Reducing IOL prediction error

Venice, FL-Intraoperative aberrometry guidance significantly improves refractive outcomes with toric IOL implantation after phacoemulsification in post-refractive surgery eyes, according to a study conducted by P. Dee G. Stephenson, MD.

The research included data from a series of 20 consecutive patients (32 eyes) with a history of prior corneal refractive surgery. All eyes had potential postoperative distance best-corrected visual acuity (BCVA) of 20/32 or better, and no preoperative ocular pathology, explained Dr. Stephenson, associate professor of ophthalmology, University of South Florida, Tampa, and private practice, Venice, FL.

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Mean preoperative keratometric astigmatism for the group was 1.39 ± 0.98 D.  

IOL spherical power, cylinder power, and axis of placement were determined preoperatively and refined by intraoperative aberrometry (ORA with VerifEye, Alcon Laboratories).

Analyses showed that the mean absolute value of the prediction error was significantly reduced using ORA guidance compared with the preoperative calculation (0.30 ± 0.23 D versus 0.64 ± 0.48 D). In addition, ORA guidance increased the proportion of eyes with a prediction error ≤0.50 D (80% versus 60%).

Data from manifest refraction measured at least 1 month after surgery showed refractive astigmatism averaged 0.23 ± 0.40 D, was ≤0.25 D in 75% of eyes, and ≤0.50 D in 85% of eyes, Dr. Stephenson said.

“This is a relatively small study, and a larger randomized, prospective, observer-masked trial would allow for a more detailed analysis of all endpoints,” she said. “Nevertheless, these are impressive outcomes for a challenging group of eyes.”

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The patients in the study had a mean age of 68 years and 12 underwent binocular cataract surgery. The majority of patients (75%) had undergone prior myopic LASIK while the others had previous radial keratotomy (RK) (15%) or hyperopic LASIK (10%).

“The eyes that had more than 0.5 D of residual astigmatism were those with a history of RK, and the explanation may involve more unpredictable corneal healing in those eyes,” Dr. Stephenson said. “It seems further work is needed to improve outcomes for that subgroup of post-refractive surgery eyes.”

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The majority of patients (75%) received a presbyopia-correcting toric IOL (Trulign, Bausch + Lomb), and the rest received the plate haptic toric IOL (STAAR Toric IOL, STAAR Surgical). Good results were achieved with both implant models.

Corresponding with the refractive results, visual acuity outcomes were excellent.

Monocular distance uncorrected visual acuity was 20/40 or better in all eyes, while 85% saw 20/30 or better and 60% achieved 20/25 or better. Distance BCVA was 20/25 or better in 100% of eyes and 20/20 or better in 75%.

Dr. Stephenson noted that there is a learning curve for using intraoperative aberrometry. She said that at first, she was spending an extra 5 minutes per case when implanting a toric IOL. However, after becoming familiar with the system, using intraoperative aberrometry adds just about 1 minute to the time.

P. Dee G Stephenson, MD

E: eyedrdee@aol.com

Dr. Stephenson is a speaker for Bausch + Lomb and served as a member of the WaveTec Vision surgical advisory board.