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EN
Background. Microbial keratitis which is also known as corneal ulcer, is a common ocular infection that can result in debilitating monocular visual impairment. Identifying the prevalence and the latest trend of the causative agents will be useful in the management of corneal ulcer. Objectives. To evaluate the demographic and epidemiology factors of microbial keratitis at a tertiary hospital in a rural state of Malaysia. Material and methods. This is a retrospective review with a total recruit of 137 patients who were admitted to the Ophthalmology ward in Hospital Universiti Sains Malaysia. A retrospective review of the demographic data and results of corneal tissue sampling were documented. Results. Demographic data showed similarity to other studies where it affected most commonly in the productive age. It was also more commonly seen in male patients than in female. Bacterial keratitis (51.1%) was found to be more common than fungal keratitis (24.8%). In cases of bacterial keratitis, Pseudomonas spp. was the commonest causative agent, while in cases of fungal keratitis, Fusarium spp. was the commonest fungus microbial agent. Conclusions. With the knowledge of the demographical and epidemiological factors of microbial keratitis of a region, clinicians will be able to initiate prompt treatment at the early stages of the disease. Thus, less complications will arise from the disease and a better visual outcome provided.
EN
Refractive surgery has stimulated significant progress in anterior segment imaging. Knowledge of epithelial thickness profile considerably increases the efficacy and safety of refractive procedures. This review aims to present new technologies evaluating corneal epithelial thickness and the most important clinical applications in the field of corneal refractive surgery.
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EN
Introduction: Conjunctival/corneal intraepithelial neoplasms are premalignant lesions usually showing conjunctival or limbal involvement. We report the rare case of an isolated corneal intraepithelial lesion. Clinical case: An 80-year-old woman with an elevated, avascular, well-demarcated grey corneal plaque. After epitheliectomy and alcohol, the excised lesion was identified as a high-grade epithelial neoplasia. Treatment was topical interferon α-2b for 1 month without recurrences. Conclusions: A well-defined greyish corneal opacity should always raise suspicion of an intraepithelial neoplasia. In the present case, epitheliectomy and topical recombinant interferon proved successful.
EN
Fuchs endothelial corneal dystrophy (FECD) is a bilateral, progressive disease originating in corneal endothelial cells. Fuchs endothelial corneal dystrophy slowly progresses, causing endothelial cell loss, subsequent corneal stromal and epithelial edema, leading to visual acuity impairment and ocular pain. Fuchs endothelial corneal dystrophy was first documented more than a hundred years ago – in 1910, when Viennese ophthalmologist Ernst Fuchs reported 13 elderly patients with bilateral central clouding. Since then, there have been a far-reaching progress in terms of pathogenesis, knowledge of etiological factors, as well as progress in diagnosis and treatment. Despite that, there are still many questions remaining unanswered, especially in the field of the genetic basis of FECD and the molecular pathomechanisms. The aim of this review is to present and discuss clinical, genetic, pathophysiologic, diagnostic and therapeutic aspects of this common corneal dystrophy. The article also focuses on innovative methods of imagining including high-resolution optical coherence tomography. Moreover, we highlight and discuss the development of traditional surgical treatment options and new minimally invasive techniques such as descemetorhexis without endothelial keratoplasty (DWEK) and Rho-associated kinase inhibitor (ROCK inhibitors) eye drops.
PL
Dystrofia śródbłonkowa rogówki Fuchsa (FECD) jest obustronną, postępującą chorobą dotyczącą komórek śródbłonka rogówki. Powoduje stopniową utratę komórek śródbłonka, doprowadzając do obrzęku istoty właściwej i nabłonka rogówki, a w konsekwencji do pogorszenia jakości widzenia, ostrości wzroku i dolegliwości bólowych oczu. Dystrofia została po raz pierwszy opisana i udokumentowana ponad 100 lat temu, w 1910 r., przez wiedeńskiego okulistę Ernsta Fuchsa na przykładzie 13 pacjentów z obustronnym centralnym zmętnieniem rogówki. Od tego czasu nastąpił daleko idący postęp w zakresie znajomości patogenezy, czynników etiologicznych wywołujących chorobę oraz rozwój metod diagnostycznych i terapeutycznych. Wciąż jednak pozostaje wiele pytań, na które dotychczas nie udzielono jednoznacznej odpowiedzi, zwłaszcza w zakresie uwarunkowań genetycznych i molekularnych patomechanizmów FECD. Celem artykułu poglądowego jest przedstawienie i omówienie klinicznych, genetycznych, patofizjologicznych, diagnostycznych i terapeutycznych aspektów dystrofii Fuchsa. Artykuł koncentruje się również na innowacyjnych metodach diagnostyki obrazowej, w tym na optycznej koherentnej tomografii wysokiej rozdzielczości. Przedstawiono także metody leczenia chirurgicznego oraz nowe, małoinwazyjne techniki, takie jak DWEK – technika descemetoreksji bez wykonywania następczego przeszczepienia czy leczenie z wykorzystaniem inhibitora kinazy Rho (ROCK).
