February 2016

 

CORNEA

 

Femtosecond laser use in eyes with corneal considerations


by Ellen Stodola EyeWorld Staff Writer

 
   
The cornea is clear

Figure 1: Patient with prior LASIK. The cornea is clear, so this patient would be a good candidate for femtosecond laser use.

Central corneal opacityFigure 2: Central corneal opacity due to prior hydrops in a keratoconus patient. This patient would not be a good candidate for femtosecond laser use.

Large pterygiumFigure 3: Large pterygium obscuring the visual axis and preventing adequate suction and obscuring laser penetration. This patient would not be a good candidate for femtosecond laser use.

Small, flat pterygiumFigure 4: Small, flat pterygium allows adequate suction and is not obscuring laser penetration. This patient would be a good candidate for femtosecond laser use.

Source: Kendall Donaldson, MD

Its important to be aware of a patients previous corneal surgery and corneal pathologies before using the femto laser

During a session on femtosecond laser-assisted cataract surgery (FLACS) at the 2015 American Academy of Ophthalmology (AAO) annual meeting, Kendall Donaldson, MD, MS, Miami, presented on Femtosecond Cataract Surgery in Eyes with Previous Corneal Surgery or Corneal Pathology. She gave tips on what to consider and what questions to ask in these scenarios.

We should always ask ourselves what we have to gain, she said. Is FLACS going to provide a better outcome? Dr. Donaldson said its important to weigh the risks and benefits, and there may not be one universally correct answer that applies to all patients.

We certainly dont want to add any risks, she said, and its important to first determine if there are any added risks of the procedure. Dr. Donaldson discussed some of the potential added risks for both the lens and the cornea. For the lens, there could be potential for an incomplete rhexis, leading to tags, anterior capsule tears, and/or posterior capsule tears. Dislocation of the nucleus into the vitreous could also be a problem. Meanwhile, for the cornea, perforation of LRIs are a potential problem because most imaging systems look at the center of the LRI only for corneal depth. There is also the unpredictable effect of LRIs and biomechanical destabilization of the cornea to consider. Femtosecond cataract surgery requires a clear cornea, Dr. Donaldson said, so for this reason, its important to identify poor candidates ahead of time. Corneal pathology and prior cornea surgery can potentially pose problems. Dr. Donaldson also recommended taking into account the density and location of any corneal opacities. Patients with prior cornea surgery include those who have had procedures such as radial keratotomy (RK), LASIK, photorefractive keratectomy (PRK), Intacs, crosslinking, or a keratoplasty procedure. Mostly, you want to be sure that scars are not going to impact laser penetration, she said. Dr. Donaldson thinks patients who previously have undergone LASIK and PRK would be good candidates for femtosecond laser use. These patients tend to love the idea of using the laser again, she said, and the corneas are clear. Patients with prior penetrating keratoplasty (PK), Descemets stripping endothelial keratoplasty (DSEK), and deep anterior lamellar keratoplasty (DALK) are certainly good candidates. We have to remember that the cornea has to be clear, she said. Patients with pre-existing corneal conditions also require special considerations when deciding if its appropriate to use the femtosecond laser. These would include patients with keratoconus, Fuchs dystrophy, corneal scarring, or pterygium. With all of these conditions, there are both good and bad candidates. Dr. Donaldson said that particularly for those with corneal scars, central corneal scars could block laser penetration. Similarly, there are some good candidates with Fuchs dystrophy. Guttata is fine, Dr. Donaldson said, but significant corneal edema or opacities would make the patient a bad candidate. When we talk about Fuchs dystrophy, she said, we can use much less ultrasound energy when we apply FLACS pre-treatment for lens softening and fragmentation. Were hoping this will translate into preservation of endothelial cells. Smaller pterygia are also fine in conjunction with the femtosecond laser, but larger pterygia are not as they may infringe on the area of laser penetration and may interfere with maintenance of patient interface suction.

The integration of technology is key to give surgeons the best results, Dr. Donaldson said. In conclusion, she said that FLACS may be performed in patients with some corneal pathology or prior corneal surgery. Always weigh the risks and benefits, she said, and always set realistic expectations.

Editors note: Dr. Donaldson has financial interests with Abbott Medical Optics (Abbott Park, Ill.) and Alcon (Fort Worth, Texas).

Contact information

Donaldson: kdonaldson@med.miami.edu

Femto laser and corneal considerations Femto laser and corneal considerations
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