Retrocorneal Membrane Research Articles

Retrocorneal membrane interception enhanced penetrating canaloplasty for patients with open angle glaucoma secondary to ICE syndrome.

To assess the efficacy and safety of retrocorneal membrane interception (RMI)-enhanced penetrating canaloplasty in glaucoma secondary to iridocorneal endothelial syndrome (GS-ICE) with open angle or small peripheral anterior synechiae (PAS). A series of 13 patients (13 eyes) with GS-ICE and uncontrolled intraocular pressure (IOP) underwent RMI-enhanced penetrating canaloplasty from March 2019 to October 2020. The patients were followed up at one week, 1month, 3months, 6months, and 12months, postoperatively. The main outcome measure was surgical success, which was defined as an IOP ≤ 18mmHg or ≤ 21mmHg, with glaucoma medications (qualified success), or without glaucoma medications (complete success). Secondary outcome measures were IOP, medication usage, and surgical complications. Among the 13 GS-ICE eyes, 12 (92%) achieved qualified success and 10 (77%) achieved complete success at 12months postoperatively. The mean IOP decreased from 36.41 ± 8.92mmHg on 3.0 (IQR 0.5) medications before surgery to 17.09 ± 7.71mmHg (p = 0.0004) on 0.0 (IQR 0.5) medications (p = 0.0004) at 12months after surgery. Transient hypotony (38%) and hyphema (38%) were the most common complications. RMI-enhanced penetrating canaloplasty appears effective and safe in treating GS-ICE with open angle or small PAS up to one year of follow up.

Retrocorneal fibrous membrane after phacoemulsification in an eye with pseudoexfoliative glaucoma

ObjectifPrésenter un cas clinique d'apparition d'une membrane fibreuse rétrocornéenne et de décompensation cornéenne à la suite d'une phacoémulsification non compliquée dans un œil atteint de glaucome pseudo-exfoliatif. Nous présentons en outre une revue de synthèse de la littérature médicale sur les causes modernes de l'apparition d'une membrane fibreuse rétrocornéenne. MéthodeCas clinique et revue de la littérature médicale. RésultatsIl s'agit d'une femme de 83 ans n'ayant qu'un seul œil et présentant une décompensation cornéenne 1 an après l'extraction non compliquée d'une cataracte par phacoémulsification. La patiente, porteuse d'antécédents de glaucome pseudo-exfoliatif, avait subi 3 ans plus tôt une trabéculoplastie sélective au laser à 3 reprises dans le même œil. Compte tenu de l’œdème cornéen qui s'en est suivi, on a procédé à une kératoplastie endothéliale de la membrane de Descemet, laquelle a révélé la présence d'une membrane fibreuse rétrocornéenne. Le pelage chirurgical de la membrane s'est révélé difficile et a produit une hémorragie intraoculaire peropératoire de même qu'une légère iridodialyse en raison de l'extension de la membrane au-delà de l'angle et de l'iris. Après l'intervention, l’état de la cornée s'est rétabli, et la vision s'est améliorée de manière significative. À terme, la vision était toutefois limitée par l'atteinte maculaire. L'examen anatomopathologique a mis au jour la présence d'une membrane de Descemet à laquelle s'annexait une membrane fibrocellulaire. L'immunocoloration a permis de déceler la présence d'actine des muscles lisses dans celle-ci, signe évocateur d'une membrane rétrocornéenne. ConclusionsLes membranes fibreuses rétrocornéennes apparaissent le plus souvent après une greffe de cornée, de sorte que le retrait chirurgical risque d’être difficile. Nous présentons ici le premier cas de membrane fibreuse rétrocornéenne objectivée par examen anatomopathologique qui soit apparue au décours d'une chirurgie non compliquée de la cataracte par phacoémulsification et d'une trabéculoplastie sélective au laser.

