Healthy Corneas Research Articles

In Vivo Evaluation of Corneal Biomechanics Following Cross-Linking Surgeries Using Optical Coherence Elastography in a Rabbit Model of Keratoconus.

Validation of the feasibility of novel acoustic radiation force optical coherence elastography (ARF-OCE) for the evaluation of biomechanical enhancement of the in vivo model of keratoconus by clinical cross-linking (CXL) surgery. Twelve in vivo rabbit corneas were randomly divided into two groups. Both groups were treated with collagenase type II, and a keratoconus model was obtained. Then, the two groups were treated with CXL procedures with different irradiation energy of 15 J and 30 J (CXL-15 J and CXL-30 J, respectively). An ARF-OCE probe with an ultrasmall ultrasound transducer was used to detect the biomechanical properties of cornea. An antisymmetric Lamb wave model was combined with the frequency dispersion relationship to achieve depth-resolved elastography. Compared with the phase velocity of the Lamb wave in healthy corneas (approximately 3.96 ± 0.27 m/s), the phase velocity of the Lamb wave was lower in the keratoconus region (P < 0.05), with an average value of 3.12 ± 0.12 m/s. Moreover, the corneal stiffness increased after CXL treatment (P < 0.05), and the average phase velocity of the Lamb wave was 4.3 ± 0.19 m/s and 4.54 ± 0.13 m/s after CXL-15 J and CXL-30 J treatment. The Young's moduli of the keratoconus regions were significantly lower than the healthy corneas. Moreover, the Young's modulus of the keratoconus regions was significantly higher after CXL-30 J treatment than after CXL-15 J treatment. We demonstrated that the ARF-OCE technique has great potential in screening keratoconus and guiding clinical CXL treatment. This work accelerates the clinical translation of OCE systems using ultrasmall ultrasound transducers and is used to guide CXL procedures.

Pearls And Pitfalls of Keratoplasty to Achieve and Optimal Visual Function: A Case Report

Introduction : Keratoplasty, also known as corneal transplant, is a surgical procedure in which a damaged or diseased cornea is replaced with a healthy donor cornea. One of the common reasons for performing this procedure is to restore vision in people with a leukoma eye. Leukoma, also known as corneal opacification, is a condition in which the cornea becomes cloudy or opaque, leading to impaired vision or even blindness. This case will explain keratoplasty procedures for treating leukoma, the benefits and risks of the surgery, and the postoperative care required for a successful recovery.&#x0D; Case Illustration : A 49 years old Female diagnosed with Leukoma due to her symptoms, signs, and examination with VOD: 1/60 ph (-) and VOS : 6/7.5. The patient then underwent keratoplasty surgery. 7th day post operation, Corneal Graft had 16 interrupted sutures with minimal edema. VOD 6/60 and Intra ocular pressure on the right eye was 13.1 mmHg. Oral and topical corticosteroids Continued and planned to taper off gradually.&#x0D; Discussion : The success of the procedure depends on several factors, including the cell count of donor, determining high/low risk patients, Intraoperative, and the postoperative care provided. Topical corticosteroids remain the mainstay to prevent immunological graft reactions. Regular evaluation of the graft is important as the risk of rejection occur up to years.&#x0D; Conclusion : Keratoplasty has proven to be an effective treatment option for individuals with a leukoma eye. The procedure can significantly improve visual acuity and quality of life for these individuals.

Comparison of corneal biomechanical parameters in healthy corneas with symmetric and asymmetric bow-tie topographic pattern with inferior and superior steepening.

To compare the corneal biomechanical parameters in healthy corneas with symmetric and asymmetric bow-tie topographic patterns. In this cross-sectional study, 144 eyes were divided based on inferior-superior asymmetry value (I-S) into symmetric (zero I-S: - 0.50 to + 0.50 D) and asymmetric bow-tie topographic patterns with inferior (positive I-S: + 0.51 to + 1.4 D) or superior (negative I-S: - 2.5 to - 0.51 D) steepening. The biomechanical assessment was performed using Corvis ST and ocular response analyzer (ORA). A general linear model univariate analysis was used to compare the parameters, while the central corneal thickness, intraocular pressure, and age were considered covariates. Only the peak distance (PD) at the highest concavity phase (P = 0.007) and tomographic biomechanical index (TBI, P = 0.001) showed statistically significant differences between the three groups. For TBI, this difference was statistically significant between the positive I-S group separately with the zero I-S group (P < 0.001), and with the negative I-S group (P = 0.022). For PD, the significant difference was between the negative I-S group separately with zero I-S (P = 0.019), and positive I-S groups (P = 0.018). There was a statistically significant correlation between the I-S value with PD (r = 0.281, P = 0.001) and TBI (r = 0.170, P = 0.044). Most corneal biomechanical parameters are not statistically significant compared to the zero I-S group. However, superior steepening is associated with a stiffer response based solely on the shorter PD values seen in this group, and the group with the inferior steepening shows the highest or more suspicious values based on TBI.

