Corneal transplantation in the modern era

Current concepts and recent trends in endothelial keratoplasty

Endothelial keratoplasty (EK) is defined as an umbrella term comprising methods for selective surgical replacement of corneal endothelium and adjacent corneal tissue, which retains healthy portions of a patient's cornea while replacing diseased innermost corneal layer(s) with healthy donor tissue, to achieve corneal dehydration and transparency before the onset of irreversible stromal edema and permanent loss of corneal clarity. Recently, the pathophysiology of corneal decompensation is increasingly being researched upon. Consequent improvement in pharmacotherapy is progressively leading to reduction in the indications of EK. In addition, EK techniques have progressed towards using thinner tissue, optimizing visual outcomes. Improvements have enabled better donor tissue formulation, usage, and attachment, and surgical modifications have enhanced the tissue utilization in difficult clinical scenarios lowering failure and rejection. However, challenges are encountered in various complex clinical scenarios including eyes with prior intraocular surgery, complex anterior chamber anatomy, glaucoma, ocular surface disease etc. These complexities demand tailored surgical strategies, including modifications in graft handling, instrumentation, and postoperative management to ensure success. Attention to these details and addressing patient-specific factors can help improve outcomes in these difficult cases. The choice of procedure depends on multiple factors, including the surgeon's experience, patient's ocular anatomy, and the specific clinical scenario. This review article encompasses the recent developments in this field presenting a comprehensive picture of our modern understanding of the indications, contraindications, surgical techniques, clinical situations, community aspects and future directions pertaining to EK.

Bioprinting of transparent and adhesive corneal patches: Integrating photo-crosslinkable dopamine-conjugated silk fibroin and decellularized cornea matrix for sutureless tissue integration and regeneration

Corneal injuries, a leading cause of visual impairment, are traditionally addressed through tissue transplantation. However, challenges such as donor shortages, graft rejection, and complications from suturing often limit their effectiveness. Current corneal adhesives frequently fall short in both adhesion strength and biocompatibility. We present an innovative solution: a photocurable hydrogel that integrates dopamine-conjugated methacrylated silk fibroin (d-MSF) with a decellularized corneal matrix (DCM). This hydrogel combines advanced materials to create a bioadhesive system that offers superior adhesion inspired by mussel adhesion and mimics the native tissue environment. FTIR and NMR analyses confirm that our conjugation process prevents unwanted beta-sheet aggregation, ensuring both stability and transparency. The hydrogel demonstrates excellent rheological properties, including enhanced shear-thinning and impressive shear and creep recovery, making it highly suitable for extrusion-based bioprinting. We successfully bioprinted a bilayer corneal patch, featuring a concentric ring of d-MSF as the first layer, overlaid with a second layer of DCM. The implants exhibit strong tissue adhesion, with an adhesion strength of 85 ± 5.6 KPa, and Young's modulus of 0.48 ± 0.064 MPa, ensuring excellent structural integrity. This results in a highly transparent (>80 %) and functional adhesive corneal patch. This advancement offers a promising, biocompatible alternative to traditional keratoprostheses, advancing corneal repair technology.

Sir Benjamin William Rycroft OBE (1902-1967): British ophthalmologist and pioneer in corneal surgery

An unsung hero of British ophthalmology is the largely forgotten Sir Benjamin Rycroft (1902-1967). This paper will discuss and analyse the undervalued career of this great man. Upon graduating from medical school, Rycroft became a General Practitioner. Rycroft then decided to train to become an ophthalmologist. Rycroft began his ophthalmology career in 1930s London focusing on the new ground-breaking surgery of keratoplasty (corneal grafting) before serving with distinction in the medical corps during the Second World War. He is chiefly remembered for his work after the war at the Queen Victoria Hospital in East Grinstead, Sussex, where he worked with renowned plastics surgeon Archibald McIndoe. During his time, there Rycroft became globally recognised for his skill in keratoplasty and started a campaign which radically changed the legal framework behind organ donation in the UK. Despite few knowing of him today, Rycroft is undoubtedly one of the most influential British ophthalmologists of the past century. He was for decades seen as one of the world's leading practitioners of keratoplasty and established a unit which restored sight to wounded veterans. His greatest achievement lies in his organ donation reform, which started the process of allowing organ donation to be carried out on a nationwide scale for the first time.

A historical view of the development of corneal transplantation: from penetrating keratoplasty to selective transplantation of the finest corneal layers

Replacement of damaged corneal tissue with a clear transplant represents a viable solution for restoring vision in patients with corneal blindness. Among organ transplants, corneal transplantation occupies a unique status due to the cornea's lack of vascularization. This avascular nature makes immune compatibility testing between donor and recipient unnecessary and reduces the risk of transplant rejection, making corneal transplantation the most successful organ transplant procedure worldwide. Over the past century, corneal transplantation has undergone a transformative journey, evolving from full-thickness keratoplasty to highly refined techniques that selectively target individual diseased corneal layers. These modern lamellar approaches aim for faster recovery times and reduced rejection rates. The global demand for corneal graft tissue far exceeds the availability of donor tissue, leading to prolonged waiting times for patients in need of transplantation. Modern therapeutic strategies are expected to support or potentially even replace transplantation of corneal layers in the future.

Impact of corneal curvature on 2-year postoperative visual outcomes after small incision lenticule extraction for high myopia

PURPOSE

High myopia requires precise surgical interventions to ensure optimal visual outcomes. Small Incision Lenticule Extraction (SMILE) has proven effective for high myopia correction, but the long-term impact of corneal curvature on refractive outcomes remains exploring. This study aimed to investigate whether preoperative low mean corneal curvature (Km) might result in refractive overcorrection, and to evaluate its influence on the refractive status of highly myopic patients 2 years post-SMILE surgery.

METHODS

67 patients underwent SMILE surgery were categorized into Low Corneal Curvature (n = 31) and Normal Corneal Curvature groups (n = 36) based on preoperative corneal curvature (Km ≤ 42.0D or 42.0D < Km < 46.0D). Corneal curvature, uncorrected distance visual acuity, and surgical parameters were analyzed over a 2-year follow-up period. Changes in corneal morphology were evaluated on Scheimpfug imaging.

RESULTS

No significant differences were observed in uncorrected distance visual acuity (UDVA) or changes in UDVA (△UDVA) at various time points between the two groups. However, differences in spherical equivalent (SE) were identified at 1 week (0.06 ± 0.47 vs. - 0.23 ± 0.23, P = 0.019) and 1 month (0.04 ± 0.41 vs. - 0.22 ± 0.39, P = 0.007), indicating relative overcorrection in the Low Corneal Curvature group. Significant disparities in corneal curvature were consistently noted between the groups throughout the 2-year postoperative period, with the Low Corneal Curvature Group exhibiting a greater change in Km compared to the Normal Corneal Curvature Group from 1 to 2 years (0.20 ± 0.17 vs. 0.12 ± 0.17, P = 0.003).

CONCLUSION

Corneal curvature significantly influences the refractive status of patients with high myopia at 2 years following SMILE surgery.

Impact of Sepsis on Corneal Transplantation

Corneal transplantation is an exceedingly common and pivotal procedure in the management of corneal disease. The increasing demand for corneal transplantation underscores the importance of current guidelines and methodologies for donor tissue screening and collection. A recent FDA notice of inspectional focus on United States eye banks brought concerns about donor sepsis being a source for recipient infections and improper eye bank screening practices. However, there is evidence to suggest that septic donors do not increase the risk of transmission of infections associated with corneal grafts. This is additionally important given the growing need for more corneal graft tissue to maximize the use of suitable tissue. Eye banks also have a number of protocols to consider when screening donors for the presence of sepsis, providing a unique challenge given the broadness of the term. This paper provides an overview of trends in clarification of the term "sepsis" as well as the screening protocol in eye banks.

Natural Extracellular Matrix Scaffold-Based Hydrogel Corneal Patch with Temperature and Light-Responsiveness for Penetrating Keratoplasty and Sutureless Stromal Defect Repair

Corneal transplantation remains the gold standard for treating corneal blindness; however, it is hampered globally by donor shortages and the complexity of suture-dependent procedures. Tissue-engineered corneas have demonstrated potential as corneal equivalents. Nevertheless, the development of adhesive corneal patches and full-thickness corneal substitutes remains challenging. In this study, a multifunctional hydrogel corneal patch (MHCP) is constructed by integrating a dual-crosslinked hybrid hydrogel with temperature and light responsiveness with a natural extracellular matrix scaffold. When applied to the ocular surface, MHCP spontaneously releases adhesives at body temperature and forms a stable adhesion with the recipient cornea through photocuring. In addition to its inherent mechanical, optical, and ultrastructural characteristics, which are similar to those of the natural stroma, MHCP demonstrates excellent suture resistance, anti-swelling, and anti-degradation properties after curing. MHCP promotes the proliferation and migration of corneal epithelial cells in vitro and maintains the phenotype of corneal stromal cells. In vivo, MHCP maintains graft hydration and restores corneal structural integrity and transparency during penetrating keratoplasty of various sizes and sutureless lamellar keratoplasty. Collectively, given the advantages of native stroma-like characteristics, operation-facilitating multiple functions, and convenient preparation, MHCP is a promising corneal substitute for clinical applications.

