February 2019

CATARACT

Research highlight
Up to the challenge


by Maxine Lipner EyeWorld Senior Contributing Writer


Brunescent dense cataract
Source: Rosa Braga-Mele, MD

 

Learning to roll with a rock-hard nuclear case

Dealing with a rock-hard cataract can be very different than performing standard phacoemulsification. As part of a study that appeared in the Journal of Cataract and Refractive Surgery,1 members of the ASCRS Challenging and Complex Cataract Surgery Subcommittee honed in on how to most safely address challenges in such cases, according to Gary Foster, MD, Fort Collins, Colorado.
Treating rock-hard lenses differs from a typical phacoemulsification in a variety of ways. “First, the overall density of the lens requires more phaco energy to dismantle the nucleus, so you need to make provisions to protect the cornea in the face of that greater energy,” Dr. Foster said. “Second, the lens is usually much thicker than a traditional lens, so you have more girth to deal with but also the working conditions are a little tighter.” Third, since the red reflex is often significantly diminished, accomplishing the capsulorhexis is more difficult, he continued, adding that the capsule itself may also be more scarred, making its management difficult. In addition, often there’s a particularly leathery posterior plate, which may keep the nucleus from cracking, Dr. Foster noted.

Altering management techniques

Slightly different management principles may apply in these rock-hard cases. “If you’re going to hydro-dissect, it needs to be a very gentle dissection because the lens is so big that it’s easy for the fluid wave to become entrapped, and the subsequent pressure would blow out the posterior capsule,” Dr. Foster said. “One of the general recommendations of the Committee is that you create a trench if you’re going to chop the nucleus,” he said, adding that this can be located central to the capsulorhexis and moving up one-third of the nucleus toward the center. This creates working room for practitioners to try and pull pieces in centripetally.
For surgeons who prefer a divide and conquer technique, investigators recommended that the troughs be about twice as wide as they would for a standard nucleus to create the needed working distance. “These are hard enough and brittle enough that except in the posterior leathery plate, you can crack these through and that wide distance doesn’t work against you,” he said. The wider space would be an issue with a softer nucleus, in which you want to keep all of the nuclear bulk that you can so that you have something to push against but is not an issue in rock-hard cases. “Plus, all
of that energy to create a trench is delivering phaco energy the maximum distance away from the cornea,” Dr. Foster said.
With phaco energy in rock-hard cases, you generally have to work with higher phaco settings in terms of stroke length, Dr. Foster noted. “Some surgeons advocate using higher levels of vacuum and aspiration to overcome the repulsive forces of greater stroke length and to overcome the more dense nuclei,” he said, adding that in most of these cases, to protect the cornea, you have to stop at least once, if not more, to replenish the OVD in the eye because of the higher flow and the higher amounts of time spent on the removal process.
In cases that require zonular protection, if any weakness is noted early on, use hooks to further stabilize the zonules so that you can minimize disruption, Dr. Foster advised. While sometimes surgeons will use a capsular tension ring in the eye in the face of loose zonules, this is particularly difficult to do in these cases because the lens is so big and noncompliant. “Sometimes there’s no room to squeeze that capsular tension ring in between the capsule and the large nucleus, so you have to stabilize it with hooks and put the capsular tension ring in later when there’s actually room to place it,” Dr. Foster said.
It’s also not uncommon to have to deal with small pupils in these rock-hard cases. When trying to decide between placing a pupil expansion ring versus hooks in a rock-hard cataract case, if there is any question about the zonules, Dr. Foster is more likely to opt for hooks. Then he not only has these in place for expanding the pupil, but also if the zonules prove to be somewhat lax, it’s easy to push these forward and grab the capsule edge.

Emerging instrumentation

Dr. Foster finds the miLOOP (Carl Zeiss Meditec, Jena, Germany) is also potentially helpful in managing such cases. This instrument has a nitinol ring that when retracted becomes very small so that it can go through an incision, Dr. Foster explained. “But once it’s in the eye, you can slowly open the ring and you can feed that loop underneath the capsule until at full extension it can be rotated around so that it’s back behind the entire cataract,” he said. “Then, as you close the loop back to its small size, it physically cuts through the lens.” One advantage of it is that it applies great pressure from the posterior to the anterior through the posterior leathery plate, which can be difficult to treat with standard phaco since you can’t crack it. Meanwhile, when trying to cut this with a vibrating phaco needle, you’re just 0.5 mm away from the posterior capsule, Dr. Foster pointed out.
Overall, Dr. Foster hopes that practitioners come away from this study on rock-hard cases aware that these can usually be effectively managed to the benefit of the patient and that there are modifications that are required to increase the chances of success. “If carefully implemented, surgeons and patients alike can anticipate good results even though it’s a more challenging circumstance,” he concluded.

Reference

1. Foster GJL, et al. Phacoemulsification of the rock-hard dense nuclear cataract: options and recommendations. J Cataract Refract Surg. 2018;44:905–916.

Editors’ note: Dr. Foster has no financial interests related to his comments.

Contact information

Foster: gjlfos@gmail.com

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