Photo-crosslinked GelMA/collagen membrane loaded with lysozyme as an antibacterial corneal implant.

Corneal transplantation is an effective treatment for corneal blindness. However, it brings risk factors for the occurrence of bacterial keratitis, which can affect the repair effect and even lead to transplantation failure. The difficulty in re-epithelialization is also a main problem faced by corneal transplantation. Herein, a collagen-GelMA composite membrane containing lysozyme (CGL) was developed as an antibacterial corneal implant to fill stromal defect and support re-epithelialization. Characterizations of physicochemical properties and in vitro biocompatibility revealed that the composite membranes have proper water content, light transmittance and mechanical strength as well as good biocompatibility. Particularly, the cell adhesion force and adhesion-related genes expression were evaluated and exhibited an improvement after the addition of GelMA. Furthermore, the formed CGL membrane could continuously release lysozyme and exhibited a bactericidal rate of 96% and 64% after 2 h and 72 h, respectively. The results demonstrated that this CGL membrane has promising application in corneal repair.

Use of viscoelastic substance for preventing Descemet's membrane rupture in deep anterior lamellar keratoplasty / Uso de substância viscoelástica na prevenção da ruptura da membrana de Descemet na ceratoplastia lamelar anterior profunda

ABSTRACT Purpose: This study aimed to investigate the effect of using a viscoelastic substance in Descemet's membrane rupture in "double bubble" deep anterior lamellar keratoplasty. Methods: The medical records and videos of surgeries of 40 patients who underwent surgery between January 2014 and July 2015 were retrospectively evaluated. The patients were divided into two groups: 20 patients whose perforation of the posterior stromal wall was performed without administration of any viscoelastic substance (group 1) and 20 patients whose perforation of the posterior stromal wall was performed with administration of viscoelastic substance onto the posterior stroma (group 2). The Descemet's membrane perforation rate was compared between groups. Results: Perforation of the Descemet's membrane was observed in 12 (60.0%) patients in group 1 and only three (15.0%) patients in group 2. This difference was statistically significant (p=0.003). Only one (5%) patient in group 2 had macroperforation during the procedure, and the surgery was converted to penetrating keratoplasty. Eleven (55.0%) patients in group 1 had macroperforation of Descemet's membrane, and surgeries were converted to penetrating keratoplasty. This difference between the groups was statistically significant (p=0.001). Conclusions: Administering a viscoelastic substance onto the posterior stromal side just before puncture is an effective method to decrease the risk of Descemet's membrane perforation in deep anterior lamellar keratoplasty.(AU)

RESUMO Objetivo: Investigar o efeito do uso de uma substância viscoelástica na ruptura da membrana de Descemet em casos de ceratoplastia lamelar anterior profunda em "bolha dupla". Métodos: Foram avaliados retrospectivamente prontuários e vídeos de cirurgias de 40 pacientes operados entre janeiro de 2014 e julho de 2015. Os pacientes foram divididos em dois grupos: 20 pacientes nos quais a parede posterior do estroma foi puncionada sem a colocação de nenhuma substância viscoelástica (grupo 1) e 20 pacientes nos quais uma substância viscoelástica foi aplicada sobre o estroma posterior ao ser puncionada a parede posterior do estroma (grupo 2). A taxa de perfuração da membrana de Descemet foi comparada entre os grupos. Resultados: Observou-se perfuração da membrana de Descemet em 12 casos (60,0%) no grupo 1 e em apenas 3 casos (15,0%) no grupo 2. Essa diferença foi estatisticamente significativa (p=0,003). Apenas um caso (5%) no grupo 2 teve macroperfuração durante o procedimento, sendo a cirurgia então convertida em uma ceratoplastia penetrante. Onze casos (55,0%) no grupo 1 tiveram macroperfuração da membrana de Descemet e essas cirurgias foram convertidas em ceratoplastias penetrantes. Essa diferença entre os grupos foi estatisticamente significativa (p=0,001). Conclusões: A aplicação de substância viscoelástica sobre o lado posterior do estroma logo antes da punção é um método eficaz para diminuir o risco de perfuração da membrana de Descemet na ceratoplastia lamelar anterior profunda.(AU)

The best thickness of cornea graft from SMILE surgery as patch graft in glaucoma drainage implant surgery.

