CHICAGO — Outcomes might be better with wavefront-guided (WG) photorefractive keratectomy (PRK) than with wavefront-optimized (WO) PRK for patients older than 40 years, according to a study presented here at the American Academy of Ophthalmology 2012 Annual Meeting
"We think that the aberrations induced by the aging cornea and lens become more important over time. WG strategies take the aberrations of each eye into account, taking a wavescan of the entire eye and attempting to correct for it," the authors write in their abstract.
Joshua Roe, MD, from the Uniformed Services Health Education Consortium in San Antonio, Texas, presented the results.
The goal of refractive surgery is to obtain a visual acuity of 20/20 or better. There is no clear consensus in the literature on whether WO or WG ablation is the better approach.
Dr. Roe and colleagues evaluated 481 eyes treated with WO ablation and 481 age-matched eyes treated with WG ablation. The eyes were stratified by age and preoperative refractive error. Mean spherical equivalent (MSE) was used for refractive error.
The 6-month outcomes for best spectacle-corrected visual acuity (BSCVA), low contrast visual acuity (BSCVA5%), MSE, and uncorrected visual acuity between the WO and WG groups were compared.
BSCVA was not significantly different between the 2 platforms for any age group or preoperative MSE. However, the WG platform was associated with significantly better BSCVA5% in patients older than 40 years in both the –1 to –3 diopter group (P = .015) and the –3 to –6 diopter group (P = .012).
The WG platform was significantly better at achieving plano in patients younger than 30 years with a preoperative MSE of –3 to –6 diopters (P = .003).
The percentage of patients with "super vision" (uncorrected visual acuity better than 20/20) was significantly higher with the WG platform in patients older than 40 years with a preoperative MSE of –3 to –6 diopters (P = .046).
"We treat a lot of military personnel, such as pilots, and we wanted to see if we could get them to 20/10 (i.e., super vision). At least in the older cohort, WG was better at this," Dr. Roe explained.
Other researchers have suggested that patients with root-mean-square (RMS) higher-order aberrations (HOAs) greater than 0.3 µm could benefit from the WG platform. Dr. Roe and colleagues suggest there might be a correlation between the RMS HOAs greater than 0.3 µm and patients older than 40 years that could help surgeons select the appropriate ablation platform.
James Salz, MD, clinical professor of ophthalmology at the University of Southern California, Los Angeles, elaborated on the 2 platforms for Medscape Medical News.
"WG and WO are similar, but WG looks at the preoperative aberrations and tries to adjust the delivery of laser energy based on this picture. WO just tries to reduce the spherical aberration and uses curvature of the eye as part of the formula," he explained. "Very few of us do traditional laser ablations that are not customized in some way, but these can work, too. You decide based on the patient's measurements — their aberrations and pupil size."
The larger the pupil, the greater the importance of one of these ablation platforms. Customization, which is more expensive to the patient, is essentially not necessary for patients with small pupils, Dr. Salz noted.
"In my practice, the patient who gets WG is the one with large pupils who is highly nearsighted. I want to do the procedure that is the least likely to cause nighttime symptoms of halos and glare, and that would be the WG treatment," he said. "I don't think age really makes much difference."
Dr. Roe has disclosed no relevant financial relationships. Dr. Salz reports consulting for Alcon and NTK Enterprises.
American Academy of Ophthalmology (AAO) 2012 Annual Meeting: Abstract P0197. Presented November 11, 2012.
Medscape Medical News © 2012 WebMD, LLC
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Cite this: Wavefront-Guided Platform May Be Preferable for PRK - Medscape - Nov 19, 2012.