for keratoplasty: a laboratory evaluation.

Purpose: This laboratory-based investigation compares the topographic outcomes of conventional penetrating keratoplasty with that of a novel procedure in which donor corneas are cross-linked prior to keratoplasty.

Methods: Penetrating keratoplasty procedures with continuous running sutures were carried out in a porcine whole globe model. Sixty eyes were randomly paired as 'donor' and 'host' tissue before being assigned to one of two groups.

The structural and optical properties of type III human collagen biosynthetic corneal substitutes.

The structural and optical properties of clinically biocompatible, cell-free hydrogels comprised of synthetically cross-linked and moulded recombinant human collagen type III (RHCIII) with and without the incorporation of 2-methacryloyloxyethyl phosphorylcholine (MPC) were assessed using transmission electron microscopy (TEM), X-ray scattering, spectroscopy and refractometry. These findings were examined alongside similarly obtained data from 21 human donor corneas. TEM demonstrated the presence of loosely bundled aggregates of fine collagen filaments within both RHCIII and RHCIII-MPC implants, which X-ray scattering showed to lack D-banding and be preferentially aligned in a uniaxial orientation throughout.