The treatment is performed using an excimer laser (VISX STAR S4 IR, Abbott Medical Optics [AMO]) and data acquired with a prototype unit of new diagnostic technology (iDesign Advanced WaveScan Studio, AMO) that takes five measurements (wavefront aberrometry, autorefraction, topography, keratometry, and pupillometry) in a single capture sequence.
The latter device incorporates a high-definition Hartmann-Shack sensor, which has both higher resolution (5×) and a higher dynamic range (sphere, –16 to +12 D; cylinder up to 8 D, higher-order aberration (HOA) RMS up to 8 μm) than the same manufacturer's current wavefront aberrometry unit (WaveScan, AMO). Its non-placido-based corneal topographer has a >8.3-mm diameter and aligns with the same axis as the aberrometer, explained Dr. Jackson, professor of ophthalmology, University of Ottawa Eye Institute, The Ottawa Hospital, Ontario, Canada.
The new advanced wavefront-guided system is being investigated in a multicenter study in Canada. Dr. Jackson presented outcomes at 6 months for 108 eyes enrolled in the myopic cohort.
The outcomes were particularly impressive, he concluded, considering that they represent data for the first clinical study using the new advanced aberrometry system and keeping in mind the device used was a prototype unit and the ablations were done without any physician or nomogram adjustments.
"Particularly interesting to me was that these seem to be our happiest LASIK patients," Dr. Jackson said. "Patients we treat with wavefront-guided LASIK are happy.
"However, these study patients were exceptionally happy and remain so," he said. "Although the subjective data from all our studies have not been fully analyzed, from the patients' perspectives, we've never seen such a satisfied group."
To be eligible for the treatment, patients had have myopia or myopic astigmatism with MRSE up to –15 D and cylinder up to –6 D. Distance best-corrected visual acuity (BCVA) had to be 20/20 or better and distance uncorrected visual acuity (UCVA) had to be 20/40 or worse.
In addition, all eyes needed to have a wavefront diameter >4 mm. LASIK flaps were created with the same femtosecond laser technology (IntraLase, AMO).
Enrolled patients had a mean age of 35 years. Preoperatively, their mean SE was –4.42 D (range –1 to –9.50 D), and cylinder averaged –1.27 D (range 0 to –5.25 D).
Distance UCVA was 20/20 or better in 93% of eyes at 1 month and in 94% of eyes at 6 months. At 6 months, 23% of eyes achieved distance UCVA of 20/12.5 or better and 77% were 20/16 or better; all eyes were 20/25 or better.
Refractive results showed good refractive stability between 1 and 6 months. MRSE changed by 0.5 D or less in almost 99% of eyes, and mean change in MRSE for the entire cohort was only –0.03 ± 0.25 D. At 6 months, 81% of eyes were within 0.5 D of their target MRSE.
Further analyses were conducted with eyes divided into two groups by level of myopia (low, 81 eyes: mean SE –3.41 D; high, 27 eyes: mean SE –7.47 D). Although the UCVA and predictability outcomes were better for low myopia, the results were still very good for high myopia. UCVA in patients with low and high myopia was 20/12.5 or better in 24% and 22%, respectively; 20/16 or better in 79% and 70%, respectively; and 20/20 or better in 96% and 85%, respectively.
Six-month predictability data for the two subgroups showed 85% of the patients with low myopia were within 0.5 D of intended refraction, but that level of accuracy was achieved in only two-thirds of those with higher myopia due to a tendency for undercorrection of sphere. The achieved sphere was within 0.5 D of target in 88% of patients with low myopia, but in only 70% of those with high myopia. Cylinder correction was within 0.5 D of target in 91% of patients with low myopia and 96% of high myopia.
Safety analyses showed no serious complications related to the surgery. No eyes lost more than 2 lines of BCVA, and a single eye had a 2-line loss at the 3-month visit only. The latter case involved high myopia with an inferiorly decentered flap; BCVA improved by 6 months.
At 6 months, 2% of eyes had a 1- to 2-line loss of BCVA, 12% had up to a 1-line loss, and the majority of eyes (57%) gained 1 or more lines, Dr. Jackson concluded.
Dr. Jackson has no direct financial interest to disclose. The study was supported by a research grant from Abbott Medical Optics.