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According to the World Health Organization, corneal diseases are the fourth leading cause of blindness worldwide accounting for 5.1% of all ocular deficiencies. Current therapies for corneal diseases, which include eye drops, oral medications, corrective surgeries, and corneal transplantation are largely inadequate, have undesirable side effects including blindness, and can require life-long applications. Adeno-associated virus (AAV) mediated gene therapy is an optimistic strategy that involves the delivery of genetic material to target human diseases through gene augmentation, gene deletion, and/or gene editing. With two therapies already approved by the United States Food and Drug Administration and 200 ongoing clinical trials, recombinant AAV (rAAV) has emerged as the in vivo viral vector-of-choice to deliver genetic material to target human diseases. Likewise, the relative ease of applications through targeted delivery and its compartmental nature makes the cornea an enticing tissue for AAV mediated gene therapy applications. This current review seeks to summarize the development of AAV gene therapy, highlight preclinical efficacy studies, and discuss potential applications and challenges of this technology for targeting corneal diseases.

Three genetic corneal dystrophies [congenital hereditary endothelial dystrophy type 2 (CHED2), Harboyan syndrome and Fuchs endothelial corneal dystrophy] arise from mutations of the SLC4a11 gene, which cause blindness from fluid accumulation in the corneal stroma. Selective transmembrane water conductance controls cell size, renal fluid reabsorption and cell division. All known water-channelling proteins belong to the major intrinsic protein family, exemplified by aquaporins (AQPs). Here we identified SLC4A11, a member of the solute carrier family 4 of bicarbonate transporters, as an unexpected addition to known transmembrane water movement facilitators. The rate of osmotic-gradient driven cell-swelling was monitored in Xenopus laevis oocytes and HEK293 cells, expressing human AQP1, NIP5;1 (a water channel protein from plant), hCNT3 (a human nucleoside transporter) and human SLC4A11. hCNT3-expressing cells swelled no faster than control cells, whereas SLC4A11-mediated water permeation at a rate about half that of some AQP proteins. SLC4A11-mediated water movement was: (i) similar to some AQPs in rate; (ii) uncoupled from solute-flux; (iii) inhibited by stilbene disulfonates (classical SLC4 inhibitors); (iv) inactivated in one CHED2 mutant (R125H). Localization of AQP1 and SLC4A11 in human and murine corneal (apical and basolateral, respectively) suggests a cooperative role in mediating trans-endothelial water reabsorption. Slc4a11(-/-) mice manifest corneal oedema and distorted endothelial cells, consistent with loss of a water-flux. Observed water-flux through SLC4A11 extends the repertoire of known water movement pathways and call for a re-examination of explanations for water movement in human tissues.

N-methyl-N-nitrosourea (MNU) is an alkylating toxicant with potent mutagenic ability. This study was designed to induce apoptosis in lens epithelial cells (LECs) and corneal endothelial cells (CECs) via MNU administration. We sought to build ocular disease models of cataract and corneal endothelial decompensation.

Oxidative stress may play a role in the pathogenesis of keratoconus (KC) and Fuchs endothelial corneal dystrophy (FECD). Iron may promote the stress by the Fenton reaction, so its homeostasis should be strictly controlled. Transferrin is essential for iron homeostasis because it transports iron from plasma into cells. The malfunction of transferrin, which may be caused by variation in its gene (TF) variation, may contribute to oxidative stress and change KC and FECD risk. To verify this hypothesis we investigated the association between three polymorphisms of the TF gene, g.3296G>A (rs8177178), g.3481A>G (rs8177179), and c.-2G>A (rs1130459), and KC and FECD occurrence. Genotyping was performed in blood lymphocytes in 216 patients with KC, 130 patients with FECD and 228 controls by PCR-RFLP. We studied also the influence of other risk factors. The A/A genotype and the A allele of the g.3296G>A polymorphism were associated with KC occurrence, while the G allele was negatively correlated with it. We observed a decrease in KC occurrence associated with the A/G genotype of the g.3481A>G polymorphism. We did not find any association between the c.-2G>A polymorphism and KC. No association was found between all three polymorphisms and FECD occurrence.

The performance of deep learning in disease detection from high-quality clinical images is identical to and even greater than that of human doctors. However, in low-quality images, deep learning performs poorly. Whether human doctors also have poor performance in low-quality images is unknown. Here, we compared the performance of deep learning systems with that of cornea specialists in detecting corneal diseases from low-quality slit lamp images. The results showed that the cornea specialists performed better than our previously established deep learning system (PEDLS) trained on only high-quality images. The performance of the system trained on both high- and low-quality images was superior to that of the PEDLS while inferior to that of a senior corneal specialist. This study highlights that cornea specialists perform better in low-quality images than the system trained on high-quality images. Adding low-quality images with sufficient diagnostic certainty to the training set can reduce this performance gap.

