Acute Hydrops After Bowman Layer Transplantation for Keratoconus May Indicate that Descemet Membrane Rupture Is Secondary to Hydrops.

PURPOSE: The aim of this study was to review the postoperative course and imaging features of 7 eyes that presented with corneal hydrops after Bowman layer (BL) transplantation was performed for advanced keratoconus to determine the potential mechanisms of hydrops formation. METHODS: A retrospective analysis was performed of 7 eyes of 5 patients with advanced keratoconus that underwent midstromal BL transplantation at 2 tertiary referral centers and developed acute corneal hydrops on average 64 (±30) months (range 14-104 months) postoperatively. Corneal tomography and anterior segment optical coherence tomography (AS-OCT) images were reviewed to document the postoperative and posthydrops course. RESULTS: For all eyes, the post-BL transplantation course was uneventful until hydrops development. Despite stable postoperative topographies in 5 of 7 eyes, eyes developed hydrops with typical hypodense areas on AS-OCT that were limited to the stromal layers posterior to the BL graft. With AS-OCT (6/7 eyes), 2 eyes showed a break in Descemet membrane, whereas Descemet membrane was intact across the cornea in 2 eyes; in 2 eyes, the images were inconclusive. All patients admitted to continued eye rubbing, and all but 1 had a clinically significant allergy and/or atopic constitution. Most eyes (5/7) showed a relatively quick (visual) recovery within 1 to 4 months after hydrops. CONCLUSIONS: Hydrops formation in keratoconic corneas after midstromal BL transplantation may indicate that a break in Descemet membrane is secondary to hydrops development (and not vice versa). With a midstromal BL graft in situ limiting hydrops dimensions, resolution of the hydrops seemed relatively quick with recovery to prehydrops visual acuity in most eyes.

Combined specular microscopy and Scheimpflug imaging to improve detection of an upcoming allograft rejection after DMEK.

PURPOSE: To assess whether combined analysis of specular microscopy and Scheimpflug imaging improves detection of an upcoming allograft rejection following Descemet membrane endothelial keratoplasty (DMEK). METHODS: Retrospective analysis of 22 eyes that had developed a clinical proven allograft rejection 28 (±22) months (range: 4-84 months) after DMEK. Specular microscopy and Scheimpflug images routinely made after DMEK were retrospectively analysed for changes in endothelial cell morphology (e.g. nuclear activation), cell density (>10%) and pachymetry (>7%), and/or the presence of subclinical keratic precipitates. The same parameters were evaluated for 22 control eyes matched for age, gender and surgery indication. RESULTS: A total of 20/22 eyes (91%) showed detectable changes 0.25-75 months before allograft rejection became clinically manifest: 13/22 (59%) showed both specular microscopy and Scheimpflug imaging changes; 5/22 (23%) only had changes on Scheimpflug imaging; and 2/22 (9%) only had specular microscopy changes. In 18/22 (82%) and 14/22 (64%) eyes, subclinical keratic precipitates and endothelial cell morphology changes could be detected, respectively. A total of 11/22 (50%) eyes concurrently showed a >10% drop in endothelial cell density and 4/22 (18%) a >7% pachymetry increase. Of the control eyes, 7/22 (32%) showed changes with specular microscopy but not with Scheimpflug imaging. CONCLUSIONS: Combined analysis of specular microscopy and Scheimpflug imaging may allow recognizing an upcoming allograft rejection in over 90% of eyes and up to 6 years before rejection becomes clinically manifest. Early recognition of eyes at risk may allow for targeted intensified steroid treatment to prevent endothelial cell damage associated with rejection.

Influence of Intraoperative Air Tamponade Time on Graft Adherence in Descemet Membrane Endothelial Keratoplasty.

PURPOSE: To study the influence of different intraoperative air tamponade times on graft adherence after Descemet membrane endothelial keratoplasty (DMEK). METHODS: In this interventional case series, we evaluated 117 eyes with Fuchs endothelial corneal dystrophy (FECD) that underwent DMEK using intraoperative air tamponade times of 60 minutes (group I; n = 39), 45 minutes (group II; n = 39), or 30 minutes (group III; n = 39). At 1 and 6 months postoperatively, graft adherence status, endothelial cell density, central pachymetry, and postoperative complications were recorded. RESULTS: At 1 month, 19 of the 117 eyes (16.2%) showed a clinically significant detachment (>1/3 of the graft surface area and affecting visual axis): 6 eyes in group I (15.4%), 5 eyes in group II (12.8%), and 8 eyes in group III (20.5%) (P = 0.82). A minor detachment (<1/3 of the graft surface area and not affecting visual axis) was observed in 6 eyes in group I (15.4%), in 7 eyes in group II (17.9%), and in 4 eyes in group III (10.3%) (P = 0.82). The overall rebubbling rate was 11%, with no difference among the groups (P = 0.07). Mean endothelial cell density decrease at 6 months was 41% (±17%) (P = 0.56), whereas mean central pachymetry decreased by 23 (±10) % (P = 0.77), with no differences between the groups. CONCLUSIONS: The incidence of graft detachment after DMEK for FECD did not differ between the eyes that had a 60-, 45-, or 30-minute intraoperative air tamponade. Reducing the intraoperative air tamponade time to 30 minutes may be considered for DMEK in eyes with uncomplicated FECD.