Transcriptional profiling specifies the pathogen-specific human host response to infectious keratitis.

Corneal infections are a leading cause of visual impairment and blindness worldwide. Here we applied high-resolution transcriptomic profiling to assess the general and pathogen-specific molecular and cellular mechanisms during human corneal infection. Clinical diagnoses of herpes simplex virus (HSV) (n=5) and bacterial/fungal (n=5) keratitis were confirmed by histology. Healthy corneas (n=7) and keratoconus (n=4) samples served as controls. Formalin-fixed, paraffin-embedded (FFPE) human corneal specimens were analyzed using the 3' RNA sequencing method Massive Analysis of cDNA Ends (MACE RNA-seq). The cellular host response was investigated using comprehensive bioinformatic deconvolution (xCell and CYBERSORTx) analyses and by integration with published single cell RNA-seq data of the human cornea. Our analysis identified 216 and 561 genes, that were specifically overexpressed in viral or bacterial/fungal keratitis, respectively, and allowed to distinguish the two etiologies. The virus-specific host response was driven by adaptive immunity and associated molecular signaling pathways, whereas the bacterial/fungal-specific host response mainly involved innate immunity signaling pathways and cell types. We identified several genes and pathways involved in the host response to infectious keratitis, including CXCL9, CXCR3, and MMP9 for viral, and S100A8/A9, MMP9, and the IL17 pathway for bacterial/fungal keratitis. High-resolution molecular profiling provides new insights into the human corneal host response to viral and bacterial/fungal infection. Pathogen-specific molecular profiles may provide the foundation for novel diagnostic biomarker and therapeutic approaches that target inflammation-induced damage to corneal host cells with the goal to improve the outcome of infectious keratitis.

Optics and quantitative assessment of corneal transparency

While some optical properties of cornea like its stromal birefringence had been known since the early nineteenth century, theories explaining its transparency remained inconclusive until the publication of David Maurice' emblematic paper in 1957 Maurice made a model calculation of light scattering by a single collagen fibril as a “dielectric needle”. The volume density of the fibrils being known, Maurice could demonstrate that in the absence of any order among the fibrils the cornea would be opaque. Maurice postulated the hexagonal structure which since has been confirmed by electron microscopy. In modern terms, the order among the collagen fibrils within a stromal collagen lamella is described by a “structure factor” in the radiative transfer equation. This term corresponds to a description of the structure in reciprocal space and is thus equivalent to the representation of crystalline lattices in the first Brillouin zone used for structural modelling in crystallography.In a recent study we further analysed the collagen structure of healthy and oedematous corneas on a nanometric level observed by transmission electron microscopy (TEM). By automated image analysis we could retrieve the so‐called “pair correlation function” and calculate light attenuation within the corresponding cornea. Our findings show that the 1/e light penetration depth within healthy cornea could be calculated as 7300 ± 800 μm, which explains well the transparency of healthy cornea. However, the photon mean free path of oedematous cornea turned out to be from two to three times that value. In oedematous cornea, the “dilution” effect of the scatters is in fact stronger than the degradation of transparency by the perturbation of the structure. The actual loss of transparency in oedematous cornea may therefore be attributed to scattering processes at the micrometric level induced by the augmented optical contrast at the sites of the keratocytes between the collagen lamellae.Perturbations in corneal transparency do not only hamper vision, they also impact optical imaging methods on cornea. This, in turn, permits to study the transparency properties of the corneal tissue. One of the main research interests of our group is to analyse corneal images recorded by optical coherence tomography (OCT) and to extract quantitative parameters like photon mean path length and the fraction of coherently transmitted light.Our partners could show that in the light scattering regime, a term in the radiation transfer equation may be neglected and the attenuation of the full field OCT signal in the volume of the tissue reduces to a Lambert–Beer law. We developed a data analysis algorithm based on Bayesian inference to extract the attenuation coefficient and used it for the analysis of ex vivo corneal high‐resolution FF‐OCT images.In a second step, we developed an image processing algorithm for clinical OCT images removing typical artefacts and compensating for inhomogeneous illumination and corneal curvature. We presently are able to extract corneal transparency parameters from routine clinical OCT images and to provide post‐op follow‐up after keratoplasty or other surgical interventions.

