A study conducted at Emory University finds the overall rate of re-treatments (“enhancements”) required after wavefront-optimized LASIK and PRK is 6.3 percent. But patients who are farsighted or have at least -1.00 diopter of astigmatism prior to surgery are significantly more likely to need an enhancement.
Retreatments after LASIK and PRK: Study design
To determine the rate of retreatment and to identify risk factors for unacceptable outcomes requiring retreatment after wavefront-optimized LASIK and PRK, researchers at Emory University (Atlanta, Ga.) conducted a retrospective review of 855 eyes undergoing these treatments from January 2005 through December 2006.
Wavefront-optimized LASIK is a semi-customized laser vision correction procedure designed to control a specific type of optical error called spherical aberration (SA). It is believed SA is a major cause of glare, halos and other night vision disturbances after laser vision correction.
Wavefront-optimized procedures differ from wavefront-guided LASIK and PRK, which are fully customized laser procedures aimed at controlling many other higher-order aberrations in addition to SA.
All wavefront-optimized procedures evaluated in the study were performed by the same surgeon using the same proprietary excimer laser platform (Allegretto Wave, WaveLight AG). All LASIK flaps were created with an Amadeus I microkeratome (Abbott Medical Optics, Santa Ana, Calif.).
Prior to surgery, 785 of the eyes (92 percent) were nearsighted, 70 eyes (8 percent) were farsighted. Additionally, 231 eyes (27 percent) had at least 1.00 D of astigmatism and 61 eyes (7 percent) had at least 2.00 D of astigmatism.
Postoperative measurements included uncorrected visual acuity (UCVA) and best-corrected visual acuity (BCVA) at three months. The decision for re-treatment surgery was not made until at least three months after the initial procedure and refractive stability was confirmed.
Retreatments after LASIK and PRK: Study results
Analysis of the study data revealed the following results:
- After the initial wavefront-optimized LASIK and PRK treatments, 72 percent of eyes achieved UCVA of 20/20 or better and 99.5 percent of eyes achieved UCVA of 20/40 or better.
- A total of 54 eyes (6.3 percent) had enhancements performed to improve uncorrected visual acuity.
- There were no significant differences in re-treatment rates based on patient age or sex, refractive procedure performed (PRK versus LASIK), operating room temperature or humidity, or the month or season during which the primary procedure was performed.
- There was no correlation between degree of myopia and re-treatment rate.
- Eyes were significantly more likely to undergo LASIK or PRK enhancement surgery if they were farsighted rather than nearsighted (12.8 percent versus 6.0 percent) or had astigmatism equal to or greater than 1.00 D (9.1 percent versus 5.3 percent).
The researchers also noted that the study employed a relatively liberal re-treatment policy, and that only 15 eyes that had enhancements (27.8 percent) had UCVA worse than 20/40 after the initial LASIK or PRK procedure.
If the criteria for enhancement surgery was UCVA worse than 20/40 prior to re-treatment, the enhancement rate for the study would have been 1.7 percent.
The researchers concluded that the re-treatment rate for wavefront-optimized LASIK and PRK performed with the WaveLight Allegretto Wave excimer laser platform is low, and eyes that are at greatest risk for needing an enhancement after these procedures are those that are farsighted or have astigmatism equal to or greater than 1.00 D prior to surgery.
SOURCE: Incidence, outcomes, and risk factors for retreatment after wavefront-optimized ablations with PRK and LASIK. Journal of Refractive Surgery. March 2009.