EN
Background: The aim of the present study was assessing the possibility of experimental allogenic transplantation of cat cornea endothelial cells, multiplied in vitro, into the anterior chamber of the eyeball in recipient cats. The reason for undertaking the research is the need to develop a method that would help in the cornea treatment in animals with corneal opacification following cataract surgery, as well as lens dislocation, injuries and endothelium degeneration. Methods: Cats aged 10-12 months were used in the experiment. Cornea fragments consisting of the posterior limiting membrane and posterior epithelium were placed in Iscove;s medium with addition of 10% foetal calf serum. Multiplied in vitro cells were injected into the anterior chamber of recipient cats. The cornea was subject to histological, histometric and SEM examination on the 3rd, 7th, 20th and 30th day after the surgery. Results: Micromorphological examination of the cornea showed full restitution of its endothelium 30 days after transplantation. Complete regeneration of structures indispensable for normal functioning of the posterior epithelium occurred as a result of implantation. Conclusions: In this study the results show that implantation of the cells of posterior corneal epithelium of donor cats, multiplied into vitro and injected into the anterior chamber of recipient cats. The cornea regained its full function, the layer of the posterior epithelium was regenerated and the stroma stabilized, presenting the image of full and proper corneal translucency.
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Content available remote Role of biochemical factors in the pathogenesis of keratoconus
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EN
Keratoconus (KC) is a corneal disease associated with structural abnormalities in the corneal epithelium, Bowman's layer and stroma and altered concentration of tear components. KC corneas show a different pattern of collagen lamellae than their normal counterparts. Also, a reduction of several collagen types in KC epithelium and stroma was observed. Altered expression and/or activity of lysyl oxidase, a critical enzyme of the biogenesis of connective tissue detected in KC corneas, may weaken covalent bonds between collagen and elastin fibrils, what may lead to biomechanical deterioration of the cornea. Increased activity of matrix metalloproteinases observed in KC may induce the degradation of the extracellular matrix causing damage to the cornea. Oxidative and nitrative stress play an important role in KC pathogenesis and KC corneas are characterized by the disturbed lipid peroxidation and nitric oxide pathways. Malfunctioning of these pathways may lead to accumulation of their toxic by-products inducing several detrimental effects, along with apoptosis of the corneal cells, which may result from the loss of β-actin or increased levels of cytokines, including interleukin-1 and -6. Change in the expression of genes associated with wound healing, including the nerve growth factor and the visual system homeobox 1, may contribute to increased susceptibility of KC corneas to injury. Consequently, biochemical changes may play an important role in KC pathophysiology and, therefore, can be considered in prevention, diagnosis, prognosis and in the therapy of this disease as well.
