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Wavefront-guided myopic LASIK with new aberrometer yields predictable outcomes
Uncorrected distance visual acuity of 20/16 or better was achieved in 79% of eyes, and spherical equivalent was within 0.5 D of target in 93% of eyes.
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Wavefront-guided myopic LASIK with a new-generation Hartmann-Shack aberrometer yielded predictable outcomes and high patient satisfaction, according to a study.
The device also offered significant cylinder correction.
“The most significant result was the refractive and acuity outcomes,” Steven Schallhorn, MD, the corresponding author, said in an interview with Ocular Surgery News. “What undoubtedly contributed was the quality of the aberrometer and this aberrometer measurement combined with the ablation profile it generated. Those were contributing factors for the high level of efficacy in the study.”
The iDesign Advanced WaveScan aberrometer (Abbott Medical Optics) is not approved in the United States and is undergoing clinical trials. The study was conducted in the United Kingdom, Schallhorn said.
Steven Schallhorn
The study was published in the Journal of Refractive Surgery.
Patients and procedure
The retrospective study included 243 eyes of 126 patients with a mean age of 34.5 years who underwent primary wavefront-guided LASIK.
The iDesign was used to capture wavefront data. An iFS femtosecond laser (AMO) or mechanical microkeratome was used to create LASIK flaps.
Schallhorn said that 82% of patients had femtosecond laser flaps and 18% had mechanical microkeratome flaps.
Ablation was performed with the Visx Star S4 IR excimer laser (AMO).
Investigators evaluated visual acuity, refraction and patient satisfaction 1 month after surgery.
Visual and refractive outcomes
Uncorrected distance visual acuity of 20/16 or better was attained in 79% of eyes, 20/20 or better in 93.4% and 20/25 or better in 96.7%. No eyes lost two or more lines of corrected distance visual acuity, and 14% of eyes gained two or more lines.
Manifest refraction decreased significantly (P < .01). Mean manifest spherical equivalent decreased from –3.28 D preoperatively to –0.03 D. Manifest spherical equivalent was within 0.5 D of emmetropia in 93% of eyes and within 1 D in 99.6%.
Mean manifest astigmatism decreased from –0.72 D to –0.14 D.
“The procedure incorporates a very precise rotational alignment on the eye prior to treatment with excimer laser,” Schallhorn said. “This combined with the improvement in the aberrometer and the creation of the unique treatment profile are responsible for the excellent outcomes. These excellent outcomes are also apparent for cylinder correction. Accurate cylinder correction is one of the standouts of the procedure.”
The authors noted that 98.5% of patients were satisfied with their outcomes.
Accurate ablation profile
Schallhorn attributed much of the accuracy to improvements in the aberrometer.
“It is a much more capable sensor,” he said.
“It has the ability to precisely sample all ocular aberrations across the entrance pupil,” he said. “It has the highest number of lenslets available in a Hartmann-Shack aberrometer. Then the internal algorithm calculates the ablation profile using an advanced Fourier reconstruction of the ocular aberrations. The ablation profile — in other words, the instructions provided to the excimer laser for where and when to place pulses on the cornea as well as the pulse size — is calculated in the aberrometer. This is a critical component to a wavefront-guided procedure and an important contributor to the high degree of efficacy.” – by Matt Hasson
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Perspective
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Karl G. Stonecipher, MD
In this article by Schallhorn et al, we see outstanding results for a new diagnostic system for use with modern LASIK. When more than 98% of the patients say they are satisfied with their treatment and 100% of the patients would recommend the procedure to their friends and relatives, you have a way to make the doctors and staff happy as well. Although only 1-month visions are reported, uncorrected distance visual acuity of 20/16, 20/20 and 20/25 or better was reported in 79%, 93.4% and 96.7% of eyes, respectively. Gain in overall vision of one or more lines of vision was 14%.
The new aberrometer is the iDesign Advanced WaveScan aberrometer, which is the latest Fourier aberrometer from Abbott Medical Optics. It captures more data points than the previous model and averages 1,250 data points from up to a 7-mm pupil. This data series was collected retrospectively from European centers, and outcomes should improve as nomograms are collected with this new technology. The R-squared values of 0.97 for sphere and 0.94 for astigmatism are evidence of great outcomes, but nomogram development should improve already outstanding postoperative results. I agree with the authors’ comments that they would like to complete a larger and longer prospective series with aberrometry outcomes, but the data collected prove that the new aberrometer is a step in the right direction.
Perspective
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Noel A. Alpins, MD
This paper describes the early results retrospectively from treatment guidance of the Visx S4 IR with the new AMO iDesign aberrometer to demonstrate equivalence at the least with its predecessor, the AMO WaveScan. As the authors themselves state, comparisons with these 243 eyes treated are difficult. One interesting finding is the spherical coupling of +0.40 D of sphere occurring in the higher astigmatism corrections, requiring a physician’s adjustment for all eyes according to the amount of astigmatism treated. There is no corneal astigmatism analysis provided at all, and the displays show only a comparison of refractive cylinder magnitudes without any vectorial assessment.
The most significant difficulty with the paper is a confusion of vector terminology, complicating reader interpretation. The paper employs parameters from a 2006 paper that was not peer-reviewed and written for regulatory purposes. The analysis parameters were copied and then terminology changed without acknowledgement of the seminal technique published in 1993. This paper of 20 years standing is now accepted as a standard for peer-reviewed published papers.
Further reports on the device’s safety and efficacy are anticipated longer than 1 month post-surgery. Hopefully, these will be prospective and contain conventional terminology.
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