Blade versus laser for astigmatism correction

Boston-Patients have high expectations regarding cataract surgery outcomes, and anything less than perfect may be considered a failure, said Kendall E. Donaldson, MD, MS.

Unfortunately, 50% to 70% of patients with cataracts also have more than 0.75 D of pre-existing astigmatism, said Dr. Donaldson during Cornea Day at the annual meeting of the American Society of Cataract and Refractive Surgery.

The goal is to leave patients with less than 0.5 D of residual cylinder, said Dr. Donaldson, Bascom Palmer Eye Institute, Miami.

She focused on correction of corneal astigmatism and discussed treatment with toric IOLs and corneal limbal-relaxing incisions (LRIs).

Two studies compared the two methods of astigmatism correction and both found toric IOLs to have better outcomes and be more stable and predictable. Toric IOLs are the appropriate choice for patients who underwent a previous refractive surgery, have a thin corneal, and higher levels of astigmatism or ocular surface disease.

LRIs can be created manually or by laser. Several nomograms can guide LRI creation, but with-the-rule and against-the-rule astigmatism behave differently and patients must be treated differently depending on age.

“We must be careful with LRIs, because small degrees of axis deviations can reduce the effects especially with high degrees of astigmatism,” Dr. Donaldson said. “Introduction of the femtosecond laser may add something to our treatment.”

Comparison of manual and femtosecond laser incisions with penetrating keratoplasty showed the femtosecond laser was safe and effective, with fewer perforations during treatment and better uncorrected visual acuity levels. The manual group had larger axis shifts, which the femtosecond laser has reduced. No nomograms have yet been published, but current guidelines indicate that LRIs should be place at 80% of the corneal thickness and 33% should be subtracted from the manual treatment.

“With toric IOLs, the femtosecond laser provides better centration and more accurate alignment with intrastromal marking LRIs,” Dr. Donaldson said. “With femto-LRIs, they are more precise, reproducible, and predictable. The accuracy is currently limited by evolving nomograms.”

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