Comparison of Graft Survival Between Full-Thickness and Lamellar Pig-to-Monkey Corneal Xenotransplantation from the Same Genetically Engineered Pig Model with Minimal Immunosuppression

The graft survival rate of full-thickness corneal xenotransplantation (XTP) with minimal immunosuppression in genetically engineered pigs is unknown, whereas lamellar corneal XTP shows satisfactory results. We compared graft survival between full-thickness and lamellar transplantations in the same genetically engineered pig. Six pig-to-monkey corneal transplantations were performed on 3 transgenic pigs. Two corneas harvested from 1 pig were transplanted into 2 monkeys using full-thickness and lamellar corneal xenotransplantation. The transgenic donor pigs used were α1,3-galactosyltransferase gene-knockout+membrane cofactor protein (GTKO+CD46) in one recipient and GTKO+CD46+ thrombomodulin (TBM) in the other. The graft survival time for GTKO+CD46 XTP was 28 days. With the addition of TBM, the survival differences between lamellar and full-thickness XTP were 98 days versus 14 days and >463 days (ongoing) versus 21 days, respectively. An excessive number of inflammatory cells was observed in failed grafts, but none were in the recipient's stromal bed. Unlike full-thickness corneal XTP, lamellar xenocorneal transplantation does not exhibit surgical complications, such as retrocorneal membrane or anterior synechia. The graft survival of lamellar XTP in this study was not as good as in our previous experiments, although the survival period was superior to that of full-thickness XTP. The difference in graft survival based on transgenic type is not definitive. Further studies using transgenic pigs and minimal immunosuppression need to focus on improving graft survival of lamellar XTP and using a larger sample size to determine the potential of full-thickness corneal XTP.

Immunohistochemical Findings in Retrocorneal Membranes of Eyes with Corneal Decompensation after Complicated Intraocular Surgery.

Retrocorneal membranes (RCMs) may result from epithelial ingrowth, stromal keratocytic downgrowth, fibrous metaplasia of the corneal endothelium, or a combination of these processes. In an institutional case series, the clinical history, ocular findings, and immunohistochemical staining results of RCMs were analysed in patients with unilateral corneal decompensation after complicated intraocular surgery. Between January 2021 and September 2022, six retrocorneal membranes were excised during Descemet's stripping automated endothelial keratoplasty (DSAEK) and Descemet membrane endothelial keratoplasty (DMEK) procedures and classified after screening with haematoxylin and eosin, periodic acid-Schiff, elastic van Gieson staining, and immunohistochemical screening with cytokeratin 7 (CK7), anti-cytokeratin (CAM5.2 and AE1/3), cell surface glycoprotein CD34, smooth muscle actin (α-SMA), and vimentin. On the basis of the immunohistochemical screening, the majority of excised RCMs (5 of 6) could histopathologically be classified as membranes originating from fibrous metaplasia of the corneal endothelium. All these RCMs were positive for CK7, α-SMA, and vimentin and negative for CAM5.2 and CD34. In one patient, an RCM had developed after 18 days of corneal contact to a free-floating dexamethasone implant in the anterior chamber and was classified as originating from stromal keratocyte downgrowth (α-SMA- and vimentin-positive, all others negative). All eyes in this series had a previous history of complicated cataract surgery, partially with subsequent intraocular lens exchange. No eyes after previous penetrating keratoplasty were in this series. In this series of eyes with previous complicated intraocular interventions (in most cases cataract surgery and revisions), the dominating RCM belonged to the type originating from fibrous metaplasia of the corneal endothelium.

Surgical outcomes of complicated cataract with pediatric trematode granulomatous uveitis.

