Donor Corneas Research Articles

Silk fibroin based interpenetrating network hydrogel for corneal stromal regeneration

There is a need to develop tissue engineering based approaches to address the shortage of donor corneas worldwide for transplantation. To do this a novel approach to fabricate three-dimensional hydrogels using free-radical polymerization was investigated to generate constructs for corneal stromal tissue regeneration. Different ratios of silk fibroin (SF) to polyacrylamide (PA) were used to fabricate semi-interpenetrating hydrogels. Scanning electron micrograph displayed the interconnectivity of pores within the fabricated hydrogels. Pore sizes ranged from 25 to 66 μm. Scaffolds with increasing concentration of SF had enhanced β-sheet structure (verified by Fourier transform infrared spectroscopy). The biological response of human corneal stromal cells to these hydrogels was examined using cellular adhesion, proliferation, cytoskeleton organization, gene expression and immunocytochemical analysis. The fabricated hydrogels possess rapid gelation (∼3 min) at 37 °C, 84 % porosity facilitating keratocyte migration during healing, improved cellular adhesion and no cytotoxicity, indicating their efficiency for in-situ corneal tissue regeneration. Presence of SF in semi-interpenetrating network hydrogel enhanced cellular proliferation, elevated GAG deposition, and increased expression of keratocyte genes, normally associated with healthy corneal stromal tissue. This study acts as an initial step towards fabricating SF based semi-interpenetrating network hydrogels for developing clinically applicable ocular implants.

Results of ultrathin Descemet stripping automated endothelial keratoplasty with donor corneas preserved in synthetic organ culture media.

To evaluate outcomes of ultrathin Descemet stripping automated endothelial keratoplasty (UT-DSAEK) with donor corneas preserved at 31°C in Cornea Syn®, a medium formulated with recombinant human serum albumin (rHSA) to replace foetal calf serum, and deswelled-transported in the xeno-free medium Cornea Trans®. Prospective, multicentre, open-label study. We evaluated the endothelial cell loss (ECL) as the percentage variation of the endothelial cell density (ECD, cells/mm2) between 6 and 12 months after surgery, corneal transparency and thickness at 12 months, and adverse events within 12 months. Endothelial lenticules of mean 89 μm, ECD ≥ 2300 cells/mm2, minimum signs of cell mortality or morphology alterations, were dissected by microkeratome in the eye bank, and grafted in patients ≥ 18 years without corneal neovascularisation, conjunctivalization, or blinking impairment. Thirty-five patients underwent UT-DSAEK, 3 showed primary failure, 1 late failure, and 2 skipped the 6-month visit. We analysed data from 29 patients, 27 with Fuchs endothelial corneal dystrophy (FECD) and 2 with pseudophakic bullous keratopathy (PBK). The median ECL between 6 and 12 months was 2.6% (p = .054, CI 0 to 12.5) and the absolute mean (SD) was 158.4 (364.1) cells/mm2. After 12 months, 96.5% of corneas were clear, with mean pachymetry of 585.9 (50.4) µm. The ECL rate after UT-DSAEK match overall that observed in DSAEK or UT-DSAEK models of endothelial survival and the overall safety compared that reported for similar follow-up. Corneas maintained in Cornea Syn® and Cornea Trans® did not affect the ECD and functional outcomes of UT-DSAEK up to 12 months.

Single cell RNA-seq of human cornea organoids identifies cell fates of a developing immature cornea.

The cornea is a protective and refractive barrier in the eye crucial for vision. Understanding the human cornea in health, disease, and cell-based treatments can be greatly advanced with cornea organoids developed in culture from induced pluripotent stem cells. While a limited number of studies have investigated the single-cell transcriptomic composition of the human cornea, its organoids have not been examined similarly. Here, we elucidated the transcriptomic cell fate map of 4-month-old human cornea organoids and human donor corneas. The organoids harbor cell clusters that resemble cells of the corneal epithelium, stroma, and endothelium, with subpopulations that capture signatures of early developmental states. Unlike the adult cornea where the largest cell population is stromal, the organoids contain large proportions of epithelial and endothelial-like cells. These corneal organoids offer a 3D model to study corneal diseases and integrated responses of different cell types.

Full-field Optical Coherence Microscopy for Histology-like Analysis of Stromal Features in Corneal Grafts.

