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Advancements in wavefront-guided technology include improved resolution that provides not only better spot quality but also the ability to scan highly aberrated eyes that often did not produce treatable images using earlier technology, according to Edward E. Manche, MD.
Reviewed by Edward E. Manche, MD
The latest generation of wavefront-guided (WFG) LASIK instruments allows ophthalmologists to treat highly aberrated eyes in a single step. WFG ablation can treat aberrations of the entire eye, not just corneal aberrations, said Edward E. Manche, MD.
This new technology has five times the resolution of the previous wavefront sensor, explained Dr. Manche, director of cornea and refractive surgery, Byers Eye Institute, Palo Alto, CA, and professor of ophthalmology, Stanford University School of Medicine, Stanford, CA.
“You now have 210-μm resolution compared with the 400-um resolution with the previous-generation aberrometer, which allows you to successfully image and treat highly aberrated eyes, eyes with keratoconus, corneal scarring, and previous trauma that we could not effectively treat before,” he said. “WFG ablations provide excellent clinical outcomes for eyes with naturally occurring refractive error, and we can rehabilitate highly irregular corneas and correct refractive errors in one step.”
Latest WFG outcomes data
Dr. Manche reviewed published data from high-volume commercial settings treating low myopia, his own results in moderate myopia, and study results in highly aberrated eyes using a particular system (iDesign, Johnson & Johnson Vision/formerly Abbott).
WFG offers improved diagnostic capabilities that take the entire optical system into account, Dr. Manche explained. Most systems are based on Hartmann-Shack technology, although early systems included Tscherning aberrometry, and ray-tracing aberrometry has shown promise, he noted.
The first generation of WFG technology was introduced about 15 years ago, Dr. Manche noted. Both WFG and wavefront-optimized (WFO) technologies create ablations customized to each eye, but WFG is more highly personalized and customized to each eye.
The latest iDesign instrument utilizes more than 1,250 datapoints over a 7-mm wavefront compared with 240 datapoints over a 6-mm wavefront used by the previous wavefront technology. The improved resolution provides better spot quality and the ability to scan highly aberrated eyes that often did not produce treatable images using earlier technology, he noted.
The LASIK market is split between WFO and WFG systems in the United States, Dr. Manche continued.
Some clinicians may view WFG as more labor intensive. WFO requires only refraction and keratometry values, whereas WFG also requires aberrometry.
Dr. Manche noted that two excimer laser technologies (VISX CustomVue, Johnson & Johnson Vision; WaveLight Allegretto, Alcon Laboratories) are integrated into the workflow in his practice.
“I don’t see a real time difference in my clinical practice,” he said.
One of the largest WFG data sets published to date is from Optical Express, a commercial optical surgical provider in the United Kingdom. The population includes 8,905 eyes treated between May 30, 2012 and Aug. 24, 2013.
The mean preoperative sphere was -2.80 and the mean preoperative cylinder was -0.81. One month after WFG LASIK, 100% of eyes had 20/40 or better uncorrected visual acuity, 95% were 20/20 or better, and 84% were 20/16 or better.
Dr. Manche reported similar results in a study of the first 78 eyes treated at Stanford after WFG was approved for use by the FDA. The manifest sphere was -4.80, the manifest cylinder 0.66, and the manifest SEQ -4.47.
One month after surgery, 100% of eyes were 20/32 or better, 96.2% were 20/20 or better, and 44.9% were 20/16 or better. Results at 4 months were similar.
The predictability of the WFG system was even more impressive, Dr. Manche added.
All of the eyes were within 1 D of the intended target at 1 month; 97.4% were within 0.5 D, and 85.9% were within 0.25 D. Predictability was even stronger 4 months after surgery; 98.5% were within 0.5 D, and 90.9% within 0.25 D of the intended target.
“Of all the laser systems I have used in my career, this one has the best predictability I have ever seen,” Dr. Manche said. “It really does have an advantage over our older technology in clinical practice.”
Data from Egypt
Published data from the Horus Vision Correction Center, Alexandria, Egypt (data courtesy of Mohamed Shafik Shaheen, MD, PhD) using the iDesign system shows excellent results in highly aberrated eyes that might not be treatable using older technology or could not be treated in a single step. A study group of 22 eyes in 18 patients included a dozen eyes with keratoconus, 4 eyes with prior keratotomy, and 6 eyes with irregularities following LASIK.
Before surgery, 80% of eyes had best-corrected distance visual acuity of 20/50 or worse. After surgery, all eyes had uncorrected visual acuity of 20/50 or better, 90% were 20/40 or better, 40% were 20/25, and 10% were 20/20 or better. Ten percent gained at least 1 line of visual acuity and 90% gained 2 or more lines.
“Many of these eyes gained 5 and 6 lines of corrected visual acuity,” Dr. Manche said. “In many cases, WFG allows for one-step treatment, eliminating irregularity and correcting refractive error at the same time.”
Edward E. Manche, MD
This article was adapted from Dr. Manche’s presentation during Refractive Subspecialty Day at the 2016 meeting of the American Academy of Ophthalmology. He is a consultant to and has received grant support from Johnson & Johnson Vision (formerly Abbott).