PAX6, FABP5 and keratocytes‐characteristic marker expression in human limbal fibroblasts and keratocytes of congenital aniridia and healthy subjects, in vitro

Aims/Purpose: To investigate PAX6, FABP5 and keratocyte‐characteristic marker expression in human limbal fibroblasts and keratocytes (LFCs and LKCs) of congenital aniridia (AN) and healthy corneas, in vitro.Methods: Primary human limbal fibroblasts (LFCs/ AN‐LFCs) were isolated from aniridia (n = 8) and healthy corneas (n = 8) and were cultured in DMEM/F12 with 5% fetal calf serum. Limbal keratocytes (LKCs/ AN‐LKCs) were cultured in low‐glucose serum‐free cell culture medium (LGSF‐medium). Stem cell marker PAX6 and ABCG2, retinoic acid marker FABP5 and keratocyte‐characteristic marker collagen I (COL1A1), collagen III (COL3A1), collagen V (COL5A1), lumican (LUM), keratocan (KER), α‐smooth muscle actin (ACTA2), CD34, aldehyde dehydrogenase 3 family, member A1 (ALDH3A1) expression analysis has been performed by qPCR and Western blot.Results: PAX6 mRNA expression was significantly lower in AN‐LFCs and AN‐LKCs than in LFCs and LKCs (p = 0.04; p = 0.014). FABP5 mRNA expression was significantly higher in LKC and AN‐LKCs than in LFCs and AN‐LFCs (p = 0.036; p = 0.012) COL5A1 mRNA expression was significantly lower (p = 0.007), KER and ALDH3A1 mRNA expression was significantly higher (p = 0.013; p = 0.007) in AN‐LFCs than in LFCs. COL1A1 and COL5A1 mRNA expression was significantly higher in AN‐LKCs than in LKCs (p = 0.009; p = 0.001). Protein expression did not differ significantly between LFCs/ AN‐LFCs or LKCs/ AN‐LKCs for any of the analysed markers (p ≥ 0.05).Conclusions: Our study confirmed altered gene expression in aniridia limbal fibroblasts and keratocytes compared to healthy controls. These may play an important role in development and progression of aniridia associated keratopathy.

Morphogeometric characterization in keratoconus according to the RETICS grading system

Aims/Purpose: Keratoconus progression characterizes by corneal thinning resulting in irregular astigmatism and visual impairment. In the present work a computerized 3D modelling method is used to describe different morphogeometric variables in healthy corneas and keratoconus. RETICS grading system was used to characterize keratoconus with best corrected visual acuity (BCVA) as the major grading parameter. Analyzing morphogeometric variables and its correlation with visual acuity (VA) may help understand structural changes associated with visual decline in keratoconus.Methods: 124 healthy corneas and 257 eyes with keratoconus were included and classified according to the RETICS grading system as grade 1 (n = 94) when VA &gt; 0.9; grade 2 (n = 65) when 0.6 &lt; VA ≤ 0.9; grade 3 (n = 50) when 0.4 &lt; VA ≤ 0.6; grade 4 (n = 31) when 0.2 &lt; VA ≤ 0.4 and grade 5 (n = 17) when VA ≤ 0.2. Computerized 3D modelling was done and morphogeometric variables analysed: anterior surface area (ASA), posterior surface area (PSA), total area (TA), total volume (TV), anterior apex deviation (AAD), posterior apex deviation (PAD), anterior minimum thickness point deviation (AMTPD) and posterior minimum thickness point deviation (PMTPD).Results: All morphogeometric variables showed differences between normal and keratconic eyes (p &lt; 0.001). ASA and PSA present higher values in keratoconus (p &lt; 0.001), while TV shows lower values in the same subjects (p &lt; 0.001). Correlation between BCVA and all variables was calculated showing a positive correlation for the ASA (p = 0.0036) and PSA (p = 0.0172), and a negative correlation for TV (p = 0.1612) and PAD (p = 0.0821).Conclusions: As keratoconus progresses and VA worsens, corneal structural changes include an increase in the PAD, in addition to an increase of both anterior and posterior corneal areas while TV tends to decrease. Morphogeometric variables represent a new parameter to characterize keratoconus and some demonstrate a statistically significant correlation with visual loss.