The quality of donor corneal stroma, which makes up about 90% of total corneal thickness, is likely to be one of the main, if not the major, limiting factor(s) for success of deep anterior lamellar and penetrating keratoplasty. These are surgical procedures that involve replacing part or all of the diseased corneal layers, respectively, by donated tissue, the graft, taken from a recently deceased individual. However, means to evaluate stromal quality of corneal grafts in eye banks are limited and lack the capability of high-resolution quantitative assessment of disease indicators. Full-field optical coherence microscopy (FF-OCM), permitting high-resolution 3D imaging of fresh or fixed ex vivo biological tissue samples, is a non-invasive technique well suited for donor cornea assessment. Here we describe a method for the qualitative and quantitative analysis of corneal stroma using FF-OCM. The protocol has been successfully applied to normal donor corneas and pathological corneal buttons, and can be used to identify healthy and pathologic features on both the macroscopic and microscopic level, thereby facilitating the detection of stromal disorders that could compromise the outcome of keratoplasty. By improving the graft quality control, this protocol has the potential to result in better selection (and rejection) of donor tissues and hence decreased graft failure.

Chinese expert consensus on femtosecond laser-assisted keratoplasty (2022)

Corneal transplantation, which can be divided into therapeutic keratoplasty and optical keratoplasty, is the main method to restore vision for patients with corneal blindness. The keys to optical keratoplasty are the regular excision and preparation of donor and recipient corneas, as well as well-developed suturing skills to reduce surgically induced astigmatism. Traditional keratoplasty mainly relies on trephination to prepare the corneal graft and the recipient bed, but this procedure lacks precision, which is an important factor affecting postoperative vision recovery. In this regard, femtosecond laser-assisted keratoplasty (FLAK) can get more precise results compared with the traditional trephine-assisted keratoplasty, thereby achieving better optical keratoplasty effects. FLAK requires the cooperation between corneal refractive surgeons and corneal transplantation surgeons, and the surgical procedure also differs from that of traditional trephine-assisted keratoplasty. To promote and standardize the implementation of FLAK in China and to provide guidance on its clinical practice, the Cornea Group of Ophthalmology Branch of Chinese Medical Association has formulated this consensus on the indications, surgical design and procedures, complications and perioperative medication management of FLAK after thoroughly discussing the domestic and foreign research results collected, combined with the clinical experience of experts in this field.

Research advances in human corneal endothelial cell regeneration

Human corneal endothelial cells (HCECs) are the prerequisite for maintaining corneal transparency, but HCECs remain arrested at the G1 phase after embryonic development and can not proliferate and regenerate. Thus, the density of HCECs decreases spontaneously with corneal development. Systemic factors, primary corneal disease, refractive factors, glaucoma, inflammation, and trauma all can cause a massive loss of HCECs, lead to corneal edema and turbidity, and ultimately induce blindness. Currently, keratoplasty is the only effective treatment, but the scarcity of donor corneas and the limitation of corneal preservation technology restrict the availability of keratoplasty. Therefore, the most appealing way to tackle the tissue shortage problem is corneal endothelial cell regeneration. In recent years, not only the endogenous regeneration of HCECs mediated by surgery, drugs and gene therapy but also the exogenous regeneration of HCECs mediated by cell therapy have made fruitful progress. Although a number of regeneration strategies have entered the clinical trial stage, the wide clinical application of corneal endothelial regeneration is still far away. This review elaborates the basic research, clinical application and limitation of current strategies of corneal endothelial cell regeneration.

Динамика кератотопографических и биомеханических параметров роговицы после проведения акселерированного ультрафиолетового кросслинкинга с использованием защитного лоскута донорской роговицы в лечении прогрессирующего кератоконуса при «тонкой роговице»

