EyeWorld Asia-Pacific September 2012 Issue

22 EWAP CAtArACt/IOL September 2012 Trumping endothelial fate by Maxine Lipner Senior EyeWorld Contributing Editor Preserving the endothelium in cataract surgery W hile endothelial cell loss is pretty much an inevitable effect of cataract surgery, advances in technique and technology have helped to optimize outcomes, according to Natalie A. Afshari, MD, associate professor of ophthalmology, Duke University Eye Center, Durham, NC, USA. The rate of endothelial cell loss these days after phacoemulsification may be as low as 1.2%, study results reported in the January issue of Current Opinion in Ophthalmology show. Recently, with the advent of DSAEK surgery, there has been a lot of attention paid to the corneal endothelium. “Instead of the full thickness corneal transplantation, we do partial endothelium because we have better techniques of replacing it,” Dr. Afshari said. Spurred by this heightened interest, investigators combed the literature to determine how endothelial cell loss is affected by surgical factors as well as the patient’s history. Studying endothelial keys One of the keys to sparing the corneal endothelium appears to be the availability of excellent viscoelastics. “Recent studies are showing that there is a reduction in corneal endothelial cell loss after phacoemulsification because we have better viscoelastic materials and we have modified our surgical technique,” Dr. Afshari said. “We are better in preparing and preoperatively knowing how to avoid it as much as possible intraoperatively.” Some studies have shown that use of a dispersive viscoelastic that diffuses all over the endothelium is an asset. “The use of dispersive Views from Asia-Pacific viscoelastic led to reduction of endothelial cell loss,” Dr. Afshari said. She pointed out, however, that the density of the cataract also plays a role. “The denser the cataract, the more energy that’s used and the more possibility that you lose endothelial cells.” Some of the patients appear to be at a higher risk of losing endothelial cells. “Some studies show that those patients who have diabetes before the cataract surgery compared to patients who don’t are losing more cells,” Dr. Afshari said. When it comes to those who have undergone some form of corneal transplant, those who retain their own endothelium with deep anterior lamellar keratoplasty do better after phacoemulsification than those who have had penetrating keratoplasty (PK). “Those patients have their own corneal endothelial cells, and they lose fewer cells during the surgery compared to patients who have had PK before,” Dr. Afshari said. “It’s interesting that those folks are predisposed to more cell loss.” Studies show that any technology that minimizes the impact on the corneal endothelium can help. “The newer technology, which decreases the amount of ultrasound delivered on the corneal endothelium, decreases the endothelial cell loss,” Dr. Afshari said. “The fluid is moving around hitting the corneal endothelium, and there would be less of that if we have less ultrasound energy on the corneal endothelium.” One technique that seemed to spare the corneal endothelium was the phaco chop. “There was a study that looked at phaco chop versus the stop-and-chop, and phaco chop obviously requires lower ultrasound energy so technical modification will help to reduce the loss of corneal endothelial cells,” Dr. Afshari said. Hungwon TCHAH, MD Professor, Department of Ophthalmology, Asan Medical Center, University of Ulsan 388-1 Pungnab-dong Songpa-gu, Seoul, 138040 Korea Tel. no. +82-2-30103680 Fax no. +82-2-4706440 hwtchah@amc.seoul.kr E ndothelial cell damage after cataract surgery is inevitable because the operation itself is a traumatic insult to the tissues and cells. However, if we understand the mechanism of endothelial cell damage, we can possibly modify the fate of the endothelium. Endothelial cells can be damaged by direct trauma from an instrument, shockwaves or heat from the ultrasound, and turbulent fluid and/or mechanical folding (corneal wrinkles). They can also be damaged indirectly by cytokines from inflammatory cells and other damaged cells, and free radicals. Therefore, if we avoid these factors, we can protect endothelial cells. The phaco-chop technique requires less ultrasound energy, so it seems to be less traumatic to endothelium. I personally prefer multiple chops, that is, 8 to 10 chops, to decrease the ultrasound energy further. As Drs. Afshari and Rostov mentioned, dispersive OVDs have more protective effect for endothelium because they coat endothelium and protect from direct trauma. When the patient has very low endothelial cell count preoperatively or a history of corneal transplantation, I prefer to use a dispersive OVD and BSS plus instead of BSS. In normal endothelial patients, I am not confident whether these are needed. But if you have free access to these, you had better use them. When you use a dispersive OVD for endothelial protective purpose, this OVD has to be frequently re-injected into the AC to coat endothelium because it is washed out by the irrigating solution. BSS plus has more components than BSS to protect endothelium. Although the amount of solution used in cataract surgery is not as large a volume as in vitreous surgery, a small difference can be critical in a marginal endothelial count patient. A small wound is usually less traumatic compared to a large wound and induces less cytokines which are toxic to endothelium. Postoperatively, sufficient coverage with an anti-inflammatory agent is very important to decrease cytotoxic cytokines in the AC, because there are cytokines even if cells are not visible in the AC. With all these procedure, we have changed the fate of endothelium, as Dr. Afshari described. We have given long life to our endothelium. Editors’ note: Prof. Tchah has no financial interests related to his comments.