Adjustable femtosecond laser incisions reduce pre-existing astigmatism

Adjustable femtosecond laser arcuate incisions performed during cataract surgery significantly reduced pre-existing corneal astigmatism, according to a study.

“What we did was look at the femtosecond laser to treat astigmatism at the same time as cataract surgery. Initial results have been very good,” Stephen G. Slade, MD, OSN Refractive Surgery Board member, said at the American Academy of Ophthalmology meeting in Orlando, Fla. “We’ve looked at the outcomes with paired incisions and single incisions, both with vector plots and absolute numbers. We had much tighter vector plots and astigmatism was reduced.”

Relatively few cataract surgeons use clear corneal arcuate incisions to treat pre-existing astigmatism, Dr. Slade said.

“On the other hand, everybody treats astigmatism when they’re doing LASIK,” he said. “Using the laser for the cataract is like using the laser for LASIK. You’re sitting there. You calculate the astigmatic error. You enter it. You run it through the nomogram. You open them during surgery. You monitor them. It’s just very effective.”

Dr. Slade noted that astigmatism increases defocus curves and diminishes vision, especially when a multifocal IOL is implanted.

Measurement and calculation

The study included 39 eyes that underwent phacoemulsification and IOL implantation. The procedures were performed by Dr. Slade, Eric D. Donnenfeld, MD, OSN Cornea/External Disease Board Member, and Richard J. Mackool, MD.

Surgeons performed adjustable astigmatic incisions with the LenSx femtosecond laser (Alcon). The Lenstar LS90 optical biometer (Haag-Streit) was used to calculate IOL power calculations, corneal curvature, axial length and other parameters.

Laser incisions were later opened manually at the time of surgery or postoperatively at the slit lamp to maximize targeted refractive results, Dr. Slade said.

IOL selection was not a controlled variable in the study protocol, Dr. Slade said.

“We didn’t use any toric IOLs, but you could,” he said. “You could combine this with a toric in a bioptic-like effect. But we did not control the type of IOLs, so there were multifocals, there were monofocals and there were accommodating IOLs in the study.”

Results and further study

Study results showed that in the first case series, cylinder was reduced by 70%. At 1 month, 77% of eyes were within 0.5 D of targeted refraction; 71% of eyes in the lower cylinder group were within 0.25 D of the target, Dr. Slade said.

The laser incisions provided better astigmatic corrections than expected, but surgeons had the option of opening incisions to maximize outcomes in select cases, he said.

“We found that it compared very favorably to arcuate incisions or [limbal relaxing incisions] done manually,” Dr. Slade said. “In fact, we were able to get better results than what we were able to find in the literature. We also found that we could adjust the incisions. If, the next day, we felt we had an under-correction, we could come back in and actually open up the incision a bit.”

Dr. Slade said he and colleagues are embarking on a subsequent study of 20 eyes in which astigmatism was under-corrected with laser arcuate incisions. Eyes will be examined 1 year out from cataract surgery.

“We’re going to measure the curvature, open the incisions up again or open them up for the first time since the cataract surgery, and then see how much effect we get,” Dr. Slade said. – by Matt Hasson

For more information:

• Stephen G. Slade, MD, can be reached at Slade & Baker Vision, 3900 Essex, Suite 101, Houston, TX 77027; 713-626-5544; fax: 713-626-7744; email: sgs@visiontexas.com.
• Disclosure: Dr. Slade is a consultant for Alcon.