Global research trend of Herpes simplex keratitis: a bibliometric analysis and visualization from 1941 to 2024

Objective

Herpes simplex keratitis (HSK), caused by the herpes simplex virus (HSV), is a leading cause of infectious blindness worldwide. This study aims to explore the research trends, key contributors, and emerging areas of focus in HSK research through bibliometric analysis.

Methods

Publications related to HSK from 1941 to 2024 were retrieved from the Web of Science Core Collection (WoSCC). Bibliometric and visual analyses were conducted using VOSviewer, CiteSpace, and R 4.3.3.

Results

A total of 1,076 publications on HSK were identified. The top three contributing countries were the United States (267 papers), China (99), and Japan (64). Harvard University was the leading institution with 75 publications, while the American Journal of Ophthalmology emerged as the most influential journal, boasting an h-index of 29. Kaufman, HE, was the most cited author, with 1,988 citations. The top three keywords were "infection" (82), "stromal keratitis" (73), and "penetrating keratoplasty" (62). Burst keyword analysis indicated a growing interest in terms such as "outcome" and "ultraviolet A" since 2018.

Conclusion

This bibliometric analysis underscores two primary research areas in HSK: the clinical management of stromal keratitis and infection, as well as the mechanisms of HSK recurrence, which include strategies for preventing reactivation and managing immune rejection. Future research is anticipated to focus on innovative treatments, particularly ultraviolet A therapy.

Rho kinase inhibitor Y-27632 and dual media culture approach promote the construction and transplantation of rabbit limbal epithelial cell sheets via cell spheroid culture and auto-bioprinting

The shortage of corneal donors and the limitations in tissue engineering grafts, such as biocompatibility and mechanical properties, pose significant challenges in corneal transplantation. Here, for the first time, we investigate the effect of Rho kinase inhibitor Y-27632 and a dual media culture approach, including proliferative media (M1) and stabilizing media (M2), on rabbit limbal epithelial stem cells (LESCs), aiming to explore the feasibility of constructing corneal cell sheets in vitro through auto-bioprinting and assessing their corneal wound healing capacity in vivo. Y-27632 has primarily demonstrated significantly enhanced LESCs growth, proliferation, and reduced apoptosis. The dual media culture approach combined with Y-27632 improved LESCs proliferation while maintaining stemness. In spheroid culture, Y-27632 decreased cell death and promoted proliferation. Immunofluorescent staining and RNA sequencing revealed upregulation of genes related to tight junctions and cell adhesion and downregulation of genes associated with aging and cell cycle. Using a bioprinter, LESC spheroids were auto-bioprinted onto a custom-made curved collagen membrane, creating a bioactive, transplantable, tissue-engineered anterior corneal sheet. Anterior superficial corneal transplantation with these LESC sheets significantly accelerated epithelial wound healing in rabbit limbal stem cell deficiency (LSCD) models. Overall, the integration of Y-27632, dual-media culture, and spheroid cell culture led to the development of a highly bioactive and therapeutically promising bio-ink derived from LESCs. Auto-bioprinting these LESC spheroids produced a bioactive, transplantable corneal cell sheet, presenting a promising therapeutic option for LSCD. STATEMENT OF SIGNIFICANCE: The renewal and wound healing of the corneal epithelium are essential for maintaining normal vision and refractive function. Limbal stem cell deficiency (LSCD) is a major cause of blinding keratopathy, and current treatment options are limited. In this study, for the first time, we developed a highly bioactive and therapeutically potent bio-ink for ocular surface regeneration by integrating Y-27632, a dual-media culture approach, and spheroid cell culture. Additionally, using auto-bioprinting technology, the limbal epithelial stem cell (LESC) spheroid bio-ink was precisely auto-bioprinted onto the curved surface of the corneal membrane, significantly accelerating corneal epithelial healing in an LSCD rabbit model.

Corneal stromal structure replicating humanized hydrogel patch for sutureless repair of deep anterior-corneal defect

A critical shortage of donor corneas exists worldwide. Hydrogel patches with a biological architecture and functions that simulate those of native corneas have garnered considerable attention. This study introduces a stromal structure replicating corneal patch (SRCP) composed of a decellularized cornea-templated nanotubular skeleton, recombinant human collagen, and methacrylated gelatin, exhibiting a similar ultrastructure and transmittance (above 80 %) to natural cornea. The SRCP is superior to the conventional recombinant human collagen patch in terms of biomechanical properties and resistance to enzymatic degradation. Additionally, SRCP promotes corneal epithelial and stromal cell migration while preventing the trans-differentiation of stromal cells into myofibroblasts. When applied to an ocular surface (37 °C), SRCP releases methacrylated gelatin, which robustly binds SRCP to the corneal stroma after activation by 405 nm light. Compared to gelatin-based photocurable hydrogel, the SRCP better supports the restoration of normal corneal curvature and withstands deformation under an elevated intraocular pressure (100 mmHg). In an in vivo deep anterior-corneal defect model, SRCP facilitated epithelial healing and vision recovery within 2 weeks, maintained graft structural stability, and inhibited stromal scarring at 4 weeks post-operation. The ideal performance of the SRCP makes it a promising humanized corneal equivalent for sutureless clinical applications.

Long-term outcomes of corneal transplantation: a review of 8,378 patients

PURPOSE

To analyze the outcomes of corneal transplantation procedures over a 13-year period at Farabi Eye Hospital, Tehran, Iran, to identify trends and determinants influencing the frequency and success of primary and re-transplantations.

METHODS

Utilizing a comprehensive dataset from the hospital's Hospital Information System, the study reviewed the records of 8,378 patients who underwent corneal transplants between 2009 and 2022. This analysis included demographic information, surgical details, and follow-up data. Statistical methods were applied to assess the impact of variables such as age, gender, surgeon experience, and surgical techniques on the likelihood of re-transplantation.

RESULTS

Of the 8,378 transplants, 7,660 (91.4%) were primary procedures while 718 (8.6%) involved re-transplantation. The most common primary transplant was penetrating keratoplasty (PKP, 50.3%), followed by Descemet's stripping endothelial keratoplasty (DSAEK, 29.3%), and deep anterior lamellar keratoplasty (DALK, 18.5%). Analysis revealed no significant association between re-transplantation rates and patient gender or nationality. Older recipient age correlates with higher re-transplantation rates, likely due to reduced regenerative capacity and increased comorbidities in older patients. Pre-transplant comorbidities (e.g., keratoconus, ulcers), concurrent surgeries (e.g., vitrectomy), and prior procedures (e.g., glaucoma surgeries, IOL implantation) significantly increase re-transplantation risk, likely due to additional ocular stress and inflammation.

CONCLUSION

The study highlights the importance of patient age, surgeon experience, and the choice of surgical technique in the success rates of corneal transplants. These factors are crucial for optimizing patient outcomes and minimizing the necessity for re-transplantations.

A Novel Artificial Endothelial Replacement Membrane for the Treatment of Chronic Corneal Edema

PURPOSE

The purpose of this study was to report the safety and efficacy results of an artificial lamellar implant for the treatment of chronic corneal edema.

METHODS

The EndoArt (EyeYon Medical, Ness Ziona, Israel), an artificial endothelial replacement membrane designed to treat corneal edema, was implanted in 24 eyes of 24 patients with low-to-normal visual potential. We present the safety and efficacy results from a prospective, open-label, single-arm, multicenter study conducted over a 12-month period.

RESULTS

Twenty-four patients were enrolled, with no device-related serious adverse events reported. Seventeen patients completed 12-month follow-up, showing a reduction in average central corneal thickness from 759 ± 116 μm to 613 ± 135 μm. Best-corrected distance visual acuity improved from 1.88 ± 0.79 logarithmic minimum angle of resolution (logMAR) to 1.34 ± 0.57 logMAR. Sixty percent gained at least 3 early treatment diabetic retinopathy study (ETDRS) lines. The EndoArt was removed in 5 cases due to incomplete attachment and replaced by corneal transplants; 1 patient was lost to follow-up, and 1 had a procedure failure. No device-related long-term complications, infections, or inflammations were reported. The implants remained transparent throughout the study.