EN
The aim of this study was to determine histotopography and age-related changes of immunoreactive substance P (SP-IR) nerve plexus in dog cornea. In this research corneas of three groups of dogs of different age were used: young (2-3 months), adult (1-3 years) and old (8 and more years). Immunohistochemical demonstration of SP was performed on 40 um serial free-floating corneal sections cut parallel to the corneal surface. Results showed that SP-IR nerve plexus of dog cornea was formed by thick (21.9-73 μm diameter), medium (7.3-21.8 μm diameter) and thin (2.19-7.2 um diameter) nerve bundles and varicose or smooth nerve fibers branching into terminals. From limbus SP-IR thick nerve bundles ran radially through superficial and intermediate layers of stroma to the central part of cornea. Thick nerve bundles split into medium ones in central and pericentral parts of cornea. They branched repeatedly forming nerve plexus of stroma. Thin nerve bundles located in subepithelium, superficial and intermediate layers of stroma split from thick and medium bundles. Nerve fibres branched from thin bundles, curved and joined with each other, forming a network of various forms. The highest amount of nerve fibres was observed in corneal epithelium and subepithelium layer. The nerve bundles of young dogs were smaller in diameter than those of adults and old ones. With age the density of nerve fibres and thin bundles decreased in corneal epithelium and subepithelium layer. The density of medium and thick bundles in superficial and intermediate stroma was similar in dogs of all ages. No nerve plexus elements were noticed in stromal deep layer and endothelium in dogs of all ages.
EN
Purpose: The aim of this study is to propose a method to construct corneal biomechanical model which is the foundation for simulation of corneal microsurgery. Methods: Corneal material has two significant characteristics: hyperelastic and viscoelastic. Firstly, Mooney–Rivlin hyperelastic model of cornea obtained based on stored-energy function can be simplified as a linear equation with two unknown parameters. Then, modified Maxwell viscoelastic model of the cornea, whose analytical form is consistent with the generalized Prony-series model, is proposed from the perspective of material mechanics. Results: Parameters of the model are determined by the uniaxial tensile tests and the stress-relaxation tests. Corneal material properties are simulated to verify the hyper-viscoelastic model and measure the effectiveness of the model in the finite element simulation. On this basis, an in vivo model of the corneal is built. And the simulation of extrusion in vivo cornea shows that the force is roughly nonlinearly increasing with displacement, and it is consistent with the results obtained by extrusion experiment of in vivo cornea. Conlusions: This paper derives a corneal hyper-viscoelastic model to describe the material properties more accurately, and explains the mathematical method for determination of the model parameters. The model is an effective biomechanical model, which can be directly used for simulation of trephine and suture in keratoplasty. Although the corneal hyper-viscoelastic model is taken as the object of study, the method has certain adaptability in biomechanical research of ophthalmology.
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Content available remote Strain-rate sensitivity of porcine and ovine corneas
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EN
Knowledge of strain-rate sensitivity of corneal tissue is important for improving the understanding of the tissue's response to mechanical actions and the accurate numerical simulation of corneal biomechanical behaviour under the effects of disease and surgery. In the study, fresh and well-preserved porcine and ovine corneal buttons were subjected to uniaxial tension loads with seven different strain rates ranging between 0.8 and 420% per minute. All specimens exhibited increased stiffness (as measured by the tangent modulus) with higher strain rates. However, clear differences in their behaviour were observed. While ovine corneas showed gradual, consistent and mostly statistically significant increases in stiffness with all elevations in strain rate, porcine corneas' response was significant over only a limited range of low strain rates. The effect of strain rate on the material's stress-strain behaviour was considered in the formation of three sets of constitutive models including: (i) a model based on a simple exponential stress-strain relationship, (ii) the Ogden model that considers the tissue's hyperelasticity but not anisotropy, and (iii) a third model by Holzapfel, Gasser and Ogden that considers both hyperelasticity and anisotropy. The three models are introduced to enable consideration of the strain rate effects in simulations employing finite element programs with varying capabilities or in modelling applications in corneal biomechanics which may or may not require consideration of mechanical anisotropy.
PL
Dekspantenol – prekursor witaminy B5 – jest związkiem pochodzenia naturalnego, który ma znany od dawna dobroczynny wpływ na nawilżenie skóry i błon śluzowych oraz na gojenie się nabłonków. W leczeniu wykorzystuje się również jego aktywność przeciwzapalną. Wpływ dekspantenolu na tkanki powierzchowne był obserwowany w licznych badaniach in vitro i in vivo, jednak dokładny mechanizm działania nie został do tej pory poznany. W okulistyce dekspantenol jest znanym i szeroko stosowanym lekiem u pacjentów z ostrymi i przewlekłymi chorobami powierzchni oka oraz następstwami urazów rogówki.