OBJECTIVE: The aim of this study was to determine the best thickness of corneal slices acquired from femtosecond laser surgery-small incision lenticule extraction (SMILE surgery) as patch graft in glaucoma drainage implantation surgery. METHODS: This study is a prospective randomized study. Patients who received glaucoma drainage implantation from September 2016 to November 2018 were observed. The patients were randomly divided into 3 groups. Group A included 102 cases (104 eyes), receiving 1 layer (120-150 µm) of allogeneic lamellar corneal tissue as the graft. Group B included 117 cases (120 eyes), receiving 2 layers of lamellar corneal tissue from one donor. Group C included 109 cases (111 eyes), using 3 layers of lamellar corneal tissue from 2 donors. The intraocular pressure, corneal graft, conjunctiva stromalysis, drainage tube exposure, and drainage plate were observed. RESULTS: Patients were followed up for 6 to 33 months. The intraocular pressure was significantly reduced after surgery in all three groups. Conjunctiva stromalysis and drainage tubes were exposed in 3 eyes (3%) in group A and 1 eye (0.8%, a special case which has nystagmus and the plate was placed infratemporally) in group B, whereas no conjunctiva stromalysis or tube exposure was reported in group C. CONCLUSIONS: The corneal graft acquired from SMILE surgery can effectively prevent drainage tube exposure and give patients a better cosmetic appearance. Two layers of lamellar corneal tissue (240-300 µm) may be the best suitable thickness because it can effectively reduce tube exposure and rejection. In some special cases, 3 layers of lamellar corneal tissue are needed.

3D Printable, Modified Trephine Designs for Consistent Anterior Lamellar Keratectomy Wounds in Rabbits.

PURPOSE: Our goal is to develop a low-cost tool that can be used to create consistent, partial-thickness defects in rabbit and other large animals with minimal surgical training and that can facilitate pre-clinical testing of lamellar and in situ-forming biosynthetic matrix materials for corneal repair. MATERIALS & METHODS: In this study, three modified trephines were designed to create deep corneal wound defects with consistent depth in large animals. The modified trephines incorporated either 3D-printed parts made from photopolymerizable resins, or custom-cut commercially available Teflon sheets. Wound defects were imaged with optical coherence tomography (OCT), and the depth was analyzed based on the OCT images. RESULTS: The results revealed that an inner-stopper guard trephine had the best performance in creating consistent and precise wound defect depth compared to modified vacuum trephine and custom guard vacuum trephine. A 75% ± 10% cut of the cornea was achieved with the inner-stopper guard trephine. The wound defect depth by created by the inner-stopper guard trephine was independent of the corneal thickness or size of the globes. Although the cut depth of the inner-stopper guard trephine differed by the experience-level of its users, the consistency (standard deviation) of the depth was independent of experience. CONCLUSIONS: Our studies provided three cost-efficient animal trephines that can create corneal wounds of consistent depth by lab researchers without extensive training in keratectomy.

Biomimetic bone-like composites as osteo-odonto-keratoprosthesis skirt substitutes.

Osteo-odonto-keratoprostheses, incorporating dental laminate material as an anchoring skirt around a central poly(methyl methacrylate) (PMMA) optic, have been used to replace the cornea for many years. However, there are many intricacies associated with the use of autologous dental laminate material, surgical complexity and skirt erosion. Tissue engineering approaches to bone replacement may offer suitable alternatives in osteo-odonto-keratoprosthesis (OOKP) surgery. In this study, a hydrogel polymer composite was investigated as a synthetic substitute for the OOKP skirt. A novel high strength interpenetrating network (IPN) hydrogel composite with nano-crystalline hydroxyapatite (nHAp) coated poly (lactic-co-glycolic acid) PLGA microspheres was created to mimic the alveo-dental lamina by employing agarose and poly(ethylene glycol) diacrylate (PEGDA) polymers. The incorporation of nHAp coated PLGA microspheres into the hybrid IPN network provide a micro-environment similar to that of skeletal tissues and improve cellular response. Agarose was used as a first network to encapsulate keratocytes/3T3 fibroblasts and PEGDA (6000 Da) was used as a second network with varying concentrations (20 and 40 wt %) to produce a strong and biocompatible scaffold. An increased concentration of either agarose or PEG-DA and incorporation of nHAp coated PLGA microspheres led to an increase in the elastic modulus. The IPN hydrogel combinations supported the adhesion and proliferation of both fibroblast and ocular human keratocyte cell types during in in-vitro testing. The cells endured the encapsulation process into the IPN and remained viable at 1 week post-encapsulation in the presence of nHAp coated microspheres. The material did not induce significant production of inflammatory cytokine IL-6 in comparison to a positive control (p < 0.05) indicating non-inflammatory potential. The nHAp encapsulated composite IPN hydrogels are mechanically strong, cell supportive, non-inflammatory materials supporting their development as OOKP skirt substitutes using a new approach to dental laminate biomimicry in the OOKP skirt material.