CONCLUSIONS

The first-in-human results of EndoArt implantation demonstrated the device's potential to treat patients suffering from corneal edema with a favorable safety profile and effective edema reduction in most subjects, with no device-related serious adverse event. The EndoArt may offer a viable solution in regions facing a shortage of donor corneas, as well as for patients who have poor prognosis with human tissue.

Analysis of the relevant factors for corneal graft rejection in the southern Liaoning region from 2019 to 2023

Background

The study aimed to review the etiology of corneal blindness and investigate the relative risk of corneal graft rejection (CGR) in the southern Liaoning region.

Methods

The clinical records of 359 patients (394 eyes) who underwent corneal transplantation at the Department of Keratoconus of the Third People's Hospital of Dalian from January 2019 to December 2023 were retrospectively analyzed. The data included patients' age, gender, occupation, diagnosis, surgical procedure, postoperative immune rejection, and neovascularization. The data were collected and descriptively analyzed to characterize the etiology of corneal blindness and to analyze the risk factors for postoperative immune rejection after corneal transplantation using logistic regression.

Results

The mean age of the patients who underwent corneal transplantation was 55.90 ± 0.80 years, and there were more male patients than female patients with corneal blindness. Infectious keratitis (41.1%) was reported as the leading cause of corneal blindness, and penetrating corneal transplantation was the main surgical procedure for the recovery of sight. Preoperative corneal vascularization and penetrating corneal graft rejection were identified as risk factors for immune rejection of corneal grafts. The preoperative corneal vascularization was performed (p = 0.044, OR = 2.607). Penetrating keratoplasty (PKP) was performed (p = 0.024, OR = 1.953), and deep anterior lamellar keratoplasty was also performed (p = 0.801, OR = 1.088). Viral infections (p < 0.001, OR = 16.871) were the major risk factor for preoperative corneal neovascularization (CNV) compared to other etiologies, such as fungal infections (p < 0.001, OR = 0.018), mechanical ocular trauma (p < 0.001, OR = 0.034), immune keratitis (p = 0.023, OR = 0.152), and endothelial dysfunction (p < 0.001, OR = 0.054).

Conclusion

Infectious keratitis was identified as the major cause of corneal blindness in the southern Liaoning region over the past 5 years. Penetrating keratoplasty and preoperative corneal vascularization were the risk factors for corneal graft rejection. In addition, virus-derived keratitis was considered to be the main risk factor for corneal neovascularization, and deep anterior lamellar keratoplasty was not found to have an effect on corneal graft rejection in this study.

Comparative Analysis of Endothelial Cell Density and Central Thickness of Corneas Used for Endothelial Keratoplasty Procedures Using Various Storage Solutions

PURPOSE

The goal of this study was to evaluate the effect of various Food and Drug Administration-approved storage solutions on endothelial cell density (ECD) and central corneal thickness (CCT).

METHOD

We analyzed 6220 tissues used for endothelial keratoplasty procedures between January 2022 and June 2023 that were stored in either Life4°C, Optisol-GS, Kerasave, or Eusol-C under hypothermic conditions. We analyzed preprocessing CCT, success rate of meeting surgeon's Descemet stripping automated endothelial keratoplasty (DSAEK) thickness preferences, and preprocessing and postprocessing ECD. Results were analyzed using one-way analysis of variance, followed by multiple pairwise comparisons using the Tukey test.

RESULTS

Mean preprocessing CCT was significantly lower in the Life4°C group (532 μm) than in Optisol-GS (549 μm), Kerasave (582 μm), and Eusol-C (589 μm) groups (all P < 0.0001). Preprocessing CCT in the Optisol-GS group was significantly lower than in Kerasave and Eusol-C groups (F (3, 3273) = 153.1, all P < 0.0001). Success rate of meeting surgeon DSAEK preferences was statistically similar among all 4 groups. Preprocessing ECD of the Kerasave group (2821 cells/mm 2 ) was numerically higher than of the Eusol-C (2791 cells/mm 2 ), Life4°C (2759 cells/mm 2 ), and Optisol-GS (2768 cells/mm 2 ) groups ( P = 0.3232, 0.0004, and 0.0015, respectively).

CONCLUSIONS

Corneal tissues stored in Kerasave and Eusol-C are significantly thicker than those in Life4°C and Optisol-GS. However, the success rate of meeting surgeon DSAEK preferences is similar among all 4 storage solutions.

Corneal endothelial cell loss with different techniques of nucleus delivery in Manual Small Incision Cataract Surgery- Randomized Controlled Trial

PURPOSE

To compare corneal endothelial loss in manual small incision cataract surgery (MSICS) following three different techniques of nucleus delivery (Viscoexpression, Irrigating Vectis, Phacosandwich).

SETTING

Mahatma Gandhi Medical College and Research Institute, Puducherry, India.

DESIGN

Prospective, single blinded, randomized controlled trial.

METHODS

Willing patients > 40years of age with immature cataract and posted for MSICS were recruited for the study. Those with systemic or ocular comorbidities which may influence corneal endothelium, dilated pupil size of <5mm, intraoperative complications and postoperative corneal haze were excluded. They were randomly divided to one of the three groups (Group 1- Viscoexpression, Group 2- Irrigating Vectis, Group 3- Phacosandwich) for nucleus delivery. Visual acuity and corneal endothelial parameters were recorded preoperatively and postoperatively at 6-8weeks.

RESULTS

A total of 90 patients with mean age of 59.13 ± 9.42 years (range 40-82years) were studied with 30 patients in each group. Following MSICS there was a 12.12% (p=0.001) endothelial cell loss. It was 10.81% in viscoexpression group, 11.3% in irrigating vectis group and 14.28% in phacosandwich group. Post hoc analysis with Dunn Bon ferroni test showed endothelial cell loss following viscoexpression and irrigating vectis methods of nucleus delivery were comparable (p=0.096) and significantly lesser (p<0.001) than in Phacosandwich group.

CONCLUSION

There was significant endothelial cell loss following MSICS. Nucleus delivery by viscoexpression and irrigating vectis had similar endothelial cell loss while it was greater with phacosandwich technique.

Biomechanical behavior of deep anterior lamellar keratoplasty: a finite element analysis

Deep Anterior Lamellar Keratoplasty (DALK) is a surgical procedure used to restore sight and manage corneal diseases by replacing cloudy corneal tissue with allogeneic normal corneal tissue or artificial corneal material. However, the limited availability and mechanical defects of artificial corneal materials pose challenges in DALK. To predicting postoperative mechanical behavior of Deep Anterior Lamellar Keratoplasty (DALK), a three-dimensional finite element model of the postoperative DALK cornea with suture holes was developed. The postoperative corneal displacement and von Mises (VM) stress changes were also simulated under varying depths of cut (DOC: 0.16-0.26 μm), intraocular pressure (IOP: 12, 15, 18 mmHg), and central corneal thickness (CCT: 420-620 μm). The model indicated that higher IOP and CCT were associated with improved postoperative corneal stability. The postoperative corneal displacement increased from the edge to the center, while the maximum VM stress value occurs at the corneal suture hole. Corneal displacement and VM stress decrease with increasing CCT and decreasing IOP. DOC has a slight effect on corneal displacement and VM stress, with an overall positive relationship. The model has potential application in the preoperative assessment of risk in keratoplasty.

A Comprehensive Review of Donor Corneal Preservation Strategies

ABSTRACT

Successful corneal transplantation relies on the viability of the corneal endothelium. Although various preservation systems have been developed in the field of eye banking, long-term storage of the corneal endothelium poses challenges and is costly. Optisol-GS in the past has been the most commonly used solution for intermediate-term corneal storage in the United States. However, disruptions in the availability of Optisol-GS, caused by rising costs and supply shortages, have necessitated alternative methods of corneal preservation. Previously described preservation methods include hypothermia (2-8°C) for short-term storage (7-14 days), organ culture (28-37°C) for intermediate storage (4-7 weeks), and cryopreservation for longer-term storage. In this review, we examine standard practice and alternative methods for corneal storage.

