Descemet Membrane

PurposeOxidative stress is implicit in the pathological changes associated with glaucoma. The purpose of this study was to compare levels of oxidative stress in glial fibrillary acid-negative protein (GFAP) lamina cribrosa (LC) cells obtained from the optic nerve head (ONH) region of 5 normal (NLC) and 4 glaucomatous (GLC) human donor eyes and to also examine mitochondrial function and calcium homeostasis in this region of the ONH.MethodsIntracellular reactive oxygen species (ROS) production was examined by a thiobarbituric acid reactive substances (TBARS) assay which measures malondialdehyde (MDA), a naturally occurring product of lipid peroxidation and is used as an indicator of oxidative stress. Mitochondrial membrane potential (MMP) and intracellular calcium ([Ca(2+)](i)) levels were evaluated by flow cytometry using the JC-1 (5,5',6,6'-tetrachloro-1,1',3,3'-tetrabenzimidazolecarbocyanine iodide) and fluo-4/AM probes respectively. Anti-oxidant and Ca(2+) transport system gene and protein expression were determined by real time polymerase chain reaction (RT-PCR) using gene-specific primer/probe sets and western immunoblotting, respectively.ResultsIntracellular ROS production was increased in GLC compared to NLC (27.19 ± 7.05 µM MDA versus 14.59 ± 0.82 µM MDA, p ConclusionsOur data finds evidence of oxidative stress, mitochondrial dysfunction and impaired calcium extrusion in GLC cells compared to NLC cells and suggests their importance in the pathological changes occurring at the ONH in glaucoma. Future therapies may target reducing oxidative stress and / or [Ca(2+)](i).

PurposeBased on current evidence, the efficiency and safety of Descemet's membrane endothelial keratoplasty (DMEK) was compared with that of Descemet's stripping endothelial keratoplasty (DSEK).MethodsPubmed, Embase, Web of Science, the Cochrane Database and conference abstracts were comprehensively searched for studies that compared the efficacy and safety of DMEK and DSEK. The efficacy outcome was the postoperative best-corrected visual acuity (BCVA). The safety outcomes included the postoperative endothelial cell density (ECD) and complications such as graft detachment, graft rejection, graft failure, postoperative elevated intraocular pressure (IOP), tissue loss, etc. The outcomes were pooled using random-effects models with Stata 13.0 software. Heterogeneity was qualified with Q statistic and I2/H2 statistic. Publication bias was assessed using funnel plot, Begg rank correlation test, and Egger or Horbard linear regression.Results19 articles were eligible, and 1124 eyes and 1254 eyes were included in the DMEK and DSEK groups, respectively. The overall pooled estimates showed a significantly better postoperative BCVA, a comparable ECD and an increased graft detachment rate in the DMEK group compared with the DSEK group (BCVA: mean difference (MD) = -0.15, 95% CI = -0.19 to -0.11, PConclusionAlthough DMEK is a more technically difficult and challenging procedure, it may represent a safe and more efficient alternative to DSEK for the treatment of corneal endothelial diseases, even during its learning curve.

Fuchs endothelial corneal dystrophy (FECD), is the most common corneal endothelial dystrophy, and contributes up to 50% of all corneal transplantations performed in developed countries. FECD develops in Descemet's membrane (DM) and possibly alters the mechanical properties and internal structures in this basal lamina. In this work, the morphology and mechanical properties of FECD-DMs are studied by transmission electron microscopy (TEM) and quantitative dynamic atomic force microscopy (QD-AFM) at nano scale. Pathological wide-space collagens that are typical of FECD display different mechanical properties in that they are softer than the remaining tissue both for dehydrated- and fully hydrated samples. Additionally, the hydration level has major influence on the mechanical properties. These findings could help to further understand the structural changes in FECD, and possibly be useful for further characterization of the disease, the diagnosis and assessment or even pathologic analysis.

Pre-Descemet's endothelial keratoplasty (PDEK) is an evolving endothelial keratoplasty (EK) procedure that merges the advantages of Descemet membrane endothelial keratoplasty (DMEK) and ultrathin EK methods. This review reports the latest anatomical, surgical, and clinical research on PDEK and discusses its potential future role in current EK practices. Anatomical data show that the Pre-Descemet/Dua's Layer (PDL/DL) acts as a biomechanical support, or "splint," for Descemet's Membrane (DM). This support facilitates the creation of grafts that are less tight and easier to handle compared to DMEK tissue. Notably, PDEK leads to rapid visual recovery and improvements in best-corrected visual acuity after surgery. Since PDEK results in an acceptable level of endothelial cell loss and has demonstrated reasonable detachment and rebubbling rates in published series, particularly in experienced hands, it is regarded as a reliable method for effectively utilising young and paediatric corneas, thereby optimising tissue use in eye bank procedures. Furthermore, advancements in surgical techniques, such as specialised PDEK clamps, an air-pump-assisted method, consistent 360-degree scoring, and the integration of optical coherence tomography into the surgical microscope, have resulted in higher success rates in creating Type 1 big-bubble, decreased overall tissue loss, and enhanced procedural consistency. Finally, PDEK merges the optical advantages of DMEK with enhanced intraoperative control and expanded donor options with the inclusion of young donor eyes, and is likely to gain wider adoption when integrated into training programs and eye bank protocols.