Webpalestra COVID-19 (Coronavírus): Bancos de Olhos e Transplantes de Córnea: impactos da pandemia COVID-19 no Brasil

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Factors influencing corneal predescemetic endothelial keratoplasty (PDEK) graft creation: It's all in a bubble.

AIM: To assess the effect of pneumatic (air) and fluidic (transport medium) injection to the type of bubble (I, II or mixed III) and the resultant dissection of corneal endothelial grafts PDEK or DMEK. MATERIALS AND METHODS: All grafts were obtained from Dr Agrawal Hospital's Eye Bank. Air injection was the initial preferred mode of graft harvest. If pneumatic dissection was unsuccessful after 10 tries, fluidic dissection with transport medium was tried. SPSS 23.0 was used to statistically analyse the data. RESULTS: 40 consecutive donor corneas with a mean age of 46.5 and a mean endothelial count of 2980 were analysed. Air dissection lead to the harvest of 27 endothelial grafts and fluid dissection led to the creation of 7 endothelial grafts. Statistically significant difference was found the different bubble types and the type of injection (χ2 chi square=10.02, 0=0.008). CONCLUSION: In young donors pneumatic (air) graft dissection leads to PDEK in a high proportion. This percentage is reduced when transport medium is tried after unsuccessful air injection. Injection of transport medium increases the percentage of grafts harvested but also increases the ratio of Type II and III DMEK grafts created.

[The Boston keratoprosthesis in the management of corneal blindness: Indications and limitations]. / La kératoprothèse de Boston dans la prise en charge de la cécité cornéenne : intérêts et limites.

INTRODUCTION: Keratoprostheses offer a therapeutic alternative to patients with bilateral corneal blindness who cannot undergo corneal allograft. The goal of this work was to evaluate the indications and limitations of Boston keratoprosthesis. MATERIALS AND METHODS: Seven patients underwent unilateral implantation of a Boston type I keratoprosthesis between December 2012 and November 2016. The following data were collected: surgical indication, preoperative visual acuity, postoperative visual acuity at D1, D7, D30, 6 months and 12 months, complications and postoperative treatment. RESULTS: The mean age of implantation was 58.7±23.4 years. The surgical indications included 1 case of congenital bilateral aniridia, 2 cases of chemical burn and 4 graft decompensations after multiple keratoplasties. Preoperative visual acuity was limited to "light perception" in 6 cases and "hand motion" in one case. A gain in visual acuity was observed in 4 patients, which corresponded to a mean gain of 1.53 logMAR at last follow-up. Postoperative visual acuity averaged 2.33 logMAR. All patients experienced an improvement in their quality of life and independence. DISCUSSION: Patients should be selected carefully, favoring patients with a remaining functional potential and able to engage in close postoperative follow-up, in order to ensure the best possible treatment success. CONCLUSION: Boston keratoprosthesis provides improved vision and improved quality of life for patients suffering from bilateral corneal blindness.

12-Year Outcomes of Microkeratome-Assisted Anterior Lamellar Therapeutic Keratoplasty (ALTK) for Disorders of the Anterior Part of the Corneal Stroma - A Comparative Review of Adult and Children.