Advancements in Hydrogels for Corneal Healing and Tissue Engineering

Hydrogels have garnered significant attention for their versatile applications across various fields, including biomedical engineering. This review delves into the fundamentals of hydrogels, exploring their definition, properties, and classification. Hydrogels, as three-dimensional networks of crosslinked polymers, possess tunable properties such as biocompatibility, mechanical strength, and hydrophilicity, making them ideal for medical applications. Uniquely, this article offers original insights into the application of hydrogels specifically for corneal tissue engineering, bridging a gap in current research. The review further examines the anatomical and functional complexities of the cornea, highlighting the challenges associated with corneal pathologies and the current reliance on donor corneas for transplantation. Considering the global shortage of donor corneas, this review discusses the potential of hydrogel-based materials in corneal tissue engineering. Emphasis is placed on the synthesis processes, including physical and chemical crosslinking, and the integration of bioactive molecules. Stimuli-responsive hydrogels, which react to environmental triggers, are identified as promising tools for drug delivery and tissue repair. Additionally, clinical applications of hydrogels in corneal pathologies are explored, showcasing their efficacy in various trials. Finally, the review addresses the challenges of regulatory approval and the need for further research to fully realize the potential of hydrogels in corneal tissue engineering, offering a promising outlook for future developments in this field.

Assessment of the Quality and Readability of Online Resources on Corneal Transplantation

PURPOSE

The aim of this study is to evaluate the quality and readability of corneal transplant websites.

METHODS

 We examined internet resources related to corneal transplantation. The search terms "cornea transplantation," "keratoplasty," "keratoprothesis," and "eye transplantation" were searched on www.google.com. A total of 200 websites were scanned, with 50 websites for each search term. In the final evaluation, 113 websites were included in the study. DISCERN and the Journal of the American Medical Association (JAMA) scales were used to evaluate the websites' quality. The Flesch-Kincaid Grade Level (FKGL) and Simple Measure of Gobbledygook (SMOG) were used to evaluate the readability of the information. The presence of the Health On the Net Foundation Code of Conduct (HONCode) certification on websites was examined in terms of quality.

RESULTS

The total DISCERN score was 42.47 ± 17.06, and the score for the JAMA was 1.58 ± 1.52. The FKGL and SMOG scores were found to be 9.19 ± 2.08 and 8.20 ± 5.23, respectively. Most of the websites we examined related to corneal transplantation were profit websites. These websites had low JAMA and DISCERN scores but relatively high readability levels. They were sites that provided low-quality information and had more financial bias and conflict of interest. Journal and book websites were found to have higher readability scores. Journal and book-sourced websites with higher FKGL and SMOG scores were more difficult to read.

CONCLUSION

Most of the websites exhibit financial bias, and as a result, they contain low-quality information. Online information must be more regulated for patients to easily access accurate, high-quality information.

Corneal higher-order aberrations in different types of irregular cornea

OBJETIVE

To assess differences in corneal higher-order aberrations (i.e., HOAs) between six different types of irregular corneas (i.e, keratoconus (KC), keratoglobus (KG), pellucid marginal degeneration (PMD), laser-assisted in situ keratomileusis (LASIK), penetrating keratoplasty (PK), and intrastromal corneal ring segments (ICRS)).

METHODS

Corneal aberration data from the 3rd and 4th order together with secondary vertical and horizontal coma, and secondary spherical aberration were retrospectively retrieved from a corneal tomographer and compared between irregular cornea types and for 3-, 5-, and 7-mm pupil diameters.

RESULTS

Significant differences were observed in vertical coma, oblique trefoil, secondary oblique astigmatism, primary spherical, and secondary spherical between irregular cornea types across all three pupil sizes (all p≤0.025). Vertical coma consistently exhibited the greatest magnitude of HOA across all irregular cornea types and pupil diameters. For the larger pupil diameters (5 and 7 mm), the 3rd order aberrations (mainly coma-like), the 4th order aberrations (mainly spherical-like), and total HOA RMS were significantly lower in the LASIK group compared to all other irregular cornea types (all p≤0.003). Additionally, at pupil sizes of 5 and 7 mm, the 3rd, 4th, coma-like, spherical-like, and total HOA RMS were significantly lower in KC compared to the ICRS and PK groups (all p≤0.01). Furthermore, the 4th, spherical-like, and total HOA RMS were significantly lower in KC compared to KG at pupil diameters of 3 and 7 mm, 5 and 7 mm, and 7 mm, respectively (all p≤0.03).

CONCLUSIONS

Vertical coma was the most elevated HOA across all irregular cornea types and pupil diameters. Corneal aberrations were lower in LASIK and KC, and higher in KG and PK.

Evolving indications and surgical techniques for corneal transplantation at a tertiary eye care center in southern China

BACKGROUND

This retrospective study aimed to analyze the evolution of primary indications and surgical techniques for corneal transplantation in Southern China from 2012 to 2021.

METHODS

The medical charts of all patients who underwent keratoplasty between January 2012 and December 2021 at Zhongshan Ophthalmic Centre, Sun Yat-Sen University, Guangzhou, Southern China were reviewed. We collected and analyzed the primary indications for corneal transplantation and the surgical methods used in each keratoplasty.

RESULTS

The total number of corneal transplantations was 7,286 during this decade, increasing from 210 cases in 2012 to 1054 cases in 2021. The primary indications for keratoplasty included acquired nontraumatic corneal diseases (56.2%), congenital corneal abnormalities (16.4%), acquired traumatic corneal diseases (14.0%), and regraft (13.4%). Infectious keratitis was the leading indication among all keratoplasties (18.5%), followed by regraft (13.4%). Over the decade, the proportion of infectious keratitis gradually decreased (P = 0.013), while the proportion of regraft increased (P = 0.019). The predominant surgical technique was penetrating keratoplasty (PKP), accounting for 56.7%. However, the number of deep anterior lamellar keratoplasty (DALK) and endothelial keratoplasty (EK) significantly increased from 2012 to 2021 (P = 0.007 and P = 0.002).

CONCLUSIONS

The annual number of corneal transplants significantly increased from 2012 to 2021. In the past decade, infectious keratitis and regraft have become the leading primary indications for corneal transplantation. Although the use of customized lamellar techniques has dramatically increased, PKP remains the predominant surgical technique for keratoplasty.

Standardizing Corneal Transplantation Records Using openEHR: Case Study

BACKGROUND

Corneal transplantation, also known as keratoplasty, is a widely performed surgical procedure that aims to restore vision in patients with corneal damage. The success of corneal transplantation relies on the accurate and timely management of patient information, which can be enhanced using electronic health records (EHRs). However, conventional EHRs are often fragmented and lack standardization, leading to difficulties in information access and sharing, increased medical errors, and decreased patient safety. In the wake of these problems, there is a growing demand for standardized EHRs that can ensure the accuracy and consistency of patient data across health care organizations.

OBJECTIVE

This paper proposes the use of openEHR structures for standardizing corneal transplantation records. The main objective of this research was to improve the quality and interoperability of EHRs in corneal transplantation, making it easier for health care providers to capture, share, and analyze clinical information.

METHODS

A series of sequential steps were carried out in this study to implement standardized clinical records using openEHR specifications. These specifications furnish a methodical approach that ascertains the development of high-quality clinical records. In broad terms, the methodology followed encompasses the conduction of meetings with health care professionals and the modeling of archetypes, templates, forms, decision rules, and work plans.

RESULTS

This research resulted in a tailored solution that streamlines health care delivery and meets the needs of medical professionals involved in the corneal transplantation process while seamlessly aligning with contemporary clinical practices. The proposed solution culminated in the successful integration within a Portuguese hospital of 3 key components of openEHR specifications: forms, Decision Logic Modules, and Work Plans. A statistical analysis of data collected from May 1, 2022, to March 31, 2023, allowed for the perception of the use of the new technologies within the corneal transplantation workflow. Despite the completion rate being only 63.9% (530/830), which can be explained by external factors such as patient health and availability of donor organs, there was an overall improvement in terms of task control and follow-up of the patients' clinical process.

CONCLUSIONS

This study shows that the adoption of openEHR structures represents a significant step forward in the standardization and optimization of corneal transplantation records. It offers a detailed demonstration of how to implement openEHR specifications and highlights the different advantages of standardizing EHRs in the field of corneal transplantation. Furthermore, it serves as a valuable reference for researchers and practitioners who are interested in advancing and improving the exploitation of EHRs in health care.

Immunopathology of Corneal Allograft Rejection and Donor-Specific Antibodies (DSAs) as Immunological Predictors of Corneal Transplant Failure

Despite tremendous developments in the field of laboratory testing in transplantation, the rules of eligibility for corneal transplantation still do not include typing of human leukocyte antigens (HLAs) in the donor and recipient or detection of donor-specific antibodies (DSAs) in the patient. The standard use of diagnostic algorithms is due to the cornea belonging to immunologically privileged tissues, which usually determines the success of transplantation of this tissue. A medical problem is posed by patients at high risk of transplant rejection, in whom the immune privilege of the eye is abolished and the risk of transplant failure increases. Critical to the success of transplantation in patients at high risk of corneal rejection may be the selection of an HLA-matched donor and recipient, and the detection of existing and/or de novo emerging DSAs in the patient. Incorporating the assessment of these parameters into routine diagnostics may contribute to establishing immune risk stratification for transplant rejection and effective personalized therapy for patients.