Kruppel‐like factor 5 (KLF5) as a genetic factor associated with the etiopathogenesis of Keratoconus

Aims: To analyse expression and genotype of Krüppel‐Like Factor 5 (KLF5) gene in the corneal epithelium of eyes with Keratoconus (KC) compared to normal eyes (controls); as well as, to determine the effect of several pro‐inflammatory cytokines on the KLF5 expression by an in vitro study.Methods: 64 corneal epithelium samples from 53 KC and 11 controls were included in this study. KC samples were collected from patients who received crosslinking epi‐off or penetrating keratoplasty for their mild to advanced KC. Control samples were collected from dead donors with healthy corneas. Molecular determinations to measure KLF5 expression and genotype on these samples were performed respectively by qPCR and TaqMan targeting the SNP of interest (rs17285550). In addition, using a cell line of healthy corneal epithelial cells, incubations with increasing concentrations of interleukin 6 (IL6), interleukin 1 beta (IL1β), and tumour necrosis factor alpha (TNFα) were performed to determine the KLF5 response to a pro‐inflammatory environment. KLF5 expression in the stimulated cell cultures was assessed by qPCR analysis.Results: KC samples evidenced significantly higher levels of KLF5 gene expression than the controls (p &lt; 0.0001). The GG genotypes showed an upward tendency for higher expression of KLF5 in the KC group. Higher IL6, IL1β, and TNFα concentrations contribute to a significatively KLF5 overexpression in corneal epithelial cell cultures.Conclusions: Overexpression of KLF5 in the corneal epithelium of KC patients and its upregulation against a proinflammatory microenvironment, could lead to an inadequate epithelial barrier function that destabilizes the surrounding corneal layers and contributes to the KC pathology. KLF5 represents a promising target for gene therapy in KC.

Gene expression in calcium triggered healthy primary limabal epithelial cells, in vitro

Aims/Purpose: Calcium supplementation can induce differentiation of several cell types. The tear film has an important role in maintenance of the ocular surface homeostasis with an ionic calcium concentration of 0.4 mM‐1.0 mM. The effect of calcium concentration on healthy primary limbal epithelial cells (LECs) has not been analysed, yet. Our purpose was to investigate the effect of calcium supplementation on gene expression of primary limbal epithelial cells (LECs) of healthy donor corneas, in vitro.Methods: Primary LECs were isolated from corneoscleral rims of healthy donors (n = 6) and were cultured in serum free low calcium (0.06 mM Ca+2) Keratocyte growth medium 3 (KGM3). The primary LECs were then supplemented by 0.3 mM‐2.0 mM Ca+2 concentrations for 72 h. Control LEC cultures were supplemented by low calcium (0.06 mM Ca+2) KGM3 medium. After cell harvesting, RNA and protein were extracted from treated and control LECs to perform qPCR and western blot analysis.Results: The calcium supplementation had no significant effect on PAX6 mRNA expression after 72 h. The differentiation marker and adhesion protein DSG1 and the cornea specific keratin K3 expression did not change significantly through Ca+2 supplementation (p ≥ 0.5). The retinoic acid signalling component fatty acid binding protein FABP5 expression (p ≥ 0.5) the wound healing and vascularization marker CAV1 gene expression (p ≥ 0.5) did not change significantly through Ca+2 supplementation, after 72 h.Conclusions: Calcium supplementation for 72 h did not change PAX6 expression and did not trigger differentiation of healthy primary limbal epithelial cells. We plan to analyse the effect of longer incubation time in the future in order to trigger a full differentiated status of limbal epithelial cells, using calcium supplementation.

Sustained and Efficient Delivery of Antivascular Endothelial Growth Factor by the Adeno-associated Virus for the Treatment of Corneal Neovascularization: An Outlook for Its Clinical Translation.

Corneal diseases represent 5.1% of all eye defects and are the fourth leading cause of blindness globally. Corneal neovascularization can arise from all conditions of chronic irritation or hypoxia, which disrupts the immune-privileged state of the healthy cornea, increases the risk of rejection after keratoplasty, and leads to opacity. In the past decades, significant progress has been made for neovascular diseases of the retina and choroid, with plenty of drugs getting commercialized. In addition, to overcome the barriers of the short duration and inadequate penetration of conventional formulations of antivascular endothelial growth factor (VEGF), multiple novel drug delivery systems, including adeno-associated virus (AAV)-mediated transfer have gone through the full process of bench-to-bedside translation. Like retina neovascular diseases, corneal neovascularization also suffers from chronicity and a high risk of recurrence, necessitating sustained and efficient delivery across the epithelial barrier to reach deep layers of the corneal stroma. Among the explored methods, adeno-associated virus-mediated delivery of anti-VEGF to treat corneal neovascularization is the most extensively researched and most promising strategy for clinical translation although currently although, it remains predominantly at the preclinical stage. This review comprehensively examines the necessity, benefits, and risks of applying AAV vectors for anti-VEGF drug delivery in corneal vascularization, including its current progress and challenges in clinical translation.