To describe the clinical characteristics and surgical outcomes of complicated cataract with pediatric trematodal granulomatous uveitis (TGU). Patients of cataract with TGU in the membranous (inactive) stage underwent cataract surgery with intraocular lens (IOL) implantation. Preoperative history and ophthalmic examination were conducted for all cases, whereas Schimphlug imaging and corneal topography were done for some patients. Postoperative follow up was done on the 1st, 2nd, and 5th postoperative days after surgery. Then, it was done at least at one, three, and six months postoperatively. Intraoperative and postoperative complications and the methods of their management were reported. Twelve eyes of 12 male children were included in this study ranging from 8 to 16y. The mean best corrected Snellen visual acuity (BCVA) was significantly improved from 0.09±0.06 preoperatively to 0.37±0.11 at the final visit 6mo postoperatively (P<0.001). Schimphlug imaging and corneal topography showed flattening of the anterior surface of the inferior cornea. Intraoperative difficulties and complications included the poor dilatability of the drown down pupil, strong posterior synechia between the anterior lens capsule and the iris at the site of the inferior retrocorneal vascularized membrane and hyphema. All cases underwent primary hydrophobic IOL implantation. Surgery for this type of cataract is relatively safe and effective. It is associated with some specific difficulties and complications that should be considered during surgery and follow up.

Full- versus partial-thickness sutures: experimental models of corneal injury repair.

To evaluate the performance of full-thickness (FT) versus partial-thickness (PT) sutures in a full-thickness corneal wound in an animal model. This is a prospective, experimental, comparative, longitudinal study. A 6-mm linear, full-thickness corneal incision was performed on the right eye of eight domestic pigs. Eyes were randomly assigned for repair with interrupted PT (80-90% depth) sutures or FT 10-0 nylon sutures. Anterior segment OCT, corneal pachymetry and clinical photographs were obtained 1, 4 and 8weeks postoperatively. Corneal thickness, depth of suture placement, perilesional edema, coaptation of wound edges and complications were noted. Histopathologic examination was performed at 8weeks. 100% of the eyes with FT sutures developed a linear, less opaque scar. 100% of the eyes with PT developed a dense, opaque stromal scar (p = 0.02). Vascularization of the cornea was present in 75% of PT group and 25% in the FT group (p = 0.50). As the corneas healed, there was a marked trend toward thicker corneas in the PT group versus FT group with a median difference of - 63µm at week 1 [median 788µm vs. 725µm, (p = 0.11)], - 38µm at week 4, (724µm vs. 686µm, (p = 0.63)) and - 47µm median difference at week 8 with (670µm vs. 623µm, (p = 0.06)). Histopathology showed disorganization of the collagen fibers and the formation of a retrocorneal fibrous membrane in the PT group. The FT group presented less corneal edema at week 8 with a more linear and less opaque scar. Histopathology showed a better-organized scar and endothelialization without the formation of a fibrous membrane.

Clinicopathologic Correlations of Retrocorneal Membranes Associated With Endothelial Corneal Graft Failure

To provide clinicopathologic correlations for retrocorneal membranes associated with Descemet stripping automated endothelial keratoplasty (DSAEK) failure. Retrospective case series. The specimens and medical records of the patients diagnosed with clinically significant retrocorneal membranes associated with DSAEK failure at the Bascom Palmer Eye Institute or the University of Miami Veterans Hospital between October 2015 and March 2020 were reviewed for demographics, clinical presentation, comorbidities, and surgeries performed. Histopathologic analysis was performed on hematoxylin-eosin and periodic acid-Schiff sections. Immunohistochemical studies were performed for smooth muscle actin (α-SMA), pancytokeratin, and CK7. Immunofluorescence was performed for vimentin, N-cadherin, ROCK1, RhoA, ZEB1, and Snail. A total of 7 patients (3 male and 4 female) were identified to have a clinically significant retrocorneal membranes at the time of graft failure. The average age at the time of first DSAEK was 70 years (range: 55-85 years). All patients were pseudophakic and had a glaucoma drainage device in place; 1 had a history of failed DSAEK. Ranging from 0 to 47months after surgery, a variably thick retrocorneal fibrous membrane was observed, eventually leading to graft failure. Four patients underwent subsequent penetrating keratoplasty and 3 underwent repeat DSAEK. On histopathologic evaluation, a pigmented fibrocellular tissue was identified along the posterior margin of the corneas and DSAEK buttons in all cases. Further characterization with immunohistochemistry and immunofluorescence demonstrated membranes to be negative for pancytokeratin and positive for α-SMA, vimentin, CK7, N-cadherin, ZEB1, Snail, ROCK1, and RhoA. Fibrocellular retrocorneal membrane proliferation may be associated with DSAEK failure in patients with previous glaucoma drainage device surgery. Our results demonstrate myofibroblastic differentiation and a lack of epithelial differentiation. Positivity for markers of an endothelial-to-mesenchymal transition indicates possible endothelial origin and could be the hallmark for future targeted pharmacotherapy.