The Systemic Risk Factors for the Development of Infectious Keratitis after Penetrating Keratoplasty: A Population-Based Cohort Study

Penetrating keratoplasty (PK) is a corneal surgery that is employed to repair the full-thickness corneal lesion. This study aimed to survey the possible systemic risk factors of infectious keratitis after penetrating keratoplasty (PK) via the Taiwan National Health Insurance Research Database (NHIRD). A retrospective case-control study was conducted, and 327 patients who received the PK were enrolled after exclusion. The main outcome was the development of infectious keratitis, and people were divided into those with infectious keratitis and those without the outcome. Cox proportional hazard regression was conducted to produce adjusted hazard ratios (aHRs) and 95% confidence intervals (CIs) of specific demographic indexes and systemic diseases on infectious keratitis. There were 68 patients who developed infectious keratitis after the whole follow-up period. The diabetes mellitus (DM) (aHR: 1.440, 95% CI: 1.122-2.874, p = 0.0310) and chronic ischemic heart disease (aHR: 1.534, 95% CI: 1.259-3.464, p = 0.0273) groups demonstrated a significant association with infectious keratitis. The DM group also revealed significant influence on infectious keratitis development in all the subgroups (all p < 0.05). Nevertheless, the effect of chronic ischemic heart disease on infectious keratitis was only significant on those aged older than 60 years (p = 0.0094) and both sexes (both p < 0.05). In conclusion, the presence of DM and chronic ischemic heart disease are associated with infectious keratitis after PK. However, local risk factors for infectious keratitis developed in those receiving PK had not been evaluated.

Jordanian nursing students' knowledge and attitudes of corneal donation

A high success rate of corneal transplants is evident. However, there is still a lack of corneal grafts available to meet demand, largely because donors are reluctant to donate. Given their critical role in future healthcare teaching and advocacy. There has not been much research on Jordanian nursing students' perspectives on corneal donation, so it's critical to identify and eliminate any obstacles. This study aims to evaluate the knowledge and attitudes of Jordanian nursing students concerning corneal donation. A cross-sectional, descriptive design was used to recruit (n = 440) nursing students from four Jordanian universities. A self-reported questionnaire was used to obtain data on knowledge and attitudes regarding corneal donation. The average age of senior nursing students was (M = 23.07, SD = 3.63) years. Varying levels of understanding were revealed amongst university students toward corneal donation items. Generally, good attitude of nursing students toward corneal donation (M = 34.1, SD = 8.1). Weak positive relationship was found between total knowledge scores and age (r = 0.141, p = 0.003) while there is no significant relationship between age and total attitude score (r = 0.031, p = 0.552). Age was found to be a significant predictor (B = 0.01, Beta = 0.12, t = 2.07, p = 0.04). Also, the educational level of fathers is a significant positive predictor (Beta = 0.128, p = 0.008) for the total attitude scores among nursing students. Limited awareness of corneal donation, highlighting the need for focused educational interventions to improve their comprehension.

The landscape of clinical trials in corneal regeneration: A systematic review of tissue engineering approaches in corneal disease

The limited availability of a healthy donor cornea and the incidence of allograft failure led researchers to seek other corneal substitutes via tissue engineering. Exploring the trend of clinical trials of the cornea with the vision of tissue engineering provides an opportunity to reveal future potential corneal substitutes. The results of this clinical trial are beneficial for future study designs to overcome the limitations of current therapeutic approaches. In this study, registered clinical trials of bio-based approaches were reviewed for corneal regeneration on March 22, 2024. Among the 3955 registered trials for the cornea, 392 trials were included in this study, which categorized in three main bio-based scaffolds, stem cells, and bioactive macromolecules. In addition to the acellular cornea and human amniotic membrane, several bio-based materials have been introduced as corneal substrates such as collagen, fibrin, and agarose. However, some synthetic materials have been introduced in recent studies to improve the desired properties of bio-based scaffolds for corneal substitutes. Nevertheless, new insights into corneal regenerative medicine have recently emerged from cell sheets with autologous and allogeneic cell sources. In addition, the future perspective of corneal regeneration is described through a literature review of recent experimental models.

Mast cells and ocular surface: An update review

Mast cells (MCs), traditionally viewed as key players in IgE-mediated allergic responses, are increasingly recognized for their versatile roles. Situated at critical barrier sites such as the ocular surface, these sentinel cells participate in a broad array of physiological and pathological processes. This review presents a comprehensive update on the immune pathophysiology of MCs, with a particular focus on the mechanisms underlying innate immunity. It highlights their roles at the ocular surface, emphasizing their participation in allergic reactions, maintenance of corneal homeostasis, neovascularization, wound healing, and immune responses in corneal grafts. The review also explores the potential of MCs as therapeutic targets, given their significant contributions to disease pathogenesis and their capacity to modulate immunity. Through a thorough examination of current literature, we aim to elucidate the immune pathophysiology and multifaceted roles of MCs in ocular surface health and disease, suggesting directions for future research and therapeutic innovation.

Evaluating a Sustained-Release Dexamethasone Insert as Adjunctive Therapy for Inflammation and Pain Post-Corneal Transplantation

Purpose

To assess the efficiency and safety of an intracanalicular dexamethasone insert (Dextenza, Ocular Therapeutix, Inc) supplemented with a reduced-frequency topical drop regimen in mitigating pain and inflammation post-penetrating keratoplasty (PKP), Descemet stripping endothelial keratoplasty (DSEK), and Descemet membrane endothelial keratoplasty (DMEK), compared to standard topical corticosteroid therapy.

Patients and Methods

Eyes were categorized within the DSEK, DMEK, or PKP groups based on ocular characteristics and surgical indications. Randomized in a 1:1 ratio, the intervention group received Dextenza alongside a lowered drop frequency, while the control group followed a conventional drop protocol with no Dextenza. Primary outcomes included average pain scores and absence of anterior chamber cell and flare. Secondary outcomes included delayed re-epithelialization, corneal rejection episodes, instances of intraocular pressure (IOP) elevation >10mmHg above baseline, cystoid macular edema (CME) occurrence, and the necessity for steroid rescue.

Results

The study included 30 eyes (10 PKP, 10 DSEK, 10 DMEK). Mean pain scores (0-100 scale; (0-39 = mild pain, 40-69 = moderate pain, 70-100 = severe pain) in the Dextenza group were 3.6 (PKP), 12 (DSEK), 8 (DMEK), compared to 1.2 (PKP), 0 (DSEK), and 4 (DMEK) in controls. PKP control (n=5): 1 delayed re-epithelialization, 1 IOP elevation, 2 CME. DSEK control (n=5): 1 corneal rejection, 1 IOP elevation, 1 CME. DMEK control (n=5): 1 IOP elevation, 1 CME. DMEK Dextenza (n=5): 1 delayed re-epithelialization, 1 CME. No cases required steroid rescue, and no cell or flare was observed one-week post-surgery. There were no statistically significant differences in pain, delayed re-epithelialization, IOP elevation, corneal rejection, or CME between the Dextenza and control groups regardless of the type of corneal transplantation performed.

Conclusion

Dextenza, when combined with a lower-frequency drop regimen, demonstrates a safety profile comparable to that of a traditional higher-frequency drop protocol in terms of pain management and the adverse events explored in this study, potentially enhancing postoperative drop adherence.

Focus on seed cells: stem cells in 3D bioprinting of corneal grafts

Corneal opacity is one of the leading causes of severe vision impairment. Corneal transplantation is the dominant therapy for irreversible corneal blindness. However, there is a worldwide shortage of donor grafts and consequently an urgent demand for alternatives. Three-dimensional (3D) bioprinting is an innovative additive manufacturing technology for high-resolution distribution of bioink to construct human tissues. The technology has shown great promise in the field of bone, cartilage and skin tissue construction. 3D bioprinting allows precise structural construction and functional cell printing, which makes it possible to print personalized full-thickness or lamellar corneal layers. Seed cells play an important role in producing corneal biological functions. And stem cells are potential seed cells for corneal tissue construction. In this review, the basic anatomy and physiology of the natural human cornea and the grafts for keratoplasties are introduced. Then, the applications of 3D bioprinting techniques and bioinks for corneal tissue construction and their interaction with seed cells are reviewed, and both the application and promising future of stem cells in corneal tissue engineering is discussed. Finally, the development trends requirements and challenges of using stem cells as seed cells in corneal graft construction are summarized, and future development directions are suggested.