Purpose. To analyze changes in the biomechanical and topographic parameters of the patient's cornea using the Corvis st (OCULUS, Germany) and Pentacam (OCULUS, Germany) device before and after accelerated ultraviolet crosslinking of the cornea using a donor cornea protective flap in the treatment of progressive keratoconus with "thin cornea" and compare the obtained data with the results after classical accelerated crosslinking. Material and methods. According to the proposed technology, 26 patients (26 eyes) were operated on with a diagnosis of progressive keratoconus 2nd stage with corneal pachymetry less than 400 µm, mean value 390 ± 40 µm. Comparison group – patients diagnosed with progressive keratoconus 2nd stage with corneal pachymetry over 400 µm, mean value 450 ± 40 µm, comparable in age and gender, being operated on using the technology of classical accelerated crosslinking. In addition to standard research methods, before and after surgery, patients underwent an assessment of the biomechanical and topographic parameters of the patient's cornea using the Corvis st (OCULUS, Germany) and Pentacam (OCULUS, Germany) devices. Results. The results obtained in both groups were comparable in all parameters: there was a decrease in keratometric parameters in the first months after the operation, with their further stabilization during the entire period of observation. The pachymetry value remained stable, no significant changes in UCVA and Correctable Visual Acuity were detected. Evaluation of specific keratotopographic indices (ISV, IVA, KI, CKI, IHD) showed their decrease both in the main and control groups, and Rmin tended to increase. The value of the inscribed radius tended to decrease, which indicates an increase in the stiffness of the cornea after classical accelerated crosslinking and crosslinking of the proposed technology. Conclusion. Application of the technology of accelerated ultraviolet crosslinking using a protective flap of the donor cornea in the treatment of progressive keratoconus with "thin cornea" leads to an increase in the rigidity of the cornea and stabilization of the ectatic process of the cornea in the postoperative period, just as with the classical technology of accelerated crosslinking. Keywords: progressive keratoconus, "thin cornea", accelerated ultraviolet crosslinking using a donor cornea protective flap, keratopotographic parameters of the cornea, biomechanical parameters of the cornea.

Intraoperative optical coherence tomography-guided donor corneal tissue assessment and preparation.

To evaluate the role of intraoperative optical coherence tomography (i-OCT) in donor grading, selection, and preparation during different types of keratoplasty. Seventy-one consecutive donor corneas collected over 6 months, after clinical grading, were observed by an experienced corneal surgeon under an i-OCT equipped microscope. The donor preparation (manual/automated) for different types of keratoplasty procedures was also undertaken under i-OCT. The mean central corneal thickness of optical and nonoptical grade tissues was 533 ± 19 and 662 ± 52 μm, respectively. The i-OCT-based grading matched with clinical grading in 98.5% cases. Irregular thickness, anterior stromal hyperreflectivity, and previous scars were appreciated in 1.4, 1.4, and 7.04% donors, respectively. During Descemet stripping automated endothelial keratoplasty, i-OCT facilitated selection of appropriate microkeratome head for automated donor preparation in all cases, besides allowing manual dissection of partially dissected lenticule, identification of site of inadvertent perforation, and eccentric trephination in one case each. During Descemet membrane endothelial keratoplasty, i-OCT-based assessment of preexisting scar (five cases) guided careful tissue selection (2/5) and preparation. During predescemetic endothelial keratoplasty, precise needle advancement allowed successful type-1 bubble formation in all cases. All manually punched donors demonstrated an extra endothelial ledge, while those with automated preparation showed tapering donor margins. i-OCT might serve as a useful imaging tool for objective assessment of donor characteristics. The modality may complement clinical evaluation for donor grading, selection, and preparation.

Our experience of regulatory justification of using donor material for keratoplastic operations in the Udmurt Republic

Purpose: to share our experience of regulatory justification to supervisory authorities of performing keratoplastic operations using native donor cornea.Methods. A comprehensive analysis of legal and regulatory framework of the Russian Federation on transplantation.Results. The Nomenclature of Medical Services includes several types of services which contain the word “transplantation” in their names. However, not all of them require a license to perform such procedures as “surgery (organ and (or) tissue transplantation)”. The procedure for providing medical care in “surgery (transplantation of organs and (or) human tissues)” is not applicable to the “ophthalmology” profile, since the equipment and staffing requirements contained therein are not necessary to perform keratoplasty. The list of medical organizations of the subjects of the Russian Federation performing transplantation of human organs and (or) tissues contains no medical organizations of the ophthalmological profile. According to methodological recommendations on ways to pay for medical care at the expense of mandatory medical insurance, keratoplasty is classified as “st21.005. Operations on the organ of vision”.Conclusion. A comprehensive analysis of existing regulatory documents demonstrates that keratoplasty is exclusively related to ophthalmology, it can be performed if there is a license for ophthalmology, transportation of human organs and (or) tissues for transplantation. A healthcare organization also needs to hold a license for removal and storage of human organs and (or) tissues for transplantation. However, if any healthcare organization in the region has such a license, it may donate a donor cornea to an ophthalmological hospital if the latter does not hold such a license.