Ocular surface immune transcriptome and tear cytokines in corneal infection patients.

Microbial keratitis is one of the leading causes of blindness globally. An overactive immune response during an infection can exacerbate damage, causing corneal opacities and vision loss. This study aimed to identify the differentially expressed genes between corneal infection patients and healthy volunteers within the cornea and conjunctiva and elucidate the contributing pathways to these conditions' pathogenesis. Moreover, it compared the corneal and conjunctival transcriptomes in corneal-infected patients to cytokine levels in tears. Corneal and conjunctival swabs were collected from seven corneal infection patients and three healthy controls under topical anesthesia. RNA from seven corneal infection patients and three healthy volunteers were analyzed by RNA sequencing (RNA-Seq). Tear proteins were extracted from Schirmer strips via acetone precipitation from 38 cases of corneal infection and 14 healthy controls. The cytokines and chemokines IL-1β, IL-6, CXCL8 (IL-8), CX3CL1, IL-10, IL-12 (p70), IL-17A, and IL-23 were measured using an antibody bead assay. A total of 512 genes were found to be differentially expressed in infected corneas compared to healthy corneas, with 508 being upregulated and four downregulated (fold-change (FC) <-2 or > 2 and adjusted p <0.01). For the conjunctiva, 477 were upregulated, and 3 were downregulated (FC <-3 or ≥ 3 and adjusted p <0.01). There was a significant overlap in cornea and conjunctiva gene expression in patients with corneal infections. The genes were predominantly associated with immune response, regulation of angiogenesis, and apoptotic signaling pathways. The most highly upregulated gene was CXCL8 (which codes for IL-8 protein). In patients with corneal infections, the concentration of IL-8 protein in tears was relatively higher in patients compared to healthy controls but did not show statistical significance. During corneal infection, many genes were upregulated, with most of them being associated with immune response, regulation of angiogenesis, and apoptotic signaling. The findings may facilitate the development of treatments for corneal infections that can dampen specific aspects of the immune response to reduce scarring and preserve sight.

The biomechanical e‐staging—In vivo assessment of corneal biomechanics in keratoconus

Aims/Purpose: Keratoconus (KC) is biomechanically characterized by a decreased resistance to deformation when compared to healthy corneas. The aim of this presentation is to give an overview about the development and clinical application of the recently introduced Homburg Biomechanical E‐Staging (BEST) for KC.Methods: The Corvis ST (Oculus, Germany) non‐contact pneumotonometer measures the corneal deformation after applying a standardized air puff. It calculates the quasi‐binary indices Corvis Biomechanical Index (CBI) and Tomographic Biomechanical Index (TBI) to separate healthy from ectatic corneas, without, however providing a biomechanical KC severity stage. The Homburg BEST based on the linearized CBI provides information about biomechanical KC severity in form of E‐stages 0 to 4, thus augmenting the existing tomographic ABCD KC classification by including corneal biomechanics. Several studies and results about the development and clinical application of the Homburg BEST are presented.Results: The Homburg BEST was developed based on two independent KC datasets (Homburg: n = 448, Milano/Rio: n = 860). Since 2022, it has been integrated into the Corvis ST software, thus providing a biomechanical KC severity and progression assessment. The software based on several individual biomechanical parameters indicates KC progression like tomographic progression parameters. However, it is influenced by corneal thickness measurements, increases within the first postoperative months after corneal crosslinking (CXL) and indicates postoperative KC stabilization more than 1 year after CXL. Intracorneal ring segment implantation permanently affects corneal thickness in the midperiphery and contributes to slightly higher postoperative BEST values.Conclusions: Although with limitations, the Homburg BEST enables a biomechanical staging and progression assessment in KC by considering several biomechanical parameters as an addition to the previously purely tomographic or even topographic analysis.