Keratoconus: imaging modalities and management

Background

Keratoconus (KCN) is characterized by gradual thinning and steepening of the cornea, which can lead to significant vision problems owing to high astigmatism, corneal scarring, or even corneal perforation. The detection of KCN in its early stages is crucial for effective treatment. In this review, we describe current advances in the diagnosis and treatment of KCN.

Methods

This narrative review focuses on recent advancements in the diagnosis and treatment of KCN, especially evolving approaches and strategies. To ensure the inclusion of the most recent literature, relevant publications discussing advanced imaging techniques and treatment options for KCN were extensively gathered from the PubMed/MEDLINE and Google Scholar databases. The following index terms and keywords were used for the online search: keratoconus, diagnosis of keratoconus, advances in the diagnosis of keratoconus, topography or tomography, anterior segment optical coherence tomography, treatment of keratoconus, advances in the treatment of keratoconus, collagen crosslinking, intrastromal ring, keratoplasty, and new techniques in keratoconus.

Results

Various screening methods such as corneal topography, tomography, anterior segment optical coherence tomography, and assessment of corneal biomechanics have been developed to identify KCN in its early stages. After diagnosis, KCN management focuses on preventing disease progression. Corneal collagen crosslinking is a minimally invasive treatment that can slow or stop the progression of the condition. Recent research has also explored the use of copper sulfate eye drops (IVMED-80) as a noninvasive treatment to prevent the progression of KCN. Current treatment options for visual improvement include scleral lenses, intracorneal ring segments, corneal allogeneic intrastromal ring segments, and deep anterior lamellar keratoplasty. Recently, novel alternative procedures, such as isolated Bowman layer transplantation, either as a corneal stromal inlay or onlay, have demonstrated encouraging outcomes. Artificial intelligence has gained acceptance for providing best practices for the diagnosis and management of KCN, and the science of its application is contentiously debated; however, it may not have been sufficiently developed.

Conclusions

Early detection and advancements in screening methods using current imaging modalities have improved diagnosis of KCN. Improvement in the accuracy of current screening or diagnostic tests and comparison of their validities are achievable by well-designed, large-scale, prospective studies. The safety and effectiveness of emerging treatments for KCN are currently being investigated. There is an ongoing need for studies to track progress and evaluate clinicians' knowledge and practices in treating patients with KCN. Artificial intelligence capabilities in management approach considering the currently available imaging modalities and treatment options would best benefit the patient.

The current landscape of antifibrotic therapy across different organs: A systematic approach

Fibrosis is a common pathological process that can affect virtually all the organs, but there are hardly any effective therapeutic options. This has led to an intense search for antifibrotic therapies over the last decades, with a great number of clinical assays currently underway. We have systematically reviewed all current and recently finished clinical trials involved in the development of new antifibrotic drugs, and the preclinical studies analyzing the relevance of each of these pharmacological strategies in fibrotic processes affecting tissues beyond those being clinically studied. We analyze and discuss this information with the aim of determining the most promising options and the feasibility of extending their therapeutic value as antifibrotic agents to other fibrotic conditions.

Artificial Endothelial Layer Implantation After Multiple Failed Keratoplasties

PURPOSE

Presenting the first case of noncellular corneal endothelial substitute after multiple failed penetrating keratoplasty (PK) and lamellar endothelial keratoplasty.

METHODS

Our case presented with pseudophakic bullous keratopathy after a history of 2 rejected PKs and 1 rejected Descemet stripping automated endothelial keratoplasty. We implanted an artificial endothelial layer.

RESULTS

The implant remained fully attached for a follow-up period of 12 months, and central corneal thickness decreased significantly. The patient reported improvement in her subjective vision, although ocular comorbidities limited the visual potential.

CONCLUSIONS

This new device could serve as an alternative to lamellar endothelial corneal transplantation in cases where tissue rejection has occurred and is highly likely to recur. The technique is simple, and the deswelling effect on the cornea persisted, although the visual results require further validation in patients with a higher visual potential.

Characterization of cornea donors at a tissue center in the city of Medellin, Colombia

The cornea transplant is considered the most frequently performed type of transplant in the world, with a demand that has been increasing in recent years. An observational descriptive study was conducted, focusing on the ocular tissue extracted from cadaveric donors from January 2019 to December 2021 at the Red Cross Eye Bank in Medellin, Colombia. This is the first epidemiological characterization of corneal donor tissues within the eye banks of our city, where high rates of violence-related deaths explain that tissue donors are mostly young individuals. This, in turn, results in excellent counts of endothelial cells and tissue viability in their microscopic studies. Additionally, there are lower rates of discarded tissues compared to similar studies.

Sox9 marks limbal stem cells and is required for asymmetric cell fate switch in the corneal epithelium

Adult tissues with high cellular turnover require a balance between stem cell renewal and differentiation, yet the mechanisms underlying this equilibrium are unclear. The cornea exhibits a polarized lateral flow of progenitors from the peripheral stem cell niche to the center; attributed to differences in cellular fate. To identify genes that are critical for regulating the asymmetric fates of limbal stem cells and their transient amplified progeny in the central cornea, we utilized an in vivo cell cycle reporter to isolate proliferating basal cells across the anterior ocular surface epithelium and performed single-cell transcriptional analysis. This strategy greatly increased the resolution and revealed distinct basal cell identities with unique expression profiles of structural genes and transcription factors. We focused on Sox9; a transcription factor implicated in stem cell regulation across various organs. Sox9 was found to be differentially expressed between limbal stem cells and their progeny in the central corneal. Lineage tracing analysis confirmed that Sox9 marks long-lived limbal stem cells and conditional deletion led to abnormal differentiation and squamous metaplasia in the central cornea. These data suggest a requirement for Sox9 for the switch to asymmetric fate and commitment toward differentiation, as transient cells exit the limbal niche. By inhibiting terminal differentiation of corneal progenitors and forcing them into perpetual symmetric divisions, we replicated the Sox9 loss-of-function phenotype. Our findings reveal an essential role for Sox9 for the spatial regulation of asymmetric fate in the corneal epithelium that is required to sustain tissue homeostasis.

Quality assurance in corneal transplants: Donor cornea assessment and oversight

The cornea is the most frequently transplanted human tissue, and corneal transplantation represents the most successful allogeneic transplant worldwide. In order to obtain good surgical outcome and visual rehabilitation and to ensure the safety of the recipient, accurate screening of donors and donor tissues is necessary throughout the process. This mitigates the risks of transmission to the recipient, including infectious diseases and environmental contaminants, and ensures high optical and functional quality of the tissues. The process can be divided into 3 stages: (1) donor evaluation and selection before tissue harvest performed by the retrieval team, (2) tissue analysis during the storage phase conducted by the eye bank technicians after the retrieval, and, (3) tissue quality checks undertaken by the surgeons in the operating room before transplantation. Although process improvements over the years have greatly enhanced safety, quality, and outcome of the corneal transplants, a lack of standardization between centers during certain phases of the process still remains, and may impact on the quality and number of transplanted corneas. Here we detail the donor screening process for the retrieval teams, eye bank operators. and ophthalmic surgeons and examine the limitations associated with each of these stages.

Cost-effectiveness of the ADVISE trial: An intraoperative OCT protocol in DMEK surgery

The intraoperative optical coherence tomography (iOCT) is recently introduced in Descemet membrane endothelial keratoplasty (DMEK) surgery, which aims to increase clinical performance and surgery safety. However, the acquisition of this modality is a substantial investment. The objective of this paper is to report on the cost-effectiveness of an iOCT-protocol in DMEK surgery with the Advanced Visualization in Corneal Surgery Evaluation (ADVISE) trial. This cost-effectiveness analysis uses data 6 months postoperatively from the multicentre prospective randomized clinical ADVISE trial. Sixty-five patients were randomized to usual care (n = 33) or the iOCT-protocol (n = 32). Quality-Adjusted Life Years (EQ-5D-5L), Vision-related Quality of Life (NEI-VFQ-25) and self-administered resources questionnaires were administered. Main outcome is the incremental cost-effectiveness ratio (ICER) and sensitivity analyses. The iOCT protocol reports no statistical difference in ICER. For the usual care group compared with the iOCT protocol, respectively, the mean societal costs are €5027 compared with €4920 (Δ€107). The sensitivity analyses report the highest variability on time variables. This economic evaluation learned that there is no added value in quality of life or cost-effectiveness in using the iOCT protocol in DMEK surgery. The variability of cost variables depends on the characteristics of an eye clinic. The added value of iOCT could gain incrementally by increasing surgical efficiency, and aiding in surgical decision-making.