PURPOSE: To report the visual outcomes and complications of automated anterior lamellar therapeutic keratoplasty (ALTK) in adults and children, and to examine these outcomes as a function of age and etiology. METHODS: A consecutive series of cases undergoing automated ALTK procedures performed at the Jules-Gonin Eye Hospital Lausanne, Switzerland, between June 2003 and January 2015. Only patients with at least 3 months of follow-up were included. RESULTS: There were 53 eyes (24 right) of 51 patients (17 female, 16 juvenile), with a mean age of 34.8 years (range from 3 months to 88 years), analyzed. The mean follow-up was 35 (± 26) months. Diagnosis in the adult (n = 37) vs. juvenile (n = 16) eyes was different: opacity following surgical complication 8 vs. 0, congenital 1 vs. 1, dystrophy 5 vs. 2, infection 12 vs. 5, keratectasia 3 vs. 0, trauma 7 vs. 0, tumor 1 vs. 3, and allergy 0 vs. 5. Visual impairment as a consequence of corneal scarring was the principle indication for surgery in both adult (70%; 26) and juvenile eyes (63%; 10); other indications were choristoma, dermoid, other tumors, astigmatism, and congenital opacity. In adult vs. juvenile eyes, the mean visual acuity (spectacle and contact lenses) was, at last visit, 0.55 vs. 0.45 LogMAR (p = 0.78), with a range of 100% to hand movements. Failure occurred in 6 (16%) vs. 2 (13%) cases and complications were observed in 14 (38%) vs. 9 (56%) cases, however, more surgical revision was required in juvenile eyes, 4 (11%) vs. 7 (43%) (p = 0.01, Fisher test). CONCLUSIONS: This study shows that anterior lamellar keratoplasty in children retains good visual function when combined with adequate amblyopic therapy. However, the rate of complications is higher in juveniles and requires more intensive interdisciplinary follow-up.

'Blue bubble' technique: an ab interno approach for Descemet separation in deep anterior lamellar keratoplasty using trypan blue stained viscoelastic device.

BACKGROUND: In this study, we examined a novel variant of 'big-bubble' deep anterior lamellar keratoplasty using trypan-blue-stained viscoelastic device for the creation of a pre-descemetic bubble. METHODS: Ten corneoscleral rims were mounted on an artificial anterior chamber (AC). The AC was filled with air through a limbal paracentesis. A Melles' triangulated spatula was inserted through the paracentesis, with its tip penetrating the AC, was then slightly retracted and pushed into the deep stroma above the roof of the paracentesis. A mixture of trypan blue and viscoelastic device (Healon, Abbott Medical Optics, Abbott Park, Illinois) was injected into this intra-stromal pocket using a 27-G cannula to create a pre-descemetic separation bubble. Bubble type and visualization of dyed viscoelastic device were noted. The method was later employed in three cases. RESULTS: In all 10 corneoscleral rims, the technique successfully created a visible pre-descemetic (type 1) bubble that could be expanded up to the predicted diameter of trephination. Subsequent trephination and the removal of corneal stroma were uneventful. In two out of four clinical cases, a type 1 bubble was created, while in two others, visco-dissection failed and dyed viscoelastic was seen in the AC. CONCLUSIONS: The presented technique holds promise of being a relatively easy to perform, predictable and well-controlled alternative for achieving a type 1 bubble during deep anterior lamellar keratoplasty surgery. The trypan-blue-stained viscoelastic device facilitates proper visualization and control of the separation bubble and assists in identifying the penetrance to the separation bubble prior to removal of the stromal cap.

[Critical endothelial procedures during posterior lamellar graft preparation and transplantation]. / Endothelkritische Prozeduren während der Herstellung und Transplantation posteriorer lamellärer Hornhauttransplantate.

BACKGROUND: In view of the very low proliferation rate and functional importance of the corneal endothelium in maintaining corneal transparency, safeguarding the integrity of this monolayer plays a central role in posterior lamellar corneal transplantation. Several critical endothelial procedural stages are necessary to carry out such a transplantation. OBJECTIVE: This article presents various preparatory and operative approaches for carrying out the necessary and critical stages within the framework of posterior lamellar corneal transplantation and concentrates on the question of optimization. METHODS: A review of our own studies and studies of other groups is presented. RESULTS: For the performance of critical endothelial procedural steps, a variety of approaches are available. These range from preparation and insertion of the transplant, through the manipulation during centralization up to the effects of postoperative air or gas bubble tamponade. CONCLUSION: Because endothelial damage can permanently impair the integrity of lamellar transplants, a minimal handling and no touch policy should be strived for in all critical procedures. Long-term data on the follow-up course will show which of the procedures favored by various authors lead to the best postoperative results.

