New wavefront indication enhances treatment for mixed astigmatism
Patient segment can be challenging to treat with LASIK
Rising to challenge
Mixed astigmatism is probably the hardest refractive error to correct with LASIK, Dr. Maloney noted.
“You have to steepen one meridian and flatten the opposite,” he said. “The ablations are more complex in terms of shape.
“One challenge is you may not get a full correction,” Dr. Maloney said. “Another challenge is that you may correct the astigmatism well but cause a shift in spherical equivalent that can be myopic or hyperopic. You correct one problem but create another. The [system] offers the possibility of more accurate correction.”
Additionally, mixed astigmatism is fairly common after a patient’s original LASIK, he added.
A clinical study of the system for mixed astigmatism in 149 eyes found that 91.9% of all eyes had uncorrected visual acuity of 20/20 or better without glasses at 3 months after surgery. Additionally, about 90% of eyes were within a half-diopter of their target refraction, and roughly 90% had 0.50 D or less of astigmatism.
“Those are really good results,” especially when up to 5 D of preoperative astigmatism was treated, Dr. Maloney said.
The new indication is for mixed astigmatism with a magnitude of 1 D to 5 D of cylinder that is greater than the magnitude of sphere and in which the cylinder and sphere have opposite signs, according to an Abbott press release.
Additionally, there must be an agreement between manifest refraction and the system refraction with a magnitude of difference of less than 0.625 D in spherical equivalent and a magnitude of difference of less than or equal to 0.5 D for cylinder.