EyeWorld Asia-Pacific June 2019 Issue

EWAP JUNE 2019 31 SECONDARY FEATURE by Stefanie Petrou Binder, MD EyeWorld Contributing Writer Glaucoma surgery and managing the corneal endothelium G laucoma patients will frequently have a reduced endothelial cell count due to various changes that come along with the disease. Glaucoma surgery, which is performed to reduce IOP in these individuals, will likely compound the problem by causing further endothelial cell loss. The ensuing corneal decompensation adversely affects vision and is best addressed by Descemet’s membrane endothelial keratoplasty (DMEK) or Descemet’s stripping endothelial keratoplasty (DSEK), procedures that replace the endothelium using donor corneal endothelium. Patients will often require both, however, combining glaucoma surgery with DMEK/DSEK warrants a great deal of caution. EyeWorld spoke to glaucoma specialists Ramesh Ayyala, MD, FRCS , University of South Florida, Tampa, Florida, and John Berdahl, MD , Vance Thompson Vision, Sioux Falls, South Dakota, about what they have learned with respect to managing glaucoma in the setting of a damaged corneal endothelium in patients with glaucoma. The endothelium The corneal endothelium is a single layer of squamous cells lining the posterior surface of the cornea that plays a unique role in the regulation of hydration through a system of active ion transport. When this regulation becomes impaired through damage to the endothelium, corneal cells can become edematous and indurated, leading to a loss in transparency and compromising clear vision. As endothelial cells do not regenerate, it is paramount to protect this fragile layer of cells. Normal corneas lose 0.6% of endothelial cells (2,500–3,000 cells per square millimeter in adults) per year. In conditions that predispose to endothelial cell damage, such as glaucoma, endothelial cell loss is enhanced. Glaucoma — and its management — can have deleterious effects on the corneal endothelium. Increased IOP, mechanical forces, and the aqueous environment have been implicated in endothelial cell loss, as have glaucoma surgery or a history of glaucoma surgery, which present a particularly Ã}wV>Ì ÀÃ vÀ i`Ìi> cell health and cornea transplant graft survival. 1 Endothelial cell damage “Corneal issues in glaucoma patients mostly have to do with endothelial decomposition, with resulting corneal edema,” Dr. Ayyala told EyeWorld . “Corneal diseases and glaucoma are seen together in almost 50% of glaucoma patients.” Precisely how the endothelium is damaged in glaucomatous eyes is incompletely understood. In a published study he conducted on penetrating keratoplasty and glaucoma, Dr. Ayyala observed that glaucoma issues in corneal patients were multifactorial in origin, usually due to angle closure, steroid ÀiÃ«Ãi] >` y>>Ì° 2 In his experience, endothelial cell damage can result from glaucoma surgery, as well as from bouts of acute or sustained elevated intraocular pressures. “Acute angle closure glaucoma is an outstanding example of increased IOP that can cause damage to endothelial AT A GLANCE • Glaucoma itself can have damaging effects on the corneal endothelium. Factors include increased IOP, mechanical forces, and the altered aqueous environment. • Glaucoma surgery combined with DMEK/DSEK is feasible, with extreme caution. • Dr. Ayyala chooses ab externo canaloplasty in his glaucoma patients to best protect the corneal endothelium. • À° iÀ`> wÀÃÌ «iÀvÀÃ glaucoma surgery to stabilize IOP and control bleedings before proceeding to DMEK. Editors’ note: Dr. Berdahl has ƂPCPEKCN KPVGTGUVU YKVJ #NEQP (Fort Worth, Texas), Glaukos, 0GY 9QTNF /GFKECN CPF %QTPGC)GP 5GCVVNG &T #[[CNC JCU PQ ƂPCPEKCN KPVGTGUVU TGNCVGF VQ JKU EQOOGPVU Contact information Ayyala: rayyala@health.usf.edu Berdahl: johnberdahl@gmail.com Figures 1 and 2. A 2.4-millimeter keratome is used to create a wound angle for the stent followed by lidocaine and viscoelastic. Glaucoma surgery will likely compound already reduced endothelial cell counts in patients 6JKU CTVKENG QTKIKPCNN[ CRRGCTGF KP VJG (GDTWCT[ KUUWG QH EyeWorld . It JCU DGGP UNKIJVN[ OQFKƂGF CPF CRRGCTU JGTG YKVJ RGTOKUUKQP HTQO VJG #5%45 1RJVJCNOKE 5GTXKEGU %QTR