Clinical outcomes of long-term corneas preserved frozen in Eusol-C used in emergency tectonic grafts.

To report the clinical results on the use of corneas frozen in Eusol-C as tectonic corneal grafts.Retrospective review of medical records of patients who received frozen corneas as emergency tectonic grafts from 2013 to 2020. Corneas had been stored in Eusol-C preservation media at − 78 °C for a mean time of 6.9 months. Diagnosis, transplant characteristics, microbial culture results, anatomic integrity, epithelial healing, neovascularization, transparency, infection and need for additional surgeries were registered. Fifty corneas were used in 40 patients (mean age 60.5 years, 20 males) with a median follow-up of 27.3 months after surgery. Need for tectonic graft was due to: perforation secondary to immune diseases (6, 12%), neurotrophic ulcer (11, 22%), trauma (3, 6%), corneal infection (11, 22%), chronic disorders of the ocular surface (9, 18%) and previous corneal graft failure (10, 22%). Mean size of grafts was 5.6 mm and 36 cases (72%) also received an amniotic membrane graft. Thirty-eight corneas achieved epithelization (76%), 25 (50%) were clear and 19 (38%) developed neovascularization. None of the corneas were rejected. Seventeen corneas (34%) failed: 7 (14%) due to reactivation of baseline disease and 10 (20%) due to primary graft failure. Four corneas (8%) had positive microbial cultures suggestive of contamination and 2 (4%) developed a cornea abscess non-related to a positive microbial culture. Long-term preservation of donor corneas in Eusol-C at − 78 °C is a viable technique to meet the needs of emergency grafts with minimal equipment.

Quantitative analysis of cornea endothelial cell damage from enucleation, corneal buttoning, and storage in donor corneas using trypan blue dye staining.

We aimed to quantitatively analyze the corneal endothelial cell damage by measuring the area stained with trypan blue dye, and to confirm the degree of corneal endothelial cell damage resulting from enucleation, corneal buttoning, and storage in donor corneas intended for use in human corneal transplantation. This study was a retrospective analysis of medical records and videos recorded during keratoplasty. Twenty-one corneal buttons of 21 donors that underwent endothelial cell staining using trypan blue for the donor preparation during DALK or DMEK were included in the study. The percentage of stained area in entire corneal endothelia and the percentage of the stained area in the 8-mm diameter circle were quantitatively analyzed using Adobe Photoshop. The mean percentage of the stained area in the entire corneal endothelia in 13 corneas was 8.1 ± 13.3% (range, 0.0-56.1%), and the mean percentage of the stained area in a circle with a diameter of 8 mm in 21 corneas was 3.4 ± 5.2% (range, 0.0-18.9%). The correlations between the death-to-preservation time, the training duration of the residents who performed donor corneal buttoning, and the percentage of the stained area in the 8-mm diameter circle were not significant(P = .441, P = .495, respectively). Cornea thickness and endothelial cell density did not differ between 10 eyes in the group with the percentage of the stained area in a circle with a diameter of 8 mm <5% and 5 eyes in the group with the percentage more than 5% damage (P = .854, P = .358). The corneal endothelial cell damage could be quantitatively analyzed using trypan blue staining before keratoplasty in donor cornea. The amount of corneal endothelial cell damage in the central 8-mm circle was mostly acceptable, but some cases showed significantly severe endothelial cell damage. The corneal thickness and endothelial cell density did not differ between 10 eyes in the group with the percentage of the stained area in a circle with a diameter of 8 mm <5% and 5 eyes in the group with the percentage more than 5% damage. Therefore, pachymetry and specular microscopy are not sufficient for evaluating donor corneas before keratoplasty.

Comparison of Graft Outcomes Reusing Original Intermediate-Term Cold Storage Solution for Entire Corneal Donor Storage Period With Exchanged Fresh Storage Solution After Donor Preparation in the Cornea Preservation Time Study.