[Results of residual ametropia correction using CIRCLE technology after femtosecond laser SMILE surgery]. / Rezul'taty ustraneniya ostatochnoi ametropii metodom CIRCLE posle lazernykh operatsii po tekhnologii SMILE.

AIM: to evaluate functional results of reoperation performed according to the CIRCLE technology and using the VisuMax femtosecond laser and MEL-80 excimer laser in cases of regression of the refractive effect after SMILE surgery. MATERIAL AND METHODS: We studied a group of post-SMILE patients. In those, who showed regression of the refractive effect at 1 year, reoperation was performed according to the CIRCLE technology and using the VisuMax femtosecond laser. The corneal flap was separated from the stromal bed and turned aside. Excimer laser ablation of the stromal bed was performed with the MEL 80 machine. The corneal flap was then placed back and rinsed from both sides. Uncorrected (UCVA) and corrected (BCVA) visual acuity as well as spherical equivalent (SE) were estimated before reoperation, on day 1, and at 1 month. RESULTS: After reoperation, BCVA and UCVA improved. Patient refraction became close to emmetropia. Specifically, UCVA was 0.23±0.18 at baseline (i.e. 1 year after SMILE) and 0.93±0.11 after the CIRCLE procedure (p<0.05). The absolute value of SE was 1.86±1.15 D and 0±0 D before and after CIRCLE, respectively (p<0.05). BCVA change was not statistically significant - from 0.95±0.1 to 0.93±0.11 (p>0.05). CONCLUSION: Reoperation performed according to the CIRCLE technology and using the VisuMax femtosecond laser and MEL-80 excimer laser provides an increase in visual acuity in case of post-SMILE regression of the refractive effect.

Obtención de tejido corneal para queratoplastia / Obtaining corneal tissue for keratoplasty

El trasplante de córnea es el más frecuente entre todos los trasplantes a nivel mundial. Al año se realizan aproximadamente unos 184.000 trasplantes de córneas. En España la detección y evaluación del potencial donante depende en muchas ocasiones de la tarea que realizan los coordinadores de trasplantes y del modelo de éxito en España para la donación de órganos y tejidos. Desde el momento de la detección de un posible donante hasta que se pueda realizar la extracción hay una exhaustiva evaluación del donante que incluye una revisión sistemática de la historia médico-social, examen físico, entrevista familiar para conocer la voluntad de donación del fallecido y análisis serológicos. La córnea, a diferencia de otros tejidos, tiene unos criterios de aceptación más amplios del donante que se describirán durante el capítulo. El objetivo de todos los estudios que se realizan durante todo el proceso es lograr una donación segura, para el donante y para el receptor, y un trasplante eficaz, intentando en todo momento ayudar a los que lo necesitan, para evitar transmitir enfermedades a través del trasplante. Además, se realiza una extracción protocolizada del tejido para que llegue en las mejores condiciones al banco de tejidos. Este capítulo analizará los criterios de selección del donante de córneas y su extracción, teniendo en cuenta también las nuevas técnicas de implante

Cornea transplant is the most common tissue transplant in the world. In Spain, tissue donation activities depend upon transplant coordinator activities and the well-known Spanish model for organ and tissue donation. Tissue donor detection system and tissue donor evaluation is performed mainly by transplant coordinators using the Spanish model on donation. The evaluation of a potential tissue donor from detection until recovery is based on an exhaustive review of the medical and social history, physical examination, family interview to determine will of the deceased, and a laboratory screening test. Corneal acceptance criteria for transplantation have a wider spectrum than other tissues, as donors with active malignancies and infections are accepted for kearatoplasty in most tissue banks. Corneal evaluation during the whole process is performed to ensure the safety of the donor and the recipient, as well as an effective transplant. Last step before processing, corneal recovery, must be performed under standard operating procedures and in a correct environment

Ultrastructural analysis of the decellularized cornea after interlamellar keratoplasty and microkeratome-assisted anterior lamellar keratoplasty in a rabbit model.

