Intrastromal femtosecond astigmatic keratotomy promising

Chicago-Initial clinical outcomes of intrastromal femtosecond astigmatic keratotomy show that the technique can safely reduce low to moderate levels of astigmatism. However, further refinement of the technique is needed to improve its predictability, said Steve C. Schallhorn, MD.

Dr. Schallhorn, global medical director, Optical Express, presented findings from follow-up to 3 months for 122 eyes of 105 patients (mean age 58 years; range 21 to 78). The patients included generally had a prior procedure, with refractive lens exchange (53%) and LASIK (37%) being most common. Time from the primary procedure ranged from several months to several years. Mean absolute cylinder was about –1.25 D.

Using a proprietary 150-kHz femtosecond laser (iFS, Abbott Medical Optics), the astigmatic treatments were performed using paired symmetric arcuate incisions centered on the steep axis with a 7-mm optical zone. The incisions were created at 60 μm from the epithelium, and the posterior incision depth was adjusted to be 80% of the corneal thickness. The initial simple nomogram titrated the amount of astigmatic correction by varying the arc angle.

Analyses of the outcome data showed there was reduction in cylinder that was stable from 1 week to 3 months and accompanied by a significant improvement in distance uncorrected visual acuity, while spherical equivalent and distance best-corrected visual acuity remained unchanged. However, there was a tendency to undercorrect the cylinder, and there was significant variability in the results.

“These data are from the very first use of the laser in this indication with a preliminary nomogram,” Dr. Schallhorn said. “Nomogram refinement is now under way, and undoubtedly, as we know from experience with other femtosecond laser procedures, outcomes will get better with time.”

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