EN
Dexpanthenol - a precursor to vitamin B5 - is a compound of natural origin that has a long-known beneficial effect on skin and mucous membrane hydration and epithelial healing. Its anti-inflammatory activity is also used in treatment. Its effects on superficial tissues have been observed in numerous in vitro and in vivo studies, but the exact mechanism of action has not yet been understood. In ophthalmology, dexpanthenol is a well-known and widely used drug in patients with acute and chronic diseases of the ocular surface, as well as for treating the sequelae of corneal injuries.
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Content available "Indolent ulcer" in Boxer
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PL
Artykuł przedstawia przypadek leczenia wrzodu rogówki u psa rasy bokser. Wrzód ten określany jest terminem "trudnogojący się" lub "indolent ulcer". Wrzody tego typu są predylekcyjne dla niektórych ras psów. Powstają często spontanicznie i niestety często mogą nawracać. istota choroby polega na oddzielaniu się nabłonka rogówki od jej istoty właściwej. Przyczyną tego może być wada hemidesmosomów, które odpowiadają za przyleganie nabłonka do stromy lub też procesy zwyrodnieniowe stromy rogówki. W obrazie klinicznym, po wybarwieniu rogówki za pomocą fluoresceiny, widoczne jest podciekanie barwnika pod warstwy rogówki. Istnieje kilka metod leczenia tego typu owrzodzenia. wymienić należy; keratotomię, powierzchowną keratektomię, chirurgiczne usunięcie martwego nabłonka rogówki. Leczeniu chirurgicznemu zawsze towarzyszy leczenie farmakologiczne. W naszym przypadku u psa zastosowaliśmy leczenie za pomocą keratotomii kratkowej skojarzonej z leczeniem farmakologicznym.
EN
A case of indolent ulcer in a Boxer is described. An indolent ulcer is a ulcer which fails to heal in the expected time. These ulcers are often breed-related, develop spontaneously and may be considered to represent a primary corneal epithelial or superficial stroma dystrophy. It is caused by a failure of attachment between the basal epithelium to the underlying membrane. There are several methods that will facilitate healing; debridement, keratotomy, superficial keratectomy and medical treatment.
EN
Trephination is one of the basic operations of keratoplasty, and the biomechanical mechanism of the operation can be revealed based on three-dimensional modeling and simulation of trephine cutting cornea. Methods: Based on the analysis of the physical and biomechanical characteristics of corneal trephination, a three-dimensional numerical model of corneal trephination is built, where the cornea can be simplified to two layers structure including stroma and epithelium, and the trephine cuts the cornea under the vertical motion load and the rotational motion load. A three-dimensional failure criterion of corneal material is proposed based on the yield strength theory. On this basis, trephination simulation is carried out, and the units of corneal material are removed from the model when they meet the defined failure criterion. Results: Under the given parameters including the velocity, the angle and the angular velocity, the trephine force curves, include the linear cutting force and the rotary cutting force are obtained, and show the change of the forces with displacement during the process of trephination simulation. The maps of the equivalent stress show the destruction and deformation of the cornea. Then, the experiment of robotic trephination is carried out under the same parameters and the effectiveness of the simulation is evaluated. Conclusions: Based on mechanics theory and finite element method, the process of trephine cutting cornea has been reproduced, and the interaction mechanism is revealed, which lays the foundation for the development of real-time simulation and virtual system of the corneal surgery.
EN
Purpose: This paper is mainly about biomechanical behavior of needle insertion into cornea, and proposes a failure criterion to simulate the insertion process which has attracted considerable attention due to its importance for the minimally invasive treatment. Methods: In the process of needle insertion into cornea, tiny and complex insertion force is generated due to contact between needle and soft tissue. Based on the distortion energy theory, there is proposed a failure criterion of corneal material that can solve contact problem between rigid body and biological tissue in insertion simulation, where Cauchy stress of corneal material is the key to numerical calculation. A finite element model of in vivo cornea is built, and the cornea constrained by sclera is simplified to two layers containing epithelium and stroma. Considering the hyper-viscoelastic property of corneal material, insertion simulation is carried out. Results: By insertion experiment, the insertion force increases with insertion depth accompanying obvious fluctuations. Different insertion forces are generated at different speeds. The punctured locations are obvious in the force-displacement curves. The results of insertion simulation are generally consistent with experimental data. Maps of von Mises stress reflect the tissue injury of the cornea during insertion process, and punctured status corresponds to the point in the curves. Conclusions: The ability of this study to reproduce the behavior of needle insertion into cornea opens a promising perspective for the control of robotic surgery operation as well as the real-time simulation of corneal suture surgery.