The purpose of this study was to evaluate outcomes of Descemet stripping automated endothelial keratoplasty comparing exchange with fresh intermediate-term cold storage solution after lenticule preparation versus reuse of the original solution in the Cornea Preservation Time Study. In the Cornea Preservation Time Study, 508 donor corneas had lenticules prepared by the eye bank with fresh solution exchange (Fresh group) and 283 with reuse of the original solution (Original group). Storage time for all donors was ≤11 days. Graft success rates, central endothelial cell loss at 3 years, and frequency of positive donor rim cultures were compared between the 2 groups. The 3-year graft success rate (95% confidence interval) was 93.4% (90.7%-95.3%) in the Fresh group and 95.2% (91.8%-97.2%) in the Original group (adjusted hazard ratio for graft failure = 0.64, 95% confidence interval, 0.33-1.24, P = 0.19). The mean percentage endothelial cell loss was significantly greater in the Fresh group versus Original group (45% ± 22% vs. 38% ± 20%, respectively, P = 0.004). Cultures were positive in 4 (1.5%) of 267 donor rims (3 fungal and 1 bacterial) in the Fresh group and in 4 (2.5%) of 158 in the Original group ( P = 0.57). There were 2 postoperative infections in the Original group and none in the Fresh group. The use of the original intermediate-term cold storage solution did not reduce the 3-year graft success rate compared with exchanging with fresh solution after lenticule preparation for Descemet stripping automated endothelial keratoplasty, while the frequency of positive donor rim cultures did not significantly differ between groups.

Identification of Treatment Protocols for Effective Cross-Linking of the Peripheral Cornea: An Experimental Study.

This study aimed to test and evaluate modified corneal cross-linking (CXL) protocols regarding improved treatment effects on the peripheral cornea in terms of tissue stability and cellular response. Peripheral CXL (pCXL) was performed within a ring of 9-11mm of 36 human donor corneas with variations in applied energy (5.4, 7.2, and 10J/cm2) at 9mW/cm2 irradiance. Each energy level was additionally modulated regarding the oxygen level surrounding the cornea during treatment (21%; 100%). Stress-strain tests with endpoints at 12% strain and collagenaseA-assisted digestions to complete digestion were performed to evaluate the rigidity and resistance of treated and control tissue. Further, corneas were processed histologically via TUNEL assay and H&E staining to demonstrate the effects on stromal cells during treatment under varying CXL conditions. Increases in energy dosage achieved significant increases in resistance to stress in all variations except when comparing protocolsA and B under normoxic conditions. Supplemental oxygen significantly increased rigidity in protocolsB (p < 0.01) and C (p = 0.018). Hyperoxic conditions significantly increased resistance to digestion in all protocols. The number of DNA strand breaks in TUNEL assay staining showed significant increases in all increases in energy as well as with oxygen supplementation. Increases in energy and supplemental oxygen improved the effect of CXL, though endothelial safety could not be verified with confidence in high-fluence CXL with supplemental oxygen. Results suggest that CXL protocols using 7.2J/cm2 with 100% O2 or 10J/cm2 without supplemental oxygen prove most effective without anticipated risk of endothelial damage.

Temple eye banking: cornea donation practice at Pashupati crematorium in Nepal

ABSTRACT In high-income countries where eye care is advanced, cornea harvesting is hidden from public view. Here entire eyeball enucleations performed on corpses are done in hospital morgues without mourners’ presence. For the last two decades, the traditional public crematorium area next to the Pashupatinath temple at the holy river Bagmati east of Kathmandu, has become a major Nepal Eye Bank site for motivated cornea donations. To be cremated in the premises of the Pashupatinath temple is considered highly auspicious. After families have given their consent, the cremation rituals are briefly interrupted by the Nepal Eye Bank staff, and cornea button excisions are performed in public space. Thus, mourners regularly view and assist during the removal of cornea button tissues from the deceased before the bodies are burned on the open funeral pyres or in the electric crematorium. How is it that Nepali mourners at Pashupati crematorium accept and comply with cornea donation practice? I argue that cornea donation at Pashupati is a collective achievement accomplished by complex socio-material arrangements that bring together various professionals, procedural manuals, legal framework, equipment, medical intervention, the deceased body, and mourners during the cremation practice.

