Exosomal microRNAs as potential biomarkers and therapeutic targets in corneal diseases.

Exosomes are a subtype of extracellular vesicle (EV) that are released and found in almost all body fluids. Exosomes consist of and carry a variety of bioactive molecules, including genetic information in the form of microRNAs (miRNAs). miRNA, a type of small non-coding RNA, plays a key role in regulating genes by suppressing their translation. miRNAs are often disrupted in the pathophysiology of different conditions, including eye disease. The stability and easy detectability of exosomal miRNAs in body fluids make them promising biomarkers for the diagnosis of different diseases. Additionally, due to the natural delivery capabilities of exosomes, they can be modified to transport therapeutic miRNAs to specific recipient cells. Most exosome research has primarily focused on cancer, so there is limited research highlighting the importance of exosomes in ocular biology, particularly in cornea-associated pathologies. This review provides an overview of the existing evidence regarding the primary functions of exosomal miRNAs and their potential role in diagnostic and therapeutic applications in the human cornea.

[Severe Conjunctival and Corneal Epithelial Dysplasia: A Case Series]. / Schwere konjunktivale und korneale epitheliale Dysplasie: eine Fallserie.

BACKGROUND/OBJECTIVES: Ocular surface squamous neoplasia (OSSN) are among the most frequent non-pigmented malignancies of the ocular surface. They have a wide range of histological characteristics - ranging from mild epithelial dysplasia to invasive carcinoma of the squamous cells of the cornea. They may be restricted to the conjunctiva or also involve the cornea. As there are no leading symptoms in the early stages, diagnosis may be very delayed in patients who do not receive regular ophthalmological treatment. The present case series describes clinical and histological data on OSSN and includes clinical and histological data on OSSN, including possible clinical presentations, important risk factors, special histological and cytological features and therapeutic options. METHODS: Retrospective case series of patients with histologically confirmed severe epithelial dysplasia of the conjunctiva and cornea consistent with OSSN who presented to the Department of Ophthalmology in Basel University Hospital. The analysis covered demographic data, symptoms, diagnostic testing (photo documentation, brush biopsy), treatment and cytological and/or histological material and findings. RESULTS: We report on five patients aged between 41 and 92 years at the time of diagnosis. The histological findings in all patients included severe epithelial dysplasia, but with a heterogenous clinical presentation. In all cases, the lesion started in the conjunctiva, but traversed the limbus and extended to the cornea. The primary treatment was always surgical removal. In one patient, this had to be repeated several times due to recurrent metaplasia and was complemented by subsequent mitomycin C therapy. The clinical outcome ranged between total restitution of the original state to inevitable enucleation. CONCLUSION: The clinical presentation of OSSN is highly heterogenous, so that the initial diagnosis is difficult. There are no official guidelines for treatment, so that the treatment of choice varied between clinics. Regular ophthalmological follow-ups are recommended, even after complete surgical excision. Possible relevant concomitant diseases and risk factors must be identified before therapy.

Process and Outcomes of Fitting Corneoscleral Profilometry-Driven Scleral Lenses for Patients With Ocular Surface Disease.

OBJECTIVES: To assess the feasibility of obtaining cornea scleral profile (CSP) measurements using Scheimpflug imaging and report on the fitting process of free-form custom scleral lenses (SLs) for patients with ocular surface disease (OSD). METHODS: This prospective study of patients fit with free-form SLs collected data on the following: demographics, indications for wear, corneal and scleral tomography, scan acquisition process, and SL fitting process. RESULTS: Cornea scleral profile scans were acquired on 15 eyes of nine patients. Mean scan time for right eyes was 10.7, and 9.7 min for left eyes. A mean of 2.9 follow-up visits were required to complete SL fitting, with a mean of 2.1 lenses ordered. One eye did not tolerate lens wear, and one eye could not be fit using the CSP scan because of insufficient data. The initial lens ordered was dispensed at the first follow-up visit for seven of the remaining 13 eyes, all of which were ultimately fit successfully in free-form lenses. CONCLUSIONS: In this study of profilometry-guided SL fitting for eyes with OSD and low magnitude corneal astigmatism, the number of lenses and follow-up visits required were similar to outcomes of previous studies that described the diagnostic approach to SL fitting. In addition, imaging technology does not negate the need for skilled clinical observation while fitting SLs.

Collagen cross-linking beyond corneal ectasia: A comprehensive review.

