WAVE-GUIDED LASER VISION CORRECTION

Wavefront-guided LASIK is a variation of LASIK surgery in which, rather than applying a simple correction of focusing power to the cornea (as in traditional LASIK), an ophthalmologistapplies a spatially varying correction, guiding the computer-controlled excimer laser with measurements from a wavefront sensor. The goal is to achieve a more optically perfect eye, though the final result still depends on the physician’s success at predicting changes that occur during healing and other factors that may have to do with the regularity/irregularity of the cornea and the axis of any residual astigmatism. In older patients, scattering from microscopic particles (cataract or incipient cataract) may play a role that outweighs any benefit from wavefront correction. Therefore, patients expecting so-called “super vision” from such procedures may be disappointed.

Australian ophthalmologist Noel A. Alpins, who developed a vector analysis method to analyze astigmatism in cataract, refractive, and corneal surgery, has long advocated combining “vector planning” with wavefront-guided LASIK. Alpins’ contention is that the purely refraction-based approach represented by wavefront analysis contradicts corneal surgical experience developed over many years. Refractive surgeons have long known that corneal regularity is the foundation of superior visual outcomes. Because refractive and corneal topographic astigmatism do not always align, corrections for internal optical errors surgically sculpted onto the cornea may increase corneal irregularity.Alpins believes that the pathway to “super vision” requires a greater customized reduction of corneal astigmatism than is usually attempted, and that any remaining astigmatism ought to be regular (as opposed to irregular), which are both fundamental principles of vector planning overlooked by a purely wavefront-guided treatment plan. Alpins’ observation was confirmed in a prospective study of LASIK patients, which found a greater reduction in corneal astigmatism and better visual outcomes under mesopic conditions using wavefront technology combined with vector analysis (the Alpins method) than using wavefront technology alone, and also found equivalent higher-order aberrations.

No good data can be found that compare the percentage of LASIK procedures that employ wavefront guidance versus the percentage that do not, nor the percentage of refractive surgeons who have a preference one way or the other. Wavefront technology continues to be positioned as an “advance” in LASIK with putative advantages; however, it is clear that not all LASIK procedures are performed with wavefront guidance.

Still, surgeons claim patients are generally more satisfied with this technique than with previous methods, particularly regarding lowered incidence of “halos,” the visual artifact caused byspherical aberration induced in the eye by earlier methods. A meta-analysis of eight trials showed a lower incidence of these higher order aberrations in patients who had wavefront-guided LASIK compared to non-wavefront-guided LASIK. Based on their experience, the United States Air Force has described WFG-Lasik as giving “superior vision results”.

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