Role of Microscope-Intraoperative Optical Coherence Tomography in Pediatric Keratoplasty: AComparative Study

We evaluate the role of microscope-integrated intraoperative optical coherence tomography (i-OCT) in pediatric keratoplasty. Combined prospective and retrospective, comparative, interventional study conducted at the Dr Rajendra Prasad Center for Ophthalmic Sciences in New Dehli, India. Seventy-five children ≤16 years of age undergoing planned keratoplasty were divided into 2 groups and compared regarding intraoperative course and postoperative outcome. In group 1 (prospective group, n= 56), preoperative anterior segment visualization was performed clinically, with ultrasound biomicroscopy (UBM) and i-OCT and keratoplasty was commenced under i-OCT microscope. In group 2 (retrospective group, n= 19), a conventional microscope was used during keratoplasty. In group 1, i-OCT, UBM, and clinical examination detected retrocorneal membrane in 10%, 7.5%, and 5% (P= .005), iris adhesions in 62.5%, 57.5%, and 20% (P= .02), iris stump in aniridia 15%, 10%, and 0% (P= .001), shallow central anterior chamber in 22.5%, 22.5%, and 7.5% (P= .003), and shallow peripheral anterior chamber in 65%, 60%, and 17.5% (P= .004) of children, respectively. The use of i-OCT affected intraoperative surgeon decision making in 45% and 33% of cases of anterior and posterior lamellar keratoplasty, respectively. During penetrating keratoplasty, concomitant intraoperative procedures were higher in group 1 than in group 2, namely synechiolysis (19/40 vs 2/15; P= .1), pupilloplasty (4/40 vs 0/15; P= .02), lens extraction (4/40 vs 1/15; P= .5), and anterior vitrectomy (2/40 vs 1/15; P= .4). Postoperative secondary interventions were lower (P= .04) in group 1 (48.21% vs 94.74%). Anterior segment imaging with i-OCT and UBM immediately before surgery improves the surgical planning of children with corneal opacities. In addition, the use of i-OCT refines intraoperative steps, thereby optimizing the postoperative outcome of pediatric keratoplasty.

ZEB1 Mediates Fibrosis in Corneal Endothelial Mesenchymal Transition Through SP1 and SP3.

PurposeZEB1 is induced during endothelial-mesenchymal transition (EnMT) in the cornea. Induction of SP1 and SP3 by ZEB1 along with identification of putative SP1 and SP3 binding sites in promoters of EnMT-associated gene lead us to investigate their roles in retrocorneal membrane formation in the corneal endothelium.MethodsExpressions of SP1, SP3, and EnMT associated genes were analyzed by immunoblotting and semiquantitative reverse transcription polymerase chain reaction. Accell SMARTpool siRNAs targeting ZEB1, SP1, and SP3 were used for gene knockdown. SP1 and SP3 binding to promoters of EnMT associated genes was investigated by chromatin immunoprecipitation assay. Corneal endothelium in mice was surgically injured in vivo under direct visualization.ResultsTransient Fibroblast Growth Factor 2 stimulation increased the expression of both SP1 and SP3 in the human corneal endothelium ex vivo. ZEB1 siRNA knockdown inhibited FGF2-induced SP1 mRNA and protein but not the expression of SP3. FGF2-induced expression of EnMT-related genes, such as fibronectin, vimentin, and type I collagen, was reduced by both SP1 and SP3 siRNA knockdown, with inhibition of SP1 having a greater inhibitory effect than SP3. Additionally, although SP1 and SP3 proteins were found to bind together, SP1 and SP3 could bind to the same promoter binding sites of EnMT-related genes in the absence of the other. Moreover, siRNA knockdown of Zeb1 inhibited injury-dependent RCM formation in mouse corneal endothelium in vivo.ConclusionsZeb1, through SP1 and SP3, plays a central role in mesenchymal transition induced fibrosis in the corneal endothelium and suggests that Zeb1 could be targeted to inhibit anterior segment fibrosis.