The history of corneal cross-linking (CXL) dates back to 2003 when some German scientists investigated possible treatments to harden the corneal structure to increase its resistance in ectatic corneal diseases. Nowadays, CXL is considered the most effective therapy in ectatic corneal diseases due to its proven efficacy in hardening the cornea, thus halting the development of the disease. Since 2003, CXL applications have dramatically expanded and have been implemented in several other areas such as infectious keratitis, corneal edema, and before performing keratoplasty for various purposes. Moreover, several irradiation patterns are being studied to correct refractive errors, taking into account the corneal refractive changes that occur after the procedure. Currently, scleral cross-linking is also being investigated as a potential therapy in cases of progressive myopia and glaucoma. In this article, we provide a comprehensive overview of the available applications of cross-linking in nonectatic ocular conditions and highlight the possible future indications of this procedure.

Corneal Epithelial Development and the Role of Induced Pluripotent Stem Cells for Regeneration.

Severe corneal disorders due to infective aetiologies, trauma, chemical injuries, and chronic cicatricial inflammations, are among vision-threatening pathologies leading to permanent corneal scarring. The whole cornea or lamellar corneal transplantation is often used as a last resort to restore vision. However, limited autologous tissue sources and potential adverse post-allotransplantation sequalae urge the need for more robust and strategic alternatives. Contemporary management using cultivated corneal epithelial transplantation has paved the way for utilizing stem cells as a regenerative potential. Humaninduced pluripotent stem cells (hiPSCs) can generate ectodermal progenitors and potentially be used for ocular surface regeneration. This review summarizes the process of corneal morphogenesis and the signaling pathways underlying the development of corneal epithelium, which is key to translating the maturation and differentiation process of hiPSCs in vitro. The current state of knowledge and methodology for driving efficient corneal epithelial cell differentiation from pluripotent stem cells are highlighted.

Late-Onset Chronic Corneal Fistula Following Phototherapeutic Keratectomy: A Case Report and Importance of Early Detection.

BACKGROUND We report a case of late-onset chronic fistula in a decompensated cornea after multiple ocular surgeries and a recent phototherapeutic keratectomy (PTK). CASE REPORT A 73-year-old woman presented to our service with a past ocular history of bilateral chronic angle closure glaucoma and pseudophakic bullous keratopathy in the left eye. Given a history of long-term uncontrolled glaucoma with advanced disc cupping and poor visual potential, the patient underwent multiple palliative procedures, including, most recently, a PTK. Few years later she presented with a spontaneous late onset of slowly appearing corneal leak on fluorescein staining upon routine clinical examination. Corrected distance visual acuity was hand motion and intraocular pressure (IOP) was 40 mmHg in the affected eye. Serial anterior segment optical coherence tomography (AS-OCT) sections were obtained, which aided in understanding the current presentation and revealed distinctive multilayer corneal changes during the healing process. The patient was successfully managed with cyanoacrylate corneal gluing and ocular hypotensive medications, which halted the corneal leak. CONCLUSIONS We report a case of a rare finding of corneal fistula in an eye with multiple previous ocular surgeries, and provide an explanation of the possible etiopathogenesis. We also highlight the pivotal role of AS-OCT for evaluating such cases and stress the importance of early detection of similar subtle leaks in the setting of a formed anterior chamber, which can often be missed, carrying a risk of infection.

Cell-based Therapies for Corneal and Retinal Disorders.

Maintenance of the visual function is the desired outcome of ophthalmologic therapies. The shortcomings of the current treatment options, like partial recovery, post-operation failure, rigorous post-operative care, complications, etc., which are usually encountered with the conventional treatment options has warranted newer treatment options that may eliminate the root cause of diseases and minimize the side effects. Cell therapies, a class of regenerative medicines, have emerged as cutting-edge treatment option. The corneal and retinal dystrophies during the ocular disorders are the major cause of blindness, worldwide. Corneal disorders are mainly categorized mainly into corneal epithelial, stromal, and endothelial disorders. On the other hand, glaucoma, retinitis pigmentosa, age-related macular degeneration, diabetic retinopathy, Stargardt Disease, choroideremia, Leber congenital amaurosis are then major retinal degenerative disorders. In this manuscript, we have presented a detailed overview of the development of cell-based therapies, using embryonic stem cells, bone marrow stem cells, mesenchymal stem cells, dental pulp stem cells, induced pluripotent stem cells, limbal stem cells, corneal epithelial, stromal and endothelial, embryonic stem cell-derived differentiated cells (like retinal pigment epithelium or RPE), neural progenitor cells, photoreceptor precursors, and bone marrow-derived hematopoietic stem/progenitor cells etc. The manuscript highlights their efficiency, drawbacks and the strategies that have been explored to regain visual function in the preclinical and clinical state associated with them which can be considered for their potential application in the development of treatment.

