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Hyperopic wavefront-guided LASIK yielding positive results
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Although wavefront analysis has been more commonly applied to the correction of myopia, it has shown promise in hyperopic correction as well. Clinical studies for hyperopic wavefront have yielded positive early results, surpassing those of conventional hyperopic LASIK and hyperopic photorefractive keratectomy (PRK).
“If you really look at it, the results are exceptional,” said W. Bruce Jackson, MD, chairman of the department of ophthalmology at the University of Ottawa, Ottawa, Canada. “Overall, the initial results have been really encouraging, and the patients have been pleased from day 1.”
Study results with CustomCornea
Omar J. Hakim, MD, medical director of TLC Laser Eye Centers in Toronto, Canada, discussed results from a clinical study he conducted using wavefront-guided hyperopic LASIK.
“The objectives for hyperopic wavefront-guided LASIK are exactly the same as for myopic wavefront,” Dr. Hakim told Primary Care Optometry News. “We are looking at capturing the wavefront using the aberrometer, and matching that wavefront data to the anatomy of the eye. This process of matching is called registration, and it is critical for wavefront-guided custom ablation.”
Dr. Hakim said registration is the concept that the wavefront should be treated exactly where it was measured.
“That just makes sense – if you don’t treat it where you measured it, then you can in fact induce new aberrations and make the patient’s postoperative results worse,” he said. “It is critical to make sure you match or link the treatment ablation to the measured wavefront on the aberrometer.”
In Dr. Hakim’s study, 106 hyperopic patients were treated. In 57 of those patients, one eye received a conventional treatment, and the other received a customized treatment. The remaining 49 patients were treated without a contralateral control eye. Up to 3.5 D of hyperopia and up to +3.75 D of cylinder were treated. According to Dr. Hakim, the first-generation CustomCornea Measurement Device (Alcon Summit Autonomous, Ft. Worth, Texas) was used. Future studies will use Alcon’s LADARWave device.
At 3 months, Dr. Hakim said 93% of the custom-treated eyes had achieved 20/32 uncorrected acuity, as opposed to 91% of conventional eyes. In terms of achieving 20/25 or better, Dr. Hakim said 88% of the custom eyes and 81% of the conventional group reached this goal.
Of the custom eyes, 60% achieved 20/20 or better, compared to 53% of the conventional eyes, Dr. Hakim said.
In terms of best-corrected visual acuity, Dr. Hakim reported that 100% of both the custom and conventional eyes achieved 20/25 at 3 months. While 100% of the custom eyes achieved 20/20 or better, 96% of the conventional eyes achieved 20/20 or better at 3 months.
An equal amount – 68% — of both the custom and conventional eyes achieved 20/16 or better at 3 months, whereas 16% of conventional eyes vs. 21% of custom eyes achieved 20/12.5.
“So, the custom eyes were doing slightly better in terms of both uncorrected and best-corrected visual acuity,” Dr. Hakim said. “In terms of change of best-corrected acuity, more of the custom patients gained lines of best-corrected visual acuity, and fewer of them lost lines of best-corrected visual acuity than the conventional group.”
Study results with WaveScan
Dr. Jackson shared with Primary Care Optometry News the preliminary results of the first hyperopic treatment with WaveScan-guided LASIK using the WavePrint System from Visx (Santa Clara, Calif.).
The prospective, non-randomized study included hyperopic patients with astigmatism up to 3 D. The study included two men and four women, all of whom had bilateral LASIK with a PreVue lens treatment verification using the variable spot scanning on the Visx Star S3 Active Track. Follow-up was done at 1 day, 1 week and 1 month.
Before treating the patient with the WavePrint correction, a plastic PreVue lens was ablated to verify that the correction would be an excellent option for the patient, Dr. Jackson said. The lens was placed in front of the patient, and if the vision could be improved to 20/20+3 letters, then the patient’s cornea was then treated.
The optical zone in these cases was blended to 9 mm total ablation area. The ablation target was created with the WaveScan wavefront map, Dr. Jackson said, including up to sixth-order aberrations.
For the 12 eyes of the participating subjects, the preoperative sphere varied up to 3 D, the cylinder varied up to 1.5 D and the mean spherical equivalent was 2.19 D.
Dr. Jackson said at 1 month for uncorrected visual acuity, 33% of the eyes were 20/16 or better, and 100% were 20/20 or better. At 1 month, the mean spherical equivalent was +0.08 D, with only +0.06 D of sphere.
“To have 100% at 20/20 or better at 1 month is really far better than we thought we could achieve,” Dr. Jackson said. “We had 92% at 20/25 or better in 1 week, and that was really quite incredible.”
There was no change from 1 week to 1 month in mean spherical equivalent, and 92% were within +50 D at 1 month postop. In terms of best-corrected visual acuity, 58% of the eyes achieved 20/16 or better, and 100% achieved 20/20 or better.
Dr. Jackson noted that the 3- and 6-month results are still being analyzed, adding that these data will provide further insight into the success of the procedure.
“This is the first go; there is no nomogram adjustment. This is right from the WaveScan, and yet we are getting these results at 1 month,” he said. “What we have to answer is, does this hold at 3 months, 6 months and longer?”
Dr. Jackson said a small change in the nomogram may be necessary if the 3- and 6-month results indicate regression. “It may be that we are so close at 1 month, there may be a little drift when we get out to 6 months,” Dr. Jackson said.
For higher-order aberrations, in a typical case, there was a reduction in the root mean square from 0.49 to 0.24. According to Dr. Jackson, the higher-order aberration point spread function reflected the change in best spectacle-corrected visual acuity from a preop 20/20 to a postoperative 20/16.
Improvement over PRK
Dr. Jackson discussed his previous work with hyperopic PRK and compared it to the results of his recent hyperopic wavefront LASIK study.
“We did a lot of hyperopic PRK. We went back and looked at a group of patients who had hyperopic PRK in the same range,” he said.
“Interestingly, in that group at 1 month, none of the patients had achieved uncorrected visual acuity of 20/16 or better, and that was compared to 33% who achieved 20/16 or better with wavefront.”
While 9% of the hyperopic PRK patients achieved 20/20 or better, 100% achieved that result in the wavefront study, Dr. Jackson said. He added, however, that while the PRK patients were initially overcorrected, they improved over the course of 6 months.
“We know that with hyperopic PRK, it takes longer for the surface to become regular,” Dr. Jackson said. “We know they tend to be overcorrected and that they tend to regress back toward plano over about 6 months. What we don’t know is whether the PRK and the wavefront will end up being pretty much the same at 6 months.”
Dr. Jackson said wavefront-guided patients will be monitored for 6 to 12 months to check for regression, and the nomogram will be adjusted if necessary to ensure they are plano at 6 months.
“There is no question that this will be the wave of the future,” Dr. Jackson said. “This study was a pilot to see if this worked. Now, we have to see what happens over time.”
For Your Information:
- W. Bruce Jackson, MD, is professor and chairman of the department of ophthalmology at the University of Ottawa. He can be reached at 501 Smyth Road, Tower 3, Ottawa, Ontario, Canada K1H 8L6; (613) 737-8759; fax: (613) 737-8374. Dr. Jackson receives research funding from Visx and is a paid consultant for 20/10 Perfect Vision.
- Omar J. Hakim, MD, is medical director of TLC Laser Eye Centers in Toronto, Canada, and also practices at the University of Waterloo. He can be reached at University of Waterloo School of Optometry, Waterloo, Ontario, Canada N2L 3G1; (519) 888-4502; fax: (519) 886-1348. Dr. Hakim is a paid consultant for Alcon.