One-year Outcomes of Ultrathin Descemet Stripping Automated Endothelial Keratoplasty Combined with Cataract Surgery in the Korean Population

PURPOSE

To evaluate the refractive outcomes after ultrathin Descemet stripping automated endothelial keratoplasty (UT-DSAEK) combined with phacoemulsification and intraocular lens implantation (triple procedure) in the South Korean population.

METHODS

This retrospective observational study included 37 eyes of 36 patients who underwent the UT-DSAEK triple procedure between 2012 and 2021 in a single tertiary hospital. Preoperative and postoperative refractive outcomes and endothelial parameters at 1, 3, 6, and 12 months were observed.

RESULTS

At the final postoperative 12-month period, the average best-corrected visual acuity was 0.4 ± 0.5 in logarithm of the minimum angle of resolution. The mean endothelial cell density at 12 months was 1,841.92 ± 731.24 cells/mm2, indicating no significant endothelial cell loss compared to the baseline (p = 0.128). The mean postoperative central corneal thickness at 12 months was 597.41 ± 86.26 μm. The postoperative mean absolute error at 12 months was 0.96 ± 0.89 diopters (D) and mean error was 0.89 ± 0.97 D.

CONCLUSIONS

The results of our South Korean cohort study on UT-DSAEK triple surgery showed favorable and safe outcomes. Regardless of graft thickness, it should be noted that a hyperopic shift of 1.00 to 2.00 D needs to be considered in the case of UT-DSAEK triple surgery.

National Consensus on Contraindications for Corneal Donation for Transplantation in Switzerland

PURPOSE

To establish a national consensus on contraindications for corneal donation for transplantation in Switzerland.

METHODS

Swisstransplant (SWT), the Swiss national foundation coordinating tissue and organ donations, convened a working group consisting of six national corneal surgeons and eye bankers and donation experts to create a contraindication list for corneal donation. The group reviewed available national and international guidelines and recommendations, while adhering to Swiss law and transplant regulations. In cases of opposing opinions, the group held follow-up meetings until a consensus was reached. A consensus was defined as agreement among all parties present.

RESULTS

From March 2021 to November 2021, the study group held six meetings and created a standardized minimal contraindication list for corneal donation in Switzerland. Thanks to this list, SWT has created a mandatory working and documentation file for donor coordinators to use when evaluating multiorgan donors for corneal harvesting. The authors agreed that while the national consensus list provides standardized minimal contraindication criteria, local eye banks may choose to introduce additional, more rigorous criteria.

CONCLUSION

Given that corneal transplantation is the most commonly performed transplantation, establishing a consensus on contraindications is crucial for recipient safety. The creation of a consensus on contraindications for corneal donation in Switzerland is an essential contribution to fulfil the legal requirements concerning quality assurance and provides sufficient high-quality donor tissue within the country. Therefore, periodic review and revision of the consensus is considered critical.

Photothermal hydrogels for infection control and tissue regeneration

In this review, we report investigating photothermal hydrogels, innovative biomedical materials designed for infection control and tissue regeneration. These hydrogels exhibit responsiveness to near-infrared (NIR) stimulation, altering their structure and properties, which is pivotal for medical applications. Photothermal hydrogels have emerged as a significant advancement in medical materials, harnessing photothermal agents (PTAs) to respond to NIR light. This responsiveness is crucial for controlling infections and promoting tissue healing. We discuss three construction methods for preparing photothermal hydrogels, emphasizing their design and synthesis, which incorporate PTAs to achieve the desired photothermal effects. The application of these hydrogels demonstrates enhanced infection control and tissue regeneration, supported by their unique photothermal properties. Although research progress in photothermal hydrogels is promising, challenges remain. We address these issues and explore future directions to enhance their therapeutic potential.

Replace or Regenerate? Diverse Approaches to Biomaterials for Treating Corneal Lesions

The inner structures of the eye are protected by the cornea, which is a transparent membrane exposed to the external environment and subjected to the risk of lesions and diseases, sometimes resulting in impaired vision and blindness. Several eye pathologies can be treated with a keratoplasty, a surgical procedure aimed at replacing the cornea with tissues from human donors. Even though the success rate is high (up to 90% for the first graft in low-risk patients at 5-year follow-up), this approach is limited by the insufficient number of donors and several clinically relevant drawbacks. Alternatively, keratoprosthesis can be applied in an attempt to restore minimal functions of the cornea: For this reason, it is used only for high-risk patients. Recently, many biomaterials of both natural and synthetic origin have been developed as corneal substitutes to restore and replace diseased or injured corneas in low-risk patients. After illustrating the traditional clinical approaches, the present paper aims to review the most innovative solutions that have been recently proposed to regenerate the cornea, avoiding the use of donor tissues. Finally, innovative approaches to biological tissue 3D printing and xenotransplantation will be mentioned.

Biopolymeric corneal lenticules by digital light processing based bioprinting: a dynamic substitute for corneal transplant

Digital light processing (DLP) technology has gained significant attention for its ability to construct intricate structures for various applications in tissue modeling and regeneration. In this study, we aimed to design corneal lenticules using DLP bioprinting technology, utilizing dual network bioinks to mimic the characteristics of the human cornea. The bioink was prepared using methacrylated hyaluronic acid and methacrylated gelatin, where ruthenium salt and sodium persulfate were included for mediating photo-crosslinking while tartrazine was used as a photoabsorber. The bioprinted lenticules were optically transparent (85.45% ± 0.14%), exhibited adhesive strength (58.67 ± 17.5 kPa), and compressive modulus (535.42 ± 29.05 kPa) sufficient for supporting corneal tissue integration and regeneration. Puncture resistance tests and drag force analysis further confirmed the excellent mechanical performance of the lenticules enabling their application as potential corneal implants. Additionally, the lenticules demonstrated outstanding support for re-epithelialization and stromal regeneration when assessed with human corneal stromal cells. We generated implant ready corneal lenticules while optimizing bioink and bioprinting parameters, providing valuable solution for individuals suffering from various corneal defects and waiting for corneal transplants.

Towards Precision Ophthalmology: The Role of 3D Printing and Bioprinting in Oculoplastic Surgery, Retinal, Corneal, and Glaucoma Treatment

In the forefront of ophthalmic innovation, biomimetic 3D printing and bioprinting technologies are redefining patient-specific therapeutic strategies. This critical review systematically evaluates their application spectrum, spanning oculoplastic reconstruction, retinal tissue engineering, corneal transplantation, and targeted glaucoma treatments. It highlights the intricacies of these technologies, including the fundamental principles, advanced materials, and bioinks that facilitate the replication of ocular tissue architecture. The synthesis of primary studies from 2014 to 2023 provides a rigorous analysis of their evolution and current clinical implications. This review is unique in its holistic approach, juxtaposing the scientific underpinnings with clinical realities, thereby delineating the advantages over conventional modalities, and identifying translational barriers. It elucidates persistent knowledge deficits and outlines future research directions. It ultimately accentuates the imperative for multidisciplinary collaboration to enhance the clinical integration of these biotechnologies, culminating in a paradigm shift towards individualized ophthalmic care.

Risk Factors for Corneal Endothelial Decompensation after Penetrating Keratoplasty: A Population-Based Cohort Study

(1) Background: Endothelial decompensation is a common complication after penetrating keratopathy (PK), while the risk factors for endothelial decompensation after PK have not been fully elucidated. Consequently, we aim to investigate the possible risk factors for endothelial decompensation after PK. (2) Methods: This retrospective study was conducted using the National Health Insurance Research Database (NHIRD) of Taiwan. The main outcome was the development of endothelial decompensation after PK surgery. The effects of potential risk factors were compared between the patients with endothelial decompensation and the patients without endothelial decompensation via Cox proportional hazard regression, which produced the adjusted hazard ratio (aHR) and a 95% confidence interval (CI). (3) Results: Overall, 54 patients developed endothelial decompensation after PK surgery, with a ratio of 16.12 percent. The pre-existing type 2 diabetes mellitus (T2DM) (aHR: 1.924, 95% CI: 1.257-2.533, p = 0.0095) and history of cataract surgery (aHR: 1.687, 95% CI: 1.328-2.440, p = 0.0026) were correlated with the development of endothelial decompensation. In the subgroup analysis, the correlation between a history of cataract surgery and post-PK endothelial decompensation was more prominent in patients older than 60 years compared to their younger counterparts (p = 0.0038). (4) Conclusions: Pre-existing T2DM and a history of cataract surgery are associated with a higher incidence of post-PK endothelial decompensation.