[Advances in gene therapy of ocular surface and corneal diseases].

With the continual advancement of gene editing technology, gene therapy has been increasingly explored as a potential treatment option for both hereditary and acquired diseases. Due to its unique physiological and anatomical characteristics, the eye has emerged as an optimal target for gene therapy. In fact, ophthalmology was among the first clinical fields to obtain approval for in vivo gene therapy. Despite the widespread development of gene therapy targeting ocular surface and corneal diseases in recent years, a systematic review of these projects is still lacking. Thus, this review aims to comprehensively summarize the research progress and clinical application of gene therapy for ocular surface and corneal diseases, providing valuable guidance for future research and clinical translation.

Posterior corneoscleral limbus: Architecture, stem cells, and clinical implications.

The limbus is a transition from the cornea to conjunctiva and sclera. In human eyes, this thin strip has a rich variation of tissue structures and composition, typifying a change from scleral irregularity and opacity to corneal regularity and transparency; a variation from richly vascularized conjunctiva and sclera to avascular cornea; the neural passage and drainage of aqueous humor. The limbal stroma is enriched with circular fibres running parallel to the corneal circumference, giving its unique role in absorbing small pressure changes to maintain corneal curvature and refractivity. It contains specific niches housing different types of stem cells for the corneal epithelium, stromal keratocytes, corneal endothelium, and trabecular meshwork. This truly reflects the important roles of the limbus in ocular physiology, and the limbal functionality is crucial for corneal health and the entire visual system. Since the anterior limbus containing epithelial structures and limbal epithelial stem cells has been extensively reviewed, this article is focused on the posterior limbus. We have discussed the structural organization and cellular components of the region beneath the limbal epithelium, the characteristics of stem cell types: namely corneal stromal stem cells, endothelial progenitors and trabecular meshwork stem cells, and recent advances leading to the emergence of potential cell therapy options to replenish their respective mature cell types and to correct defects causing corneal abnormalities. We have reviewed different clinical disorders associated with defects of the posterior limbus and summarized the available preclinical and clinical evidence about the developing topic of cell-based therapy for corneal disorders.

Mesenchymal Stem Cells and Exosomes: A Novel Therapeutic Approach for Corneal Diseases.

The cornea, with its delicate structure, is vulnerable to damage from physical, chemical, and genetic factors. Corneal transplantation, including penetrating and lamellar keratoplasties, can restore the functions of the cornea in cases of severe damage. However, the process of corneal transplantation presents considerable obstacles, including a shortage of available donors, the risk of severe graft rejection, and potentially life-threatening complications. Over the past few decades, mesenchymal stem cell (MSC) therapy has become a novel alternative approach to corneal regeneration. Numerous studies have demonstrated the potential of MSCs to differentiate into different corneal cell types, such as keratocytes, epithelial cells, and endothelial cells. MSCs are considered a suitable candidate for corneal regeneration because of their promising therapeutic perspective and beneficial properties. MSCs compromise unique immunomodulation, anti-angiogenesis, and anti-inflammatory properties and secrete various growth factors, thus promoting corneal reconstruction. These effects in corneal engineering are mediated by MSCs differentiating into different lineages and paracrine action via exosomes. Early studies have proven the roles of MSC-derived exosomes in corneal regeneration by reducing inflammation, inhibiting neovascularization, and angiogenesis, and by promoting cell proliferation. This review highlights the contribution of MSCs and MSC-derived exosomes, their current usage status to overcome corneal disease, and their potential to restore different corneal layers as novel therapeutic agents. It also discusses feasible future possibilities, applications, challenges, and opportunities for future research in this field.

Evidence of Contact Lenses for Vision Rehabilitation in Corneal Diseases: A Review.

