Historical Review and Update of Surgical Treatment for Corneal Endothelial Diseases

The cornea remains in a state of deturgescence, maintained by endothelial cell Na+/K+ ATPase and by tight junctions between endothelial cells that limit entrance of fluid into the stroma. Fuchs' endothelial corneal dystrophy (FECD) was initially described by Fuchs in 1910 as a combination of epithelial and stromal edema in older patients. It manifests as bilateral, albeit asymmetric, central corneal guttae, corneal edema, and reduced vision. When edema is severe, the corneal epithelium can detach from its basement membrane, creating painful bullae on the anterior surface of the cornea. The course of this dystrophy can be further accelerated after intraocular surgery, specifically cataract extraction. Pseudophakic bullous keratopathy (PBK) is endothelial cell loss caused by surgery in the anterior chamber. If the corneal endothelium is damaged during surgery, the same spectrum of symptoms as found in FECD can develop. In the nineteenth century, penetrating keratoplasty was the only surgical procedure available for isolated endothelial disease. In the 1960s, Dr. José Barraquer described a method of endothelial keratoplasty using an anterior approach via laser-assisted in situ keratomileusis (LASIK) flap. In 1999, Melles and colleague described their technique of posterior lamellar keratoplasty. Later, Melles et al. started to change host dissection using simple "descemetorhexis" in a procedure known as Descemet's stripping endothelial keratoplasty. Following the widespread adoption of Descemet's stripping automated endothelial keratoplasty, the Melles group revisited selective Descemet's membrane transplantation and reported the results of a new procedure, Descemet's membrane endothelial keratoplasty (DMEK). Recently, some eye banks have experimented with the preparation of DMEK/Descemet's membrane automated endothelial keratoplasty donor tissue that may help the surgeon avoid the risk of tissue loss during the stromal separation step. Recently, the authors described a new bimanual technique for insertion and positioning of endothelium-Descemet membrane grafts in DMEK