Intraoperative collagen imaging of sutured cornea: A way towards managing post-penetrating keratoplasty astigmatism

The birefringent nature of the human cornea plays an important role in comprehending its structural behavior in both diseased and surgical conditions. During corneal transplantation, irregular astigmatism is a common post-surgical complication that depends on the characteristics of suturing. Four human cadaver corneas are subjected to an in-vitro model of a typical full-thickness penetrating keratoplasty (PK) procedure using 16 simple interrupted 10-0 vicyrl sutures. The birefringence of these four corneas is analyzed using digital photoelasticity and compared with the control cornea (without PK). It is found that the sutures and their mutual interaction influence the morphology of the peripheral birefringence of the cornea. The findings of the present investigation are pertinent to intraoperative suture management during PK. Results suggest conserving the typical diamond-shaped morphology of peripheral birefringence would ensure uniform distribution of sutures. Therefore, birefringence imaging could be useful in suture management to ensure proper apposition of the graft-host junction, thus minimizing the risk of irregular astigmatism.

[Options for contact correction after keratoplasty]

Keratoplasty is a radical surgical method for treating various corneal pathologies. Today, there are many types of keratoplasty, each aiming to restore the integrity and transparency of the cornea. However, keratoplasty-induced ametropia often prevents achieving high visual acuity and makes impossible the use of conventional optical correction methods such as glasses or soft and traditional rigid contact lenses. In this regard, the use of scleral contact lenses is the most optimal method for optical correction of postoperative refractive anomalies, ensuring successful visual rehabilitation and preventing the need for additional keratorefractive interventions.

[Modern techniques and features of selective keratoplasty]

Selective keratoplasty involves replacing the affected layers of the cornea with similar donor tissue. In case of pathological changes in the middle and posterior stroma, deep anterior lamellar keratoplasty (DALK) is performed. Chronic corneal edema caused by endothelial dysfunction is an indication for endothelial keratoplasty - Descemet membrane endothelial keratoplasty (DMEK) or Descemet Stripping Endothelial Keratoplasty (DSAEK). Compared to penetrating keratoplasty (PK), these operations are characterized by a low risk of damage to intraocular structures and a relatively short rehabilitation period. Complications of selective keratoplasty include the formation of a false chamber between the lamellar graft and the recipient's cornea, ocular hypertension during anterior chamber air tamponade. Persistent epithelial defect can be a sign of primary graft failure in DALK, DSAEK and DMEK. Selective keratoplasty is characterized by a lower incidence of immune rejection than PK. In some cases, DALK can be complicated by corneal changes related to suture fixation of the graft. Long-term postoperative use of topical glucocorticoids can cause ocular hypertension and cataracts.

[Outcomes of hemi-Descemet membrane endothelial keratoplasty and phacoemulsification for the treatment of primary Fuchs' endothelial corneal dystrophy combined with cataract]

PURPOSE

This study evaluates the long-term results of surgical treatment of patients with Fuchs' endothelial corneal dystrophy and cataract.

MATERIAL AND METHODS

The study included 24 patients (24 eyes) with primary Fuchs' endothelial corneal dystrophy and cataract, who underwent cataract phacoemulsification with IOL implantation and of Descemet's membrane endothelial keratoplasty with a semicircular graft (hemi-DMEK). The effect of treatment was assessed by best corrected visual acuity (BCVA), central corneal thickness (CCT) and endothelial cell density (ECD).

RESULTS

In total, surgical treatment involved 14 donor corneas that were divided in half during the preparation and isolation of the Descemet's membrane (DM). By month 12 after the surgery an increase in visual functions and graft transparency were observed in 23 patients (23 eyes) out of 24. Repeated keratoplasty was required in one case due to fibrosis of the posterior layers of recipient's corneal stroma. At 12 months postoperatively, the study group showed an increase in BCVA from 0.16±0.1 to 0.75±20, a decrease in CCT from 650.9±4.5 μm to 519.6±43.9, and a decreased in ECD from 2850.5±84.7 cells/mm2 up to 1285.5±277.2 cells/mm2. Thus, the loss of endothelial cells at one year after surgery amounted to 54.9%.

CONCLUSIONS

The developed method for transplantation of a semicircular DM fragment provides a tissue-saving approach to endothelial keratoplasty, and considering the high percentage of transparent engraftment of grafts and complete visual rehabilitation, it can be recommended in the treatment of patients with cataract and Fuchs' endothelial corneal dystrophy.

Robotic cell processing facility for clinical research of retinal cell therapy

The consistent production of high-quality cells in cell therapy highlights the potential of automated manufacturing. Humanoid robots are a useful option for transferring technology to automate human cell cultures. This study evaluated a robotic cell-processing facility (R-CPF) for clinical research on retinal cell therapy, incorporating the versatile humanoid robot Maholo LabDroid and an All-in-One CP unit. The R-CPF platform consists of a robot area for handling cells and an operator area for the maintenance of the robot, designed with a clean airflow to ensure sterility. Monitoring the falling, floating, and adhering bacteria demonstrated that the required cleanliness and aseptic environment for cell manufacturing were satisfied. We then conducted cell manufacturing equivalent to the transplantation therapy of induced pluripotent stem cell (iPSC)-derived retinal pigment epithelial cells that met the clinical quality standards for transplantation. These results indicate that R-CPF is suitable for cell manufacturing purposes and suggest that utilizing the same robotic system in basic and clinical research can accelerate the translation of basic research findings into clinical applications.

An effective method for culturing functional human corneal endothelial cells using a xenogeneic free culture medium

Endothelial dysfunction is a leading cause of corneal blindness in developed countries and the only available treatment is the endothelial transplantation. However, the limited availability of suitable donors remains a significant challenge, driving the exploration of alternative regenerative therapies. Advanced Therapy Medicinal Products show promise but must adhere to strict regulations that prohibit the use of animal-derived substances. This study investigates a novel culture methodology using Plasma Rich in Growth Factors (PRGF) as the only source of growth factors for primary cultures of human corneal endothelial cells (CECs). CECs were obtained from discarded corneas or endothelial rings and cultured in two different media: one supplemented with xenogeneic factors and other xenogeneic-free, using PRGF. Comprehensive characterization through immunofluorescence, morphological analyses, trans-endothelial electrical resistance measurements, RNA-seq, and qPCR was conducted on the two groups. Results demonstrate that CECs cultured in the xenogeneic-free medium exhibit comparable gene expression, morphology, and functionality to those cultured in the xenogeneic medium. Notably, PRGF-expanded CECs share 46.9% of the gene expression profile with native endothelium and express all studied endothelial markers. In conclusion, PRGF provides an effective source of xenogeneic-free growth factors for the culture of CECs from discarded corneal tissue. Further studies will be necessary to demonstrate the applicability of these cultures to cell therapies that make clinical translation possible.

Efficacy and safety of UT-DSAEK combined with Carlevale's sutureless scleral fixation IOL

PURPOSE

To evaluate a novel surgical combination of ultrathin Descemet stripping automated endothelial keratoplasty (UT-DSAEK) and sutureless scleral fixation for Carlevale intraocular lens (SSF-Carlevale IOL) implantation to manage corneal endothelial decompensation when there is a concomitant need for secondary IOL fixation.

METHODS

Clinical data collected from 10 eyes of 9 patients with bullous keratopathy (BK) who underwent combined UT-DSAEK and SSF-Carlevale IOL implantation in a single procedure were retrospectively analyzed. Anterior chamber IOL (4 cases), aphakia (4 cases, 1 of which associated with PEX), and previous trauma (2 cases) were the conditions responsible for BK. Corrected distance visual acuity (CDVA), intraocular pressure (IOP), endothelial cell density (ECD), central corneal thickness (CCT), graft thickness (GT) and complications were recorded over a 12-month follow-up period.

RESULTS

In 90% (9/10) of eyes graft clarity was maintained during follow-up. The mean CDVA improved significantly (p < 0.0001) from 1.78 ± 0.76 logMAR preoperatively to 0.53 ± 0.3 logMAR at 12 months. ECD on average decreased from 2575 ± 125.3 cells/mm2 (donor tissue) to 1697 ± 133.3 cells/mm2 in 12 months. The mean CCT decreased from 870 ± 200 µm to 650 µm ± 9 at 12 months (ANOVA, p = 0.0005).

CONCLUSIONS

Combined UT-DSAEK and SSF-Carlevale IOL implantation was associated with good corneal graft survival and IOP control, with few complications. These findings suggest that this surgical approach is a practical option for patients requiring both treatment for corneal endothelial dysfunction and secondary IOL implantation.