OBJECTIVES: To evaluate the efficacy and safety of contact lenses (CL) as a therapeutic option for patients affected by a corneal disease and to determinate which is the best lens modality for each disease. METHODS: A literature review using PubMed was performed. All relevant articles published during the last 15 years have been included. RESULTS: Various studies point to CL as the best therapeutic option for some corneal diseases and even as an alternative to surgery in some cases. After fitting, patients show an improvement in their functional vision and quality of life, in some cases being able to drive or work again. CONCLUSIONS: There is a lack of scientific evidence to determine which lens modality is suitable for each corneal pathology. Currently, according to this review, the reason for choosing between the different options depends on the severity of symptoms, and it is worth mentioning that scleral lenses seem to be the best option in advanced stages of disease. However, the expertise of professionals is also an important factor at the time of choosing a particular CL modality. Standardized criteria are still necessary for correct selection of lens modality for a correct management of the disease.

[The diagnosis and treatment of contact lens-induced limbal stem cell deficiency].

Objective: To analyze the clinical features and treatment outcomes of eyes with contact lens-induced limbal stem cell deficiency (CL-iLSCD). Methods: This cross-sectional study involved patients diagnosed with CL-iLSCD at the Eye, Ear, Nose & Throat Hospital of Fudan University between October 2018 and September 2022. A total of 17 patients (25 eyes) with a mean age of (36.4±6.9) years were enrolled. Among them, 14 were females (82.4%). Corneal and limbal abnormalities, especially the range of epitheliopathy, were observed under a slit lamp biomicroscope with fluorescein staining. Anterior segment optical coherence tomography and in vivo laser scanning confocal microscopy were performed to obtain the central corneal epithelial thickness, density of basal epithelial cells and corneal nerve fiber length. The clinical features of CL-iLSCD, along with their treatment outcomes and related risk factors, were analyzed. Results: All patients wore soft contact lenses, with an average daily wearing time of (10.5±2.5) hours and a median wearing duration of 10 (4 to 30) years. Ocular symptoms, including decreased vision, ocular discomfort or pain, redness, and photophobia, were present in 22 eyes (88.0%). The most characteristic clinical sign of CL-iLSCD was comb-or whorl-pattern late fluorescein staining under cobalt blue light, which was most commonly seen at the superior limbus (25/25, 100.0%). Additionally, reductions in central corneal epithelial thickness, basal cell density, and corneal nerve fiber length were observed. A comprehensive score was assigned to each eye based on clinical findings and in vivo imaging biomarkers. LSCD was mild, moderate, and severe in 5, 11, and 8 eyes, respectively. A history of misdiagnosis was found in 20 eyes (80.0%). After discontinuing the use of contact lenses and receiving medical treatment, significant improvement was observed in all eyes, with 13 eyes fully recovered. Conclusions: The symptoms and clinical signs of CL-iLSCD can be subtle at the early stage. Discontinuing contact lens wear and medication are effective to treat CL-iLSCD.

New developments in the management of persistent corneal epithelial defects.

A persistent epithelial defect (PED) is a corneal epithelial defect that failed to heal after 2weeks. It is a condition that carries much morbidity, and our understanding of PED remains poor, with current treatment methods often having unsatisfactory outcomes. With PEDs becoming more prevalent, more efforts are required to establish reliable treatment modalities. Our reviews describe the causes of PEDs and the different approaches developed to manage them, as well as their associated limitations. Emphasis is placed on understanding various advances in the development of new treatment modalities. We have also described a case of a woman with a background of graft-versus-host disease on long-term topical corticosteroids who developed complicated PED involving both eyes. The current approach to managing PEDs generally involves exclusion of an active infection, followed by treatment modalities that aim to encourage corneal epithelial healing. Success rates, however, remain far from desirable, as treatment remains challenging due to multiple underlying etiologies. In summary, advances in the development of new therapies may be able to facilitate progress in the understanding and treatment of PED.

Future directions in managing aniridia-associated keratopathy.

Congenital aniridia is a panocular disorder that is typically characterized by iris hypoplasia and aniridia-associated keratopathy (AAK). AAK results in the progressive loss of corneal transparency and thereby loss of vision. Currently, there is no approved therapy to delay or prevent its progression, and clinical management is challenging because of phenotypic variability and high risk of complications after interventions; however, new insights into the molecular pathogenesis of AAK may help improve its management. Here, we review the current understanding about the pathogenesis and management of AAK. We highlight the biological mechanisms involved in AAK development with the aim to develop future treatment options, including surgical, pharmacological, cell therapies, and gene therapies.

Corneal Regeneration Using Gene Therapy Approaches.

