Surgeon offers tips to help reduce endothelial trauma during cataract surgery

Appropriate strategies can minimize risk to the endothelium.

Patients with Fuchs’ dystrophy, brunescent lenses or narrow angles are at greatest risk for increased corneal edema following phacoemulsification, according to a physician.

David F. Chang

OSN U.S. Edition Cataract Surgery Board Member David F. Chang, MD, offered pearls on how to reduce endothelial trauma during cataract surgery in these higher-risk eyes at Hawaiian Eye 2010.

Chopping technique

Compared to sculpting techniques such as divide-and-conquer, phaco chop decreases ultrasound time and energy, according to four separate studies reviewed by Dr. Chang.

However, only one of three comparative studies showed statistically less endothelial cell loss with phaco chop. Dr. Chang speculated that studies that did not look specifically at grade 4+ nuclei might not find a significant difference.

In addition, it can be helpful to subchop fragments of a brunescent lens into smaller pieces with a horizontal chopper. “By decreasing their size, it makes it more likely for the phaco tip to catch rather than to repel these rigid pieces,” he said.

Dr. Chang emphasized that reducing nuclear particle turbulence at the phaco tip is just as important as decreasing total ultrasound time.

“Reducing axial phaco tip movement, such as with the torsional (OZil, Alcon) and transversal (Ellips, Abbott Medical Optics) ultrasound modulations, improves nuclear followability by lessening the tendency for the phaco tip to repel and kick fragments away,” he said.

Dyes and OVDs

With brunescent lenses, capsular dye staining is often needed. According to Dr. Chang, there is ample evidence that trypan blue is safe for the corneal endothelium.

“There is one controlled study showing no greater loss of endothelial cells compared to not using dye,” he said. But surgeons must be careful to never use methylene blue, which is toxic and has been associated with multiple cases of corneal decompensation.

Dr. Chang believes that a dispersive ophthalmic viscosurgical device results in less endothelial loss than a cohesive OVD, with the difference being more evident with higher-risk eyes, such as those with Fuchs’ dystrophy, brunescent nuclei or shallow anterior chambers.

“During phacoemulsification of a dense lens, it makes sense to repeatedly pause and re-coat the endothelium with a protective layer of dispersive OVD,” Dr. Chang said. “Remember that the longer it takes to fragment and emulsify a large nucleus, the less OVD will be left.”

Dr. Chang also noted that the paucity of epinucleus with brunescent cataracts allows more trampolining of the posterior capsule to occur. This in turn causes surgeons to emulsify the final sharp-edged fragments in closer proximity to the endothelium.

“In this situation, it helps to inflate the capsular bag with a dispersive OVD, which will resist aspiration and restrain the posterior capsule as the final fragments are emulsified in the pupillary plane,” he said.

Extracapsular cataract extraction

Finally, Dr. Chang emphasized the importance of considering when to perform or convert to a manual extracapsular cataract extraction in higher-risk eyes.

“Posterior capsule rupture and vitreous loss with a rock-hard nucleus will really traumatize the endothelium,” he said. “Every surgeon needs to make an individual assessment of their own expertise and of the patient’s eye in deciding when it might be safer for the endothelium to perform a manual [extracapsular cataract extraction].”

In high-risk eyes, he encouraged surgeons to consider a retro or peri-bulbar block to facilitate converting to a manual extracapsular cataract extraction if necessary. Another problem is the lack of experience and training in manual extracapsular cataract extraction that characterizes most residency programs.

“If I had a brunescent cataract and bad zonules, for example, the advantages of a small incision are just not that critical that I’d be willing to trade a significant percentage of my endothelial cells to have phaco,” Dr. Chang said. – by Stephanie Vasta

• David F. Chang, MD, clinical professor of ophthalmology at the University of California, San Francisco, can be reached at 762 Altos Oaks Drive, Suite 1, Los Altos, CA 94024, U.S.A.; +1-650-948-9123; e-mail: dceye@earthlink.net. Dr. Chang’s consultant fees from AMO and Alcon are donated to Project Vision and the Himalayan Cataract Project.