Adequate suction does not guarantee safety in femto

April 19, 2015

In the first study to directly compare two femtosecond lasers for cataract surgery, both were considered safe and efficacious-but surgeons should be alert to eyes that move while under the docking station, said Seth M. Pantanelli, MD, MS.

In the first study to directly compare two femtosecond lasers for cataract surgery, both were considered safe and efficacious-but surgeons should be alert to eyes that move while under the docking station, said Seth M. Pantanelli, MD, MS.

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Platforms included in the study were the LenSx (Alcon Laboratories) and Catalys (Abbott Medical Optics) femtosecond lasers.

“Femtosecond laser for cataract comprises more than 2.5% of U.S. cataract surgeries,” he said. “There is mounting evidence on its advantages, including decreased energy/time and more precise astigmatic keratotomies.”

However, there still remains controversy over the devices’ advantages, as there has been an association with pupillary miosis and a higher incidence of capsular complications, said Dr. Patenelli, who is in practice in Hershey, PA.

“Some recent papers suggest the learning curve is responsible for the increase in complications,” he said.

While still in Miami, Dr. Patanelli and colleagues conducted a prospective comparative case series, with data collected on 97 LenSx and 108 Catalys cases.

For each case, the status of the anterior capsulotomy was classified using the following method:

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  • Type 1 indicated a complete treatment pattern,

  • Type 2 indicated micro-adhesions, and

  • Type 3 indicated an incomplete treatment pattern.

Pupil size was measured pre- and post-docking on both laser platforms.

In the LenSx eyes, 94 of the 97 capsulotomies were considered Type 1, with the remaining three type 2. In the Catalys eyes, all of the capsulotomies were considered Type 1, he said.

To account for the potential learning curve, Dr. Patanelli discounted the first 25 cases from each femto laser from each of the two surgeons performing the procedures.

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Once the laser was properly aligned and training cases were excluded, the rate of incomplete capsulotomies was 5.9% with the LenSx and 0% with the Catalys (p = 0.157). Pupil size decreased by 0.631 in LenSx (p < 0.001) and 0.377 mm in Catalys (p < 0.001) cases. The greater change in pupil size with LenSx cases was significant (p = 0.027).

In this study, the rhexis size was 4.8 mm, and the study criteria mandated that size. One pearl-use a bevel-down technique when applying to the microadhesion is welcome, as it turns a microadhesion into a full capsulotomy.

“There were no posterior capsule complications or vitreous loss,” he said.

“If you start to see a continuous ring of ‘champagne bubbles,’ that’s a good sign you have a good capsulorhexis,” he said.

Next: 'You really shouldn't use these on pupils under 3 mm'

 

But, he warned “look out for eye movement when the eye is under suction. The device may tell you there’s adequate suction, but in reality there’s not,” he said.

“Adequate suction as the machine defines it or determines it does not always mean it’s safe to proceed, as the eye may be moving under the docking procedure,” Dr. Patanelli said.

Postoperatively and retrospectively, the group realized that poor patient interface alignment can lead to lens tilt, he said.

“The nasal iris can be compessed and there is evidence of height differences between the nasal and temporal iris,” Dr. Patanelli said.

During the question-and-answer session, Dr. Patenelli said that in real-world settings, “you realy shouldn’t use these on pupils under 3 mm,” but some of the panelists disagreed, adding the “safest thing” to use is scissors when there is an incomplete capsulotomy.