Analysis of internet search queries (ISQ) could be useful to study public interest and medical need for corneal, cataract, and refractive surgery. To date, there are preliminary data on seasonal trends in ophthalmic conditions, but only few studies correlate these data with real data from healthcare systems. The aim of this study is to analyze ISQ and correlate it with real healthcare system data. Data were retrieved from the KBV registry of patients who underwent outpatient ophthalmic surgery in Germany from 2017 to 2019 and from Statista GmbH from 2010 to 2020 for corneal refractive surgery. Time Series analysis of ISQ was analyzed from 2004 to 2020 and correlated with healthcare system data using bivariate correlation analysis. ISQ correlated significantly with the incidence of ophthalmic procedures such as corneal transplantations (r = 0.69, p < 0.05), cataract- (r = 0.59, p < 0.05) and refractive laser surgery (r = 0.83, p < 0.05) in Germany. In addition, specific trends were observed with respect to individual surgical procedures. The correlation between search intensities and surgical procedures varied significantly. Thus, interests in surgical procedures can be tracked by observing changes in ISQ over time. These data correlate with real healthcare data and could be used in the future for now-casting or even forecasting.

Central corneal thickness (CCT) is a highly heritable trait associated with complex eye diseases such as keratoconus and glaucoma. We perform a genome-wide association meta-analysis of CCT and identify 19 novel regions. In addition to adding support for known connective tissue-related pathways, pathway analyses uncover previously unreported gene sets. Remarkably, >20% of the CCT-loci are near or within Mendelian disorder genes. These included FBN1, ADAMTS2 and TGFB2 which associate with connective tissue disorders (Marfan, Ehlers-Danlos and Loeys-Dietz syndromes), and the LUM-DCN-KERA gene complex involved in myopia, corneal dystrophies and cornea plana. Using index CCT-increasing variants, we find a significant inverse correlation in effect sizes between CCT and keratoconus (r = -0.62, P = 5.30 × 10-5) but not between CCT and primary open-angle glaucoma (r = -0.17, P = 0.2). Our findings provide evidence for shared genetic influences between CCT and keratoconus, and implicate candidate genes acting in collagen and extracellular matrix regulation.

Corneal hysteresis and corneal resistance factor are parameters that reflect the dynamic biomechanical properties of the cornea and have been shown to be biomarkers of corneal disease. In this genome-wide association study of over 100 000 participants, we identified over 200 genetic loci, all but eight novel, significantly associated with either one or both of these traits. In addition to providing key insights into the genetic architecture underlying normal corneal function, these results identify many candidate loci in the study of corneal diseases that lead to severe visual impairment. Additionally, using Mendelian randomization, we were able to identify causal relationships between corneal biomechanics and intraocular pressure measurements, which help elucidate the relationship between corneal properties and glaucoma.

Corneal biomechanical properties are important for the diagnosis of corneal diseases, individualized design and prognosis of corneal surgery. Clinical available devices such as Ocular Response Analyzer (ORA) and Corneal Visualization Scheimpflug Technology (Corvis ST) can provide corneal biomechanics related parameters, while corneal elastic modulus cannot be extracted directly from them at present. The aim of this study is to suggest a method to determine corneal elastic modulus based on the results of Corvis ST test according to Reissner's theory on the relation between stress and small displacement in shallow spherical shell.

Purpose. To evaluate surgically induced astigmatism (SIA) and the average corneal power change in symmetric intrastromal corneal ring segment (ICRS) implantation. Methods. The study included 34 eyes of 34 keratoconus patients who underwent symmetric Intacs SK ICRS implantation. The corneal pocket incision meridian was the preoperative steep meridian. Corneal power data were obtained before and 3 months after Intacs SK ICRS implantation using scanning-slit topography. Polar value analysis was used to evaluate the SIA. Hotelling's trace test was used to compare intraindividual changes. Results. Three months postoperatively, the combined mean polar value for SIA changed significantly (Hotelling's T2 = 0.375; P = 0.006). The SIA was 1.54 D at 99° and the average corneal power decreased significantly by 3.8 D. Conclusion. Intacs SK ICRS placement decreased the average corneal power and corneal astigmatism compared to the preoperative corneal power and astigmatism when the corneal pocket incision was made at the preoperative steep meridian.