The decellularized cornea has received considerable attention for use as an artificial cornea. The decellularized cornea is free from cellular components and other immunogens, but maintains the integrity of the extracellular matrix. However, the ultrastructure of the decellularized cornea has yet to be demonstrated in detail. We investigated the influence of high hydrostatic pressure (HHP) on the decellularization of the corneal ultrastructure and its involvement in transparency, and assessed the in vivo behaviour of the decellularized cornea using two animal transplantation models, in relation to remodelling of collagen fibrils. Decellularized corneas were prepared by the HHP method. The decellularized corneas were executed by haematoxylin and eosin and Masson's trichrome staining to demonstrate the complete removal of corneal cells. Transmission electron microscopy revealed that the ultrastructure of the decellularized cornea prepared by the HHP method was better maintained than that of the decellularized cornea prepared by the detergent method. The decellularized cornea after interlamellar keratoplasty and microkeratome-assisted anterior lamellar keratoplasty using a rabbit model was stable and remained transparent without ultrastructural alterations. We conclude that the superior properties of the decellularized cornea prepared by the HHP method were attributed to the preservation of the corneal ultrastructure.

[Non-antagonistic influence of Krumeich's intrastromal corneal ring in an experimental tissue culture system]. / Nichtantagonistische Wirkungsweise des intrastromalen Krumeich-Kornearings in einem experimentellen Gewebekultursystem.

BACKGROUND: Intrastromal insertion of Krumeich's corneal ring between graft and residual host corneal tissue appears to impair preripheral, superficial and superfluous vascularization of donor corneal tissue. OBJECTIVES: The purpose of this study was to investigate the cytotoxic effects of Krumeich's ring using tissue cultures composed of primary human dermal microvascular endothelial cells from adult donors (HMVEC). MATERIALS AND METHODS: Soluble growth medium extracts of the individual components of Krumeich's ring alloy were prepared and HMVEC were exposed to these extracts in triplicate for 1 day followed by investigation with 3­(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays. Furthermore, HMVEC were cultured for 5 days on either Krumeich's ring or polypropylene (PP) discs coated with individual components of the Krumeich's ring alloy followed by double vital staining with fluorescein diacetate (FDA) and propidium iodide (PI). RESULTS: The MTT assays revealed that higher doses of the extracts appeared to reduce the viability of HMVEC, while highly diluted extracts of molybdenum (Mo) powder appeared to increase the metabolic activity of HMVEC. The FDA-PI staining showed only a few live HMVEC on either cobalt (Co) or Mo-coated PP discs, compared to the respective titanium (Ti) and chromium (Cr) counterparts. Viable HMVEC appeared to attach to Krumeich's ring after a 5­day incubation period. CONCLUSION: The results confirm that Krumeich's ring does not exert measurable cytotoxic effects in our chosen assay system. High dilutions of medium-soluble Mo powder extracts appear to increase the metabolic activity of HMVEC.

Coloured cornea replacements with anti-infective properties: expanding the safe use of silver nanoparticles in regenerative medicine.

Despite the broad anti-microbial and anti-inflammatory properties of silver nanoparticles (AgNPs), their use in bioengineered corneal replacements or bandage contact lenses has been hindered due to their intense yellow coloration. In this communication, we report the development of a new strategy to pre-stabilize and incorporate AgNPs with different colours into collagen matrices for fabrication of corneal implants and lenses, and assessed their in vitro and in vivo activity.

[Boston-keratoprosthesis : Preliminary experiences in 13 high-risk eyes from the Department of Ophthalmology of the University of Cologne]. / Boston-Keratoprothese : Erste Erfahrungen bei 13 Hochrisikoaugen aus der Kölner Universitätsaugenklinik.