EXPERIENCE OF USING OPTICAL COHERENCE TOMOGRAPHY IN CORNEAL INJURIES

Background. Eye trauma is one of the most common causes of monocular visual impairment and blindness worldwide. Modern classification divides eye trauma into two groups: open (penetrating) and closed (non-penetrating) eye trauma. During the diagnostic phase, it is important to thoroughly examine and establish the correct diagnosis according to the existing classification, which affects the further patient management and treatment outcomes. Optical coherence tomography (OCT) allows for real-time imaging of eye tissues with high resolution. In our study, we present our experience in using optical coherence tomography in cases of traumatic corneal injuries as an additional method for assessing the depth and extent of damage and monitoring corneal erosion healing.&#x0D; Aim. To utilize optical coherence tomography of the anterior segment of the eye for the diagnosis and assessment of corneal wound healing processes.&#x0D; Materials and Methods. The research involved 46 patients with non-penetrating corneal injuries who were observed at the clinics of Bogomolets National Medical University. A control group consisting of 15 healthy patients was also included in the study. Data collection included patient demographic information, occupation, mechanism and duration of the trauma, the presence of recurrences, and the period of seeking medical assistance. All patients underwent visual acuity assessment, biomicroscopy, evaluation of the conjunctiva and corneal condition, and fluorescein testing. Using Optical Coherence Tomography (OCT) of the anterior segment, we monitored corneal thickness and the size of the epithelial defect before and after treatment.&#x0D; Results. In optical coherence tomography of traumatic corneal erosion, in most cases, a defect in the epithelium of irregular shape with uneven edges, an irregular mixed anterior surface of the stroma, non-uniform reflectivity of the stroma, and corneal thinning were visualized. After treatment, the results corresponded to corneal epithelialization: thick intact epithelium, hyperreflective stroma, and a demarcation line confirming the wound healing process. After treatment, the corneal thickness was restored to (529 ± 144 μm), which is comparable to the thickness of a healthy cornea.&#x0D; Conclusion. Optical Coherence Tomography (OCT) is an informative supplementary diagnostic method for corneal injuries, allowing for the assessment of corneal morphology, including the condition of the basal membrane, corneal thickness, and epithelialization. Based on these findings, we can predict the course of corneal trauma and its potential consequences, enabling us to adjust treatment strategies to prevent the development of fibrosis and minimize the long-term effects of the injury.

The extraction and application of antisymmetric characteristics of the cornea during air-puff perturbations

BackgroundA non-contact tonometer is used to measure intraocular pressure, and studies have primarily relied on apex displacements to assess corneal properties. However, previous studies have overlooked the asymmetric characteristics of lateral corneal perturbations, leading to a gap in understanding of the lateral mechanical properties and its application. MethodTo investigate these lateral perturbations, we designed an experiment to sequentially record the corneal profiles when two consecutive air-puffs were applied at the center of the same cornea within a short period. Moreover, we used modal decomposition to decompose anterior surface profiles into symmetric and antisymmetric modes to comprehensively analyze the asymmetric characteristics. To extract mechanical properties, we utilized high-pass frequency analysis (>250 Hz) to filter out noise and errors. ResultsSymmetric modes between the two consecutive air-puffs exhibited major similarities during vibration; however, antisymmetric modes exhibited minor differences in lateral perturbations of asymmetric vibration. The antisymmetric modes might be related to air-puff misalignment and mechanical properties. Through applying frequency analysis, the mechanical properties could be proven at high frequencies and misalignment shown at low frequencies. Furthermore, we compared the corneal vibration profiles of 259 healthy participants and 50 patients with keratoconus. Their properties showed that the antisymmetric modes of the keratoconus group exhibited a completely opposite direction of deformation compared to that in the healthy group. ConclusionsOur proposed algorithm not only extracts antisymmetric characteristics but also offers valuable insights into decompose misalignment and mechanical properties of healthy and keratoconus corneas, presenting a new perspective for corneal biomechanics.

Human cornea-derived extracellular matrix hydrogel for prevention of post-traumatic corneal scarring: A translational approach.

