Intraoperative aberrometer optimizes IOL calculations after previous laser correction

Study shows a difference of less than 0.5 D between 1-month postop spherical equivalent and predicted spherical equivalent for the IOL power implanted.

Intraoperative wavefront aberrometry enabled real-time refractive measurements and maximized refractive outcomes in eyes undergoing cataract surgery after previous refractive surgery, a speaker said.

Renée Solomon, MD, presented results of a study in which the ORange intraoperative wavefront aberrometer (WaveTec Vision Systems) was used to make IOL power calculations in eyes that had undergone laser vision correction.

“The intraoperative wavefront aberrometer enables real-time, on-the-table refractive measurements,” Dr. Solomon said at the American Society of Cataract and Refractive Surgery meeting in Boston. “It limits refractive surprises in post-refractive eyes and enables aphakic IOL power calculation to eliminate the need for intraoperative IOL exchange.”

Dr. Solomon elucidated the difficulty of making IOL power calculations in eyes that have previously undergone LASIK or PRK for myopia or hyperopia.

“There are many methods that are used to calculate post-refractive surgery IOL calculation,” Dr. Solomon said. “It is a challenge to calculate IOL power following refractive surgery for many reasons, including inaccurate corneal curvature measurements, and [keratometry] values may be higher than actual power.”

The ORange intraoperative wavefront aberrometer was developed to deliver on-demand, real-time intraoperative refractive data that allow aphakic and pseudophakic IOL power calculations, Dr. Solomon said.

Intraoperative measurement

Dr. Solomon and colleagues set out to investigate the accuracy of real-time intraoperative wavefront aberrometry in IOL power selection in eyes undergoing cataract surgery after previous refractive surgery.

To qualify, all eyes must have had a prior uncomplicated LASIK or PRK with a well-centered topographic ablation profile, Dr. Solomon said.

Clinicians used a mean predictive value to compare outcomes from the standard preoperative measurement method to those from intraoperative wavefront aberrometer. The comparison involved subtracting the predicted postoperative spherical equivalent from the 1-month postoperative spherical equivalent.

The retrospective, multicenter study included 29 eyes of 29 patients that underwent phacoemulsification with IOL implantation. The patient group included five previous hyperopic LASIK cases and 24 previous myopic LASIK cases.

Surgeons used the intraoperative wavefront aberrometer to determine if the visual target was attained. They recorded intraoperative aphakic and pseudophakic measurements of the refractive status of all eyes.

Most errors lower than 1 D

Results showed that the intraoperative aberrometer revealed a difference of less than 0.5 D between 1-month postop spherical equivalent and predicted postop spherical equivalent for the IOL power implanted. The standard method yielded a difference of 0.72 D. Ninety-three percent of patients evaluated with the intraoperative aberrometer had a difference of less than 1 D.

In addition, the intraoperative aberrometer yielded a maximum refractive error of 1.5 D. The standard method produced a maximum error of 2.38 D.

“The intraoperative wavefront aberrometer enables measurement of the true real-time refractive power of the cornea, which leads to the true corneal refractive power,” Dr. Solomon said. “This is important in post-refractive corneas because the refractive power of the cornea influences the selection of the intraocular lens power.” – by Matt Hasson

• Renée Solomon, MD, can be reached at rensight@yahoo.com.