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Beveled astigmatic keratotomy effective in eyes after penetrating keratoplasty
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Beveled astigmatic keratotomy performed with a femtosecond laser maximized comfort and wound stability in eyes that previously underwent penetrating keratoplasty, a physician said.
“The femtosecond laser is a very attractive tool for making arcuate incisions just inside the graft-host junction in post-PK corneas,” David Huang, MD, PhD, said at the meeting of the American Academy of Ophthalmology and Middle East Africa Council on Ophthalmology. “At least for me, that was tricky to do very accurately.”
Studies show that astigmatic keratotomy (AK) incisions made perpendicular to the corneal surface result in wound gaping and epithelial plugging, regardless of whether the incisions are made with a blade or laser, Dr. Huang said.
In Dr. Huang’s first case of femtosecond AK, the incision was made perpendicular to the corneal surface at 80% depth. Because of gaping, the patient was uncomfortable.
“I sutured the wound and took it out a few months later,” Dr. Huang said. “The final result was very good. The residual astigmatism went from 6 D to 0.4 D. But I did not like having to suture the wound.”
Bevel, arc,depth
Because the femtosecond laser can cut at an angle, Dr. Huang and colleagues reasoned that by beveling the incision, they could eliminate gaping. They performed a small series of procedures in six eyes of six patients who had high astigmatism after PK.
After the sutures had been taken out of the corneal transplant for at least 6 months, the patients underwent femtosecond-beveled AK with the IntraLase 60-kHz femtosecond laser (Abbott Medical Optics). Manifest refraction and simulated keratometry on topography (Orbscan II, Bausch + Lomb) were used to measure astigmatism.
Dr. Huang and colleagues created paired arcuate incisions 0.4 mm inside the keratoplasty wound at a 135° bevel. Incisional arc ranged from 60° to 90°, and depth ranged from 65% to 75%. Investigators used asymmetric and skewed arc pairs to treat asymmetric and skewed topographic astigmatism patterns.
High-resolution Fourier-domain optical coherence tomography (RTVue, Optovue) was used to evaluate wound configuration at 1 week, 1 month and 3 months after surgery. Patients were followed up for 3 to 6 months.
Wound stability
Study results showed that uncorrected visual acuity improved by five lines and best corrected visual acuity improved by 1.4 lines. Keratometric astigmatism was reduced by about 70%, Dr. Huang said.
“You could produce up to 16 D flattening with only up to 75% cut depth, 90° arc,” Dr. Huang said. “There was no gaping. Only one out of 12 images shows epithelial plugs.”
Due to the lack of gaping, the wounds were nearly invisible at the slit lamp after postoperative day 1. However, OCT showed that, instead of gaping, the wound margins were tightly opposed, with the anterior side sliding forward.
“Anterior to the wound, the cornea was thicker,” Dr. Huang said. “Posterior to the wound, the stroma is compressed but the epithelium is thicker.”
“Because of the lack of wound gaping, there is a smooth epithelial surface, and the patients were comfortable from day 1,” Dr. Huang said. “We accomplished our goal of eliminating gaping while retaining effective astigmatism correction by using the femtosecond laser to its fullest advantage.” – by Matt Hasson
- David Huang, MD, PhD, can be reached at Casey Eye Institute, 3375 SW Terwilliger Blvd., Portland, OR 97239; e-mail: davidhuang@alum.mit.edu.
- Disclosure: Dr. Huang received stock options, travel support, speaker fee, research grants and patent royalty from Optovue.