Corneal scarring and opacification are a significant cause of blindness affecting millions worldwide. The current standard of care for corneal blindness is corneal transplantation, which suffers from several drawbacks. One alternative approach that has shown promise is the use of xenogeneic corneal extracellular matrix (ECM), but its clinical applicability is challenging due to safety concerns. This study reports the innovative use of human cornea-derived ECM to prevent post-traumatic corneal scarring. About 30 - 40% of corneas donated to the eye banks do not meet the standards defined for clinical use and are generally discarded, although they are completely screened for their safety. In this study, human cornea-derived decellularized ECM hydrogel was prepared from the non-transplantation grade human cadaveric corneas obtained from an accredited eye-bank. The prepared hydrogel was screened for its efficacy against corneal opacification following an injury in an animal model. Our in vivo study revealed that, the control collagen-treated group developed corneal opacification, while the prophylactic application of human cornea-derived hydrogel effectively prevented corneal scarring and opacification. The human hydrogel-treated corneas were indistinguishable from healthy corneas and comparable to those treated with the xenogeneic bovine corneal hydrogel. We also demonstrated that the application of the hydrogel retained the biological milieu including cell behavior, protein components, optical properties, curvature, and nerve regeneration by remodeling the corneal wound after injury. The hydrogel application is also sutureless, resulting in faster corneal healing. We envision that this human cornea-derived ECM-based hydrogel has potential clinical application in preventing scarring from corneal wounding. STATEMENT OF SIGNIFICANCE: There are significant challenges surrounding corneal regeneration after injury due to extensive scarring. Although there is substantial research on corneal regeneration, much of it uses synthetic materials with chemical cross-linking methods or xenogeneic tissue-based material devices which have to undergo exhaustive safety analysis before clinical trials. Herein, we demonstrate the potential application of a human corneal extracellular matrix hydrogel without any additional materials for scarless corneal tissue regeneration, and a method to reduce the wasting of donated allogenic corneal tissue from eye banks. We found no difference in efficacy between the usage of human tissues compared to xenogeneic sources. This may help ease clinical translation and can be used topically without sutures as an outpatient procedure.

Влияние низкомолекулярного натрия гиалуроната на течение дистрофических заболеваний роговицы при глаукоме

Introduction. Chronic dystrophic corneal diseases (cdcd) are often accompanied by increased intraocular pressure, which has a negative effect on the regeneration processes in the tissues of the anterior surface of the eye. this leads to the progression of dystrophic lesions and dry eye disease. Purpose. Development, experimental substantiation and proof of clinical efficacy of photo-induced 1 % low molecular weight sodium hyaluronate (lm-nah) for the treatment of patients with cdcd in glaucoma, based on the increased activity of local regenerative processes. Materials and methods. The clinical study was carried out on the basis of health care institution «3 municipal clinical hospital named after E. V. Klumov» in minsk from 2016 to 2020. the study group included 21 patients (24 eyes) with cdcd in glaucoma. The comparison group included 16 patients (22 eyes), comparable in gender and age. there was no positive dynamics from standard treatment during 2–10 years with the use of instillations of tear substituting solutions. This was the indication for the use of subconjunctival injections of 1 % lm-nah once a week for 3 weeks. When dense central lenses were formed, keratoplasty was performed with histological, histochemical and immunohistochemical studies of corneal explants and determination of TGF-β1 expression level in 10 patients (10 eyes) with glaucoma and 3 healthy donor corneas. Results. Application of 1 % lm-nah solution has a positive effect on objective indices of anterior ocular surface condition with normalization of Schirmer’s test, tear film break-up time, oSdI index, corneal thickness. a high level of TGF-β1 expression is detected in patients with cdcd in glaucoma compared with the level of expression in healthy corneal tissues. This marker of inflammation and fibrosis is significantly reduced to normal values with subconjunctival injections of 1 % lm-nah. Conclusion. Application of 1 % lm-nah promotes activation of regenerative processes in the cornea and restores its structure. Key words: hyaluronic acid, corneal dystrophy, TGF-β1, intraocular pressure, dry eye disease, OSDI index

Optical quality of the cornea after Descemet membrane endothelial keratoplasty surgery: early results from Türkiye.

Descemet membrane endothelial keratoplasty (DMEK) is increasingly favored in the treatment of endothelial dysfunction due to its benefits, which include swift visual rehabilitation and recovery, a relatively low rejection rate, and superior refractive stability. In this study, we examined alterations in corneal clarity among patients who underwent DMEK and correlated these densitometry findings with other optical parameters of corneal topography. The study incorporated 35 eyes from 35 patients who had previously undergone DMEK surgery for pseudophakic bullous keratopathy at Ankara Bilkent City Hospital. The results from these patients were compared with those from a healthy control group. The preoperative and postoperative optical parameters of the patients were assessed using Pentacam Scheimpflug topography (Oculus). We observed significant decreases in corneal densitometry in the 0-2 mm and 2-6 mm zones of the anterior, posterior, central, and total layers at the sixth month postoperatively compared to the preoperative period (P<0.05). The corneal densitometry values at postoperative month 6 were elevated in all layers and zones relative to the healthy group (P<0.05). The root mean square of higher-order aberrations in postoperative period was elevated significantly (P<0.001). Six months after operation, the optical quality of the cornea following DMEK surgery did not achieve the level of a healthy cornea.

