Using femtosecond lasers in eyes with previous surgery

Dr. Donaldson explains that prior corneal surgery does not necessarily indicate that FLACS would be ineffective. However, there are some immediate disqualifications to bear in mind.

Reviewed by Kendall Donaldson, MD

Take-home message: Dr. Donaldson explains that prior corneal surgery does not necessarily indicate that FLACS would be ineffective. However, there are some immediate disqualifications to bear in mind.

Miami-Femtosecond laser technology may not be the right choice for every patient presenting for cataract surgery, said Kendall Donaldson, MD, associate professor of clinical ophthalmology and medical director of Bascom Palmer Eye Institute at Plantation, Bascom Palmer Eye Institute, Miami.

“As we approach these cases, we need to ask how the femtosecond laser will provide this patient with a better outcome,” she said. Each case should be treated individually with consideration toward reducing additional risk to either the lens or cornea.

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“We certainly don’t want to add risk to the cornea by having a perforated limbal relaxing incision if there is thinning of the cornea,” she said. “With the lens, we don’t want to have an incomplete rhexis that leads to tags or adds difficulty to the case.”

Requirements for FLACS

A primary requirement for femtosecond cataract surgery (FLACS) to be successful is a clear cornea; for patients with corneal pathology and scarring, it is imperative that any corneal pathology not impact the visual axis or the area to which the laser is being applied, she said.

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“Think about patients with prior corneal surgery-say, RK-and bear in mind those scars (particularly if hypertrophic) cannot block the laser penetration,” she said. “Think also about the density and location of the corneal opacities we’re trying to laser through. I frequently do FLACS safely and effectively through fine, well-healed RK incisions.”

Prior corneal surgery should not represent an automatic disqualification, she said. “Patients with previous RK, LASIK, PRK, those with Intacs, or those who have undergone collagen cross-linking can all be good candidates for FLACS. Even post-keratoplasty patients can be considered,” Dr. Donaldson said.

For those with prior RK, “not all incisions were created equal-some will be nice and small and well-healed, but others may be hypertrophic and will block all laser penetration,” Dr. Donaldson said.

In her experience, patients with prior LASIK or PRK are great candidates for FLACS “because they really like the idea of having laser. They’ve had laser before, it worked well, and the technology appeals to them,” she said. Surgeons should ensure those candidates do not have epithelial ingrowth that might have resulted in scar tissue that could block the laser energy and cause an incomplete capsulotomy.

With prior RK, surgeons may need to increase the energy a little bit higher for the capsulotomy to ensure complete scar penetration, Dr. Donaldson said. In a patient with Intacs, consider placing the laser in a smaller diameter zone to ensure the Intacs will not block penetration.

“You might need to decrease the diameter of your capsulotomy diameter and your lens fragmentation pattern to compensate,” Dr. Donaldson said.

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Post-keratoplasty patients may be considered potential candidates, since the degree of suction is very low in most of the femtosecond lasers, with “an average increase in pressure of 10-15 mmHg,” she said.

Exclusionary factors

Just as surgeons should not discount prior corneal or post-refractive surgery patients, Dr. Donaldson also will consider patients with keratoconus.

“With their central apical scarring and very steep corneas, most are not candidates, but if the patient has mild keratoconus without severe thinning and more regular astigmatism, they should not be automatically disqualified,” she said. The femtosecond laser used with a toric IOL is an effective tool in patients who may have severe, primarily regular astigmatism.

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However, poor candidates are those with corneal scarring severe enough to limit laser penetration. For those with Fuchs’ dystrophy, candidates fall into two groups: those that have guttatae without corneal edema-where the femtosecond laser would be effective-and those with “significant corneal edema and stromal opacities/scarring within the cornea” that should not be considered, Dr. Donaldson said.

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Because all of the femtosecond laser platforms have been found to use between 50-99% less energy during the cataract surgery than traditional techniques, “we hope that will translate into the preservation of endothelial cells,” she said. “Some early, smaller studies are showing this to be the case, but larger confirmatory studies still need to be undertaken.”

Finally, she also cautions against using the femtosecond laser on patients with larger pterygia for three reasons: they may prevent adequate suction, may interfere with laser penetration, and may be associated with significant amounts of irregular astigmatism, which may limit ultimate visual potential.

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In short, we need to have a more detailed discussion with these patients about their expectations with consideration of their best potential vision post-cataract surgery. Although the femtosecond laser can be such an important tool for many of these patients we need to understand it may not be right for every patient with a history of prior corneal disease or surgery.

“Like all our surgeries, setting realistic expectation preoperatively will prevent disappointed patients postoperatively,” she said. The ultimate goal of doing what is right for the patient-minimizing risk and maximizing gain-may mean that FLACS is not the perfect solution for every patient, but can certainly be an effective tool for many.

Kendall Donaldson, MD

E: kdonaldson@med.miami.edu

This article was adapted was Dr. Donaldson’s presentation at the 2015 meeting of the American Academy of Ophthalmology. Dr. Donaldson is a consultant for Abbott Medical Optics, Alcon Laboratories, and Allergan.