P11.34: Tissue Donation Indicators in Latin American and European Countries. A Way to Measure the Efficiency of the Organizational System

Introduction: The demand for corneas is increasing in the world. Organizational aspects of the health system and procurement are decisive to improve the number of corneal donors. There are no corneal donation indicators at the international level that allow results to be compared other than the total number and donation rate. Objectives: Analyze the corneal donation situation worldwide, defining indicators related to the deceased in the country. Compare the donation indicators defined in countries of both continents: Latin America and Europe. Material and methods: The following data in Latin America and Europe were analyzed: number of corneal donors/ pmp (Dc/ pmp), number of organ donors/ pmp (DO/ pmp), corneal donors in PCR/ pmp, and total number of deceased from the country. The relationship between the total number of corneal donors in each country and the number of deaths in 2019, grouped by continent, was analyzed. Indicator: Cornea donors/Deceased in the country. The relationship between the number of corneal donors in PCR and the total number of corneal donors of all countries grouped by continent was also analyzed. Indicator: Corneal donors in PCR/Total corneal donors. The data was obtained from the Newsletter Transplant 2019 and the number of deceased at https://ourworldindata.org/. Results: In Latin America, the average number of Cornea donors/deceases per country is 0.51%, with Brazil being the most efficient with 2.1%. In Europe, the average number of Cornea donors/deceased is 0.48%, where Italy, France and the Netherlands stand out with 1%, 1.4% and 1.3%. In the Latin American countries analyzed, the average number of Cornea donors in PCR/ total cornea donors is 69% and in European countries it is 59%. Conclusions: We believe that the indicator Corneal donors/deceased in a country or hospital is a strong indicator that can be used to define the effectiveness of corneal procurement work and compare results in different countries. Analyzing the percentage of donors of corneas in PCR, we can evaluate the work as a country in the procurement of this tissue in PCR to improve the organizational level in the detection of donors of PCR.

The impact of amphotericin B-fortified preservation media on donor rim cultures and posttransplant infection.

To determine the impact of amphotericin B supplementation to donor cornea preservation solutions on the rates of positive donor rim fungal cultures and postkeratoplasty fungal infections. This was a retrospective analysis of cases undergoing corneal transplantations at a single tertiary referral center from 2016 to 2021. Patients undergoing corneal transplantations with and without amphotericin B supplementation to the storage media were reviewed for donor rim culture results and postoperative infection. The primary outcome measures were positive donor rim fungal culture results and postkeratoplasty fungal infection. A total of 1238 corneal transplants were analyzed. Of these, 849 were stored in preservation solution without amphotericin B, while 389 had amphotericin B included. There was a lower incidence of positive donor rim fungal cultures in cases with amphotericin B supplementation (1.8%) compared to the cases without amphotericin B (2.9%), although this difference was not statistically significant (P = 0.24). Of the 389 cases with amphotericin B supplementation, one (0.25%) went on to develop clinically significant infection, while three of 849 (0.35%) cases without amphotericin B developed infection. The sample size was too small to determine the effect of amphotericin B on the incidence of postkeratoplasty fungal infection. The addition of amphotericin B to donor cornea preservation solution resulted in a downward trend of positive donor rim fungal cultures and postkeratoplasty fungal infections, although these differences did not reach statistical significance. Further studies with larger sample sizes are necessary to appropriately determine the impact of amphotericin B supplementation in the storage solution on positive donor rims and postkeratoplasty fungal infections.

Метод лечения рецидивирующего герпетического кератита на основе послойной кератопластики с фемтосекундным сопровождением (серия клинических случаев)

Purpose. To evaluate the clinical efficacy of lamellar keratoplasty in the treatment of recurrent herpetic keratitis with femtosecond laser-assisted corneal surgery. Material and methods. In two clinical cases, lamellar keratoplasty with femtosecond laser-assisted corneal surgery was performed. Preoperative and postoperative visual acuity, refractometry, keratotopography, pachymetry were examined. Conducted courses of conservative treatment: antiviral, anti-inflammatory, desensitization therapy using vaccination «Vitogerpavak». Results. Evidence of the effectiveness of the proposed method was obtained - stabilization and relief of the inflammatory process, increased visual acuity and cosmetic effect. Conclusion. Cases of successful treatment of recurrent herpetic keratitis after intensive courses of conservative treatment followed by lamellar keratoplasty with femtosecond laser-assisted surgery are presented. The use of femtolaser technologies, which allow dosed excision of the affected tissue at a certain depth according to predetermined parameters, contributes to the achievement of high functional results. Lamellar keratoplasty with the maximum possible excision of scar tissue and its replacement with a donor cornea is a minimally invasive effective method to restore the transparency of the cornea after therapeutic treatment of recurrent herpetic keratitis. Key words: keratoplasty, herpetic keratitis, femtosecond laser

Optically Clear Silk Fibroin Films with Tunable Properties for Potential Corneal Tissue Engineering Applications: A Process-Property-Function Relationship Study.