One of the most remarkable advancements in medical treatments of corneal diseases in recent decades has been corneal transplantation. However, corneal transplants, including lamellar strategies, have their own set of challenges, such as graft rejection, delayed graft failure, shortage of donor corneas, repeated treatments, and post-surgical complications. Corneal defects and diseases are one of the leading causes of blindness globally; therefore, there is a need for gene-based interventions that may mitigate some of these challenges and help reduce the burden of blindness. Corneas being immune-advantaged, uniquely avascular, and transparent is ideal for gene therapy approaches. Well-established corneal surgical techniques as well as their ease of accessibility for examination and manipulation makes corneas suitable for in vivo and ex vivo gene therapy. In this review, we focus on the most recent advances in the area of corneal regeneration using gene therapy and on the strategies involved in the development of such therapies. We also discuss the challenges and potential of gene therapy for the treatment of corneal diseases. Additionally, we discuss the translational aspects of gene therapy, including different types of vectors, particularly focusing on recombinant AAV that may help advance targeted therapeutics for corneal defects and diseases.

Genetic predisposition to ocular surface disorders and opportunities for gene-based therapies.

The ocular surface, comprised of the corneal and conjunctival epithelium, innervation system, immune components, and tear-film apparatus, plays a key role in ocular integrity as well as comfort and vision. Gene defects may result in congenital ocular or systemic disorders with prominent ocular surface involvement. Examples include epithelial corneal dystrophies, aniridia, ectrodactyly-ectodermal dysplasia-clefting (EEC) syndrome, xeroderma pigmentosum (XP), and hereditary sensory and autonomic neuropathy. In addition, genetic factors may interact with environmental risk factors in the development of several multifactorial ocular surface disorders (OSDs) such as autoimmune disorders, allergies, neoplasms, and dry eye disease. Advanced gene-based technologies have already been introduced in disease modelling and proof-of-concept gene therapies for monogenic OSDs. For instance, patient-derived induced pluripotent stem cells have been used for modelling aniridia-associated keratopathy (AAK), XP, and EEC syndrome. Moreover, CRISPR/Cas9 genome editing has been used for disease modelling and/or gene therapy for AAK and Meesmann's epithelial corneal dystrophy. A better understanding of the role of genetic factors in OSDs may be helpful in designing personalized disease models and treatment approaches. Gene-based approaches in monogenic OSDs and genetic predisposition to multifactorial OSDs such as immune-mediated disorders and neoplasms with known or possible genetic risk factors has been seldom reviewed. In this narrative review, we discuss the role of genetic factors in monogenic and multifactorial OSDs and potential opportunities for gene therapy.

Insights into the clinical development of regenerative medical products through a comparison of three cell-based products recently approved for limbal stem cell deficiency.

Three regenerative medical products for limbal stem cell deficiency (LSCD), a rare and intractable ocular surface disease, have recently been approved in Japan. To our knowledge, this is the first time multiple stem-cell-based medical products have been approved for the same ocular disease. Development plans and study designs for each product differ, resulting in differences in indications. Since cell-based products have a heterogeneous formulation and often target rare diseases, they require a flexible approach to development. This review article describes the status and prospects of the clinical development of regenerative medical products by summarizing the issues of the three products from the Pharmaceuticals and Medical Devices Agency (PMDA) standpoint. Implementing stem cell-based products is challenging, requiring scientific and flexible review by regulatory authorities. To overcome these issues in the development process, developers and regulatory authorities need to communicate and fully discuss study protocols from the early stage of development.

Contact lenses for the treatment of ocular surface diseases.

Contact lens wear is useful in ocular conditions such as high refractive errors, irregular astigmatism, corneal ectasias, corneal dystrophies, post-keratoplasty, post-refractive surgeries, trauma, and ocular surface diseases. The new innovations of highly oxygen-permeable contact lens materials have broadened the applications of contact lens suitability. Therapeutic contact lenses are medically used in the management of a wide variety of corneal conditions and ocular surface diseases. These lenses aid in pain relief, enhance corneal healing, maintain ocular homeostasis, and act as a drug delivery system. Drug delivery applications of contact lenses hold promise for improving topical therapy. The modern rigid gas permeable scleral contact lens provides symptomatic relief in painful corneal diseases such as bullous keratopathy, corneal epithelial abrasions, and erosions. It has been useful in therapeutic management as well as visual rehabilitation by enhancing the ocular surface and protecting the cornea from adverse environmental conditions. This review provides a summary of contact lenses used for the treatment of ocular surface diseases based on the current evidence available in the literature. This can help enhance the understanding and management of ocular surface diseases with respect to contact lens use in our day-to-day ophthalmology practice.