TGF-β1-activated type 2 dendritic cells promote wound healing and induce fibroblasts to express tenascin c following corneal full-thickness hydrogel transplantation.

We showed previously that 1-ethyl-3-(3-dimethylamino-propyl)-carbodiimide hydrochloride (EDC) cross-linked recombinant human collagen III hydrogels promoted stable regeneration of the human cornea (continued nerve and stromal cell repopulation) for over 4years. However, as EDC cross linking kinetics were difficult to control, we additionally tested a sterically bulky carbodiimide. Here, we compared the effects of two carbodiimide cross linkers-bulky, aromatic N-cyclohexyl-N0-(2-morpholinoethyl)-carbodiimide (CMC), and nonbulky EDC-in a mouse corneal graft model. Murine corneas undergoing full-thickness implantation with these gels became opaque due to dense retro-corneal membranes (RCM). Corneal epithelial cytokeratin 12 and alpha smooth muscle actin indicative of functional tissue regeneration and wound contraction were observed in RCM surrounding both hydrogel types. However, quantitatively different levels of infiltrating CD11c+ dendritic cells (DC) were found, suggesting a hydrogel-specific innate immune response. More DC infiltrated the stroma surrounding EDC-N-hydroxysuccinimide (NHS) hydrogels concurrently with higher fibrosis-associated tenascin c expression. The opposite was true for CMC-NHS gels that had previously been shown to be more tolerising to DC. In vitro studies showed that DC cultured with transforming growth factor β1 (TGF-β1) induced fibroblasts to secrete more tenascin c than those cultured with lipopolysaccharide and this effect was blocked by TGF-β1 neutralisation. Furthermore, tenascin c staining was found in 40- to 50μm long membrane nanotubes formed in fibroblast/DC cocultures. We suggest that TGF-β1 alternatively activated (tolerising) DC regulate fibroblast-mediated tenascin c secretion, possibly via local production of TGF-β1 in early wound contraction, and that this is indirectly modulated by different hydrogel chemistries.

Десцеметопексия под контролем интраоперационной оптической когерентной томографии при отслойке задней пограничной мембраны роговицы после хирургии катаракты

Десцеметопексия под контролем интраоперационной оптической когерентной томографии при отслойке задней пограничной мембраны роговицы после хирургии катаракты

Histopathology of a retrocorneal membrane after Descemet membrane endothelial keratoplasty: a case report

BackgroundWe report the first histopathologically proven occurrence of a retrocorneal membrane after Descemet’s membrane endothelial keratoplasty.Case presentationA white Caucasian 76-year-old woman received penetrating keratoplasty on her right eye 2 years after Descemet’s membrane endothelial keratoplasty surgery with combined cataract extraction and intraocular lens implantation for Fuchs’ endothelial corneal dystrophy due to an allograft rejection with ensuing graft failure.Her preoperative vision was counting fingers (20/2000) caused by immunological debris, corneal edema, and secondary membrane formation. Her postoperative vision at 3 months was 20/125.The histopathological evaluation showed a membranous structure overlying the denuded Descemet membrane.ConclusionsWe report a case of a histopathologically proven retrocorneal membrane after Descemet’s membrane endothelial keratoplasty surgery.