Sex-based differences in susceptibility have been reported for a number of neovascular ocular diseases. We quantified corneal neovascularization, induced by superficial silver nitrate cautery, in male and female inbred albino Sprague-Dawley, inbred albino Fischer 344, outbred pigmented Hooded Wistar and inbred pigmented Dark Agouti rats of a range of ages. Corneal neovascular area was quantified on haematoxylin-stained corneal flatmounts by image analysis. Pro-and anti-angiogenic gene expression was measured early in the neovascular response by quantitative real-time polymerase chain reaction. Androgen and estrogen receptor expression was assessed by immunohistochemistry. Male rats from all strains, with or without ocular pigmentation, exhibited significantly greater corneal neovascular area than females: Sprague-Dawley males 43±12% (n = 8), females 25±5% (n = 12), p = 0.001; Fischer 344 males 38±10% (n = 12) females 27±8% (n = 8) p = 0.043; Hooded Wistar males 32±6% (n = 8) females 22±5% (n = 12) p = 0.002; Dark Agouti males 37±11% (n = 9) females 26±7% (n = 9) p = 0.015. Corneal vascular endothelial cells expressed neither androgen nor estrogen receptor. The expression in cornea post-cautery of Cox-2, Vegf-a and Vegf-r2 was significantly higher in males compared with females and Vegf-r1 was significantly lower in the cornea of males compared to females, p<0.001 for each comparison. These data suggest that male corneas are primed for angiogenesis through a signalling nexus involving Cox-2, Vegf-a, and Vegf receptors 1 and 2. Our findings re-enforce that pre-clinical animal models of human diseases should account for sex-based differences in their design and highlight the need for well characterized and reproducible pre-clinical studies that include both male and female animals.

This systematic review investigates the prevalence and underlying causes of corneal edema following cataract surgery employing manual phacoemulsification. A comprehensive search encompassing databases such as PubMed, Embase, ProQuest, Cochrane Library, and Scopus was conducted, focusing on variables encompassing cataract surgery and corneal edema. Two independent reviewers systematically extracted pertinent data from 103 articles, consisting of 62 theoretical studies and 41 clinical trials. These studies delved into various aspects related to corneal edema after cataract surgery, including endothelial cell loss, pachymetry measurements, visual performance, surgical techniques, supplies, medications, and assessments of endothelial and epithelial barriers. This review, encompassing an extensive analysis of 3060 records, revealed significant correlations between corneal edema and endothelial cell loss during phacoemulsification surgery. Factors such as patient age, cataract grade, and mechanical stress were identified as contributors to endothelial cell loss. Furthermore, pachymetry and optical coherence tomography emerged as valuable diagnostic tools for assessing corneal edema. In conclusion, this systematic review underscores the link between corneal edema and endothelial cell loss in manual phacoemulsification cataract surgery. It highlights the relevance of factors like patient demographics and diagnostic modalities. However, further research is essential to unravel the complexities of refractive changes and the underlying mechanisms.

The most common cause of corneal graft failure is corneal graft rejection (CGR). Although cornea is one of the immune-privileged sites, it can still get a rejection episode due to a breach in its natural protective mechanism. Both anatomical and structural properties of cornea and anterior chamber contribute toward its immune tolerance. Clinically, every layer of the transplanted cornea can get a rejection episode. A proper understanding of immunopathogenesis will help in understanding the various mechanism of CGR and the development of newer strategies for the prevention and management of such cases.

To determine the effectiveness and safety of photoactivated chromophore-corneal cross-linking (PACK-CXL) adjuvant in infectious keratitis by April 5, 2022.

Purpose: To determine the 6-month effect of conventional (CXL30) and accelerated cross-linking with a UVA intensity of 9 mW/cm2 (CXL10) on corneal stability and to investigate whether there was a difference in ABCD grading system parameters regarding the two different procedures. Methods: Twenty-eight eyes of 28 patients with a documented keratoconus (KN) progression were included. Patients were selected to undergo either epi off CXL30 or CXL10. At the baseline and the follow-up visits after one (V1), three (V2), and six months (V3), the patients underwent complete ophthalmic examination and corneal tomography. Results: In the CXL30 group, all the parameters from the ABCD grading system significantly changed from baseline to V3; parameter A decreased (p = 0.048), B and C increased (p = 0.010, p < 0.001), and D decreased (p < 0.001). In the CXL10 group, there were no changes in parameters A (p = 0.247) and B (p = 0.933), though parameter C increased (p = 0.001) and D decreased (p < 0.001). After an initial decline after one month, visual acuity (VA) recovered on V2 and V3 (p < 0.001), and median maximal keratometry (Kmax) decreased in both groups (p = 0.001, p = 0.035). In the CXL30 group, there were significant changes in other parameters; average pachymetric progression index (p < 0.001), Ambrósio relational thickness maximum (ARTmax) (p = 0.008), front and back mean keratometry (p < 0.001), pachymetry apex (PA) (p < 0.001), and front elevation (p = 0.042). However, in the CXL10 group, there were significant changes only in ARTmax (p = 0.019) and PA (p < 0.001). Conclusion: Both epi-off CXL protocols showed similar short-term efficacy in improving VA and Kmax, halting the progression of KN, and both similarly changed tomographic parameters. However, the conventional protocol modified the cornea more significantly.

