Specialist offers pearls on managing corneal astigmatism with an IOL

A surgeon discusses treatment options in the absence of an FDA-approved toric presbyopia-correcting IOL.

Mitchell A. Jackson

A surgeon at OSN New York 2011 offered pearls on managing astigmatism with limbal relaxing incisions and toric IOLs.

It is important that practitioners differentiate corneal astigmatism from lenticular astigmatism and set realistic patient expectations, Mitchell A. Jackson, MD, said.

“Corneal topography is essential in determining if you have with-the-rule astigmatism, against-the-rule astigmatism, forme fruste keratoconus or an epithelial basement membrane dystrophy, which you need to address postoperatively as well,” Dr. Jackson said. “If there is no corneal cylinder preop, cataract removal alone is sufficient in eradicating astigmatism. But if there is corneal cylinder preop, then that is the real driver to a successful outcome.”

Dr. Jackson said there are devices that distinguish corneal astigmatism and lenticular astigmatism.

“These are great patient education tools as well,” he said.

Treatment options

Because the U.S. Food and Drug Administration has yet to approve a toric presbyopia-correcting IOL, surgeons are left with four treatment choices: a monofocal IOL with limbal relaxing incision (LRI), a toric IOL, a presbyopia-correcting IOL with LRI, and a presbyopia-correcting IOL with either LASIK or PRK.

A thorough preoperative analysis of patient lifestyle factors is critical, as is treating the ocular surface to maximize diagnostic data capture.

“Most patients who come in for cataract surgery are asymptomatic, and dry eye signs are actually very common in these patients,” Dr. Jackson said. “If you have a poor ocular surface, even in the asymptomatic cataract patient, this will impact accurate topography readings, keratometry readings and biometry readings.”

Before surgery, Dr. Jackson recommended performing vector analysis for an LRI or toric IOL.

With the manual technique for LRI, surgeons should place their LRI at about a 9-mm optical zone, inside the limbal vascular arcade, to avoid regression and improve visualization.

“These incisions can be done either intraoperatively or postoperatively with a number of blades, and even at the slit lamp with a cooperative patient,” Dr. Jackson said.

Femtosecond laser technology for LRI, on the other hand, offers fewer perforations, less irregularity and more precision.

“But the procedure must be done intraop,” Dr. Jackson said. “However, you can refine postop, such as opening or lengthening the incisions.”

Furthermore, intraoperative aberrometry allows for real-time adjustment for either the femtosecond laser or manual technique.

Placement of incision, IOL

Before performing a femtosecond laser-assisted LRI, Dr. Jackson determines whether he will make an on-axis incision.

“At least 50% to 60% of patients have at least 0.75 D of astigmatism,” he said.

If the astigmatism axis is less than 15° from the incision site, he places the incision at the steep axis. But if the astigmatism axis is more than 15° from the incision site, he places the incision where he is comfortable operating.

“Surgeons also need to know their own surgically induced astigmatism number for vector analysis purposes,” Dr. Jackson said.

LRI nomograms assist in this process.

“You can also personalize your own nomogram. … A little more for against-the-rule, a little more for younger patients, and a little less for older patients. You might also want to adjust for pachymetry and avoid the limbal vascular arcade directly,” he said.

When using the laser vision correction option, it is always safer to wait for refractive stability, according to Dr. Jackson. Typically, a surgeon should wait at least 3 months, but no less than 1 month if there is stability.

Unless there is diffuse posterior capsular haze, the astigmatism from multifocal IOL enhancements should be treated first, before considering YAG treatment.

“The femtolaser technology with its LRI application now may solve the crisis for precision as compared to laser vision correction postoperatively for those surgeons without excimer laser access,” Dr. Jackson said.

For toric lenses, alignment is key. And as with LRI, the surgically induced astigmatism value and vector analysis are important. The accurate placement of a toric IOL with a planned marking technique is also crucial.

Dr. Jackson said he anticipates the introduction of some toric multifocal or accommodating IOLs and looks forward to optimizing LRI nomograms with femtosecond laser technology. – by Bob Kronemyer

• Mitchell A. Jackson, MD, can be reached at 300 N. Milwaukee Ave., Suite L, Lake Villa, IL 60046; 847-356-0700; email: mjlaserdoc@msn.com.
• Disclosure: Dr. Jackson is on the speakers bureau for Alcon, Allergan, Ista Pharmaceuticals, Abbott Medical Optics and Bausch + Lomb.