A recent study finds wavefront-guided LASIK induces fewer higher-order aberrations than a related customized laser vision correction procedure called wavefront-optimized LASIK.
Typically, fewer higher-order aberrations means better visual outcomes after LASIK surgery. The study suggests wavefront-guided LASIK offers the best results for most patients, with a lower incidence of re-treatments.
What are higher-order aberrations?
Higher-order aberrations (HOAs) are subtle optical defects in the focusing system of the eye that can cause blur, glare, halos and other visual disturbances. Higher order aberrations differ from common refractive errors — nearsightedness, farsightedness and astigmatism — which are easier to identify and can be corrected with eyeglasses and contact lenses.
Higher-order aberrations that are significant enough to affect vision can be present in eyes that have little or no refractive error. Vision problems caused by HOAs typically are most noticeable in low-light conditions, such as night driving.
Spherical aberration is one particular type of higher-order aberration. Uncorrected spherical aberration can cause glare and halos around street lights and headlights at night.
What is wavefront-guided LASIK?
Wavefront-guided LASIK uses pre-operative aberrometry measurements to determine the level of pre-existing higher-order aberrations and to develop a computerized laser treatment (ablation) to reduce these aberrations.
What is wavefront-optimized LASIK?
Wavefront-optimized LASIK, on the other hand, is an enhanced version of conventional LASIK. It does not address pre-operative HOAs, but the laser ablation is adjusted, based on the patient’s eyeglasses prescription, to minimize any increase in spherical aberration induced by the treatment.
So whereas the goal of wavefront-guided LASIK is to identify and treat multiple HOAs (including spherical aberration) and refractive error during the corneal reshaping of the eye, the goal of wavefront-optimized LASIK is only to limit any increase in spherical aberration during the treatment of refractive error by the laser.
Study design
To evaluate the effect of wavefront-guided and wavefront-optimized LASIK on higher-order aberrations, Jack T. Holladay, MD, clinical professor of ophthalmology at Baylor College of Medicine (Houston, Texas) and colleagues reviewed the results of 109 wavefront-guided procedures and 102 wavefront-optimized procedures performed in 2006 and early 2007.
Results and conclusions
Findings of the study revealed:
- Overall, the wavefront-guided LASIK treatments induced significantly less higher-order aberrations (including spherical aberration) than the wavefront-optimized procedures.
- Among eyes treated with wavefront-guided LASIK, approximately 12 percent had less HOAs after surgery than they had prior to surgery, 76 percent had essentially the same amount before and after surgery, and 12 percent had more HOAs after LASIK.
- Among eyes treated with wavefront-optimized treatment, approximately eight percent had less HOAs after surgery, 51 percent had essentially the same amount before and after surgery, and 41 percent had more HOAs after LASIK.
- There was more variation in outcomes among eyes receiving wavefront-optimized procedure.
The researchers concluded that wavefront-guided LASIK reduces or induces fewer higher-order aberrations than wavefront-optimized LASIK and therefore is the better procedure for optimizing post-surgical vision quality.
SOURCE: Fewer higher-order aberrations yields better visual performance. EyeWorld. May 2009. (Supplement: Premium Clinical Options for Cataract and Refractive Surgery, sponsored by Abbott Medical Optics.)
Tags: astigmatism, farsighted, Higher-order aberrations, nearsighted