August 2016

 

CATARACT

 

Tips and tricks

Technique for cortex removal with the femtosecond laser


by Ellen Stodola EyeWorld Senior Staff Writer

 
 

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Watch a video of this technique now at EyeWorld Clinical rePlay clinical.ewreplay.org

 
Irrigate subincisional cortex

Dr. Dewey uses a J-cannula to irrigate subincisional cortex from the capsule.

Source: Steven Dewey, MD

Dr. Dewey shares insights from using his technique for more than 20 years

Steven Dewey, MD, Colorado Springs, Colorado, has been using his technique for cortical removal with the J-cannula for almost 25 years, but more recently, he found that it can be particularly useful with the femtosecond laser. He started irrigating cortex out of the capsule with this cannula in 1991. “At first, I didn’t think it was anything all that special,” Dr. Dewey said, although it certainly was effective. “I found it interesting that the cannula was already developed,” he said, and because of this, Dr. Dewey expected this technique would have already been developed. However, he discovered that the cannula was specifically designed for aspiration, not irrigation. The cannula was developed during the extracapsular cataract extraction era with much larger incisions. Irrigating to remove cortex would have translated into a lot of issues with chamber stability and iris prolapse, he said. After doing the technique for nearly 10 years in only phaco cases, Dr. Dewey said he accumulated 3,000 cases and was very pleased with his unplanned vitrectomy rate during cortical removal, which was one.

Applications with the femtosecond laser

It all starts with hydrodissection, he said. “Every ophthalmologist knows that you stage getting the cortex out by doing hydrodissection, which you do before you get the nucleus out,” he said. “You visualize this wave to determine its effectiveness.

“The critical difference about doing hydrodissection in a manual case is that the anatomy of the nucleus is intact,” he said. “The fluid wave is going to be confined to the cortical capsular plane as defined by the nucleus.” With femto, the nucleus isn’t intact, so the anatomy isn’t the same. There are channels cut within the nucleus, and in most cases, gas is within those channels. The hydrodissection wave will find less resistance to flow within the cuts of the softened nucleus—displacing the gas rather than the cortex.

The cortex is also fundamentally altered by the femto laser, Dr. Dewey said. With capsulotomy creation, there is a safety zone, and the physician is firing in front and behind the capsule. This fuses the cortex posterior to the anterior capsule—both to itself and to the capsule. Because of this, the cortex will not aspirate as easily.

The second point has to do with the posterior and lateral safety zones. As with the subcapsulotomy cortex, there is a thick layer of cortex that’s intact and inherent to itself, Dr. Dewey said. “The J-cannula irrigation technique is much like hydrodissection, but after the nucleus has been removed,” he said. The tip of the J-cannula is placed between the intact cortex and the capsule, and this self-adherent cortex can be used to confine the wave of fluid to the corticocapsular plane. “I started irrigating the subincisional cortex, using the I&A to remove the rest. It took awhile to start displacing all of the cortex, first out of the capsule, then out of the eye,” Dr. Dewey said. “It is very effective, but it takes practice.” Any time you’re pressurizing the eye, you can easily displace the iris through the incision. “The worst thing to do with this technique is push the iris out of the eye, but that’s possible in a number of techniques, including standard hydrodissection,” he said. Dr. Dewey has become a strong advocate of making the patient as immobile as possible, taping the head and placing a gentle restraining strap across the chest just above the elbows. “The thing to remember is, this instrument is a hook. If the patient moves on the table, the J-cannula can hook the iris or capsule, making it difficult to remove. If the physician hooks the incision, it’s not a huge deal,” he said. This technique is a bimanual technique, Dr. Dewey said, so the physician needs to use both hands. “It’s a lot like hydrodissection in how you hold the cannula, but you’re putting it in different places and trying to get a different angle,” he added. The J-cannula has to have a bit of a flare to the “J,” and the slightly flared short leg will allow it to achieve access to the cortical capsular plane without difficulty.

Tools needed

For this technique, the size of the needle and syringe are important, Dr. Dewey said. A 5-cc syringe is ideal, and he mainly uses it with a 26-gauge needle. A 30-gauge cannula can be used, but it will take a lot of hand strength to push balanced salt solution through that small of a bore, and a 3-cc syringe is useful. With a 3-cc syringe, physicians can also run out of balanced salt solution quickly, finding themselves with a flat chamber and needing to remove a hook from the capsule. An advantage of the 30-gauge is that it doesn’t require as much applied force, Dr. Dewey said, but it will still displace the cortex from the posterior capsule. It just doesn’t do it as vigorously. Additionally, the metal is a bit flimsier on the 30-gauge, thus, placement of the tip in the precise location is a bit trickier.

With the 26-gauge, the cannula is stiffer so the physician can place it more accurately, he said. This flow is more vigorous, but this effect can be controlled by restricting the pressure placed on the syringe. “If you run out of fluid, there is a hooked structure inside the eye, so you do have to be careful to make sure you stabilize the cannula with one hand and use a side port to add viscoelastic,” he said.

Additional information

For a manual surgery, hydrodissection is usually more effective, and this technique will only take about 20–30 seconds, Dr. Dewey said. In femto cases, the extra cortex usually requires two passes, with or without using the automated I&A. This technique is also ideal for polishing the adherent debris off of the posterior capsule.

In a manual case, Dr. Dewey said he’s usually able to have the cortex removed before the staff has the I&A handpiece set up.

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

Contact information

Dewey: deweys@prodigy.net

Cortex removal with the femto laser Cortex removal with the femto laser
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