Atypical Presentation of Iridocorneal Endothelial Syndrome With Band Keratopathy but No Corneal Edema Managed With Descemet Membrane Endothelial Keratoplasty.

PURPOSE: To report an unusual presentation of iridocorneal endothelial (ICE) syndrome associated with band keratopathy and its management with ethylenediamine-tetraacetic acid (EDTA) chelation and Descemet membrane endothelial keratoplasty (DMEK). METHODS: A 57-year-old female patient presented with unilateral progressive painless visual impairment, corneal band keratopathy, and morphological corneal endothelial changes without corneal edema or any previous ophthalmic, medical, or family history. Routine specular and confocal microscopy imaging, as well as biomicroscopy, best-corrected visual acuity, and pachymetry measurements were performed before and after the surgical procedures. Histopathologic and immunohistochemical evaluations of the surgically excised diseased DM-endothelium were performed. RESULTS: Superficial epithelial keratectomy with EDTA chelation was performed. After an initial period of a few months of corneal clearance, the patient presented with recurrence of visually significant band keratopathy. After 1 year, she underwent retreatment with superficial epithelial keratectomy and EDTA chelation, followed by DMEK. Histopathologic and immunohistochemical analysis showed ICE syndrome. Two years after DMEK surgery, the cornea was still clear and band keratopathy had not recurred. CONCLUSIONS: To the best of our knowledge, this is the first case in the literature that reports the association of ICE syndrome with band keratopathy. As band keratopathy recurred shortly after EDTA chelation, endothelial keratoplasty (DMEK) may be indicated to successfully treat such cases.

Activation of Rac1 and RhoA Preserve Corneal Endothelial Barrier Function.

PURPOSE: The corneal endothelium is responsible for the correct hydration of the corneal stroma. Corneal endothelial cells have a low proliferative capacity, so preserving their barrier function under suboptimal conditions that cause osmotic imbalance, such as those arising from corneal pathologies, age, cryopreservation, and transplantation, is essential for maintaining corneal transparency. We have investigated the signaling induced by hyperosmotic shock that reversibly disrupts corneal endothelial barriers in human endothelial cells and in murine corneas. METHODS: Endothelial barrier properties were analyzed in vitro by electric cell substrate impedance sensing (ECIS) and confocal microscopy of the human endothelial cell line B4G12-HCEC, and, ex vivo, by confocal microscopy and stimulated emission-depletion (STED) super-resolution microscopy of murine corneas. Cell signaling in response to hyperosmotic stress, induced with an excess of sodium chloride, was investigated in B4G12-HCECs. Rho GTPase activity was detected by pulldown assays with recombinant GST proteins fused to the Rho binding domains of Rho effectors. RESULTS: Hyperosmotic stress increased actin polymerization and activated the Rho GTPases Rac1 and RhoA, but not Cdc42. Rac1- and RhoA-mediated pathway inhibition had a minor effect on barrier disruption but partially delayed barrier reformation after stress withdrawal. In contrast, Rac1 and RhoA activation enhanced constitutive endothelial barrier function and accelerated barrier repair. CONCLUSIONS: Our results indicate that Rac1 and RhoA activation do not mediate stress-induced cell contraction but are endothelial responses that act to restore and maintain barrier homeostasis. Therefore, pharmacological activation of these two GTPases could be a therapeutic strategy for preserving corneal endothelial barrier function.

A human cellular system for analyzing signaling during corneal endothelial barrier dysfunction.

Correct corneal endothelial barrier function is essential for maintaining corneal transparency. However, research on cell signaling pathways mediating corneal endothelial barrier dysfunction has progressed more slowly than that involving other cellular barriers because of the lack of human corneal endothelial cell models. Here we have optimized the culture of the human corneal endothelial cell (HCEC) line B4G12 as a model for studying paracellular permeability. We show that B4G12-HCECs form confluent monolayers with stable cell-cell junctions when cultured on plastic, but not glass, surfaces precoated with various extracellular matrix components. Cell morphometry and measuring intercellular spaces and transendothelial electric resistance indicate that B4G12-HCECs form optimal monolayers on collagen and fibronectin. Based on the use of specific inhibitors, it has been proposed that the Rho-regulated kinases, ROCK-I and ROCK-II, mediate actomyosin-induced contraction in corneal endothelial cell barriers. ROCKs are effectors of RhoA, RhoB and RhoC. We show that the GTPase RhoA and its effector ROCK-II are predominantly expressed in B4G12-HCECs and primary human corneal endothelial cells. The activation of Rho GTPases during acute barrier disruption has not been investigated in corneal endothelial cells. RhoA, but not other related GTPases that are highly expressed in B4G12-HCECs, such as Rac1 and Cdc42, is transiently activated during barrier disruption in response to the inflammatory mediator thrombin. Pharmacological inhibition of RhoA and ROCK reduces B4G12-HCEC acute contraction. We propose that exploiting B4G12-HCECs is a useful experimental strategy for gaining further insight into the signaling pathways involved in human corneal endothelial barrier function.