Trasplante de membrana amniótica en patología de la superfície ocular

Disponible des del TDXTítol obtingut de la portada digitalitzadaEl trasplante de membrana amniótica (TMA) ha demostrado en los últimos años ser eficaz en el tratamiento de distintas patologías de la superficie ocular. Sin embargo, los trabajos publicados recogen series cortas de pacientes y con periodos de seguimiento breves. Hemos analizado los resultados obtenidos en todos los casos intervenidos por el autor mediante TMA durante los años 1999 y 2000, incluyendo estudios histológicos tras el trasplante en algunos de los receptores. El primer trabajo analiza los resultados obtenidos con el TMA en 53 casos de patología corneal y conjuntival, utilizando distintas formas de implante y con un periodo de seguimiento medio de 32 meses (rango 24-48 meses). Tras la resección de lesiones conjuntivales extensas el injerto de membrana amniótica (MA) consiguió la epitelización completa, con mínima formación de cicatrices residuales, en el 100% de los casos. En las úlceras corneales tróficas, degeneraciones estromales cálcicas, y los defectos epiteliales el TMA se mostró como un procedimiento terapéutico eficaz y una alternativa quirúrgica útil en aquellos casos en los que el tratamiento médico fracasa. Los resultados obtenidos fueron estables durante el periodo de seguimiento realizado. En ninguno de los casos intervenidos se observaron complicaciones intraoperatorias ni postoperatorias. En el segundo trabajo se analiza la eficacia y seguridad del recubrimiento con MA en el tratamiento de los defectos epiteliales persistentes sin respuesta al tratamiento médico. El recubrimiento con MA se mostró muy eficaz cuando el implante se mantuvo en la superficie corneal durante dos o más semanas, siendo el principal problema en estos pacientes el desprendimiento precoz de la membrana. De entre los distintos tipos de implante ensayados el recubrimiento de la córnea asociado a una lente de contacto terapéutica fue el que mantuvo durante más tiempo el implante. En el tercer estudio se describen los hallazgos histológicos encontrados tras el injerto de membrana amniótica en la córnea de dos pacientes que varios meses después del TMA precisaron de un trasplante de córnea. En ambos casos la membrana amniótica consiguió una epitelización completa y de características histológicas normales y, tras su reabsorción, el espacio ocupado inicialmente por la membrana fue sustituido por un estroma neoformado de características fibróticas. En la córnea avascular no se evidenció ningún tipo de reacción inflamatoria ni de rechazo alrededor del injerto y el proceso de reabsorción fue lento, probablemente a expensas de los queratocitos activados. En presencia de neovascularización estromal y de inflamación crónica subyacente la reabsorción se produjo de manera más rápida por la abundante presencia de células inflamatorias en la zona. En el cuarto trabajo se demuestra como el injerto de MA puede conseguir la regeneración de zonas extensas de conjuntiva incluso sobre un lecho escleral severamente isquémico.In recent years amniotic membrane transplantation (AMT) has shown to be effective in the treatment of different patologies of the ocular surface. Nevertheless, the published articles usually consist of short series of patients with brief follow-up periods. We have reviewed the results obtained in all the cases operated on by the author with AMT during the year 1999 and 2000, including histological studies after the transplantation in some of the patients. The first paper analyzes the results obtained with the AMT in 53 cases of corneal and conjuntival pathology, using different forms of implantation with a mean follow-up of 32 months (range 24-48 months). After the resection of extensive conjunctival lesions the amniotic membrane (AM) graft achieved complete epithelialization, with minimal scarring, in 100 % of the cases. In the eyes with neurotrophic corneal ulcer, calcific degeneration, and persistent epithelial defects, the AMT appears to be an effective procedure and represents an aditional therapeutic alternative when conservative medical treatments fail. The obtained results were stable during the follow-up period. No intraoperative or postoperative complications ocurred in any of the 53 cases operated. The second paper analyzes the efficacy and safety of the AM patch in the treatment of persistent epithelial defects without response to the medical treatment. The AM patch proved to be effective when the implant was maintained on the corneal surface for two or more weeks, being the main problem in these patients the early detachment of the membrane. Among the different types of implantation tested, the technic of covering the entire cornea associated with a therapeutic contact lens achieved longer duration of the AM. The third study describes the histopathologic findings in the cornea of two patients who required a corneal transplantation several months after an AM graft. In both cases a complete epithelialization was observed over the basement membrane of the AM. In the cornea with avascular stroma no inflammatory reaction or graft rejection was seen. In this case the process of reabsorption was slow, probably at the expense of the activated keratocytes. In the cornea with stromal neovascularization the AM was rapidly reabsorbed because of the presence of abundant inflammatory cells. Once reabsorbed, the AM was replaced by a new fibrotic stroma, which was different to that found in the rest of the cornea but which helped to maintain corneal thickness. The fourth paper demonstrates that AM graft can be useful even in the regeneration of conjunctiva over large areas of ischemic sclera

Historical Review and Update of Surgical Treatment for Corneal Endothelial Diseases

The cornea remains in a state of deturgescence, maintained by endothelial cell Na+/K+ ATPase and by tight junctions between endothelial cells that limit entrance of fluid into the stroma. Fuchs' endothelial corneal dystrophy (FECD) was initially described by Fuchs in 1910 as a combination of epithelial and stromal edema in older patients. It manifests as bilateral, albeit asymmetric, central corneal guttae, corneal edema, and reduced vision. When edema is severe, the corneal epithelium can detach from its basement membrane, creating painful bullae on the anterior surface of the cornea. The course of this dystrophy can be further accelerated after intraocular surgery, specifically cataract extraction. Pseudophakic bullous keratopathy (PBK) is endothelial cell loss caused by surgery in the anterior chamber. If the corneal endothelium is damaged during surgery, the same spectrum of symptoms as found in FECD can develop. In the nineteenth century, penetrating keratoplasty was the only surgical procedure available for isolated endothelial disease. In the 1960s, Dr. José Barraquer described a method of endothelial keratoplasty using an anterior approach via laser-assisted in situ keratomileusis (LASIK) flap. In 1999, Melles and colleague described their technique of posterior lamellar keratoplasty. Later, Melles et al. started to change host dissection using simple "descemetorhexis" in a procedure known as Descemet's stripping endothelial keratoplasty. Following the widespread adoption of Descemet's stripping automated endothelial keratoplasty, the Melles group revisited selective Descemet's membrane transplantation and reported the results of a new procedure, Descemet's membrane endothelial keratoplasty (DMEK). Recently, some eye banks have experimented with the preparation of DMEK/Descemet's membrane automated endothelial keratoplasty donor tissue that may help the surgeon avoid the risk of tissue loss during the stromal separation step. Recently, the authors described a new bimanual technique for insertion and positioning of endothelium-Descemet membrane grafts in DMEK