Owing to the shortage of donor corneas and issues associated with conventional corneal transplantation, corneal tissue engineering has emerged as a promising therapeutic alternative. Biocompatibility and other attractive features make silk fibroin a biomaterial of choice for corneal tissue engineering applications. The current study presents three modes of silk fibroin film fabrication by solvent casting with popular solvents, viz. aqueous (aq), formic acid (FA), and hexafluoroisopropanol (HFIP), followed by three standard modes of postfabrication annealing with water vapor, methanol vapor, and steam, and systematic characterization studies including corneal cell culture in vitro. The results indicated that silk fibroin films made from aq, FA, and HFIP solvents had surface roughness (Rq) of 1.39, 0.32, and 0.13, contact angles of 73°, 85°, and 89°, water uptake% of 58, 29, and 27%, swelling ratios of 1.58, 1.3, and 1.28, and water vapor transmission% of 39, 26, and 22%, respectively. The degradation rate was in the order of aq > HF > FA, whereas the tensile strength was in the order of aq < HF < FA. Further, the results of the annealing process indicated notable changes in morpho-topographical, physical, degradation, and tensile properties. However, the films showed no detectable changes in chemical composition and remained optically clear with >90% transmission in the visible range, irrespective of fabrication and postfabrication processing conditions. The films were noncytotoxic against L929 cells and were cytocompatible with rabbit cornea-derived SIRC cells in vitro. The study demonstrated the potential of fine-tuning various properties of silk fibroin films by varying the fabrication and postfabrication processing conditions.

Bioengineered corneal tissue for minimally invasive vision restoration in advanced keratoconus in two clinical cohorts

Visual impairment from corneal stromal disease affects millions worldwide. We describe a cell-free engineered corneal tissue, bioengineered porcine construct, double crosslinked (BPCDX) and a minimally invasive surgical method for its implantation. In a pilot feasibility study in India and Iran (clinicaltrials.gov no. NCT04653922), we implanted BPCDX in 20 advanced keratoconus subjects to reshape the native corneal stroma without removing existing tissue or using sutures. During 24 months of follow-up, no adverse event was observed. We document improvements in corneal thickness (mean increase of 209 ± 18 µm in India, 285 ± 99 µm in Iran), maximum keratometry (mean decrease of 13.9 ± 7.9 D in India and 11.2 ± 8.9 D in Iran) and visual acuity (to a mean contact-lens-corrected acuity of 20/26 in India and spectacle-corrected acuity of 20/58 in Iran). Fourteen of 14 initially blind subjects had a final mean best-corrected vision (spectacle or contact lens) of 20/36 and restored tolerance to contact lens wear. This work demonstrates restoration of vision using an approach that is potentially equally effective, safer, simpler and more broadly available than donor cornea transplantation.

Corneal bioprinting using a high concentration pure collagen I transparent bioink

The use of 3D printing to produce a bioengineered cornea is emerging as an approach to help alleviate the global shortage of donor corneas. Collagen Type 1 (Col-1) is the most abundant collagen in the human cornea. However, Col-I presents challenges as a bioink. It can self-assemble at neutral pH, making phase transitions as required for 3D printing difficult to control. Furthermore, low concentration solutions required for the transparency of printed Col-I lead to weak mechanical properties in its printed structures. In this study, Col-I at high concentrations, was tested with 15 different solutions to identify the composition preventing Col-I self-assembly. A stable Col-I bioink was then developed using riboflavin as a photoinitiator and UV irradiation-induced crosslinking. The mechanical properties and transparency, of the structures produced, were evaluated. The optimised Col-I bioink with corneal stromal cells was tested using a spiral printing method. The printed structure was transparent, and the encapsulated corneal stromal cells had over 90% viability after three weeks of culturing.