Myopia: wavefront-guided PRK or wavefront-guided LASIK?
San Diego--Results from 12 months of follow-up in a prospective, randomized study show wavefront-
guided PRK (WFG-PRK) and wavefront-guided LASIK (WFG-LASIK) are similarly safe and effective
procedures for the treatment of low-to-moderate myopia. WFG-LASIK, however, offers a
http://www.youtube.com/watch?v=usS63qoqOTA definite advantage of faster visual recovery, said
Capt. David J. Tanzer, MD.
The investigative device exemption study was conducted at Naval Medical Center San Diego to
evaluate the efficacy and safety of WFG-PRK, which is not an FDA-approved procedure, and to
validate further the safety of WFG-LASIK in a larger warfighter patient population. The study
enrolled 200 subjects with myopia between -1 and -6 D and up to 2.5 D of astigmatism. The
participants were randomly assigned to undergo bilateral WFG-PRK or WFG-LASIK, and the two
treatment groups were well-matched at baseline with respect to mean age (~30 years), mean sphere
(~-2.7 D), mean cylinder (-0.7 D), and mean SE (-3 D).
By 6 months, outcomes of the two procedures were essentially comparable for predictability, safety
(change from preoperative best spectacle-corrected visual acuity [BSCVA]), quality of vision metrics
(higher-order aberrations [HOAs] and low-contrast acuity), and the participants' subjective appraisal
of outcomes. However, there was an early loss in mean best-corrected visual acuity (BCVA) in the
WFG-PRK group and there were highly statistically lasik eye surgery recovery significant differences
favoring the WFG-LASIK group for better uncorrected visual acuity (UCVA) through 3 months as
well as for better predictability.
"Based on the results of this study, WFG-PRK is clearly a safe and effective procedure, and the
slower visual recovery in the WFG-PRK group was expected," Dr. Tanzer said. "However, in our
population, it represents the Achilles' heel that hampers us from performing surface ablation
procedures, especially for personnel with warfighter status.
"WFG-LASIK with femtosecond laser flap creation is the refractive surgery procedure of choice for
warfighters who are then eligible sooner for return to full duty and deployability," he added.
All of the ablations were performed using a certain platform (Star S4 CustomVue platform with the
3.64V Fourier software, Abbott Medical Optics) using no nomogram adjustments and with a 6-mm
optical zone and 8-mm transition zone. Dr. Tanzer and Steven Schallhorn, MD, principal investigator
for the study, performed all of the procedures.
Epithelial removal was done using an Amoils brush for the PRK procedures, and the postoperative
regimen included bandage contact lens application, nonpreserved tetracaine drops, topical
antibiotic, and 2-month corticosteroid taper.
LASIK procedures were done with a 15-kHz femtosecond laser (IntraLase) to create a 100- or 110-
?m thick flap with a 9.2-mm diameter. Patients received a 1-week postoperative course of topical
antibiotic and corticosteroid.
At 1 week after surgery, there was a clear and highly statistically significant difference in the UCVA
outcomes favoring the LASIK procedure. UCVA of 20/20 or better was achieved by 94% of eyes
treated by WFG-LASIK and 42% of those that had WFG-PRK; UCVA was 20/16 or better in 78% of
WFG-LASIK eyes but in only 10% of eyes treated with WFG-PRK.
A statistically significant difference favoring WFG-LASIK for better UCVA outcomes was maintained
at 1 and 3 months. At 3 months, 96% of WFG-LASIK eyes and 92% of WFG-PRK eyes achieved UCVA
of 20/20 or better, and rates of 20/16 or better for the two groups were 87% and 80%, respectively.
By 6 months, there was still a numerical difference in UCVA outcomes favoring the WFG-LASIK
group, but the differences were not statistically significant.
BSCVA analyses showed a significant difference in the safety margin favoring LASIK at 1 month
when there was a mean, statistically significant gain in logMAR BSCVA in the WFG-LASIK group and
a mean loss in the WFG-PRK group, +0.04 versus -0.003. At 6 months, both the WFG-LASIK and
WFG-PRK groups had a statistically significant mean gain from baseline logMAR BSCVA, +0.05
versus +0.04, but there was still a statistically significant difference favoring LASIK. By 12 months,
both groups achieved a further mean gain but the difference between groups was not statistically
Quality-of-vision assessments included measurement of low-contrast (25% mesopic) BCVA, and there
was no statistically significant difference between groups at any follow-up visit. Both treatments
caused a slight induction of HOAs. While there was no difference between groups at 1 month,
induced HOA at 3 months was slightly and significantly greater in the WFG-LASIK versus WFG-PRK
group, 0.1 versus 0.05 ?m.