Fibroblast growth factor 2 induces proliferation and fibrosis via SNAI1-mediated activation of CDK2 and ZEB1 in corneal endothelium

Investigating stimulation of endogenous wound healing in corneal endothelial cells (CECs) may help address the global shortage of donor corneas by decreasing the number of transplants performed for blindness because of endothelial dysfunction. We previously reported that IL-1β stimulation leads to fibroblast growth factor (FGF2) expression, enhancing migration and proliferation of mammalian CECs. However, FGF2 also promotes the endothelial-mesenchymal transition, which can lead to retrocorneal membrane formation and blindness. This prompted us to investigate downstream FGF2 signaling targets that could be manipulated to prevent retrocorneal membrane formation. FGF2 stimulation altered cell morphology and induced expression of mesenchymal transition marker genes such as snail family transcriptional repressor 1 (SNAI1), SNAI2, zinc finger E-box-binding homeobox 1 (ZEB1), and ZEB2 This, in turn, induced expression of fibronectin, vimentin, and type I collagen, and suppressed E-cadherin in CECs in vitro and ex vivo siRNA-mediated SNAI1 knockdown revealed that SNAI1 induces ZEB1 expression, in turn inducing expression of type I collagen, the major component of retrocorneal membranes, and of cyclin-dependent kinase 2 (CDK2) and cyclin E1, promoting cell proliferation. siRNA-mediated knockdown of SNAI1 or ZEB1, but not of CDK2, inhibited FGF2-dependent expression of fibronectin, vimentin, and type I collagen and of suppression of E-cadherin expression. We conclude that SNAI1 is a key regulator of FGF2-dependent mesenchymal transition in human ex vivo corneal endothelium, with ZEB1 regulating type I collagen expression and CDK2 regulating cell proliferation. These results suggest that SNAI1 promotes fibrosis and cell proliferation in human corneal endothelium through ZEB1 and CDK2.

Mesenchymal stem cell therapy for retro-corneal membrane - A clinical challenge in full-thickness transplantation of biosynthetic corneal equivalents.

The manuscript addresses the potential value of bone marrow-derived mesenchymal stem cell therapy for retro-corneal membrane (RCM) formation in full-thickness transplantation of biosynthetic corneal equivalents. This work reports the pathophysiological changes in the anterior chamber of the mouse eye following full-thickness recombinant human cross-linked collagen-based hydrogel implants in which persistent fibrin promotes the development of dense RCM. Furthermore, pre-treatment with mesenchymal stem cells reduces RCM formation and enhances corneal transparency.

Descemet Membrane Thickening as a Sign for the Diagnosis of Corneal Graft Rejection: An Ex Vivo Study.

To disclose, using an ex vivo study, the histopathological mechanism behind in vivo thickening of the endothelium/Descemet membrane complex (En/DM) observed in rejected corneal grafts (RCGs). Descemet membrane (DM), endothelium, and retrocorneal membranes make up the total En/DM thickness. These layers are not differentiable by high-definition optical coherence tomography; therefore, the source of thickening is unclear from an in vivo perspective. A retrospective ex vivo study (from September 2015 to December 2015) was conducted to measure the thicknesses of DM, endothelium, and retrocorneal membrane in 54 corneal specimens (31 RCGs and 23 controls) using light microscopy. Controls were globes with posterior melanoma without corneal involvement. There were 54 corneas examined ex vivo with mean age 58.1 ± 12.2 in controls and 51.7 ± 27.9 years in RCGs. The ex vivo study uncovered the histopathological mechanism of En/DM thickening to be secondary to significant thickening (P < 0.001) of DM (6.5 ± 2.4 μm) in RCGs compared with controls (3.9 ± 1.5 μm). Our ex vivo study shows that DM is responsible for thickening of the En/DM in RCGs observed in vivo by high-definition optical coherence tomography and not the endothelium or retrocorneal membrane.

Initial study of α1,3-galactosyltransferase gene-knockout/CD46 pig full-thickness corneal xenografts in rhesus monkeys.

