Take steps to avoid phaco wound burn
This dreaded complication can happen to any cataract surgeon.
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The development of phacoemulsification using ultrasonic energy by Charles Kelman, MD, transformed the way that we perform cataract surgery.
With Kelman’s innovations, we are now able to remove a 9 mm wide cataract via incisions that are about 2 mm in size. The ultrasonic energy is effective at breaking up and emulsifying the cataract, but it can also have side effects within the eye.
The ultrasonic vibrations are a form of mechanical energy in which the phaco needle travels back and forth or circumferentially with longitudinal or torsional movement, respectively. The friction from this rapid movement causes heat, and it can build up much faster than we realize, often in just a second or two. To protect the eye from this, we can limit the energy, cool it with fluid and keep it away from the ocular tissues.
Limiting the ultrasonic energy
Phaco power modulations are a way of delivering smaller amounts of ultrasonic energy typically in bursts or pulses, allowing time in between for cooling and heat dissipation. The duty cycle in a pulse mode relates to the on:off ratio, with lower ratios offering more cooling time. If we use a low ratio such as 10:90, then each cycle will have 10% of the time for energy delivery and then 90% for tip cooling. While this will not cause heat buildup and virtually eliminate the risk for a wound burn, it may not offer enough power to effectively emulsify the cataract. Most surgeons tend to use closer to a 50:50 ratio to balance cooling with efficiency and then rely on the cooling benefit of the balanced salt solution.
Effective fluidic cooling
The fluidic inflow in cataract surgery is important to keep the anterior segment inflated and provide replacement fluid as the phaco tip performs aspiration of the cataract. In our method of coaxial phaco, we encase the metal phaco needle with a silicone sleeve, which serves as the fluid inflow channel while also providing a degree of insulation to protect the tissues. This inflow of balanced salt solution will cool the phaco needle, and then any egress of fluid from our incisions will add additional thermal benefit. This is why we intentionally make our phaco incisions slightly leaky for cataract surgery. We must also be aware that an excess of viscoelastic in the anterior chamber can block fluid flow and lead to a phaco wound burn.
Pivoting within the incision
The most important factor in preventing a phaco wound burn is the surgeon’s technique of pivoting within the incision. The phaco tip, including the metal needle, should stay centered within the incision, floating between the roof, floor and lateral sides of the incision at all times. Pressing the phaco needle against the incision will place the metal needle closer to the delicate corneal tissue, and it will also block the inflow and outflow of saline, which would normally cool the tip. This is what happened in the case presented here.
Case presentation
The patient was noted to have a dense white cataract at the preoperative consultation with vision of just hand motions (Figure 1). We know that a larger amount of ultrasonic energy will be required to emulsify this brunescent nucleus. The phaco machine was programmed with power modulations to limit the heat creation from friction, and the larger 2.75 mm phaco sleeve was selected for added protection compared with the 2.2 mm tip.
Source: Uday Devgan, MD
The surgery was performed by a senior resident with less than 100 cataract cases of experience. A good capsulorrhexis was performed, and then the phaco tip was introduced to sculpt an initial groove in the nucleus. As the surgeon was applying energy, the phaco tip was being pushed against the lateral wall of the incision because of a lack of pivoting. This placed the metal phaco needle right up against the corneal stroma, and it also blocked the flow of balanced salt solution.
Within just a few seconds, the cornea burned, and an opaque white spot was noted at the incision (Figure 2). This caused the corneal stroma to coagulate and distort with the incision becoming excessively leaky, which altered the phaco fluidics and created anterior chamber instability. The decision was made to convert to a manual extraction of the nucleus via a new scleral tunnel incision. After the cataract was removed and the IOL was placed into the capsular bag, the corneal incision was sealed. This required many sutures because of the distortion of the incision architecture from the burn (Figure 3). This irregular incision also induced a significant degree of corneal astigmatism in the postoperative period.
After a few months of healing, the sutures were removed, and the patient was left with just a moderate degree of corneal astigmatism. The postoperative vision improved dramatically, and the patient was happy. The resident surgeon also learned some valuable lessons: Denser cataracts will require more ultrasonic energy and pose a higher risk for phaco wound burns. Phaco power modulations allow for cooling as the energy is delivered in pulses or bursts. Fluidic flow around the phaco needle is important for cooling, and we must pivot within the incisions to avoid pressing the tip against the delicate corneal tissue. Using these techniques, we can limit the risk for a phaco wound burn.
Go to cataractcoach.com/category/complications to see surgical video of this case at CataractCoach.com.
- For more information:
- Uday Devgan, MD, is in private practice at Devgan Eye Surgery, Chief of Ophthalmology at Olive View UCLA Medical Center and Clinical Professor of Ophthalmology at the Jules Stein Eye Institute, UCLA School of Medicine. He can be reached at 11600 Wilshire Blvd. #200, Los Angeles, CA 90025; email: devgan@gmail.com; website: www.CataractCoach.com.
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