Nonlinear fourth-order elastic characterization of the cornea using torsional wave elastography

Measuring the mechanical nonlinear properties of the cornea remains challenging due to the lack of consensus in the methodology and in the models that effectively predict its behaviour. This study proposed developing a procedure to reconstruct nonlinear fourth-order elastic properties of the cornea based on a mathematical model derived from the theory of Hamilton et al. and using the torsional wave elastography (TWE) technique. In order to validate its diagnostic capability of simulated pathological conditions, two different groups were studied, non-treated cornea samples (n=7), and ammonium hydroxide (NH4OH\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$NH_4OH$$\\end{document}) treated samples (n=7). All the samples were measured in-plane by a torsional wave device by increasing IOP from 5 to 25 mmHg with 5 mmHg steps. The results show a nonlinear variation of the shear wave speed with the IOP, with higher values for higher IOPs. Moreover, the shear wave speed values of the control group were higher than those of the treated group. The study also revealed significant differences between the control and treated groups for the Lamé parameter μ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\mu$$\\end{document} (25.9–6.52 kPa), third-order elastic constant A (215.09–44.85 kPa), and fourth-order elastic constant D (523.5–129.63 kPa), with p-values of 0.010, 0.024, and 0.032, respectively. These findings demonstrate that the proposed procedure can distinguish between healthy and damaged corneas, making it a promising technique for detecting diseases associated with IOP alteration, such as corneal burns, glaucoma, or ocular hypertension.

Localized Refractive Changes Induced by Symmetric and Progressive Asymmetric Intracorneal Ring Segments Assessed with a 3D Finite-Element Model.

To build a representative 3D finite element model (FEM) for intracorneal ring segment (ICRS) implantation and to investigate localized optical changes induced by different ICRS geometries, a hyperelastic shell FEM was developed to compare the effect of symmetric and progressive asymmetric ICRS designs in a generic healthy and asymmetric keratoconic (KC) cornea. The resulting deformed geometry was assessed in terms of average curvature via a biconic fit, sagittal curvature (K), and optical aberrations via Zernike polynomials. The sagittal curvature map showed a locally restricted flattening interior to the ring (Kmax -11 to -25 dpt) and, in the KC cornea, an additional local steepening on the opposite half of the cornea (Kmax up to +1.9 dpt). Considering the optical aberrations present in the model of the KC cornea, the progressive ICRS corrected vertical coma (-3.42 vs. -3.13 µm); horizontal coma (-0.67 vs. 0.36 µm); and defocus (2.90 vs. 2.75 µm), oblique trefoil (-0.54 vs. -0.08 µm), and oblique secondary astigmatism (0.48 vs. -0.09 µm) aberrations stronger than the symmetric ICRS. Customized ICRS designs inspired by the underlying KC phenotype have the potential to achieve more tailored refractive corrections, particularly in asymmetric keratoconus patterns.

Topical ropivacaine hydrochloride 0.5% and lidocaine hydrochloride 2% significantly reduce corneal sensitivity without short-term negative side effects in horses.

To evaluate corneal sensitivity and acute side effects following application of ropivacaine hydrochloride 0.5% and lidocaine hydrochloride 2% on the healthy equine cornea. Eight healthy adult horses. A randomized, masked, crossover study design was utilized. Baseline Semiquantitative Preclinical Ocular Toxicology (SPOT) scores and corneal touch thresholds (CTT) using a Cochet-Bonnet esthesiometer were recorded and measured, respectively, for eight healthy adult horses before medication application. Commercially available eyewash was used as a negative control. Ropivacaine hydrochloride 0.5% or lidocaine hydrochloride 2% solution was sprayed on a randomly selected eye, and the contralateral eye received eyewash. CTT was measured in both eyes at 1, 5, 15, 25, 35, 45, 55, 65, and 75 min post-application. Post-application SPOT scores were recorded immediately following the trial. Linear mixed model statistical analyses (mean ± standard error) were performed (p < .05). Mean eyewash CTT (3.41 cm ± 0.464) was significantly different from ropivacaine-treated (1.44 cm ± 0.562) (p = .008) and lidocaine-treated eyes (1.75 cm ± 0.562) (p = .024); CTT was not significantly different between drug groups (p = .88). Time to maximum anesthesia was not significantly different between ropivacaine (13.25 min ± 3.353) and lidocaine (16.25 min ± 3.353) (p = .40). No side effects were appreciated as confirmed by SPOT. Ropivacaine and lidocaine similarly decreased corneal sensitivity when applied topically without clinically evident short-term ocular side effects. Lidocaine may be preferable in clinical settings due to its large, multi-use vials and similar effects to ropivacaine.