BACKGROUND: Corneal transplantation in high-risk eyes remains a challenge. The Boston keratoprosthesis (B-KPro) is a final option for patients with end-stage corneal disease and a poor prognosis with conventional penetrating keratoplasty. In this article the results of the first 13 eyes that received a B-KPro type I at the Department of Ophthalmology, University of Cologne, Germany are reported and the usefulness of postoperative slit-lamp optical coherence tomography (SL-OCT) for control purposes is evaluated. MATERIAL AND METHODS: All recipients of a B-KPro type I between September 2013 and May 2015 were included in the study. The feasibility of the operation, clinical outcomes, complications and revision surgery were investigated. The visualization of wound healing by SL-OCT was analyzed. RESULTS: The age of the patients ranged from 26 to 92 years (mean 57.3 ± 20.9 years). In all 13 eyes from 12 patients (6 males and 6 females) dense corneal opacification with vascularization and sometimes also conjunctivalization was present. Preoperative visual acuity was reduced and ranged from mere light perception up to a maximum of 1/35 eye chart. All 13 eyes could be supplied with a B-KPro type I without any intraoperative complications, in 6 eyes no significant postoperative complications occurred, whereas in 7 eyes various additional surgical interventions were required and 1 B-KPro could not be preserved. Postoperative visual acuity ranged from light perception to 20/32 and was significantly improved in 85 % of the treated eyes. The use of SL-OCT reproducibly allowed the postoperative assessment of stromal thinning. CONCLUSION: The B-KPro provides the possibility of visual rehabilitation in high-risk eyes that could never be achieved without artificial cornea replacement. Despite higher complication rates this technique represents a significant progress in the surgical treatment of complex corneal pathologies. Regular and intensive postoperative controls are necessary to achieve good long-term results.

Application of retinoic acid improves form and function of tissue engineered corneal construct.

Retinoic acid has recently been shown to control the phenotype and extracellular matrix composition of corneal stromal cells cultured in vitro as monolayers. This study set out to investigate the effects of retinoic acid on human corneal keratocytes within a 3D environment. Human corneal keratocytes were encapsulated in collagen gels, which were subsequently compressed under load, and cultured in serum-free media supplemented with 10 µM retinoic acid or DMSO vehicle for 30 days. Cell proliferation was quantified on selected days, while the expression of several important keratocytes markers was evaluated at day 30 using RT-PCR and immunoblotting. The weight and size of the collagen constructs were measured before and after hydration and contraction analyses. Retinoic acid enhanced keratocyte proliferation until day 30, whereas cells in control culture conditions showed reduced numbers after day 21. Both gene and protein expressions of keratocyte-characteristic proteoglycans (keratocan, lumican and decorin), corneal crystallins and collagen type I and V were significantly increased following retinoic acid supplementation. Retinoic acid also significantly reduced the expression of matrix metalloproteases 1, 3 and 9 while not increasing α-smooth muscle actin and fibronectin expression. Furthermore, these effects were also correlated with the ability of retinoic acid to significantly inhibit the contractility of keratocytes while allowing the build-up of corneal stromal extracellular matrix within the 3D constructs. Thus, retinoic acid supplementation represents a promising strategy to improve the phenotype of 3D-cultured keratocytes, and their usefulness as a model of corneal stroma for corneal biology and regenerative medicine applications.

[Justification of the use of particular biopolymers as matrix materials for artificial corneas].

This article reviews distinctive features, advantages, and drawbacks of different biopolymers used to construct the 3D matrices of artificial corneas. Modern requirements for matrices are provided.

Collagen based film with well epithelial and stromal regeneration as corneal repair materials: Improving mechanical property by crosslinking with citric acid.

Corneal disease can lead to vision loss. It has become the second greatest cause of blindness in the world, and keratoplasty is considered as an effective treatment method. This paper presents the crosslinked collagen (Col)-citric acid (CA) films developed by making use of 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) and N-hydroxysuccinimide (NHS). The results showed that the Col-CA films had necessary optical performance, water content. The collagenase resistance of CA crosslinked films was superior to that of EDC crosslinked films. And CA5 film (Col:CA:EDC:NHS=60:3:10:10) had the best mechanical properties. Cell experiments showed that CA5 film was non-cytotoxic and human corneal epithelial cells could proliferate well on the films. Lamellar keratoplasty showed that the CA5 film could be sutured in the rabbit eyes and was epithelialized completely in about 10 days, and the transparency was restored quickly in 30±5 days. No inflammation and corneal neovascularization were observed at 6 months. Corneal stroma had been repaired; stromal cells and neo-stroma could be seen in the area of operation from the hematoxylin-eosin stained histologic sections and anterior segment optical coherence tomography images. These results indicated that Col-CA films were highly promising biomaterials that could be used in corneal tissue engineering and a variety of other tissue engineering applications.