Cataract surgery image guidance may improve results

June 15, 2011

An image-guided femtosecond laser may improve safety and outcomes during cataract surgery by automating some of the manual steps such as capsulorhexis, incisions and nucleus chopping.

Further, the efficacy of premium IOL surgery may be improved with a perfectly centered capsulotomy of optimal dimension, exact surgical incisions, and precise intrastromal astigmatic cuts, said Stephen G. Slade, MD, at the annual meeting of the American Society of Cataract and Refractive Surgery.

Interestingly, this image-guided laser is positioned outside of the operating room. Using this laser, the surgeon can design precisely how he or she wants to perform cataract surgery while looking at a real-time optical coherence tomography (OCT) image.

"The surgeon views an image that is interactive and can 'drag and drop' the off-sets for the capsulorhexis and set the nuclear chop, the incision, the size, and the number of planes-whatever the surgeon desires," said Dr. Slade, who is in private practice in Houston.

The laser is docked to the eye with a suction ring. As the surgery progresses, the laser can be viewed as it starts to do the chop, the capsulorhexis, and the incisions. Parameters of any of the formerly manual maneuvers can be adjusted based on surgeon preference.

When the surgeon goes into the operating room, he or she has to find rather, than perform, the capsulorhexis and other already completed procedures.

"The surgeon's first maneuver can be entering the eye with the phaco tip," he said.

Dr. Slade described several other fortunate characteristics.

"Not only are you cutting the capsule, you also are cutting the cortex, which results in a very nice cortex rim around the capsulotomy that can speed up cortex removal," he said.

The laser requires about 30 seconds to carry out its maneuvers and about 1 minute to dock on the eye.

Inserting an accommodating lens

Dr. Slade said he and his colleagues have performed about 40 cases of cataract surgery and implantation of an accommodating IOL (Crystalens, Bausch + Lomb) using this laser. He reported on the first 19 consecutive cases.

The best-corrected visual acuity on day 1 postoperatively was 20/15 to 20/30 or better. The spherical equivalent was within 0.5 to 1 D of the intended correction in these cases.

When Zoltan Nagy, MD, evaluated the laser in Budapest, he found that the phacoemulsification times and the amount of energy used in the eye were reduced.

Dr. Slade pointed out that the refractive component of the laser is the key factor.

"We have 11% conversion rates for premium IOLs in the United States because we are not doing a good enough job. We have low visual outcomes; there has been no improvement in safety; and surgeon confidence is lower," he said. "Even if we disregard what the laser can do with incisions, cuts, and the upcoming astigmatic cuts, just the effect of the position of the lens is very important."

The lens power is calculated based on the keratometry and axial length plus empirical factors, such as a surgeon factor or A constant, which can be a source of error in the IOL power and where the IOL will sit, he said.

"This also is affected by the size of the capsulorhexis," he continued. "The smaller the capsulorhexis, the more posterior the lens will vault. A capsulorhexis created with the laser is simply more accurate in size and positioning than a manually created capsulorhexis."

Lens positioning

Dr. Slade said he believes that the use of this femtosecond laser will have a positive impact on the results obtained with multifocal IOLs as well.

"When we look at the anterior chamber depth and the variability of the axial length, at 1 week and 1 month postoperatively we are getting a more predictable effect of lens positioning with this technology," he said. "This makes sense, because all parameters are being precisely controlled. For the first time, we have a baseline to build on.

"We have been very happy with the device when using it with accommodating IOLs in our practice," Dr. Slade concluded.

FYI

Stephen G. Slade, MDE-mail: sgs@visiontexas.com

Dr. Slade has a financial interest in the femtosecond laser. In April, the laser was approved for use in the United States for phacofragmentation during cataract surgery.