To investigate graft survival after full-thickness corneal xenotransplantation from α1,3-galactosyltransferase gene-knockout (GTKO) pigs expressing a human complement regulatory protein (GTKO/CD46 pigs) in rhesus monkeys. Rhesus monkeys (n=10) were transplanted with full-thickness corneas from wild-type (WT; n=4) and GTKO/CD46 (n=4) pigs or from monkeys (n=2). All recipient monkeys received post-transplant subconjunctival injections of betamethasone. Corneal grafts were evaluated by slit-lamp. Histopathology, immunohistochemistry of the grafts, and cytokine concentrations in the aqueous humor were tested 6months after transplantation. Anti-pig IgM/IgG and anti-galactose-α1,3-galactose (Gal) antibodies were determined by flow cytometry and ELISA, respectively. The longest graft survival of WT and GTKO/CD46 xenografts was 157 and 171days, respectively. There was no significant difference in graft survival between WT and GTKO pig corneas. Anterior synechiae occurred in two recipients of WT and all recipients of GTKO/CD46 grafts. All xenograft recipients developed a retrocorneal membrane, inflammatory cells (CD3+ T lymphocytes) infiltrated the corneal stroma, and in the aqueous humor, IL-6 was increased 6months after transplantation. Induced antibody responses were documented against Gal and/or non-Gal pig antigens. In contrast, allografts survived >180days without any rejection, with no increase in cytokines in the aqueous humor, and no elicited serum anti-pig antibodies were detected. α1,3-galactosyltransferase gene-knockout/CD46 pig corneas were not associated with prolonged graft survival or a reduced antibody response compared with WT pig corneas. The prevention of the development of anterior synechiae and a retrocorneal membrane after corneal xenotransplantation would appear to be important if prolonged corneal xenograft survival is to be achieved.

Development of retrocorneal membrane following pig-to-monkey penetrating keratoplasty.

Recent reports of long-term survival after wild-type (WT) pig-to-monkey corneal xenotransplantation are encouraging. We experienced the rapid development of retrocorneal membranes, a rare complication after corneal allotransplantation (although seen in infants and young children). The original specific aim of the study was to determine the factors associated with successful (young) pig corneal transplantation in monkeys. However, when it was obvious that retrocorneal membranes rapidly developed, our aims became to determine the factors involved in its development after both WT and Genetically engineered (GE ) pig corneal xenotransplantation and to investigate the characteristics of the retrocorneal membrane. Rhesus monkeys were recipients of penetrating keratoplasty using WT and GE pigs (n=2, respectively, 1-3months old). Local/systemic steroids were administered for 3months. Grafts were evaluated by slit lamp for corneal transparency, edema, and neovascularization. Hematoxylin and eosin, Masson trichrome staining, and immunohistochemical analysis were performed. Gal staining was also carried out to distinguish the origin of the membrane. All penetrating keratoplasty recipients developed fibrous retrocorneal membranes in the early post-transplantation period, regardless of whether the graft was from a WT or GE pig. There were no features of rejection, with no cell infiltrate in the graft or anterior chamber during the three-month follow-up. There was no difference in the clinical course between the two groups (WT or GE corneas). Immunohistochemistry indicated that the retrocorneal membranes were CK negative, α-SMA positive, and vimentin positive, suggesting that they were of fibrous (keratocytic) origin. Also, the membrane was Gal positive, suggesting that it is derived from pig cornea. Following pig-to-monkey corneal xenotransplantation, we report that retrocorneal membranes are derived from donor pig keratocytes. Prevention of retrocorneal membranes will be necessary to achieve successful corneal xenotransplantation.

Chondro‐keratoprosthesis: an alternative to OOKP?

