June 2012

 

CATARACT

 

Trumping endothelial fate


by Maxine Lipner Senior EyeWorld Contributing Editor
 

 

 

An eye post-DSAEK. With the advent of the surgery (pictured here), the corneal endothelium has received significant attention Source: Mark Gorovoy, M.D.

Preserving the endothelium in cataract surgery

While 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, M.D., associate professor of ophthalmology, Duke University Eye Center, Durham, N.C. 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 pre-operatively 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 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.

In the clinic

Audrey R. Talley Rostov, M.D., Northwest Eye Surgeons, Seattle, has found that both technique and technology can make a difference here. She prefers a biaxial phacoemulsification technique, using two small incisions. "I find that works extremely well for minimizing my cell loss," she said. State-of-the-art technology should not be overlooked. "I would say that with the newer phaco machines that allow you to use less energy, less phaco power, the decreased duration and amount of phaco that you use can help preserve corneal endothelial cells," Dr. Talley Rostov said. She pointed out that there has been a lot of talk about torsional phaco in which the handpiece delivers side-to-side oscillating ultrasonic movements, which can be helpful in sparing the endothelium. However, she doesn't see this technology as the "holy grail." "The torsional phaco is good but I'd say that any of the newer phaco machines are actually quite good," she said. "By using any of the newer phaco technologies I think that you can minimize the amount of cell loss because you're maximizing your phaco efficiency, and that's really what it's about."

Viscoelastic devices can also help with deferring endothelial cell loss. For some patients Dr. Talley Rostov finds a dispersive agent to be preferable. "A dispersive OVD such as Viscoat [Alcon, Fort Worth, Texas] or Duovisc [Alcon], which has a Viscoat-type molecule in it, those are going to coat the endothelium more," she said. "But for the average cataract, do you need to use that? I think the answer is no." Dr. Talley Rostov reserves this for special situations such as cases involving a patient who has undergone a previous corneal transplant or someone with Fuchs' endothelial dystrophy. Viscoelastic devices can also help with deferring endothelial cell loss.

Overall, Dr. Afshari sees the fortune of the corneal endothelium as dramatically improving. "There was a study in which there was only a 1.2% cell loss after phacoemulsification," she said. "We have come a long way and we are doing great; the rate has gone way down to nearly insignificant." Because of all of the improvements in technique and technology, practitioners are seeing much less pseudophakic bullous keratopathy. "We have changed the fate of the corneal endothelial cells for the better because of these advances," Dr. Afshari said.

Editors' note: Dr. Afshari has financial interests with Bausch + Lomb (Rochester, N.Y.). Dr. Talley Rostov has financial interests with Abbott Medical Optics (Santa Ana, Calif.).

Contact information

Afshari: 919-681-3937, natalie.afshari@duke.edu
Talley Rostov: 206-528-6000, ATalley-Rostov@nweyes.com

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