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Content available remote Segmentation of anterior segment boundaries in swept source OCT images
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EN
Quantification of the eye’s anterior segment morphology from optical coherence tomography (OCT) images is crucial for research and clinical decision-making, including the diagnosis and monitoring of many ocular diseases. Structural parameters, such as tissue thickness and area are the most common metrics used to quantify these medical images, and tissue segmentation is required before these metrics can be extracted. Currently, swept source OCTallows the capture of cross-sectional images that encompass the entire anterior segment with a high level of detail. However, the manual annotation of tissue boundaries is time-consuming. In this work, an algorithm based on graph-search theory combined with boundary-specific image transformation is applied for the segmentation of anterior segment OCT images. We demonstrate that the method can reliably segment 5 different tissue boundaries in healthy eyes with low boundary error (mean error below 1 pixel across all boundaries). The technique can be used to extract clinically relevant parameters such as central corneal and crystalline lens thickness as well as anterior chamber depth and area, with a high level of agreement with manual segmentation (normalized errors below 1.6%). The proposed method provides a tool that can support clinical and research OCT data analysis.
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PL
Stożek rogówki jest chorobą degeneracyjną, polegającą na postępującym ścieńczeniu i uwypukleniu rogówki. Choroba ta, w postaciach zaawansowanych, prowadzi do znacznych zaburzeń ostrości wzroku – jedynym rozwiązaniem staje się wówczas przeszczep rogówki. Nowoczesna diagnostyka stożka bazuje na analizie powierzchni rogówki przy użyciu topo-tomografii komputerowej, która pozwala na ocenę wczesnych zmian chorobowych z możliwością wdrożenia odpowiedniego leczenia w stadiach początkowych. Taką procedurą jest wprowadzone w ostatnich latach sieciowanie włókien kolagenowych. Zabieg ten, dzięki reakcji fotochemicznej wywołanej oddziaływaniem UVA i ryboflawiny, prowadzi do tworzenia nowych wiązań pomiędzy łańcuchami kolagenu, z następującym usztywnieniem miąższu rogówki i zahamowaniem rozwoju stożka. Wczesna diagnoza, możliwa dzięki obrazowaniu rogówki przy użyciu nowoczesnych systemów topo-tomograficznych w połączeniu z efektywnym zabiegiem powstrzymującym rozwój stożka, stanowią istotne osiągniecie ostatnich lat.
EN
Keratoconus is a degenerative disease with progressive thinning and steepening of the cornea. In the advanced stages with severe reduction of visual acuity, a corneal transplantation is required. Modern diagnostic procedures are based on corneal topography and tomography that permit early diagnosis and therapy. Corneal Cross-linking is the modern therapeutic procedure that allows arrest of disease progression with maintenance of good visual acuity if performed in early stages. This therapeutic procedure is based on the photochemical reaction induced by riboflavin and UVA radiation that creates new bonds between collagen fibers that results in stromal stiffening that arrest keratoconus progression. It could be stated that significant achievements in keratoconus management are related to the possibility of early detection due to the modern tomographic systems and possibility of effective treatment with corneal cross linking procedure that arrests progression of ectasia.
EN
The aim of the study was mycological examination of ulcerated corneal tissues from an ophthalmic patient. Tissue fragments were analyzed on potato-glucose agar (PDA) and maltose (MA) (Difco) media using standard laboratory techniques. Cultures were identified using classical and molecular methods. Macro- and microscopic colony morphology was characteristic of fungi from the genus Aspergillus (restricted growth series), most probably Aspergillus penicillioides Speg. Molecular analysis of the following rDNA regions: ITS1, ITS2, 5.8S, 28S rDNA, LSU and β-tubulin were carried out for the isolates studied. A high level of similarity was found between sequences from certain rDNA regions, i.e. ITS1-5.8S-ITS2 and LSU, what confirmed the classification of the isolates to the species A. penicillioides. The classification of our isolates to A. penicillioides species was confirmed also by the phylogenetic analysis.
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