Device guides IOL selection in certain patients

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Mark Packer, MD, describes how he uses a proprietary intraoperative aberrometer to guide IOL selection in patients with cataract surgery with a history of keratorefractive surgery.

By Cheryl Guttman Krader; Reviewed by Mark Packer, MD

Portland, OR-Intraoperative wavefront aberrometry has been a helpful tool for refining refractive outcomes after cataract surgery in the difficult group of eyes with previous keratorefractive surgery.

Mark Packer, MD, described his method of IOL power calculation in these challenging cases and he reported outcomes demonstrating good accuracy. His technique involves first inputting all of the preoperative data available for each case into the online ASCRS IOL calculator. Depending on the amount of information entered, the calculator generally suggests several lenses with different powers that can vary by 2 to 3 D. Then, all of the suggested lenses are brought into the OR, and after the cataract is removed, the aphakic refraction is performed with the intraoperative aberrometer (ORA, WaveTec Vision Systems).

Generally the lens power chosen by the intraoperative aberrometer is within the range suggested by the ASCRS IOL calculator, and in that situation Dr. Packer uses the aberrometer-determined power and the lens that he has the most experience with because it will have the best A-constant optimization. When the aberrometer suggests a power outside of the range of the IOL calculator, the difference has been 0.5 D at most, and then he chooses the IOL calculator-suggested lens with the power closest to that determined by the aberrometer.

“There is still some art involved in my approach, but it is more scientific than randomly picking from the options offered by the IOL calculator,” said Dr. Packer, clinical associate professor of ophthalmology, Oregon Health & Science University School of Medicine, Portland.

Refractive outcomes in a series of 12 eyes with a history of myopic LASIK support use of the technique. Dr. Packer noted that postoperative SE at 1 month averaged 0.30 ± 0.22 D, was within 0.5 D of intended in 75% of the eyes and within 1 D of intended in all 12 eyes.

In addition, he discussed its use in a patient who presented for bilateral cataract surgery with a history of LASIK monovision. The patient’s left eye was corrected for near, and he wanted to maintain monovision after cataract surgery.

The ASCRS IOL calculator generated a list of IOL options for each eye with powers ranging from 18 to 21 D for the right eye and 16 to 21 D for the left eye, and the intraoperative aphakic refraction determined that 21 D was the proper IOL power for each eye. Postoperatively, the patient achieved 20/25 distance uncorrected visual acuity (UCVA) in his right eye and J1 near UCVA in his left eye. Spherical refractions were –0.50 OD (target plano) and –2.25 D OS (target -2.25 D) with some residual astigmatism in both eyes.

New platform, better performance

The first generation of the intraoperative aberrometry platform used by Dr. Packer was first introduced by the manufacturer in April 2009 as the ORange. The current device, which was released in 2011, represents a 70% hardware change and offers a greater dynamic range (–5 to +20 D) as well as increased speed and accuracy. 

Pooled data from standard cases (not postLASIK eyes) derived from multiple investigators show increased accuracy was achieved with the changeover to the new system. Dr. Packer noted that among 295 eyes that underwent intraoperative aberrometry using the ORange 2.6, mean postoperative SE at 1 month was 0.36 ± 0.29 D compared with 0.32 ± 0.29 D in 82 eyes measured with the ORA. Among 131 postmyopic LASIK eyes measured with the ORange 2.6, the mean 1-month postoperative refractive was 0.51 ± 0.38 D, 60% of eyes were within 0.5 D of intended SE and 92% were within 1 D.

Interim data from a prospective multicenter study evaluating refractive outcomes using the ] for intraoperative aphakic refraction in postkeratorefractive surgery eyes show that the SE was within 0.5 D of intended in 68% of 45 eyes.

“This outcome compares well with published results for series where the IOL power was selected using various empirical formulas,” Dr. Packer said.

Dr. Packer noted he also uses intraoperative aberrometry to guide treatment of astigmatism at the time of cataract surgery in both toric IOL recipients and limbal relaxing incision cases. He presented a case where the system was used to determine optimal positioning of a toric lens, but noted it can also be used in toric IOL recipients to determine the aphakic spherical power and aphakic cylinder power and axis.

Mark Packer, MD

E: mark@markpackerconsulting.com

Dr. Packer is a consultant to WaveTec Vision Systems. This article is adapted from Dr. Packer’s presentation during the Spotlight on Cataract session during the annual meeting of the American Academy of Ophthalmology.