This paper compares and evaluates the corneal morphological changes occurring after cataract surgery through a 2.2 mm corneal incision. We use two platforms for comparison and evaluation, transversal and torsional phacoemulsification.

Corneal neovascularization (CNV) is a heavy attribute of blinding disease changes. Existing medications need numerous infusions and have a limited absorption. Investigating novel drugs with safety, efficacy, and convenience is crucial. In this study, we developed a bone morphogenetic protein 4 (BMP4)-loaded poloxamer-oxidized sodium alginate (F127-OSA) thermosensitive hydrogel. The 14 % F127-OSA hydrogel transformed from sol to gel at 31-32 °C, which might extend the application period on the ocular surface. The hydrogel's porous structure and uniform dispersion made it possible for drugs to release gradually. We used a suture-induced rat CNV model to investigate the mechanism of CNV inhibition by hydrogel. We discovered that F127-OSA hydrogel loaded with BMP4 could significantly reduce the length and area of CNV, relieve corneal edema, and stop aberrant epithelial cell proliferation. The hydrogel's efficacy was superior to that of the common solvent group. Additionally, BMP4 thermosensitive hydrogel repaired ultrastructure, including microvilli, intercellular junctions, and damaged apical junctional complexes (AJCs), suggesting a potential mechanism by which the hydrogel prevented CNV formation. In conclusion, our investigation demonstrates that F127-OSA thermosensitive hydrogel loaded with BMP4 can repair corneal epithelial AJCs and is a promising novel medication for the treatment of CNV.

Corneal tissue regeneration is of crucial importance for maintaining normal vision. We aimed to isolate and cultivate human corneal stroma-derived mesenchymal stem-like cells (CSMSCs) from the central part of cadaver corneas and study their phenotype, multipotency, role in immunity and wound healing. The isolated cells grew as monolayers in vitro, expressed mesenchymal- and stemness-related surface markers (CD73, CD90, CD105, CD140b), and were negative for hematopoietic markers as determined by flow cytometry. CSMSCs were able to differentiate in vitro into fat, bone and cartilage. Their gene expression profile was closer to bone marrow-derived MSCs (BMMSCs) than to limbal epithelial stem cells (LESC) as determined by high-throughput screening. The immunosuppressive properties of CSMSCs were confirmed by a mixed lymphocyte reaction (MLR), while they could inhibit proliferation of activated immune cells. Treatment of CSMSCs by pro-inflammatory cytokines and toll-like receptor ligands significantly increased the secreted interleukin-6 (IL-6), interleukin-8 (IL-8) and C-X-C motif chemokine 10 (CXCL-10) levels, as well as the cell surface adhesion molecules. CSMSCs were capable of closing a wound in vitro under different stimuli. These cells thus contribute to corneal tissue homeostasis and play an immunomodulatory and regenerative role with possible implications in future cell therapies for treating sight-threatening corneal diseases.

Gene editing has recently emerged as a promising technology to engineer genetic modifications precisely in the genome to achieve long-term relief from corneal disorders. Recent advances in the molecular biology leading to the development of Clustered Regularly Interspaced Short Palindromic Repeats (CRISPRs) and CRISPR-associated systems, zinc finger nucleases and transcription activator like effector nucleases have ushered in a new era for high throughput in vitro and in vivo genome engineering. Genome editing can be successfully used to decipher complex molecular mechanisms underlying disease pathophysiology, develop innovative next generation gene therapy, stem cell-based regenerative therapy, and personalized medicine for corneal and other ocular diseases. In this review we describe latest developments in the field of genome editing, current challenges, and future prospects for the development of personalized gene-based medicine for corneal diseases. The gene editing approach is expected to revolutionize current diagnostic and treatment practices for curing blindness.