PurposeTo evaluate the use of cartilage as a potential graft material in order to explore a new approach toward osteo‐odontal tissue replacement in keratoprosthesis surgeryMethodsWe describe a modification of the osteo‐odonto‐keratoprosthesis that involves the use of autogenous auricular conchal cartilage graft (ACCG) in 2 patients. In stage 1, ACCG was harvested via a posterior approach. Then, an optical polymethyl‐methacrylate cylinder was embedded into a double‐layered fragment of the conchal cartilage and secured by cyanoacrylate glue. The optical cylinder and cartilage complex were then implanted into the cheek. The stage 2, performed 2–4 months later, involved retrieval of the complex and implantation into the cornea, after reflection of the buccal mucosal flap, corneal trephination, iris and lens removal, and anterior vitrectomy. Cartilage specimens were then processed for histological evaluation after retrieval.ResultsWe report 2 cases of chondro‐keratoprosthesis (CKPRO) who underwent surgery with a 9 months follow‐up following a bilateral limbal stem cell deficiency associated with severe corneal changes. On patient 1, vision was improved to 20/100 J6 during the follow‐up. On patient 2, postoperative visual acuity stay limited to LP related to preoperative retinal lesions. During the follow‐up, any postoperative complication as extrusion, epithelial downgrowth, retrocorneal membrane or endophtalmia was observed.ConclusionsACCG could be a good alternative to replace osteo‐odontal graft in keratoprosthesis surgery especially in young patients with healthy teeth. ACCG has already been widely used for reconstructive surgery and provides safe and stable support to the optical cylinder. However, further comprehensive studies with larger sample size and longer follow‐up are required.

Spontaneous Descemet Membrane Detachment 20 Years After Penetrating Keratoplasty for Keratoconus

To report 2 cases of spontaneous Descemet membrane (DM) detachment 20 years after penetrating keratoplasty for keratoconus. A retrospective chart review of 2 patients was performed. Two male patients-ages 59 and 50-presented 21 and 25 years, respectively, after uncomplicated penetrating keratoplasty for keratoconus, complaining of foreign body sensation. Best-corrected vision was 20/40 and 20/30, respectively. For both patients, slit-lamp examination revealed peripheral corneal thinning and steepening and temporal peripheral microcystic edema of the graft without any sign of rejection. Subsequent anterior segment optical coherence tomography demonstrated a DM detachment localized to the area of the corneal edema. One patient's DM failed to reattach after anterior chamber air injection and he then underwent successful Descemet stripping automated endothelial keratoplasty with resultant best-corrected vision of 20/20. The other patient failed mechanical incision at the graft-host interface with air injection for possible retrocorneal membrane and then successfully underwent a sequential cataract and Descemet stripping automated endothelial keratoplasty with visual acuity of 20/30. Spontaneous DM detachment more than 2 decades after uncomplicated penetrating keratoplasty for keratoconus is a previously unrecognized entity. Novel imaging modalities such as anterior segment optical coherence tomography should be used to identify this clinically difficult to detect etiology of microcystic corneal edema. The cause of DM detachment is unclear, but it may be because of mechanical forces from a retrocorneal membrane or from progressive keratoconus leading to peripheral host corneal steepening and thinning.

Ultrasound biomicroscopy in diagnosis of anterior segment pathology

SummaryPurposeTo demonstrate the role of ultrasound biomicroscopy (UBM) for the diagnosis of anterior segment pathology.MethodsUBM was performed in 7 patients with corneal opacity (6 eyes) and with anterior chamber (AC) opacity (1 eye).ResultsIn first case with total hyphema UBM demonstrated thickening of the iris. Second case with post‐contusional corneal edema and hyphema demonstrated signs of iridodialysis and cyclodialysis. Third patient with central corneal scar had a signs of intraocular epithelial proliferation. With UBM the epibulbar cyst extension into anterior chamber was confirmed in fourth clinical case. In patient with fungal corneal ulcer (fifth case) UBM demonstrated central corneal defect and anterior chamber opacities. Lipodermoid was found in sixth clinical case. UBM helped to confirm that the sclera was not involved. In seventh case with corneal nebula after ocular burns UBM demonstrated iridocorneal adhesion and retrocorneal fibrous membrane. UBM results in all clinical cases determined tactics of treatment.ConclusionsUBM is a safe and effective diagnostic tool in the management of eyes with disorders of the anterior segment especially when visualisation is limited and multiple traumatic injures are involved.